oxideav-dvd 0.0.3

//! IFO body parser — Video Manager Information (VMGI), Video Title
//! Set Information (VTSI), Program Chain Information (PGCI), Title
//! Search Pointer Table (TT_SRPT), Part-of-Title Search Pointer Table
//! (VTS_PTT_SRPT), Cell Address Table (VTS_C_ADT).
//!
//! Phase 2: structural decoding of the IFO files only — title list,
//! chapter list, program-chain layout, cell sector ranges. No VOB
//! demuxing, no cell concatenation, no virtual-machine command
//! execution, no playback. Those are Phase 3.
//!
//! ## Sector / byte addressing convention
//!
//! IFO files are sequences of 2048-byte logical sectors. Field
//! offsets in `VMGI_MAT` / `VTSI_MAT` that are described as "sector
//! pointers" are sector indexes **relative to the start of the IFO
//! file**, not absolute disc-LBA values. The "start sector" fields
//! inside `TT_SRPT` entries, by contrast, are absolute disc LBAs
//! (referenced to the whole disc, where `VIDEO_TS.IFO` lives at LBA
//! 0 of that title set).
//!
//! All multi-byte integer fields are big-endian (network byte order).
//!
//! ## Clean-room references
//!
//! Material consulted while writing this module:
//!
//! - `docs/container/dvd/application/mpucoder-ifo.html`
//!   (VMGI_MAT / VTSI_MAT field layout, sector-pointer offsets,
//!   C_ADT / VOBU_ADMAP entry format).
//! - `docs/container/dvd/application/mpucoder-ifo_vmg.html`
//!   (TT_SRPT, VMGM_PGCI_UT, VMG_PTL_MAIT, VMG_VTS_ATRT).
//! - `docs/container/dvd/application/mpucoder-ifo_vts.html`
//!   (VTS_PTT_SRPT, VTS_PGCI, VTSM_PGCI_UT, VTS_TMAPTI).
//! - `docs/container/dvd/application/mpucoder-pgc.html`
//!   (PGC header at offset 0..0xEC, command table, program map,
//!   cell playback information table, cell position information).
//! - `docs/container/dvd/application/stnsoft-vmindx.html`
//!   (cross-reference for VTS_C_ADT entry layout).
//!
//! Field layouts derive from the
//! `docs/container/dvd/application/` references listed above.

use crate::error::{Error, Result};

/// Logical-sector size on a DVD-ROM (per ECMA-267 §1.7).
pub const DVD_SECTOR: usize = 2048;

/// Magic at byte 0 of `VIDEO_TS.IFO`.
pub const VMG_MAGIC: &[u8; 12] = b"DVDVIDEO-VMG";

/// Magic at byte 0 of `VTS_xx_0.IFO`.
pub const VTS_MAGIC: &[u8; 12] = b"DVDVIDEO-VTS";

// ------------------------------------------------------------------
// Common helpers
// ------------------------------------------------------------------

fn read_u16(buf: &[u8], off: usize) -> Result<u16> {
    let slice = buf
        .get(off..off + 2)
        .ok_or(Error::InvalidUdf("ifo: u16 read past end"))?;
    Ok(u16::from_be_bytes([slice[0], slice[1]]))
}

fn read_u32(buf: &[u8], off: usize) -> Result<u32> {
    let slice = buf
        .get(off..off + 4)
        .ok_or(Error::InvalidUdf("ifo: u32 read past end"))?;
    Ok(u32::from_be_bytes([slice[0], slice[1], slice[2], slice[3]]))
}

fn read_u8(buf: &[u8], off: usize) -> Result<u8> {
    buf.get(off)
        .copied()
        .ok_or(Error::InvalidUdf("ifo: u8 read past end"))
}

// ------------------------------------------------------------------
// PgcTime — BCD playback time + frame-rate bits
// ------------------------------------------------------------------

/// Playback time field used by `PGC_GI` and per-cell `C_PBI` entries.
///
/// Layout per mpucoder-pgc.html: 4 bytes — `hh:mm:ss:ff` in BCD, with
/// bits 7 & 6 of the last byte encoding the frame rate. `11b` = 30 fps
/// (NTSC drop / non-drop), `01b` = 25 fps (PAL). `10b` and `00b` are
/// declared illegal by the spec — we surface them as
/// [`FrameRate::Illegal`] rather than rejecting outright since some
/// authoring tools emit zero-time placeholder fields.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct PgcTime {
    pub hours: u8,
    pub minutes: u8,
    pub seconds: u8,
    pub frames: u8,
    pub frame_rate: FrameRate,
}

/// Frame-rate encoding used by [`PgcTime`].
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum FrameRate {
    /// `00b` — illegal per spec, but present in some authoring outputs.
    Illegal,
    /// `01b` — 25 fps (PAL).
    Pal25,
    /// `10b` — illegal per spec.
    Reserved,
    /// `11b` — 30 fps (NTSC; the spec lumps drop/non-drop together).
    Ntsc30,
}

impl PgcTime {
    /// Decode a 4-byte BCD playback time field.
    pub fn from_bytes(bytes: [u8; 4]) -> Self {
        fn bcd(b: u8) -> u8 {
            ((b >> 4) & 0x0F) * 10 + (b & 0x0F)
        }
        let hours = bcd(bytes[0]);
        let minutes = bcd(bytes[1]);
        let seconds = bcd(bytes[2]);
        // Frames byte: bits 7+6 = frame-rate; bits 5..0 = BCD frames.
        // Per mpucoder-pgc.html the frames nibble pair is itself BCD,
        // but only the low 6 bits encode frames (so the tens digit is
        // 0..3, sufficient for max 29 frames at 30 fps).
        let frame_rate = match (bytes[3] >> 6) & 0x03 {
            0b00 => FrameRate::Illegal,
            0b01 => FrameRate::Pal25,
            0b10 => FrameRate::Reserved,
            0b11 => FrameRate::Ntsc30,
            _ => unreachable!(),
        };
        let f_lo = bytes[3] & 0x0F;
        let f_hi = (bytes[3] >> 4) & 0x03;
        let frames = f_hi * 10 + f_lo;
        Self {
            hours,
            minutes,
            seconds,
            frames,
            frame_rate,
        }
    }

    /// Total integer seconds (frames truncated, frame-rate ignored).
    /// Convenient when callers just need a "ballpark length" without
    /// the per-frame rounding.
    pub fn total_seconds(self) -> u32 {
        u32::from(self.hours) * 3600 + u32::from(self.minutes) * 60 + u32::from(self.seconds)
    }

    /// Convert this BCD field to absolute nanoseconds.
    ///
    /// `hh:mm:ss` resolves to whole seconds via [`Self::total_seconds`],
    /// then the `frames` count is scaled by the per-rate frame period
    /// (33,333,333 ns at 30 fps, 40,000,000 ns at 25 fps). Rational
    /// arithmetic — `(frames * 1e9) / fps` — caps the per-call truncation
    /// at ±1 ns instead of accumulating ~5e-9 per frame.
    ///
    /// Spec-`Illegal` and reserved-`10b` frame-rate codes contribute
    /// only the whole-second portion; the fractional frames are
    /// dropped because the spec defines no rate to scale them by.
    /// This keeps a malformed BCD field from poisoning a chapter
    /// length with a wildly-wrong scaled value, while still letting a
    /// caller surface a "best-effort" duration.
    ///
    /// Layout per `mpucoder-pgc.html` (PgcTime) and
    /// `mpucoder-dsi_pkt.html` `c_eltm` (same BCD shape).
    pub fn to_nanoseconds(self) -> u64 {
        let secs = u64::from(self.total_seconds());
        let secs_ns = secs.saturating_mul(1_000_000_000);
        let frames_ns = match self.frame_rate {
            FrameRate::Ntsc30 => u64::from(self.frames).saturating_mul(1_000_000_000) / 30,
            FrameRate::Pal25 => u64::from(self.frames).saturating_mul(1_000_000_000) / 25,
            FrameRate::Illegal | FrameRate::Reserved => 0,
        };
        secs_ns.saturating_add(frames_ns)
    }
}

// ------------------------------------------------------------------
// VMGI_MAT — Video Manager Information Management Table
// ------------------------------------------------------------------

/// Parsed VMGI_MAT (the first 0x200 bytes of `VIDEO_TS.IFO`).
///
/// Fields are surfaced in the order they appear in mpucoder-ifo.html's
/// "VMG IFO Contents" column. Sector-pointer fields are kept as-is
/// (`0` denotes "table absent" per spec).
#[derive(Debug, Clone)]
pub struct VmgIfo {
    /// Last sector of the VMG set (last sector of `VIDEO_TS.BUP`).
    pub last_sector_vmg_set: u32,
    /// Last sector of `VIDEO_TS.IFO`.
    pub last_sector_ifo: u32,
    /// VMGI version number, packed as `(major << 4) | minor` in the
    /// low byte of a 16-bit BE field (mpucoder-ifo.html "Version
    /// Number"). DVD-Video is typically `0x10` (1.0) or `0x11` (1.1).
    pub version: u16,
    /// VMG category (region mask in byte 1; rest reserved).
    pub vmg_category: u32,
    /// Number of volumes in this title set (e.g. 1 for single-volume
    /// discs; >1 for jukebox-style multi-side authoring).
    pub number_of_volumes: u16,
    /// Volume number (1-based) within the set above.
    pub volume_number: u16,
    /// Side ID (0 = side A, 1 = side B for double-sided discs).
    pub side_id: u8,
    /// Number of Video Title Sets (1..=99).
    pub number_of_title_sets: u16,
    /// Provider ID (32 ASCII bytes, NUL-padded).
    pub provider_id: String,
    /// Last byte address of `VMGI_MAT` itself.
    pub vmgi_mat_end: u32,
    /// Start address (byte offset) of First-Play PGC. `0` if absent.
    pub fp_pgc_addr: u32,
    /// Sector pointer to the VMG menu VOB (`0` if no menu).
    pub menu_vob_sector: u32,
    /// Sector pointer to TT_SRPT. Mandatory; always non-zero on a
    /// well-formed disc.
    pub tt_srpt_sector: u32,
    /// Sector pointer to VMGM_PGCI_UT. `0` if no VMG menu.
    pub vmgm_pgci_ut_sector: u32,
    /// Sector pointer to VMG_PTL_MAIT. `0` if no parental management.
    pub ptl_mait_sector: u32,
    /// Sector pointer to VMG_VTS_ATRT.
    pub vts_atrt_sector: u32,
    /// Sector pointer to VMG_TXTDT_MG (disc text data). `0` if absent.
    pub txtdt_mg_sector: u32,
    /// Sector pointer to VMGM_C_ADT (menu cell address table).
    pub vmgm_c_adt_sector: u32,
    /// Sector pointer to VMGM_VOBU_ADMAP (menu VOBU address map).
    pub vmgm_vobu_admap_sector: u32,
    /// VMGM (First-Play / VMG menu) stream attributes at
    /// 0x0100..0x015C. Empty when the buffer was too short to
    /// cover that region.
    pub menu_attributes: MenuAttributes,
}

impl VmgIfo {
    /// Parse a `VIDEO_TS.IFO` byte buffer. The buffer must cover at
    /// least the VMGI_MAT region (the first 0x200 bytes).
    pub fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 0x200 {
            return Err(Error::InvalidUdf("VMGI_MAT: buffer shorter than 0x200"));
        }
        if &buf[0..12] != VMG_MAGIC {
            return Err(Error::InvalidUdf("VMGI_MAT: bad magic"));
        }
        let last_sector_vmg_set = read_u32(buf, 0x000C)?;
        let last_sector_ifo = read_u32(buf, 0x001C)?;
        let version = read_u16(buf, 0x0020)?;
        let vmg_category = read_u32(buf, 0x0022)?;
        let number_of_volumes = read_u16(buf, 0x0026)?;
        let volume_number = read_u16(buf, 0x0028)?;
        let side_id = read_u8(buf, 0x002A)?;
        let number_of_title_sets = read_u16(buf, 0x003E)?;
        let provider_id_raw = &buf[0x0040..0x0060];
        let provider_id = decode_ascii_trim(provider_id_raw);
        let vmgi_mat_end = read_u32(buf, 0x0080)?;
        let fp_pgc_addr = read_u32(buf, 0x0084)?;
        let menu_vob_sector = read_u32(buf, 0x00C0)?;
        let tt_srpt_sector = read_u32(buf, 0x00C4)?;
        let vmgm_pgci_ut_sector = read_u32(buf, 0x00C8)?;
        let ptl_mait_sector = read_u32(buf, 0x00CC)?;
        let vts_atrt_sector = read_u32(buf, 0x00D0)?;
        let txtdt_mg_sector = read_u32(buf, 0x00D4)?;
        let vmgm_c_adt_sector = read_u32(buf, 0x00D8)?;
        let vmgm_vobu_admap_sector = read_u32(buf, 0x00DC)?;
        let menu_attributes = parse_menu_attribute_block(buf, 0x0100)?;

        Ok(Self {
            last_sector_vmg_set,
            last_sector_ifo,
            version,
            vmg_category,
            number_of_volumes,
            volume_number,
            side_id,
            number_of_title_sets,
            provider_id,
            vmgi_mat_end,
            fp_pgc_addr,
            menu_vob_sector,
            tt_srpt_sector,
            vmgm_pgci_ut_sector,
            ptl_mait_sector,
            vts_atrt_sector,
            txtdt_mg_sector,
            vmgm_c_adt_sector,
            vmgm_vobu_admap_sector,
            menu_attributes,
        })
    }
}

fn decode_ascii_trim(buf: &[u8]) -> String {
    let end = buf.iter().position(|&b| b == 0).unwrap_or(buf.len());
    String::from_utf8_lossy(&buf[..end]).trim_end().to_string()
}

// ------------------------------------------------------------------
// TT_SRPT — Title Search Pointer Table (VMG-side)
// ------------------------------------------------------------------

/// One entry of the VMG-side TT_SRPT (title search pointer table).
///
/// Per mpucoder-ifo_vmg.html "TT_SRPT" each entry is 12 bytes and
/// indexes the disc-global "title number" to the (title-set, title-
/// in-title-set) pair plus the VTS's start sector on the disc.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct DvdTitleEntry {
    /// Title type byte (jump/link/call permission bits — see spec).
    pub title_type: u8,
    /// Number of angles (1..=9).
    pub angle_count: u8,
    /// Number of chapters / parts-of-title (PTTs) in this title.
    pub chapter_count: u16,
    /// Parental management mask (16-bit; bit N set = blocked at level N).
    pub parental_mask: u16,
    /// VTS number (1..=99) this title lives in.
    pub vts_number: u8,
    /// Title number within that VTS.
    pub vts_title_number: u8,
    /// Start sector of the VTS (whole-disc-relative LBA).
    pub vts_start_sector: u32,
}

impl DvdTitleEntry {
    /// 2-bit UOP-prohibition subset packed into the low bits of
    /// [`Self::title_type`].
    ///
    /// Per `docs/container/dvd/application/mpucoder-uops.html`,
    /// TT_SRPT carries only UOP-0 (`TimePlayOrSearch`) and UOP-1
    /// (`PttPlayOrSearch`); they live in the two low bits of
    /// `title_type`. The remaining `title_type` bits encode the
    /// title's jump/link/call permission flags per
    /// `mpucoder-ifo_vmg.html` and stay outside the UOP surface.
    #[inline]
    pub fn uop_mask(&self) -> crate::uops::UopMask {
        crate::uops::title_type_uop_mask(self.title_type)
    }

    /// `true` when `op` is **not** prohibited at the TT_SRPT level
    /// for this title. Only the two TT_SRPT-applicable ops
    /// (`TimePlayOrSearch`, `PttPlayOrSearch`) ever yield a `false`
    /// here; every other op returns `true` because TT_SRPT has no
    /// bit to encode them. The PGC-level and PCI-VOBU-level masks
    /// still need to be consulted via
    /// [`crate::uops::UopMask::merge_or`].
    #[inline]
    pub fn is_user_op_allowed(&self, op: crate::uops::UserOp) -> bool {
        self.uop_mask().is_allowed(op)
    }
}

/// Parsed TT_SRPT body — 8-byte header plus N × 12-byte entries.
#[derive(Debug, Clone)]
pub struct TtSrpt {
    /// Number of titles (= entry count).
    pub title_count: u16,
    /// `end_address` field (last byte of last entry, relative to TT_SRPT start).
    pub end_address: u32,
    /// Parsed entries.
    pub entries: Vec<DvdTitleEntry>,
}

impl TtSrpt {
    /// Parse a TT_SRPT byte buffer. Buffer must include the 8-byte
    /// header and at least `title_count * 12` entry bytes.
    pub fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 8 {
            return Err(Error::InvalidUdf("TT_SRPT: shorter than 8-byte header"));
        }
        let title_count = read_u16(buf, 0)?;
        let end_address = read_u32(buf, 4)?;
        let needed = 8usize.saturating_add(usize::from(title_count) * 12);
        if buf.len() < needed {
            return Err(Error::InvalidUdf(
                "TT_SRPT: buffer shorter than title_count*12",
            ));
        }
        let mut entries = Vec::with_capacity(usize::from(title_count));
        for i in 0..usize::from(title_count) {
            let base = 8 + i * 12;
            entries.push(DvdTitleEntry {
                title_type: read_u8(buf, base)?,
                angle_count: read_u8(buf, base + 1)?,
                chapter_count: read_u16(buf, base + 2)?,
                parental_mask: read_u16(buf, base + 4)?,
                vts_number: read_u8(buf, base + 6)?,
                vts_title_number: read_u8(buf, base + 7)?,
                vts_start_sector: read_u32(buf, base + 8)?,
            });
        }
        Ok(Self {
            title_count,
            end_address,
            entries,
        })
    }
}

// ------------------------------------------------------------------
// Stream attribute extension blocks
//
// mpucoder-ifo.html documents a shared attribute layout that lives
// at fixed offsets inside both `VMGI_MAT` (one block at 0x0100..
// 0x015C covering the VMGM menu VOBS) and `VTSI_MAT` (the menu
// block at 0x0100..0x015C plus the title-content block at 0x0200..
// 0x0318 plus the 8×24-byte multichannel-extension table at
// 0x0318..0x03D8). Each block is a self-contained `(video, audio
// list, sub-picture list)` triple; the multichannel-extension
// table is karaoke-only and only present on the VTS title side.
// ------------------------------------------------------------------

/// MPEG coding mode field of `<a name="vidatt">video attributes</a>`.
/// (mpucoder-ifo.html byte 0 bits 7..6 of the 2-byte video-attr field.)
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum VideoCodingMode {
    Mpeg1,
    Mpeg2,
}

/// Display standard — bits 5..4 of byte 0.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum VideoStandard {
    Ntsc,
    Pal,
}

/// Display aspect ratio — bits 3..2 of byte 0. The "1" and "2"
/// values are reserved by the spec; we surface them as
/// [`VideoAspectRatio::Reserved`] rather than rejecting outright.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum VideoAspectRatio {
    /// `00b` — 4:3 frame, no display-mode pulldown.
    Ratio4x3,
    /// `11b` — 16:9 frame, anamorphic or letterboxed delivery.
    Ratio16x9,
    /// `01b` / `10b` — reserved by the spec.
    Reserved(u8),
}

/// Decoded NTSC / PAL pixel resolution — byte 1 bits 5..3 of the
/// 2-byte video-attr field. The spec encodes resolution as a 3-bit
/// index whose meaning depends on the standard byte; we resolve it
/// to absolute pixel dimensions for the caller.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum VideoResolution {
    /// Full-D1 — `0` index. 720×480 (NTSC) / 720×576 (PAL).
    FullD1,
    /// Three-quarter D1 — `1` index. 704×480 (NTSC) / 704×576 (PAL).
    ThreeQuarterD1,
    /// Half-D1 — `2` index. 352×480 (NTSC) / 352×576 (PAL).
    HalfD1,
    /// SIF — `3` index. 352×240 (NTSC) / 352×288 (PAL).
    Sif,
    /// `4..=7` — reserved by the spec.
    Reserved(u8),
}

impl VideoResolution {
    /// Decoded `(width, height)` in pixels for this resolution code +
    /// the parent's `VideoStandard`. Returns `None` for reserved
    /// codes (caller can fall back to the raw resolution index from
    /// [`VideoAttributes::resolution_code`]).
    pub fn dimensions(self, standard: VideoStandard) -> Option<(u16, u16)> {
        let h = match standard {
            VideoStandard::Ntsc => 480,
            VideoStandard::Pal => 576,
        };
        let w = match self {
            VideoResolution::FullD1 => 720,
            VideoResolution::ThreeQuarterD1 => 704,
            VideoResolution::HalfD1 => 352,
            VideoResolution::Sif => 352,
            VideoResolution::Reserved(_) => return None,
        };
        let h = if matches!(self, VideoResolution::Sif) && matches!(standard, VideoStandard::Ntsc) {
            240
        } else if matches!(self, VideoResolution::Sif) && matches!(standard, VideoStandard::Pal) {
            288
        } else {
            h
        };
        Some((w, h))
    }
}

/// Decoded 2-byte VMGM / VTSM / VTS video-attribute field.
///
/// mpucoder-ifo.html "Video Attributes" lays the field out as:
///
/// ```text
///   byte 0:
///     bit 7..6  coding mode (00=MPEG-1, 01=MPEG-2)
///     bit 5..4  standard (00=NTSC, 01=PAL)
///     bit 3..2  aspect ratio (00=4:3, 11=16:9, 01/10 reserved)
///     bit 1     1 = automatic pan/scan disallowed
///     bit 0     1 = automatic letterbox disallowed
///   byte 1:
///     bit 7     CC for line 21 field 1 in GOP (NTSC only)
///     bit 6     CC for line 21 field 2 in GOP (NTSC only)
///     bit 5..3  resolution index (see VideoResolution)
///     bit 2     1 = letterboxed source
///     bit 1     reserved
///     bit 0     PAL only: 0 = camera, 1 = film
/// ```
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct VideoAttributes {
    /// Raw 2-byte field, kept for fidelity / round-trip diagnostics.
    pub raw: [u8; 2],
    pub coding_mode: VideoCodingMode,
    pub standard: VideoStandard,
    pub aspect_ratio: VideoAspectRatio,
    /// `true` when `byte0 bit 1` is set — pan/scan delivery
    /// disabled at the disc level even for 4:3 displays.
    pub pan_scan_disallowed: bool,
    /// `true` when `byte0 bit 0` is set — letterbox delivery
    /// disabled at the disc level.
    pub letterbox_disallowed: bool,
    /// `true` when `byte1 bit 7` is set — line-21 closed captioning
    /// is present on field 1 of every GOP (NTSC only; ignored on PAL).
    pub line21_field1_cc: bool,
    /// `true` when `byte1 bit 6` is set — closed captioning on field 2.
    pub line21_field2_cc: bool,
    /// Raw 3-bit resolution index — see [`VideoResolution`] for the
    /// decoded form.
    pub resolution_code: u8,
    pub resolution: VideoResolution,
    /// `true` when the source itself is letterboxed (separate from
    /// the delivery-mode "letterbox disallowed" bit).
    pub letterboxed_source: bool,
    /// PAL-only: `false` = camera-captured, `true` = film-source
    /// (progressive at 24 fps, telecined to 25 fps). Always `false`
    /// on NTSC.
    pub film_source_pal: bool,
}

impl VideoAttributes {
    /// Parse a 2-byte video-attribute field.
    pub fn parse(buf: &[u8; 2]) -> Self {
        let b0 = buf[0];
        let b1 = buf[1];
        let coding_mode = match (b0 >> 6) & 0b11 {
            0 => VideoCodingMode::Mpeg1,
            _ => VideoCodingMode::Mpeg2,
        };
        let standard = match (b0 >> 4) & 0b11 {
            0 => VideoStandard::Ntsc,
            _ => VideoStandard::Pal,
        };
        let aspect_ratio = match (b0 >> 2) & 0b11 {
            0 => VideoAspectRatio::Ratio4x3,
            3 => VideoAspectRatio::Ratio16x9,
            x => VideoAspectRatio::Reserved(x),
        };
        let resolution_code = (b1 >> 3) & 0b111;
        let resolution = match resolution_code {
            0 => VideoResolution::FullD1,
            1 => VideoResolution::ThreeQuarterD1,
            2 => VideoResolution::HalfD1,
            3 => VideoResolution::Sif,
            x => VideoResolution::Reserved(x),
        };
        Self {
            raw: *buf,
            coding_mode,
            standard,
            aspect_ratio,
            pan_scan_disallowed: (b0 & 0b0000_0010) != 0,
            letterbox_disallowed: (b0 & 0b0000_0001) != 0,
            line21_field1_cc: (b1 & 0b1000_0000) != 0,
            line21_field2_cc: (b1 & 0b0100_0000) != 0,
            resolution_code,
            resolution,
            letterboxed_source: (b1 & 0b0000_0100) != 0,
            film_source_pal: (b1 & 0b0000_0001) != 0,
        }
    }
}

/// Audio coding mode — byte 0 bits 7..5 of the 8-byte audio-attr
/// field. `0` = AC-3, `2` = MPEG-1, `3` = MPEG-2 extended, `4` = LPCM,
/// `6` = DTS. Codes `1`, `5`, `7` are reserved by the spec.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum AudioCodingMode {
    Ac3,
    Mpeg1,
    Mpeg2Ext,
    Lpcm,
    Dts,
    Reserved(u8),
}

/// Application mode — byte 0 bits 1..0. `0` = unspecified,
/// `1` = karaoke (multichannel extension applies), `2` = surround
/// (Dolby-Surround-suitable bit lives in byte 7).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum AudioApplicationMode {
    Unspecified,
    Karaoke,
    Surround,
    Reserved(u8),
}

/// Audio quantization / dynamic-range-control field — byte 1 bits
/// 7..6. The interpretation switches with the coding mode:
/// LPCM uses the field as a sample-depth selector (16 / 20 / 24 bps),
/// MPEG-1/2 uses it as a DRC flag.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum AudioQuantizationDrc {
    /// LPCM-only: 16 bps per sample.
    Lpcm16,
    /// LPCM-only: 20 bps per sample.
    Lpcm20,
    /// LPCM-only: 24 bps per sample.
    Lpcm24,
    /// MPEG-only: dynamic-range control absent.
    NoDrc,
    /// MPEG-only: dynamic-range control present.
    Drc,
    /// Field present but caller didn't supply the coding mode
    /// hint — surface the raw 2-bit value.
    Raw(u8),
}

/// Language type — byte 0 bits 3..2. `0` = unspecified (bytes 2..=4
/// reserved), `1` = ISO-639 language code present in bytes 2..=4.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum AudioLanguageType {
    Unspecified,
    Iso639,
    Reserved(u8),
}

/// Decoded 8-byte audio-attribute field.
///
/// Layout per mpucoder-ifo.html "Audio Attributes":
///
/// ```text
///   byte 0:
///     bit 7..5  coding mode (0=AC3, 2=MPEG-1, 3=MPEG-2ext, 4=LPCM, 6=DTS)
///     bit 4     multichannel-extension present (karaoke)
///     bit 3..2  language type (0=unspecified, 1=ISO-639 in bytes 2..=4)
///     bit 1..0  application mode (0=unspec, 1=karaoke, 2=surround)
///   byte 1:
///     bit 7..6  quantization / DRC (interpretation switches on coding mode)
///     bit 5..4  sample-rate selector (only `0` = 48 kHz defined)
///     bit 3     reserved
///     bit 2..0  channels - 1   (so `1` = stereo, `5` = 5.1)
///   bytes 2..=3:  ISO-639 two-letter language code (if `language_type == Iso639`)
///   byte 4:       reserved for language-code extension
///   byte 5:       code-extension byte — `0..=4` per `SPRM #17`
///   byte 6:       reserved
///   byte 7:       Application-information byte (karaoke channel
///                 assignment or surround Dolby-suitable bit, per
///                 the application mode)
/// ```
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct AudioAttributes {
    pub raw: [u8; 8],
    pub coding_mode: AudioCodingMode,
    /// `true` when the karaoke multichannel-extension entry for this
    /// stream is populated. Always `false` outside karaoke titles.
    pub multichannel_extension_present: bool,
    pub language_type: AudioLanguageType,
    pub application_mode: AudioApplicationMode,
    pub quantization: AudioQuantizationDrc,
    /// Sample-rate index (only `0` = 48 kHz is defined; any other
    /// value is reserved).
    pub sample_rate_code: u8,
    /// Channel count, post-decoding the `channels - 1` field.
    pub channel_count: u8,
    /// Two-character ISO-639 language code, or empty when
    /// `language_type` is `Unspecified`.
    pub language_code: [u8; 2],
    pub code_extension: u8,
    /// Raw application-information byte at offset 7. Karaoke and
    /// surround application modes both pack secondary flags in here;
    /// callers can decode them with the helpers below.
    pub application_info: u8,
}

impl AudioAttributes {
    /// Parse an 8-byte audio-attribute field.
    pub fn parse(buf: &[u8; 8]) -> Self {
        let b0 = buf[0];
        let b1 = buf[1];
        let coding_mode_raw = (b0 >> 5) & 0b111;
        let coding_mode = match coding_mode_raw {
            0 => AudioCodingMode::Ac3,
            2 => AudioCodingMode::Mpeg1,
            3 => AudioCodingMode::Mpeg2Ext,
            4 => AudioCodingMode::Lpcm,
            6 => AudioCodingMode::Dts,
            x => AudioCodingMode::Reserved(x),
        };
        let language_type = match (b0 >> 2) & 0b11 {
            0 => AudioLanguageType::Unspecified,
            1 => AudioLanguageType::Iso639,
            x => AudioLanguageType::Reserved(x),
        };
        let application_mode = match b0 & 0b11 {
            0 => AudioApplicationMode::Unspecified,
            1 => AudioApplicationMode::Karaoke,
            2 => AudioApplicationMode::Surround,
            x => AudioApplicationMode::Reserved(x),
        };
        let quant_raw = (b1 >> 6) & 0b11;
        let quantization = match coding_mode {
            AudioCodingMode::Lpcm => match quant_raw {
                0 => AudioQuantizationDrc::Lpcm16,
                1 => AudioQuantizationDrc::Lpcm20,
                2 => AudioQuantizationDrc::Lpcm24,
                _ => AudioQuantizationDrc::Raw(quant_raw),
            },
            AudioCodingMode::Mpeg1 | AudioCodingMode::Mpeg2Ext => match quant_raw {
                0 => AudioQuantizationDrc::NoDrc,
                1 => AudioQuantizationDrc::Drc,
                _ => AudioQuantizationDrc::Raw(quant_raw),
            },
            _ => AudioQuantizationDrc::Raw(quant_raw),
        };
        Self {
            raw: *buf,
            coding_mode,
            multichannel_extension_present: (b0 & 0b0001_0000) != 0,
            language_type,
            application_mode,
            quantization,
            sample_rate_code: (b1 >> 4) & 0b11,
            channel_count: (b1 & 0b0000_0111).saturating_add(1),
            language_code: [buf[2], buf[3]],
            code_extension: buf[5],
            application_info: buf[7],
        }
    }

    /// Decoded sample rate in hertz. Returns `Some(48_000)` for
    /// `sample_rate_code == 0` (the only defined value) and `None`
    /// for the reserved codes.
    pub fn sample_rate_hz(self) -> Option<u32> {
        match self.sample_rate_code {
            0 => Some(48_000),
            _ => None,
        }
    }

    /// Surround application mode only: `true` when byte 7 bit 3 is
    /// set (Dolby-Surround-decodable downmix). Always `false`
    /// outside `AudioApplicationMode::Surround`.
    pub fn dolby_surround_suitable(self) -> bool {
        matches!(self.application_mode, AudioApplicationMode::Surround)
            && (self.application_info & 0b0000_1000) != 0
    }

    /// Karaoke application mode only — channel-assignment index
    /// from byte 7 bits 6..4. The spec maps:
    /// `2` = 2/0 L,R / `3` = 3/0 L,M,R / `4` = 2/1 L,R,V1 /
    /// `5` = 3/1 L,M,R,V1 / `6` = 2/2 L,R,V1,V2 / `7` = 3/2 L,M,R,V1,V2.
    /// `0` and `1` are flagged "not valid" by the spec.
    pub fn karaoke_channel_assignment(self) -> Option<u8> {
        if matches!(self.application_mode, AudioApplicationMode::Karaoke) {
            Some((self.application_info >> 4) & 0b0000_0111)
        } else {
            None
        }
    }

    /// Karaoke version index — byte 7 bits 3..2.
    pub fn karaoke_version(self) -> Option<u8> {
        if matches!(self.application_mode, AudioApplicationMode::Karaoke) {
            Some((self.application_info >> 2) & 0b11)
        } else {
            None
        }
    }

    /// Karaoke MC-intro flag — byte 7 bit 1.
    pub fn karaoke_mc_intro_present(self) -> Option<bool> {
        if matches!(self.application_mode, AudioApplicationMode::Karaoke) {
            Some((self.application_info & 0b10) != 0)
        } else {
            None
        }
    }

    /// Karaoke solo / duet flag — byte 7 bit 0 (`0` = solo, `1` = duet).
    pub fn karaoke_duet(self) -> Option<bool> {
        if matches!(self.application_mode, AudioApplicationMode::Karaoke) {
            Some((self.application_info & 0b01) != 0)
        } else {
            None
        }
    }
}

/// Sub-picture coding mode — byte 0 bits 7..5 of the 6-byte sub-
/// picture-attribute field. Only `0` (2-bit RLE) is defined.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum SubpictureCodingMode {
    Rle2Bit,
    Reserved(u8),
}

/// Language type — same as the audio variant.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum SubpictureLanguageType {
    Unspecified,
    Iso639,
    Reserved(u8),
}

/// Decoded 6-byte sub-picture attribute field.
///
/// Layout per mpucoder-ifo.html "Subpicture Attributes":
///
/// ```text
///   byte 0:
///     bit 7..5  coding mode (0 = 2-bit RLE)
///     bit 4..2  reserved
///     bit 1..0  language type
///   byte 1:     reserved
///   bytes 2..=3: ISO-639 two-letter language code
///   byte 4:     reserved for language-code extension
///   byte 5:     code extension — see SPRM #19
/// ```
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct SubpictureAttributes {
    pub raw: [u8; 6],
    pub coding_mode: SubpictureCodingMode,
    pub language_type: SubpictureLanguageType,
    pub language_code: [u8; 2],
    pub code_extension: u8,
}

impl SubpictureAttributes {
    /// Parse a 6-byte sub-picture-attribute field.
    pub fn parse(buf: &[u8; 6]) -> Self {
        let b0 = buf[0];
        let coding_mode = match (b0 >> 5) & 0b111 {
            0 => SubpictureCodingMode::Rle2Bit,
            x => SubpictureCodingMode::Reserved(x),
        };
        let language_type = match b0 & 0b11 {
            0 => SubpictureLanguageType::Unspecified,
            1 => SubpictureLanguageType::Iso639,
            x => SubpictureLanguageType::Reserved(x),
        };
        Self {
            raw: *buf,
            coding_mode,
            language_type,
            language_code: [buf[2], buf[3]],
            code_extension: buf[5],
        }
    }
}

/// One 8-byte karaoke multichannel-extension entry, decoded per
/// mpucoder-ifo.html "MultiChannel Extension - Karaoke mode".
///
/// Bytes 0x05..=0x17 are reserved-zero and absorbed silently.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
pub struct McExtensionEntry {
    pub raw: [u8; 8],
    /// Byte 0 bit 0 — guide melody on audio channel 0 of the
    /// downmix is present.
    pub ach0_guide_melody: bool,
    /// Byte 1 bit 0 — guide melody on audio channel 1.
    pub ach1_guide_melody: bool,
    /// Byte 2 bit 3 — guide vocal 1 on audio channel 2.
    pub ach2_guide_vocal_1: bool,
    /// Byte 2 bit 2 — guide vocal 2 on audio channel 2.
    pub ach2_guide_vocal_2: bool,
    /// Byte 2 bit 1 — guide melody 1 on audio channel 2.
    pub ach2_guide_melody_1: bool,
    /// Byte 2 bit 0 — guide melody 2 on audio channel 2.
    pub ach2_guide_melody_2: bool,
    /// Byte 3 bit 3 — guide vocal 1 on audio channel 3.
    pub ach3_guide_vocal_1: bool,
    /// Byte 3 bit 2 — guide vocal 2 on audio channel 3.
    pub ach3_guide_vocal_2: bool,
    /// Byte 3 bit 1 — guide melody A on audio channel 3.
    pub ach3_guide_melody_a: bool,
    /// Byte 3 bit 0 — sound effect A on audio channel 3.
    pub ach3_sound_effect_a: bool,
    /// Byte 4 bit 3 — guide vocal 1 on audio channel 4.
    pub ach4_guide_vocal_1: bool,
    /// Byte 4 bit 2 — guide vocal 2 on audio channel 4.
    pub ach4_guide_vocal_2: bool,
    /// Byte 4 bit 1 — guide melody B on audio channel 4.
    pub ach4_guide_melody_b: bool,
    /// Byte 4 bit 0 — sound effect B on audio channel 4.
    pub ach4_sound_effect_b: bool,
}

impl McExtensionEntry {
    /// Parse one 8-byte multichannel-extension entry. (The spec
    /// labels the entry's footprint as `8*24` bytes — actually 24
    /// entries × 8 bytes each — but each individual entry is 8
    /// bytes wide.)
    pub fn parse(buf: &[u8; 8]) -> Self {
        let b0 = buf[0];
        let b1 = buf[1];
        let b2 = buf[2];
        let b3 = buf[3];
        let b4 = buf[4];
        Self {
            raw: *buf,
            ach0_guide_melody: (b0 & 0b0000_0001) != 0,
            ach1_guide_melody: (b1 & 0b0000_0001) != 0,
            ach2_guide_vocal_1: (b2 & 0b0000_1000) != 0,
            ach2_guide_vocal_2: (b2 & 0b0000_0100) != 0,
            ach2_guide_melody_1: (b2 & 0b0000_0010) != 0,
            ach2_guide_melody_2: (b2 & 0b0000_0001) != 0,
            ach3_guide_vocal_1: (b3 & 0b0000_1000) != 0,
            ach3_guide_vocal_2: (b3 & 0b0000_0100) != 0,
            ach3_guide_melody_a: (b3 & 0b0000_0010) != 0,
            ach3_sound_effect_a: (b3 & 0b0000_0001) != 0,
            ach4_guide_vocal_1: (b4 & 0b0000_1000) != 0,
            ach4_guide_vocal_2: (b4 & 0b0000_0100) != 0,
            ach4_guide_melody_b: (b4 & 0b0000_0010) != 0,
            ach4_sound_effect_b: (b4 & 0b0000_0001) != 0,
        }
    }
}

// ------------------------------------------------------------------
// VTSI_MAT — Video Title Set Information Management Table
// ------------------------------------------------------------------

/// VMGM / VTSM-side menu-attribute block — video format plus the
/// audio + sub-picture stream lists for the menu VOBS.
///
/// `audio_streams` and `subpicture_streams` are populated to the
/// declared `number_of_*_streams` count (≤ 8 for audio per the
/// 8×8-byte attribute slot, ≤ 1 for sub-picture per the single
/// 6-byte slot). Any tail attribute slots beyond the declared
/// counts are ignored.
#[derive(Debug, Clone, Default, PartialEq, Eq)]
pub struct MenuAttributes {
    pub video: Option<VideoAttributes>,
    pub audio_streams: Vec<AudioAttributes>,
    pub subpicture_streams: Vec<SubpictureAttributes>,
}

/// VTS_VOBS-side title-attribute block — video format plus the
/// title audio (≤ 8) and sub-picture (≤ 32) stream lists, plus the
/// karaoke multichannel-extension table (24 × 8-byte entries; one
/// per audio stream slot, even for slots not populated).
#[derive(Debug, Clone, Default, PartialEq, Eq)]
pub struct TitleAttributes {
    pub video: Option<VideoAttributes>,
    pub audio_streams: Vec<AudioAttributes>,
    pub subpicture_streams: Vec<SubpictureAttributes>,
    /// Karaoke multichannel extension entries — populated when the
    /// buffer is long enough to cover offset 0x0318..0x03D8 of
    /// VTSI_MAT. Empty for non-karaoke titles and for buffers
    /// shorter than 0x03D8.
    pub multichannel_extension: Vec<McExtensionEntry>,
}

/// Parsed VTSI_MAT (the first 0x300 + audio/sub-picture extension
/// bytes of a `VTS_xx_0.IFO` file).
///
/// Like [`VmgIfo`], sector-pointer fields stay raw — `0` denotes
/// "absent".
#[derive(Debug, Clone)]
pub struct VtsiMat {
    /// Last sector of this title set (last sector of `VTS_xx_0.BUP`).
    pub last_sector_title_set: u32,
    /// Last sector of this IFO file (`VTS_xx_0.IFO`).
    pub last_sector_ifo: u32,
    /// Version number — see [`VmgIfo::version`].
    pub version: u16,
    /// VTS category (0 = unspecified, 1 = Karaoke).
    pub vts_category: u32,
    /// Last byte of the VTSI_MAT region.
    pub vtsi_mat_end: u32,
    /// Start sector of the menu VOB (`0` if no menu).
    pub menu_vob_sector: u32,
    /// Start sector of the title VOBs.
    pub title_vob_sector: u32,
    /// Sector pointer to VTS_PTT_SRPT.
    pub vts_ptt_srpt_sector: u32,
    /// Sector pointer to VTS_PGCI.
    pub vts_pgci_sector: u32,
    /// Sector pointer to VTSM_PGCI_UT (menu PGCI).
    pub vtsm_pgci_ut_sector: u32,
    /// Sector pointer to VTS_TMAPTI (time map table).
    pub vts_tmapti_sector: u32,
    /// Sector pointer to VTSM_C_ADT (menu cell address table).
    pub vtsm_c_adt_sector: u32,
    /// Sector pointer to VTSM_VOBU_ADMAP (menu VOBU address map).
    pub vtsm_vobu_admap_sector: u32,
    /// Sector pointer to VTS_C_ADT (title-set cell address table).
    pub vts_c_adt_sector: u32,
    /// Sector pointer to VTS_VOBU_ADMAP (title-set VOBU address map).
    pub vts_vobu_admap_sector: u32,
    /// VTSM (menu) stream attributes at 0x0100..0x015C. Empty
    /// when the buffer was too short to cover that region — the
    /// minimal buffer-length check is still `0x200` for backwards
    /// compatibility with the original sector-only parse.
    pub menu_attributes: MenuAttributes,
    /// VTS_VOBS (title-content) stream attributes at 0x0200..
    /// 0x03D8. Empty when the buffer was too short to cover that
    /// region.
    pub title_attributes: TitleAttributes,
}

impl VtsiMat {
    /// Parse a `VTS_xx_0.IFO` byte buffer. Buffer must cover at least
    /// the VTSI_MAT region (the first 0x200 bytes).
    ///
    /// Audio / sub-picture / multichannel attribute extension blocks
    /// are decoded opportunistically — fields populated up to the
    /// last full block the buffer covers, the rest stays empty.
    pub fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 0x200 {
            return Err(Error::InvalidUdf("VTSI_MAT: buffer shorter than 0x200"));
        }
        if &buf[0..12] != VTS_MAGIC {
            return Err(Error::InvalidUdf("VTSI_MAT: bad magic"));
        }
        let menu_attributes = parse_menu_attribute_block(buf, 0x0100)?;
        let title_attributes = parse_title_attribute_block(buf)?;
        Ok(Self {
            last_sector_title_set: read_u32(buf, 0x000C)?,
            last_sector_ifo: read_u32(buf, 0x001C)?,
            version: read_u16(buf, 0x0020)?,
            vts_category: read_u32(buf, 0x0022)?,
            vtsi_mat_end: read_u32(buf, 0x0080)?,
            menu_vob_sector: read_u32(buf, 0x00C0)?,
            title_vob_sector: read_u32(buf, 0x00C4)?,
            vts_ptt_srpt_sector: read_u32(buf, 0x00C8)?,
            vts_pgci_sector: read_u32(buf, 0x00CC)?,
            vtsm_pgci_ut_sector: read_u32(buf, 0x00D0)?,
            vts_tmapti_sector: read_u32(buf, 0x00D4)?,
            vtsm_c_adt_sector: read_u32(buf, 0x00D8)?,
            vtsm_vobu_admap_sector: read_u32(buf, 0x00DC)?,
            vts_c_adt_sector: read_u32(buf, 0x00E0)?,
            vts_vobu_admap_sector: read_u32(buf, 0x00E4)?,
            menu_attributes,
            title_attributes,
        })
    }
}

/// Decode a menu-attribute block (VMGM- or VTSM-side) that starts at
/// `block_off`. The block's footprint per mpucoder-ifo.html
/// 0x0100..0x015C is:
///
/// ```text
///   +0x00  u16  video attributes (2 bytes)
///   +0x02  u16  number of audio streams (≤ 8)
///   +0x04  8 × 8 bytes  audio attributes
///   +0x44  16 bytes     reserved
///   +0x54  u16  number of subpicture streams (0 or 1)
///   +0x56  6 bytes      subpicture attribute slot (slot 0)
///   +0x5C  ...           reserved tail
/// ```
fn parse_menu_attribute_block(buf: &[u8], block_off: usize) -> Result<MenuAttributes> {
    // Need at least the 2-byte video field + 2-byte audio count.
    if buf.len() < block_off + 0x04 {
        return Ok(MenuAttributes::default());
    }
    let video = read_video_attr(buf, block_off)?;
    let audio_count = read_u16(buf, block_off + 0x02)? as usize;
    let mut audio_streams = Vec::new();
    if buf.len() >= block_off + 0x04 + 8 * 8 {
        for i in 0..audio_count.min(8) {
            audio_streams.push(read_audio_attr(buf, block_off + 0x04 + i * 8)?);
        }
    }
    let subp_count_off = block_off + 0x54;
    let mut subpicture_streams = Vec::new();
    if buf.len() >= subp_count_off + 2 + 6 {
        let subp_count = read_u16(buf, subp_count_off)? as usize;
        if subp_count >= 1 {
            subpicture_streams.push(read_subp_attr(buf, subp_count_off + 2)?);
        }
    }
    Ok(MenuAttributes {
        video: Some(video),
        audio_streams,
        subpicture_streams,
    })
}

/// Decode the VTS-VOBS title attribute block at fixed offset 0x0200.
/// The block's footprint is:
///
/// ```text
///   0x0200  u16  video attributes
///   0x0202  u16  number of audio streams (≤ 8)
///   0x0204  8 × 8 bytes  audio attributes
///   0x0244  16 bytes     reserved
///   0x0254  u16  number of subpicture streams (≤ 32)
///   0x0256  32 × 6 bytes  subpicture attributes
///   0x0316  2 bytes      reserved
///   0x0318  24 × 8 bytes  multichannel-extension entries (karaoke only)
///   0x03D8  end
/// ```
fn parse_title_attribute_block(buf: &[u8]) -> Result<TitleAttributes> {
    if buf.len() < 0x0204 {
        return Ok(TitleAttributes::default());
    }
    let video = read_video_attr(buf, 0x0200)?;
    let audio_count = read_u16(buf, 0x0202)? as usize;
    let mut audio_streams = Vec::new();
    if buf.len() >= 0x0204 + 8 * 8 {
        for i in 0..audio_count.min(8) {
            audio_streams.push(read_audio_attr(buf, 0x0204 + i * 8)?);
        }
    }
    let mut subpicture_streams = Vec::new();
    if buf.len() >= 0x0256 + 32 * 6 {
        let subp_count = read_u16(buf, 0x0254)? as usize;
        for i in 0..subp_count.min(32) {
            subpicture_streams.push(read_subp_attr(buf, 0x0256 + i * 6)?);
        }
    }
    // Multichannel extension — the spec slot is 24 × 8 = 192 bytes
    // starting at 0x0318 and ending at 0x03D8. Only decode the
    // entries that fit; non-karaoke titles leave the slot all-zero
    // (which Default-decodes cleanly, hence we still populate the
    // table — callers can inspect `vts_category` or the audio
    // `multichannel_extension_present` flag to know whether to
    // consume them).
    let mut multichannel_extension = Vec::new();
    if buf.len() >= 0x03D8 {
        for i in 0..24 {
            let off = 0x0318 + i * 8;
            let slice: [u8; 8] = buf[off..off + 8]
                .try_into()
                .map_err(|_| Error::InvalidUdf("VTSI_MAT: MC ext slice"))?;
            multichannel_extension.push(McExtensionEntry::parse(&slice));
        }
    }
    Ok(TitleAttributes {
        video: Some(video),
        audio_streams,
        subpicture_streams,
        multichannel_extension,
    })
}

fn read_video_attr(buf: &[u8], off: usize) -> Result<VideoAttributes> {
    let slice = buf
        .get(off..off + 2)
        .ok_or(Error::InvalidUdf("ifo: video attr read past end"))?;
    Ok(VideoAttributes::parse(&[slice[0], slice[1]]))
}

fn read_audio_attr(buf: &[u8], off: usize) -> Result<AudioAttributes> {
    let slice = buf
        .get(off..off + 8)
        .ok_or(Error::InvalidUdf("ifo: audio attr read past end"))?;
    let arr: [u8; 8] = slice
        .try_into()
        .map_err(|_| Error::InvalidUdf("ifo: audio attr slice"))?;
    Ok(AudioAttributes::parse(&arr))
}

fn read_subp_attr(buf: &[u8], off: usize) -> Result<SubpictureAttributes> {
    let slice = buf
        .get(off..off + 6)
        .ok_or(Error::InvalidUdf("ifo: subp attr read past end"))?;
    let arr: [u8; 6] = slice
        .try_into()
        .map_err(|_| Error::InvalidUdf("ifo: subp attr slice"))?;
    Ok(SubpictureAttributes::parse(&arr))
}

// ------------------------------------------------------------------
// VTS_PTT_SRPT — Part-of-Title Search Pointer Table (chapters)
// ------------------------------------------------------------------

/// One PTT (chapter) — points to a `(PGCN, PGN)` pair within the VTS.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct Ptt {
    /// Program Chain number (1-based).
    pub pgcn: u16,
    /// Program number within the PGC (1-based).
    pub pgn: u16,
}

/// One title in the PTT search pointer table — the list of chapters
/// for that title.
#[derive(Debug, Clone)]
pub struct PttTitle {
    pub chapters: Vec<Ptt>,
}

/// Parsed VTS_PTT_SRPT — 8-byte header + per-title offset list +
/// per-title PTT entries.
#[derive(Debug, Clone)]
pub struct VtsPttSrpt {
    pub title_count: u16,
    pub end_address: u32,
    pub titles: Vec<PttTitle>,
}

impl VtsPttSrpt {
    /// Parse a VTS_PTT_SRPT body.
    ///
    /// Layout per mpucoder-ifo_vts.html:
    ///
    /// ```text
    ///   0000: u16 number_of_titles (Nt)
    ///   0002: u16 reserved
    ///   0004: u32 end_address (last byte of last VTS_PTT)
    ///   0008: u32 offset_to_PTT[1]     ← VTS_PTTI[1]
    ///   000C: u32 offset_to_PTT[2]     ← VTS_PTTI[2]
    ///   ...
    ///   ...
    /// ```
    ///
    /// Each title's PTT region is a list of 4-byte `(PGCN, PGN)` pairs.
    /// The end of title i's region is bounded by either title i+1's
    /// offset (for i < Nt) or by `end_address + 1` (for i == Nt). We
    /// divide that span by 4 to recover the chapter count.
    pub fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 8 {
            return Err(Error::InvalidUdf(
                "VTS_PTT_SRPT: shorter than 8-byte header",
            ));
        }
        let title_count = read_u16(buf, 0)?;
        let end_address = read_u32(buf, 4)?;
        let nt = usize::from(title_count);
        let offsets_end = 8usize.saturating_add(nt * 4);
        if buf.len() < offsets_end {
            return Err(Error::InvalidUdf(
                "VTS_PTT_SRPT: offset list past end of buffer",
            ));
        }
        let mut offsets = Vec::with_capacity(nt);
        for i in 0..nt {
            offsets.push(read_u32(buf, 8 + i * 4)? as usize);
        }
        let mut titles = Vec::with_capacity(nt);
        for i in 0..nt {
            let start = offsets[i];
            // End of this title's PTT region: next title's offset, or
            // (end_address + 1) for the last title.
            let end_excl = if i + 1 < nt {
                offsets[i + 1]
            } else {
                (end_address as usize).saturating_add(1)
            };
            if end_excl < start {
                return Err(Error::InvalidUdf(
                    "VTS_PTT_SRPT: title offsets not monotonic",
                ));
            }
            let span = end_excl - start;
            if span % 4 != 0 {
                return Err(Error::InvalidUdf(
                    "VTS_PTT_SRPT: title span not a multiple of 4",
                ));
            }
            let n_ptt = span / 4;
            if buf.len() < start + n_ptt * 4 {
                return Err(Error::InvalidUdf(
                    "VTS_PTT_SRPT: title body past end of buffer",
                ));
            }
            let mut chapters = Vec::with_capacity(n_ptt);
            for j in 0..n_ptt {
                let off = start + j * 4;
                chapters.push(Ptt {
                    pgcn: read_u16(buf, off)?,
                    pgn: read_u16(buf, off + 2)?,
                });
            }
            titles.push(PttTitle { chapters });
        }
        Ok(Self {
            title_count,
            end_address,
            titles,
        })
    }
}

// ------------------------------------------------------------------
// PGC — Program Chain (header + cells)
// ------------------------------------------------------------------

/// Per-cell playback information (16 bytes per entry in C_PBI).
///
/// Field layout per mpucoder-pgc.html "cell playback information
/// table entry":
///
/// - byte 0: cell category bits (cell type, block type, seamless,
///   interleaved, STC discontinuity, seamless-angle).
/// - byte 1: restricted flag (`0x80` = trick-play disallowed).
/// - byte 2: cell still time.
/// - byte 3: cell command # (1..=128, 0 = no command).
/// - bytes 4..8: cell playback time (BCD).
/// - bytes 8..12: first VOBU start sector.
/// - bytes 12..16: first ILVU end sector.
/// - bytes 16..20: last VOBU start sector.
/// - bytes 20..24: last VOBU end sector.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct CellPlaybackInfo {
    pub category_byte0: u8,
    pub restricted: bool,
    pub still_time: u8,
    pub cell_command: u8,
    pub playback_time: PgcTime,
    pub first_vobu_start_sector: u32,
    pub first_ilvu_end_sector: u32,
    pub last_vobu_start_sector: u32,
    pub last_vobu_end_sector: u32,
}

impl CellPlaybackInfo {
    fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 24 {
            return Err(Error::InvalidUdf("C_PBI entry shorter than 24 bytes"));
        }
        let category_byte0 = read_u8(buf, 0)?;
        let restricted = (read_u8(buf, 1)? & 0x80) != 0;
        let still_time = read_u8(buf, 2)?;
        let cell_command = read_u8(buf, 3)?;
        let mut t = [0u8; 4];
        t.copy_from_slice(&buf[4..8]);
        let playback_time = PgcTime::from_bytes(t);
        let first_vobu_start_sector = read_u32(buf, 8)?;
        let first_ilvu_end_sector = read_u32(buf, 12)?;
        let last_vobu_start_sector = read_u32(buf, 16)?;
        let last_vobu_end_sector = read_u32(buf, 20)?;
        Ok(Self {
            category_byte0,
            restricted,
            still_time,
            cell_command,
            playback_time,
            first_vobu_start_sector,
            first_ilvu_end_sector,
            last_vobu_start_sector,
            last_vobu_end_sector,
        })
    }
}

/// Per-cell position information (4 bytes per entry in C_POS).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct CellPositionInfo {
    pub vob_id: u16,
    pub cell_id: u8,
}

impl CellPositionInfo {
    fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 4 {
            return Err(Error::InvalidUdf("C_POS entry shorter than 4 bytes"));
        }
        let vob_id = read_u16(buf, 0)?;
        // byte 2 reserved
        let cell_id = read_u8(buf, 3)?;
        Ok(Self { vob_id, cell_id })
    }
}

/// One entry of the PGC subpicture/highlight colour-LUT.
///
/// Per mpucoder-pgc.html the PGC header at offset `0x00A4` carries a
/// `16 × 4`-byte palette laid out as `(0, Y, Cr, Cb)`: byte 0 is a
/// reserved/zero pad, then the luma + the two chroma-difference
/// samples in 8-bit BT.601-range form. These sixteen entries are the
/// colour source a subpicture (SPU) display-control sequence indexes
/// into via its 4-bit colour codes (the SPU itself only stores the
/// 0..=15 palette index + a contrast/alpha nibble — see
/// mpucoder-spu.html), so a renderer needs this table to resolve a
/// subtitle/menu pixel to an actual YCrCb value.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
pub struct PaletteEntry {
    /// Luma (Y) sample, 8-bit.
    pub y: u8,
    /// Cr (red chroma-difference) sample, 8-bit.
    pub cr: u8,
    /// Cb (blue chroma-difference) sample, 8-bit.
    pub cb: u8,
}

impl PaletteEntry {
    /// Parse one 4-byte `(0, Y, Cr, Cb)` palette cell. The leading
    /// byte is reserved and ignored.
    fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 4 {
            return Err(Error::InvalidUdf("PGC palette entry shorter than 4 bytes"));
        }
        Ok(Self {
            y: buf[1],
            cr: buf[2],
            cb: buf[3],
        })
    }
}

/// One 8-byte DVD-Video navigation command (VM instruction word).
///
/// Per mpucoder-pgc.html every command in a PGC command table is a
/// fixed 8-byte word. Decoding the opcode/operand semantics is
/// Phase 3c VM work (mpucoder-vmi.html); at the container layer we
/// surface the raw word so a downstream interpreter can execute it.
/// We expose the leading byte's top three bits as `command_type`
/// (the VMI command-group selector) for convenience without
/// committing to a full opcode model.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
pub struct NavCommand {
    /// The eight raw command bytes, big-endian on the wire.
    pub bytes: [u8; 8],
}

impl NavCommand {
    /// Wrap an 8-byte command word.
    fn parse(buf: &[u8]) -> Result<Self> {
        let slice = buf
            .get(0..8)
            .ok_or(Error::InvalidUdf("PGC command shorter than 8 bytes"))?;
        let mut bytes = [0u8; 8];
        bytes.copy_from_slice(slice);
        Ok(Self { bytes })
    }

    /// VMI command-type selector — the top three bits of byte 0.
    ///
    /// This is the coarse command-group field per mpucoder-vmi.html;
    /// full opcode decode is delegated to the Phase 3c VM via
    /// [`Self::decode_instruction`]. Provided so callers can classify
    /// a word (e.g. distinguish a link/jump from a SetSystem/Compare)
    /// without a full interpreter.
    pub fn command_type(&self) -> u8 {
        self.bytes[0] >> 5
    }

    /// Decode this raw command word into a typed
    /// [`crate::nav::NavInstruction`].
    ///
    /// Convenience wrapper around the Phase 3c-precursor disassembler
    /// in the `nav` module, which adds a `decode()` method to this
    /// same `NavCommand` type. Callers iterating a
    /// [`PgcCommandTable`] can stay inside the `ifo` namespace and
    /// reach the typed instruction tree via a single method call
    /// rather than importing the `nav` module's surface explicitly.
    #[inline]
    pub fn decode_instruction(&self) -> crate::nav::NavInstruction {
        self.decode()
    }
}

/// PGC command table — pre, post, and cell command lists.
///
/// Per mpucoder-pgc.html "command table" the table opens with an
/// 8-byte header (`pre count`, `post count`, `cell count`, and an
/// `end address` relative to the table start), followed by the three
/// command lists back to back, each entry a fixed 8-byte
/// [`NavCommand`]. The total `pre + post + cell` count is `<= 128`.
///
/// *Pre* commands run before the PGC's first cell; *post* commands
/// run after the last cell finishes; *cell* commands are referenced
/// by the per-cell `cell_command` index in [`CellPlaybackInfo`]
/// (1-based; `0` = none). Executing the words is Phase 3c VM work —
/// here we only carve the raw 8-byte words out of the table.
#[derive(Debug, Clone, Default, PartialEq, Eq)]
pub struct PgcCommandTable {
    /// Commands executed when the PGC starts.
    pub pre: Vec<NavCommand>,
    /// Commands executed when the PGC ends.
    pub post: Vec<NavCommand>,
    /// Commands indexed by a cell's `cell_command` field (1-based).
    pub cell: Vec<NavCommand>,
    /// `end address` field — last byte offset of the table relative
    /// to its own start.
    pub end_address: u16,
}

impl PgcCommandTable {
    /// Parse a command table. `buf` must start at the table's first
    /// byte (the `pre count` u16) and span at least through the last
    /// command word.
    fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 8 {
            return Err(Error::InvalidUdf("PGC command table shorter than header"));
        }
        let pre_count = read_u16(buf, 0)?;
        let post_count = read_u16(buf, 2)?;
        let cell_count = read_u16(buf, 4)?;
        let end_address = read_u16(buf, 6)?;

        let total = usize::from(pre_count) + usize::from(post_count) + usize::from(cell_count);
        // Spec invariant: the three lists together hold <= 128 words.
        if total > 128 {
            return Err(Error::InvalidUdf("PGC command table claims > 128 commands"));
        }

        let read_list = |start: usize, count: u16| -> Result<Vec<NavCommand>> {
            let mut out = Vec::with_capacity(usize::from(count));
            for i in 0..usize::from(count) {
                let off = start + i * 8;
                let word = buf
                    .get(off..off + 8)
                    .ok_or(Error::InvalidUdf("PGC command table list past end"))?;
                out.push(NavCommand::parse(word)?);
            }
            Ok(out)
        };

        let pre_start = 8usize;
        let post_start = pre_start + usize::from(pre_count) * 8;
        let cell_start = post_start + usize::from(post_count) * 8;

        let pre = read_list(pre_start, pre_count)?;
        let post = read_list(post_start, post_count)?;
        let cell = read_list(cell_start, cell_count)?;

        Ok(Self {
            pre,
            post,
            cell,
            end_address,
        })
    }

    /// Iterate the **pre** command list as typed
    /// [`crate::nav::NavInstruction`]s.
    ///
    /// Per `docs/container/dvd/application/mpucoder-pgc.html` the
    /// pre-command list runs once at PGC entry, before the first
    /// cell. Each 8-byte [`NavCommand`] word is fed through the
    /// `nav` disassembler so iterator consumers receive the typed
    /// instruction tree directly without a manual decode step.
    pub fn pre_instructions(&self) -> impl Iterator<Item = crate::nav::NavInstruction> + '_ {
        self.pre.iter().map(NavCommand::decode_instruction)
    }

    /// Iterate the **post** command list as typed
    /// [`crate::nav::NavInstruction`]s.
    ///
    /// The post-command list runs once when the last cell of the
    /// PGC finishes, per `mpucoder-pgc.html`. Same shape as
    /// [`Self::pre_instructions`].
    pub fn post_instructions(&self) -> impl Iterator<Item = crate::nav::NavInstruction> + '_ {
        self.post.iter().map(NavCommand::decode_instruction)
    }

    /// Iterate the **cell** command list as typed
    /// [`crate::nav::NavInstruction`]s.
    ///
    /// The cell command list is indexed by each
    /// [`CellPlaybackInfo`]'s 1-based `cell_command` field per
    /// `mpucoder-pgc.html`; this iterator walks it in storage order.
    /// Use [`Self::cell_instruction`] for the indexed lookup a
    /// cell actually performs.
    pub fn cell_instructions(&self) -> impl Iterator<Item = crate::nav::NavInstruction> + '_ {
        self.cell.iter().map(NavCommand::decode_instruction)
    }

    /// Look up a cell command by its 1-based index — the encoding
    /// `CellPlaybackInfo::cell_command` carries on the wire — and
    /// return the typed [`crate::nav::NavInstruction`].
    ///
    /// Per `mpucoder-pgc.html` `cell_command = 0` means "no command
    /// associated with this cell"; the spec stores cell commands in
    /// a 1-based table. Passing `0` returns `None`; passing any
    /// out-of-range index also returns `None` rather than panicking,
    /// matching the malformed-disc-tolerance pattern used elsewhere
    /// in this crate's typed decoders.
    pub fn cell_instruction(&self, index_1based: u16) -> Option<crate::nav::NavInstruction> {
        if index_1based == 0 {
            return None;
        }
        let idx = usize::from(index_1based - 1);
        self.cell.get(idx).map(NavCommand::decode_instruction)
    }
}

/// Parsed PGC header + cell tables.
///
/// Layout per mpucoder-pgc.html:
///
/// - 0x0000..0x00E4: PGC general information (PGC_GI) +
///   PGC_AST_CTL + PGC_SPST_CTL + PGC_PB_TIME + still time +
///   playback mode + palette (16 × 4-byte `(0, Y, Cr, Cb)` at
///   0x00A4).
/// - 0x00E4: u16 offset_to_commands (relative to PGC start). The
///   command table at that offset holds the pre/post/cell
///   navigation command lists ([`PgcCommandTable`]).
/// - 0x00E6: u16 offset_to_program_map.
/// - 0x00E8: u16 offset_to_cell_playback_information.
/// - 0x00EA: u16 offset_to_cell_position_information.
#[derive(Debug, Clone)]
pub struct Pgc {
    /// Number of programs in this PGC.
    pub number_of_programs: u8,
    /// Number of cells.
    pub number_of_cells: u8,
    /// PGC playback time (BCD).
    pub playback_time: PgcTime,
    /// Prohibited user-operation mask.
    pub prohibited_user_ops: u32,
    /// Next PGCN (`0` = none).
    pub next_pgcn: u16,
    /// Previous PGCN (`0` = none).
    pub prev_pgcn: u16,
    /// "Goup" (group-up) PGCN (`0` = none).
    pub goup_pgcn: u16,
    /// PGC still time (`255` = infinite).
    pub still_time: u8,
    /// Playback mode (0 = sequential; non-zero encodes
    /// random/shuffle + program count, see spec).
    pub playback_mode: u8,
    /// Subpicture/highlight colour-LUT — 16 `(Y, Cr, Cb)` entries
    /// from PGC offset `0x00A4` per mpucoder-pgc.html.
    pub palette: [PaletteEntry; 16],
    /// Offset within PGC to commands table (`0` = absent).
    pub offset_commands: u16,
    /// Offset within PGC to program map (`0` = absent).
    pub offset_program_map: u16,
    /// Offset within PGC to cell-playback-information table.
    pub offset_cell_playback: u16,
    /// Offset within PGC to cell-position-information table.
    pub offset_cell_position: u16,
    /// Per-program entry-cell numbers, length = `number_of_programs`.
    pub program_map: Vec<u8>,
    /// Per-cell playback info.
    pub cells: Vec<CellPlaybackInfo>,
    /// Per-cell position info (VOB id + Cell id pairs).
    pub cell_positions: Vec<CellPositionInfo>,
    /// Parsed pre/post/cell navigation command table. `None` when
    /// `offset_commands == 0` (no command table present).
    pub commands: Option<PgcCommandTable>,
}

impl Pgc {
    /// Parse one PGC blob. `buf` must start at the PGC's first byte
    /// and span at least through the last table referenced by the
    /// offset fields.
    pub fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 0xEC {
            return Err(Error::InvalidUdf("PGC: buffer shorter than header"));
        }
        let number_of_programs = read_u8(buf, 0x0002)?;
        let number_of_cells = read_u8(buf, 0x0003)?;
        let mut t = [0u8; 4];
        t.copy_from_slice(&buf[0x0004..0x0008]);
        let playback_time = PgcTime::from_bytes(t);
        let prohibited_user_ops = read_u32(buf, 0x0008)?;
        let next_pgcn = read_u16(buf, 0x009C)?;
        let prev_pgcn = read_u16(buf, 0x009E)?;
        let goup_pgcn = read_u16(buf, 0x00A0)?;
        let still_time = read_u8(buf, 0x00A2)?;
        let playback_mode = read_u8(buf, 0x00A3)?;

        // Palette (subpicture colour-LUT): 16 × 4-byte (0, Y, Cr, Cb)
        // entries at PGC offset 0x00A4. This is part of the fixed
        // header (which the 0xEC length check above already covers).
        let mut palette = [PaletteEntry::default(); 16];
        for (i, slot) in palette.iter_mut().enumerate() {
            let base = 0x00A4 + i * 4;
            *slot = PaletteEntry::parse(&buf[base..base + 4])?;
        }

        let offset_commands = read_u16(buf, 0x00E4)?;
        let offset_program_map = read_u16(buf, 0x00E6)?;
        let offset_cell_playback = read_u16(buf, 0x00E8)?;
        let offset_cell_position = read_u16(buf, 0x00EA)?;

        // Program map: number_of_programs × 1 byte. Padded to word
        // boundary with zero per spec, but we only need the first N.
        let mut program_map = Vec::with_capacity(usize::from(number_of_programs));
        if offset_program_map != 0 {
            let base = usize::from(offset_program_map);
            for i in 0..usize::from(number_of_programs) {
                program_map.push(read_u8(buf, base + i)?);
            }
        }

        // Cell playback information table: number_of_cells × 24 bytes.
        let mut cells = Vec::with_capacity(usize::from(number_of_cells));
        if offset_cell_playback != 0 {
            let base = usize::from(offset_cell_playback);
            for i in 0..usize::from(number_of_cells) {
                let entry = &buf
                    .get(base + i * 24..base + (i + 1) * 24)
                    .ok_or(Error::InvalidUdf("PGC: C_PBI past end of buffer"))?;
                cells.push(CellPlaybackInfo::parse(entry)?);
            }
        }

        // Cell position information table: number_of_cells × 4 bytes.
        let mut cell_positions = Vec::with_capacity(usize::from(number_of_cells));
        if offset_cell_position != 0 {
            let base = usize::from(offset_cell_position);
            for i in 0..usize::from(number_of_cells) {
                let entry = &buf
                    .get(base + i * 4..base + (i + 1) * 4)
                    .ok_or(Error::InvalidUdf("PGC: C_POS past end of buffer"))?;
                cell_positions.push(CellPositionInfo::parse(entry)?);
            }
        }

        // Command table (pre/post/cell command lists). Absent when
        // offset_commands == 0 per mpucoder-pgc.html.
        let commands = if offset_commands != 0 {
            let base = usize::from(offset_commands);
            let tbl = buf
                .get(base..)
                .ok_or(Error::InvalidUdf("PGC: command table past end of buffer"))?;
            Some(PgcCommandTable::parse(tbl)?)
        } else {
            None
        };

        Ok(Self {
            number_of_programs,
            number_of_cells,
            playback_time,
            prohibited_user_ops,
            next_pgcn,
            prev_pgcn,
            goup_pgcn,
            still_time,
            playback_mode,
            palette,
            offset_commands,
            offset_program_map,
            offset_cell_playback,
            offset_cell_position,
            program_map,
            cells,
            cell_positions,
            commands,
        })
    }

    /// Typed view over [`Self::prohibited_user_ops`].
    ///
    /// The PGC-level UOP-prohibition mask follows the same 25-bit
    /// layout as the PCI / TT_SRPT levels; this accessor wraps the
    /// raw word so callers can use named [`UserOp`] variants
    /// instead of magic bit numbers. Per
    /// `docs/container/dvd/application/mpucoder-uops.html`, a set
    /// bit inhibits the associated control.
    #[inline]
    pub fn uop_mask(&self) -> crate::uops::UopMask {
        crate::uops::UopMask::from_bits(self.prohibited_user_ops)
    }

    /// `true` when `op` is **not** prohibited at the PGC level.
    /// The full player-visible answer is still subject to the
    /// TT_SRPT and PCI-VOBU masks per the spec's three-level OR
    /// rule; use [`crate::uops::UopMask::merge_or`] to combine.
    #[inline]
    pub fn is_user_op_allowed(&self, op: crate::uops::UserOp) -> bool {
        self.uop_mask().is_allowed(op)
    }
}

// ------------------------------------------------------------------
// PGCI — Program Chain Information (table of PGCs)
// ------------------------------------------------------------------

/// One entry in the PGCI SRP — category byte + offset to the PGC body.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct PgciSrp {
    pub category: u32,
    /// Offset to the PGC body, relative to the PGCI start.
    pub offset: u32,
}

/// Parsed PGCI (VTS_PGCI or VMGM_PGCI body).
#[derive(Debug, Clone)]
pub struct Pgci {
    pub number_of_pgcs: u16,
    pub end_address: u32,
    pub srp: Vec<PgciSrp>,
    pub pgcs: Vec<Pgc>,
}

impl Pgci {
    /// Parse a PGCI body. `buf` must start at the first byte of the
    /// PGCI table and span at least through the last PGC.
    pub fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 8 {
            return Err(Error::InvalidUdf("PGCI: shorter than 8-byte header"));
        }
        let number_of_pgcs = read_u16(buf, 0)?;
        let end_address = read_u32(buf, 4)?;
        let n = usize::from(number_of_pgcs);
        let srp_end = 8usize.saturating_add(n * 8);
        if buf.len() < srp_end {
            return Err(Error::InvalidUdf("PGCI: SRP list past end of buffer"));
        }
        let mut srp = Vec::with_capacity(n);
        for i in 0..n {
            let base = 8 + i * 8;
            srp.push(PgciSrp {
                category: read_u32(buf, base)?,
                offset: read_u32(buf, base + 4)?,
            });
        }
        let mut pgcs = Vec::with_capacity(n);
        for entry in &srp {
            let off = entry.offset as usize;
            if off == 0 || off >= buf.len() {
                return Err(Error::InvalidUdf("PGCI: PGC offset out of range"));
            }
            let pgc_buf = &buf[off..];
            pgcs.push(Pgc::parse(pgc_buf)?);
        }
        Ok(Self {
            number_of_pgcs,
            end_address,
            srp,
            pgcs,
        })
    }
}

// ------------------------------------------------------------------
// VMGM_PGCI_UT / VTSM_PGCI_UT — Menu PGCI Unit Table
// ------------------------------------------------------------------
//
// Per `docs/container/dvd/application/mpucoder-ifo_vmg.html` §VMGM_PGCI_UT
// and `mpucoder-ifo_vts.html` §VTSM_PGCI_UT. Two-level hierarchy:
//
//   VMGM_PGCI_UT / VTSM_PGCI_UT
//     ├── language-unit search-pointer list (one per ISO 639 language)
//     │     each entry: ISO639 code (2 B) + language-code ext (1 B)
//     │     + menu-existence-flag byte (1 B) + offset to LU (4 B)
//     └── Language Unit (PGCI_LU)
//           ├── PGC search-pointer list (one per menu PGC in this LU)
//           │     each entry: PGC category (4 B) + offset to PGC (4 B)
//           └── PGC bodies (parsed via `Pgc::parse`)
//
// The 8-byte unit-header at the LU and the unit-table top use the same
// `{ u16 count, u16 reserved, u32 end_address }` shape, then each list
// entry is 8 bytes.

/// Menu existence-flag bits used in a VTSM language-unit entry's byte 3.
///
/// Per `mpucoder-ifo_vts.html` §VTSM_PGCI_UT — bit set ⇒ the
/// corresponding menu exists in that language unit. Bit `0x80` ("root")
/// is the only flag VMGM_PGCI_UT uses (treated as "title" on the VMG
/// side per `mpucoder-ifo_vmg.html`).
pub mod menu_existence {
    /// `0x80` — root menu exists (VTSM) / title menu exists (VMGM).
    pub const ROOT: u8 = 0x80;
    /// `0x40` — sub-picture menu exists (VTSM only).
    pub const SUBPICTURE: u8 = 0x40;
    /// `0x20` — audio menu exists (VTSM only).
    pub const AUDIO: u8 = 0x20;
    /// `0x10` — angle menu exists (VTSM only).
    pub const ANGLE: u8 = 0x10;
    /// `0x08` — PTT (chapter) menu exists (VTSM only).
    pub const PTT: u8 = 0x08;
}

/// Menu-type enum decoded from a PGC category byte 0 (low nibble) per
/// `mpucoder-ifo_vts.html` §VTSM_PGCI_UT (PGC category breakdown).
///
/// Only meaningful when the entry-PGC flag (`category[0] >> 7`) is set;
/// for non-entry PGCs the menu-type field is unused per the spec.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum MenuType {
    /// VMGM-side: title menu (`2`).
    Title,
    /// VTSM-side: root menu (`3`).
    Root,
    /// VTSM-side: sub-picture menu (`4`).
    Subpicture,
    /// VTSM-side: audio menu (`5`).
    Audio,
    /// VTSM-side: angle menu (`6`).
    Angle,
    /// VTSM-side: PTT (chapter) menu (`7`).
    Ptt,
    /// Any other value the spec doesn't define (reserved).
    Unknown(u8),
}

impl MenuType {
    /// Decode the low nibble of PGC category byte 0.
    pub fn from_nibble(n: u8) -> Self {
        match n & 0x0F {
            2 => MenuType::Title,
            3 => MenuType::Root,
            4 => MenuType::Subpicture,
            5 => MenuType::Audio,
            6 => MenuType::Angle,
            7 => MenuType::Ptt,
            other => MenuType::Unknown(other),
        }
    }
}

/// One PGC search-pointer inside a Language Unit (`PGCI_LU`).
///
/// `category` is the 32-bit PGC category dword; the high bit of byte 0
/// is the entry-PGC flag and the low nibble of byte 0 is the menu type
/// (only valid when the entry-PGC flag is set). Bytes 2..4 carry the
/// parental management mask. `offset` is the byte distance from the
/// start of the enclosing Language Unit to the PGC body.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct PgciLuSrp {
    /// Raw 32-bit PGC category dword.
    pub category: u32,
    /// Byte offset to the PGC body, relative to this Language Unit's
    /// start.
    pub offset: u32,
}

impl PgciLuSrp {
    /// `true` when the entry-PGC flag (byte 0 bit 7) is set.
    pub fn is_entry_pgc(&self) -> bool {
        (self.category >> 24) & 0x80 != 0
    }

    /// Decode the menu-type nibble (only meaningful when
    /// [`Self::is_entry_pgc`] is `true`).
    pub fn menu_type(&self) -> MenuType {
        MenuType::from_nibble((self.category >> 24) as u8)
    }

    /// Parental management mask (low 16 bits of the category dword).
    pub fn parental_mask(&self) -> u16 {
        (self.category & 0xFFFF) as u16
    }
}

/// One Language Unit (`PGCI_LU`) — a PGC search-pointer list plus the
/// parsed PGC bodies it points at.
#[derive(Debug, Clone)]
pub struct PgciLu {
    /// Number of PGCs in this language unit.
    pub number_of_pgcs: u16,
    /// Last byte address of the last PGC body in this LU, relative to
    /// the LU's start.
    pub end_address: u32,
    /// PGC search pointers in declaration order.
    pub srp: Vec<PgciLuSrp>,
    /// Parsed PGC bodies in the same order as `srp`.
    pub pgcs: Vec<Pgc>,
}

impl PgciLu {
    /// Parse a Language Unit body. `buf` must start at the LU's first
    /// byte and span at least through the last PGC body.
    pub fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 8 {
            return Err(Error::InvalidUdf("PGCI_LU: shorter than 8-byte header"));
        }
        let number_of_pgcs = read_u16(buf, 0)?;
        // bytes 2..4 reserved
        let end_address = read_u32(buf, 4)?;
        let n = usize::from(number_of_pgcs);
        let srp_end = 8usize
            .checked_add(
                n.checked_mul(8)
                    .ok_or(Error::InvalidUdf("PGCI_LU: SRP list × 8 overflow"))?,
            )
            .ok_or(Error::InvalidUdf("PGCI_LU: SRP list size overflow"))?;
        if buf.len() < srp_end {
            return Err(Error::InvalidUdf("PGCI_LU: SRP list past end of buffer"));
        }
        let mut srp = Vec::with_capacity(n);
        for i in 0..n {
            let base = 8 + i * 8;
            srp.push(PgciLuSrp {
                category: read_u32(buf, base)?,
                offset: read_u32(buf, base + 4)?,
            });
        }
        let mut pgcs = Vec::with_capacity(n);
        for entry in &srp {
            let off = entry.offset as usize;
            if off == 0 || off >= buf.len() {
                return Err(Error::InvalidUdf("PGCI_LU: PGC offset out of range"));
            }
            pgcs.push(Pgc::parse(&buf[off..])?);
        }
        Ok(Self {
            number_of_pgcs,
            end_address,
            srp,
            pgcs,
        })
    }
}

/// One language-unit search-pointer in the menu PGCI Unit Table.
///
/// `language_code` is the raw 16-bit ISO 639 alpha-2 code (two ASCII
/// letters packed big-endian — e.g. `b"en"` = `0x656E`).
/// `language_code_ext` is the 1-byte language-code extension slot (the
/// spec keeps it reserved-zero; mirrors the SPRM-17 / SPRM-19 layout).
/// `menu_existence` is the byte 3 flag byte — see the
/// [`menu_existence`] constants.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct PgciUtSrp {
    /// Big-endian-packed ISO 639 language code.
    pub language_code: u16,
    /// Language-code extension byte (reserved-zero by the spec).
    pub language_code_ext: u8,
    /// Menu existence flag byte — bitset of [`menu_existence`] bits.
    pub menu_existence: u8,
    /// Byte offset to the Language Unit body, relative to the start
    /// of `PGCI_UT`.
    pub offset: u32,
}

impl PgciUtSrp {
    /// `true` when bit `0x80` (root / title menu) is set.
    pub fn has_root_menu(&self) -> bool {
        self.menu_existence & menu_existence::ROOT != 0
    }

    /// `true` when bit `0x40` (sub-picture menu) is set. Only
    /// meaningful for VTSM_PGCI_UT.
    pub fn has_subpicture_menu(&self) -> bool {
        self.menu_existence & menu_existence::SUBPICTURE != 0
    }

    /// `true` when bit `0x20` (audio menu) is set. Only meaningful for
    /// VTSM_PGCI_UT.
    pub fn has_audio_menu(&self) -> bool {
        self.menu_existence & menu_existence::AUDIO != 0
    }

    /// `true` when bit `0x10` (angle menu) is set. Only meaningful for
    /// VTSM_PGCI_UT.
    pub fn has_angle_menu(&self) -> bool {
        self.menu_existence & menu_existence::ANGLE != 0
    }

    /// `true` when bit `0x08` (PTT menu) is set. Only meaningful for
    /// VTSM_PGCI_UT.
    pub fn has_ptt_menu(&self) -> bool {
        self.menu_existence & menu_existence::PTT != 0
    }
}

/// Parsed VMGM_PGCI_UT or VTSM_PGCI_UT body.
///
/// Two-level table: an outer search-pointer list keyed by ISO 639
/// language code, with each entry pointing at a Language Unit that
/// itself holds the menu PGCs for that language. The wire format is
/// identical between the VMG and VTS sides; the only difference is
/// the documented set of `menu_existence` / `MenuType` values
/// (the VMG side only authors a "title" menu type, while the VTS
/// side authors root / subpicture / audio / angle / PTT menus).
#[derive(Debug, Clone)]
pub struct PgciUt {
    /// Number of Language Units in this table.
    pub number_of_language_units: u16,
    /// Last byte address of the last PGC body in the last LU,
    /// relative to the start of `PGCI_UT`.
    pub end_address: u32,
    /// Outer search-pointer list — one entry per language unit.
    pub srp: Vec<PgciUtSrp>,
    /// Parsed Language Units in the same order as `srp`.
    pub language_units: Vec<PgciLu>,
}

impl PgciUt {
    /// Parse a `VMGM_PGCI_UT` or `VTSM_PGCI_UT` body. `buf` must start
    /// at the first byte of the table and span at least through the
    /// last PGC body in the last LU.
    pub fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 8 {
            return Err(Error::InvalidUdf("PGCI_UT: shorter than 8-byte header"));
        }
        let number_of_language_units = read_u16(buf, 0)?;
        // bytes 2..4 reserved
        let end_address = read_u32(buf, 4)?;
        let n = usize::from(number_of_language_units);
        let srp_end = 8usize
            .checked_add(
                n.checked_mul(8)
                    .ok_or(Error::InvalidUdf("PGCI_UT: SRP list × 8 overflow"))?,
            )
            .ok_or(Error::InvalidUdf("PGCI_UT: SRP list size overflow"))?;
        if buf.len() < srp_end {
            return Err(Error::InvalidUdf("PGCI_UT: SRP list past end of buffer"));
        }
        let mut srp = Vec::with_capacity(n);
        for i in 0..n {
            let base = 8 + i * 8;
            srp.push(PgciUtSrp {
                language_code: read_u16(buf, base)?,
                language_code_ext: buf[base + 2],
                menu_existence: buf[base + 3],
                offset: read_u32(buf, base + 4)?,
            });
        }
        let mut language_units = Vec::with_capacity(n);
        for entry in &srp {
            let off = entry.offset as usize;
            if off == 0 || off >= buf.len() {
                return Err(Error::InvalidUdf("PGCI_UT: LU offset out of range"));
            }
            language_units.push(PgciLu::parse(&buf[off..])?);
        }
        Ok(Self {
            number_of_language_units,
            end_address,
            srp,
            language_units,
        })
    }

    /// Look up the Language Unit for the given 16-bit ISO 639 language
    /// code (e.g. `b"en"` packed big-endian = `0x656E`).
    pub fn language_unit(&self, language_code: u16) -> Option<&PgciLu> {
        self.srp
            .iter()
            .position(|s| s.language_code == language_code)
            .and_then(|i| self.language_units.get(i))
    }
}

// ------------------------------------------------------------------
// VTS_C_ADT — Cell Address Table
// ------------------------------------------------------------------

/// One row of the cell address table.
///
/// Per stnsoft-vmindx.html / mpucoder-ifo.html `c_adt`: each entry is
/// 12 bytes — `(vob_id u16, cell_id u8, reserved u8, start_sector
/// u32, end_sector u32)`.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct CellAddrEntry {
    pub vob_id: u16,
    pub cell_id: u8,
    pub start_sector: u32,
    pub end_sector: u32,
}

/// Parsed VTS_C_ADT body — also covers VMGM_C_ADT and VTSM_C_ADT
/// since they share the wire format.
#[derive(Debug, Clone)]
pub struct VtsCAdt {
    /// Number of distinct VOB IDs covered (NOT the entry count —
    /// per spec, multiple entries can share a VOB ID for the cells
    /// inside that VOB).
    pub number_of_vob_ids: u16,
    /// `end_address` field.
    pub end_address: u32,
    /// Parsed cell-address entries.
    pub entries: Vec<CellAddrEntry>,
}

impl VtsCAdt {
    /// Parse a C_ADT body. Entry count is recovered from
    /// `(end_address - 7) / 12` — the spec stores it implicitly.
    pub fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 8 {
            return Err(Error::InvalidUdf("C_ADT: shorter than 8-byte header"));
        }
        let number_of_vob_ids = read_u16(buf, 0)?;
        let end_address = read_u32(buf, 4)?;
        // end_address = byte index of the last entry's last byte
        // relative to start of C_ADT. The entries start at byte 8.
        // Entry count = (end_address + 1 - 8) / 12.
        let body_bytes = (end_address as usize).saturating_add(1).saturating_sub(8);
        if body_bytes % 12 != 0 {
            return Err(Error::InvalidUdf(
                "C_ADT: end_address implies non-12-byte entry size",
            ));
        }
        let n = body_bytes / 12;
        let needed = 8 + n * 12;
        if buf.len() < needed {
            return Err(Error::InvalidUdf("C_ADT: buffer shorter than entry table"));
        }
        let mut entries = Vec::with_capacity(n);
        for i in 0..n {
            let base = 8 + i * 12;
            entries.push(CellAddrEntry {
                vob_id: read_u16(buf, base)?,
                cell_id: read_u8(buf, base + 2)?,
                // byte 3 reserved
                start_sector: read_u32(buf, base + 4)?,
                end_sector: read_u32(buf, base + 8)?,
            });
        }
        Ok(Self {
            number_of_vob_ids,
            end_address,
            entries,
        })
    }

    /// Look up the disc-LBA range for a `(vob_id, cell_id)` pair.
    /// Sectors are relative to the start of the title's VOB chunks.
    pub fn lookup(&self, vob_id: u16, cell_id: u8) -> Option<(u32, u32)> {
        self.entries
            .iter()
            .find(|e| e.vob_id == vob_id && e.cell_id == cell_id)
            .map(|e| (e.start_sector, e.end_sector))
    }
}

// ------------------------------------------------------------------
// VOBU_ADMAP — VOBU Address Map (absolute sector list)
// ------------------------------------------------------------------

/// Parsed VOBU address map — covers `VMGM_VOBU_ADMAP`,
/// `VTSM_VOBU_ADMAP`, and `VTS_VOBU_ADMAP` (the three tables share
/// the same wire layout per `mpucoder-ifo.html`).
///
/// Layout (per the same source):
///
/// ```text
///   0x00: u32 end_address (last byte of last entry, relative to map start)
///   0x04: u32 starting sector within VOB of VOBU 1
///   0x08: u32 starting sector within VOB of VOBU 2
///   ...
/// ```
///
/// Entry count is implicit in `end_address`: each entry is exactly
/// four bytes, so `(end_address + 1 - 4) / 4` rounds down to the
/// number of VOBUs.
///
/// The 4-byte sector values are VOB-relative (i.e. relative to the
/// start of the first VOB the map covers — `VTS_xx_1.VOB` for
/// `VTS_VOBU_ADMAP`, the menu VOB for the menu variants); a player
/// adds the title-set VOB base LBA recorded in the corresponding
/// `VTSI_MAT::title_vob_sector` to recover the absolute disc LBA.
#[derive(Debug, Clone)]
pub struct VobuAdmap {
    /// `end_address` field — last byte of the last entry, relative
    /// to the start of the address map.
    pub end_address: u32,
    /// VOB-relative starting sectors, one per VOBU, in playback
    /// order. Index 0 = VOBU 1; index `entries.len() - 1` = the last
    /// VOBU declared by the map.
    pub entries: Vec<u32>,
}

impl VobuAdmap {
    /// Parse a VOBU_ADMAP body. `buf` must start at the 4-byte
    /// `end_address` field and span at least through the last entry.
    pub fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 4 {
            return Err(Error::InvalidUdf("VOBU_ADMAP: shorter than 4-byte header"));
        }
        let end_address = read_u32(buf, 0)?;
        // end_address points at the last byte of the last entry,
        // relative to the table start. Entries begin at byte 4; each
        // entry is 4 bytes wide.
        let body_bytes = (end_address as usize).saturating_add(1).saturating_sub(4);
        if body_bytes % 4 != 0 {
            return Err(Error::InvalidUdf(
                "VOBU_ADMAP: end_address implies non-4-byte entry size",
            ));
        }
        let n = body_bytes / 4;
        let needed = 4 + n * 4;
        if buf.len() < needed {
            return Err(Error::InvalidUdf(
                "VOBU_ADMAP: buffer shorter than entry table",
            ));
        }
        let mut entries = Vec::with_capacity(n);
        for i in 0..n {
            entries.push(read_u32(buf, 4 + i * 4)?);
        }
        Ok(Self {
            end_address,
            entries,
        })
    }

    /// Number of VOBUs covered by this map.
    #[inline]
    pub fn vobu_count(&self) -> usize {
        self.entries.len()
    }

    /// VOB-relative starting sector of the 1-based VOBU number.
    /// Returns `None` for `vobu_number == 0` or any number past the
    /// last entry.
    pub fn vobu_start_sector(&self, vobu_number: u32) -> Option<u32> {
        if vobu_number == 0 {
            return None;
        }
        self.entries.get((vobu_number - 1) as usize).copied()
    }

    /// Translate a VOB-relative sector into the 1-based VOBU number
    /// whose range covers it. Returns `None` when the sector falls
    /// before the map's first VOBU or the map is empty.
    ///
    /// Because consecutive entries delimit each VOBU's range
    /// (entry `i` starts VOBU `i + 1`; entry `i + 1` starts the next
    /// one), the lookup is a partition search: the matching VOBU is
    /// the highest-indexed entry whose value `<= sector`.
    pub fn vobu_containing(&self, sector: u32) -> Option<u32> {
        if self.entries.is_empty() {
            return None;
        }
        // Binary partition.
        let idx = self.entries.partition_point(|&v| v <= sector);
        if idx == 0 {
            None
        } else {
            Some(idx as u32)
        }
    }
}

// ------------------------------------------------------------------
// VTS_TMAPTI — Time Map Table (one map per PGC)
// ------------------------------------------------------------------

/// One time-map entry: VOB-relative sector of the VOBU at the
/// associated time stamp.
///
/// Bit 31 of the on-disc value is a discontinuity flag; the remaining
/// 31 bits carry the VOB-relative sector. Per `mpucoder-ifo_vts.html`
/// "VTS_TMAP" the discontinuity bit signals that the previous entry's
/// time stamp is **not** continuous with this one — typically because
/// the underlying VOBU sits across a cell boundary or an `STC`
/// reset.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct TmapEntry {
    /// VOB-relative sector of the VOBU at this time index.
    pub sector: u32,
    /// `true` when the source flagged a time discontinuity with the
    /// previous entry (bit 31 of the raw word).
    pub discontinuous: bool,
}

impl TmapEntry {
    /// Bit 31 of the raw entry word: discontinuity-with-previous
    /// flag per `mpucoder-ifo_vts.html`.
    pub const DISCONTINUITY_BIT: u32 = 1 << 31;

    /// Low-31-bit sector mask.
    pub const SECTOR_MASK: u32 = 0x7FFF_FFFF;

    /// Decode one 4-byte entry word.
    fn from_raw(raw: u32) -> Self {
        Self {
            sector: raw & Self::SECTOR_MASK,
            discontinuous: (raw & Self::DISCONTINUITY_BIT) != 0,
        }
    }
}

/// One per-PGC time map: time-unit length plus the per-step sector
/// list.
///
/// Layout (per `mpucoder-ifo_vts.html` "VTS_TMAP"):
///
/// ```text
///   0x00: u8  time_unit (seconds per step)
///   0x01: u8  reserved
///   0x02: u16 number_of_entries (`0` for empty map)
///   0x04: u32 entry[0]   ← VOB-relative VOBU sector
///   0x08: u32 entry[1]
///   ...
/// ```
///
/// An empty time map (number_of_entries = 0) is legal and is the
/// authoring convention for a PGC the disc decided not to time-index
/// (typically very short menus or warning still-frames).
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct VtsTmap {
    /// Seconds covered by one entry step.
    pub time_unit: u8,
    /// Decoded entry list, one per step.
    pub entries: Vec<TmapEntry>,
}

impl VtsTmap {
    /// Parse one VTS_TMAP. `buf` must start at the `time_unit` byte
    /// and span at least through the last entry.
    pub fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 4 {
            return Err(Error::InvalidUdf("VTS_TMAP: shorter than 4-byte header"));
        }
        let time_unit = read_u8(buf, 0)?;
        // byte 1 reserved
        let number_of_entries = read_u16(buf, 2)?;
        let n = usize::from(number_of_entries);
        let needed = 4usize.saturating_add(n * 4);
        if buf.len() < needed {
            return Err(Error::InvalidUdf(
                "VTS_TMAP: buffer shorter than entry table",
            ));
        }
        let mut entries = Vec::with_capacity(n);
        for i in 0..n {
            let raw = read_u32(buf, 4 + i * 4)?;
            entries.push(TmapEntry::from_raw(raw));
        }
        Ok(Self { time_unit, entries })
    }

    /// Translate a playback time `seconds` (PGC-relative) into the
    /// VOB-relative starting sector of the VOBU whose time bracket
    /// contains it. Returns `None` for an empty map or when the
    /// requested time falls before the first step.
    ///
    /// Bracket assignment per the spec: entry `i` (1-based) covers
    /// `[(i - 1) * time_unit, i * time_unit)` seconds.
    pub fn sector_at(&self, seconds: u32) -> Option<u32> {
        if self.entries.is_empty() || self.time_unit == 0 {
            return None;
        }
        let step = u32::from(self.time_unit);
        let idx_zero_based = (seconds / step) as usize;
        let idx = idx_zero_based.min(self.entries.len() - 1);
        Some(self.entries[idx].sector)
    }

    /// Total time covered by the map, in seconds. `time_unit *
    /// number_of_entries` — the upper edge of the last step's
    /// bracket.
    pub fn total_seconds(&self) -> u32 {
        u32::from(self.time_unit) * self.entries.len() as u32
    }
}

/// Parsed VTS_TMAPTI — one [`VtsTmap`] per program chain.
///
/// Layout (per `mpucoder-ifo_vts.html`):
///
/// ```text
///   0x00: u16 number_of_program_chains (Npgc)
///   0x02: u16 reserved
///   0x04: u32 end_address (last byte of last VTS_TMAP)
///   0x08: u32 offset_to_VTS_TMAP[1]
///   0x0C: u32 offset_to_VTS_TMAP[2]
///   ...
/// ```
///
/// "Each PGC MUST have a time map, even if it is empty" — the spec
/// guarantees `maps.len() == number_of_program_chains`.
#[derive(Debug, Clone)]
pub struct VtsTmapti {
    /// Number of program chains covered (= maps.len()).
    pub number_of_pgcs: u16,
    /// `end_address` field.
    pub end_address: u32,
    /// Decoded time maps, one per program chain. Index `i` (0-based)
    /// is the map for `PGCN = i + 1`.
    pub maps: Vec<VtsTmap>,
}

impl VtsTmapti {
    /// Parse a VTS_TMAPTI body. `buf` must start at byte 0 of the
    /// time-map table and span at least through the last `VTS_TMAP`.
    pub fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 8 {
            return Err(Error::InvalidUdf("VTS_TMAPTI: shorter than 8-byte header"));
        }
        let number_of_pgcs = read_u16(buf, 0)?;
        let end_address = read_u32(buf, 4)?;
        let n = usize::from(number_of_pgcs);
        let offsets_end = 8usize.saturating_add(n * 4);
        if buf.len() < offsets_end {
            return Err(Error::InvalidUdf(
                "VTS_TMAPTI: offset list past end of buffer",
            ));
        }
        let mut offsets = Vec::with_capacity(n);
        for i in 0..n {
            offsets.push(read_u32(buf, 8 + i * 4)? as usize);
        }
        let mut maps = Vec::with_capacity(n);
        for off in &offsets {
            let tmap_buf = buf.get(*off..).ok_or(Error::InvalidUdf(
                "VTS_TMAPTI: VTS_TMAP offset past end of buffer",
            ))?;
            maps.push(VtsTmap::parse(tmap_buf)?);
        }
        Ok(Self {
            number_of_pgcs,
            end_address,
            maps,
        })
    }

    /// Look up the time map for the 1-based program-chain number.
    pub fn get(&self, pgcn: u16) -> Option<&VtsTmap> {
        if pgcn == 0 {
            return None;
        }
        self.maps.get((pgcn - 1) as usize)
    }
}

// ------------------------------------------------------------------
// High-level chapter / title materialisation
// ------------------------------------------------------------------

/// A chapter (Part-of-Title) at the API surface — pulls fields from
/// the PTT entry, the referenced PGC's cell list, and the C_ADT.
#[derive(Debug, Clone)]
pub struct DvdChapter {
    /// 1-based chapter number within the title.
    pub number: u16,
    /// Program-chain number this chapter lives in.
    pub pgcn: u16,
    /// Program number within that PGC.
    pub pgn: u16,
    /// First cell of this chapter (inclusive, 1-based).
    pub start_cell: u8,
    /// Last cell of this chapter (inclusive, 1-based). For all
    /// chapters but the last in a PGC this is the cell immediately
    /// before the next chapter's `start_cell`; for the last chapter
    /// it is the PGC's final cell.
    pub end_cell: u8,
    /// PGC-relative playback time for this chapter — the BCD field
    /// from the PGC header itself (chapters within a PGC don't carry
    /// their own playback time field, so we surface the PGC total).
    pub playback_time: PgcTime,
}

/// A title at the API surface — pulls fields from TT_SRPT (for the
/// title-level header) and VTS_PTT_SRPT (for the chapter list).
#[derive(Debug, Clone)]
pub struct DvdTitle {
    /// 1-based VTS_TTN — title number within its VTS.
    pub number: u8,
    /// Number of camera angles (1..=9).
    pub angle_count: u8,
    /// Number of chapters (= `chapters.len()`).
    pub chapter_count: u16,
    /// Per-chapter detail.
    pub chapters: Vec<DvdChapter>,
}

/// Parsed VTS — pulls VTSI_MAT, VTS_PTT_SRPT, VTS_PGCI, VTS_C_ADT,
/// VTS_VOBU_ADMAP, and VTS_TMAPTI into a single materialised view
/// that's convenient for chapter enumeration and time-based seek
/// without re-walking the byte buffer.
#[derive(Debug, Clone)]
pub struct VtsIfo {
    /// VTS number (1..=99).
    pub vts_number: u8,
    /// Number of titles in this VTS.
    pub title_count: u8,
    /// Per-title chapter list.
    pub titles: Vec<DvdTitle>,
    /// All program chains in the VTS.
    pub pgcs: Vec<Pgc>,
    /// Cell address table.
    pub cell_adt: VtsCAdt,
    /// Per-VOBU sector list for the title-set VOBs
    /// (`VTS_xx_1.VOB` … `VTS_xx_9.VOB`). `None` when the IFO's
    /// `vts_vobu_admap_sector` field is zero (rare; the spec lists
    /// `VTS_VOBU_ADMAP` as mandatory but some authoring tools
    /// elide it on title sets that hold only menu VOBs).
    pub vobu_admap: Option<VobuAdmap>,
    /// Per-PGC time map. `None` when the IFO's `vts_tmapti_sector`
    /// field is zero (the spec lists `VTS_TMAPTI` as optional —
    /// without it the title set is not time-seekable).
    pub time_map: Option<VtsTmapti>,
    /// Raw VTSI_MAT (kept around so callers can reach sector
    /// pointers for the bits we don't materialise — the
    /// VMGM/VTSM menu tables, the VOBU address maps on the menu
    /// side, etc.).
    pub mat: VtsiMat,
}

impl VtsIfo {
    /// Build a `VtsIfo` from the full IFO byte buffer (the entire
    /// `VTS_xx_0.IFO`, which is `last_sector_ifo` + 1 sectors long).
    ///
    /// Sector pointers in `VTSI_MAT` are interpreted as offsets into
    /// `buf` after multiplication by [`DVD_SECTOR`].
    pub fn parse(buf: &[u8], vts_number: u8) -> Result<Self> {
        let mat = VtsiMat::parse(buf)?;

        // VTS_PTT_SRPT
        let ptt_off = (mat.vts_ptt_srpt_sector as usize)
            .checked_mul(DVD_SECTOR)
            .ok_or(Error::InvalidUdf("VTSI: PTT sector overflow"))?;
        let ptt_buf = buf
            .get(ptt_off..)
            .ok_or(Error::InvalidUdf("VTSI: PTT sector past end"))?;
        let ptt_srpt = VtsPttSrpt::parse(ptt_buf)?;

        // VTS_PGCI
        let pgci_off = (mat.vts_pgci_sector as usize)
            .checked_mul(DVD_SECTOR)
            .ok_or(Error::InvalidUdf("VTSI: PGCI sector overflow"))?;
        let pgci_buf = buf
            .get(pgci_off..)
            .ok_or(Error::InvalidUdf("VTSI: PGCI sector past end"))?;
        let pgci = Pgci::parse(pgci_buf)?;

        // VTS_C_ADT
        let cadt_off = (mat.vts_c_adt_sector as usize)
            .checked_mul(DVD_SECTOR)
            .ok_or(Error::InvalidUdf("VTSI: C_ADT sector overflow"))?;
        let cadt_buf = buf
            .get(cadt_off..)
            .ok_or(Error::InvalidUdf("VTSI: C_ADT sector past end"))?;
        let cell_adt = VtsCAdt::parse(cadt_buf)?;

        // VTS_VOBU_ADMAP (optional — sector 0 means absent).
        let vobu_admap = if mat.vts_vobu_admap_sector != 0 {
            let off = (mat.vts_vobu_admap_sector as usize)
                .checked_mul(DVD_SECTOR)
                .ok_or(Error::InvalidUdf("VTSI: VOBU_ADMAP sector overflow"))?;
            let body = buf
                .get(off..)
                .ok_or(Error::InvalidUdf("VTSI: VOBU_ADMAP sector past end"))?;
            Some(VobuAdmap::parse(body)?)
        } else {
            None
        };

        // VTS_TMAPTI (optional — sector 0 means absent).
        let time_map = if mat.vts_tmapti_sector != 0 {
            let off = (mat.vts_tmapti_sector as usize)
                .checked_mul(DVD_SECTOR)
                .ok_or(Error::InvalidUdf("VTSI: TMAPTI sector overflow"))?;
            let body = buf
                .get(off..)
                .ok_or(Error::InvalidUdf("VTSI: TMAPTI sector past end"))?;
            Some(VtsTmapti::parse(body)?)
        } else {
            None
        };

        // Materialise the chapter list. The PTT entry gives us
        // (PGCN, PGN). To recover (start_cell, end_cell) we look at
        // the referenced PGC's program_map — entry `pgn-1` is the
        // start cell, entry `pgn` (if it exists) is the next chapter's
        // start cell minus one. The last chapter runs through the
        // PGC's last cell.
        let title_count_u8 = u8::try_from(ptt_srpt.title_count.min(255))
            .map_err(|_| Error::InvalidUdf("VTSI: title count > 255"))?;
        let mut titles = Vec::with_capacity(usize::from(title_count_u8));
        for (i, ptt_title) in ptt_srpt.titles.iter().enumerate() {
            let title_number = (i as u8).saturating_add(1);
            let mut chapters = Vec::with_capacity(ptt_title.chapters.len());
            for (ch_i, ptt) in ptt_title.chapters.iter().enumerate() {
                let pgc = pgci
                    .pgcs
                    .get(usize::from(ptt.pgcn.saturating_sub(1)))
                    .ok_or(Error::InvalidUdf(
                        "VTSI: PTT references PGCN past end of PGCI",
                    ))?;
                let pgn_idx = usize::from(ptt.pgn.saturating_sub(1));
                let start_cell = *pgc
                    .program_map
                    .get(pgn_idx)
                    .ok_or(Error::InvalidUdf("VTSI: PTT PGN past program_map"))?;
                // Determine end_cell: next chapter in the same PGC
                // gives us its start_cell - 1; otherwise the PGC's
                // last cell.
                let next_in_same_pgc = ptt_title.chapters.get(ch_i + 1).and_then(|next_ptt| {
                    if next_ptt.pgcn == ptt.pgcn {
                        pgc.program_map
                            .get(usize::from(next_ptt.pgn.saturating_sub(1)))
                            .copied()
                            .map(|next_start| next_start.saturating_sub(1))
                    } else {
                        None
                    }
                });
                let end_cell = next_in_same_pgc.unwrap_or(pgc.number_of_cells);
                chapters.push(DvdChapter {
                    number: (ch_i as u16).saturating_add(1),
                    pgcn: ptt.pgcn,
                    pgn: ptt.pgn,
                    start_cell,
                    end_cell,
                    playback_time: pgc.playback_time,
                });
            }
            let chapter_count = chapters.len() as u16;
            titles.push(DvdTitle {
                number: title_number,
                angle_count: 1,
                chapter_count,
                chapters,
            });
        }

        Ok(Self {
            vts_number,
            title_count: title_count_u8,
            titles,
            pgcs: pgci.pgcs,
            cell_adt,
            vobu_admap,
            time_map,
            mat,
        })
    }

    /// VOB-relative starting sector of the VOBU that covers playback
    /// time `seconds` (PGC-relative) for the 1-based program-chain
    /// number `pgcn`.
    ///
    /// Convenience wrapper around [`VtsTmapti::get`] + [`VtsTmap::sector_at`].
    /// Returns `None` when this title set carries no time map, when
    /// the requested PGCN is past the table, when the map for that
    /// PGC is empty, or when its `time_unit` field is zero.
    ///
    /// To recover the disc-absolute LBA, add
    /// [`VtsiMat::title_vob_sector`] to the returned VOB-relative
    /// sector.
    pub fn vobu_sector_at_pgc_time(&self, pgcn: u16, seconds: u32) -> Option<u32> {
        self.time_map
            .as_ref()
            .and_then(|t| t.get(pgcn))
            .and_then(|m| m.sector_at(seconds))
    }
}

// ------------------------------------------------------------------
// VMG_VTS_ATRT — per-VTS attribute table on the VMG side
// ------------------------------------------------------------------

/// One entry of the `VMG_VTS_ATRT` table.
///
/// Per `mpucoder-ifo_vmg.html` each `VTS_ATRT` body is:
///   - offset `0..4`: end address (EA) of this entry, relative to the
///     entry's own start.
///   - offset `4..8`: `VTS_CAT` — a 32-bit category copy of `0x022..0x025`
///     of the corresponding VTS IFO (`0` = unspecified, `1` = Karaoke).
///   - offset `8..EA-7`: raw copy of the VTS attribute block starting
///     at offset `0x0100` of the VTS IFO (usually `0x300` bytes long;
///     equivalent to the buffer fed to [`parse_menu_attribute_block`] +
///     the title-side block that [`VtsiMat::parse`] already handles).
///
/// We keep the attribute blob as raw bytes so callers that want the
/// typed shape can feed it back through [`MenuAttributes`] /
/// [`TitleAttributes`] reuse without us re-decoding the same fields
/// twice (once here, once in the VTSI proper). The 1-based VTS index
/// is the entry's position in the table.
#[derive(Debug, Clone)]
pub struct VmgVtsAtrtEntry {
    /// 1-based VTS number this entry mirrors.
    pub vts_number: u8,
    /// `VTS_CAT` copy of the VTS IFO's `0x022..0x025` field.
    pub vts_category: u32,
    /// Raw VTS attribute block — a verbatim copy of bytes `0x0100..`
    /// of the corresponding `VTS_xx_0.IFO` file (length = entry-EA - 7).
    pub attributes_blob: Vec<u8>,
}

/// Parsed `VMG_VTS_ATRT` — the per-VTS attribute copies stored on the
/// VMG side.
///
/// `VIDEO_TS.IFO` carries `VMG_VTS_ATRT` so a player can answer
/// per-VTS attribute queries (audio/subpicture stream counts, codec
/// IDs, language codes, …) without having to open every `VTS_xx_0.IFO`
/// individually. Each entry mirrors the attribute block found at the
/// start of the corresponding VTSI body.
#[derive(Debug, Clone)]
pub struct VmgVtsAtrt {
    /// Number of title sets referenced by this table.
    pub number_of_title_sets: u16,
    /// Last byte address of the last `VTS_ATRT` entry — relative to
    /// the start of `VMG_VTS_ATRT` itself.
    pub end_address: u32,
    /// One entry per title set, in `vts_number` order (1-based).
    pub entries: Vec<VmgVtsAtrtEntry>,
}

impl VmgVtsAtrt {
    /// Parse the `VMG_VTS_ATRT` table from a buffer that starts at
    /// the table's first byte.
    pub fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 8 {
            return Err(Error::InvalidUdf("VMG_VTS_ATRT: header < 8 bytes"));
        }
        let number_of_title_sets = read_u16(buf, 0)?;
        // bytes 2..4 reserved
        let end_address = read_u32(buf, 4)?;

        let count = usize::from(number_of_title_sets);
        let offset_table_len = count.checked_mul(4).ok_or(Error::InvalidUdf(
            "VMG_VTS_ATRT: title-set count × 4 overflow",
        ))?;
        let header_len = 8usize
            .checked_add(offset_table_len)
            .ok_or(Error::InvalidUdf("VMG_VTS_ATRT: header length overflow"))?;
        if buf.len() < header_len {
            return Err(Error::InvalidUdf("VMG_VTS_ATRT: offset table past end"));
        }

        // Read the offset list first so we can derive the EA of each
        // entry (next-entry-offset minus one, or table EA for the last).
        let mut offsets = Vec::with_capacity(count);
        for i in 0..count {
            offsets.push(read_u32(buf, 8 + i * 4)?);
        }

        let mut entries = Vec::with_capacity(count);
        for (i, &off) in offsets.iter().enumerate() {
            // Per-entry "end address" lives in the entry header at
            // offset 0 (relative to the entry start). Trust the header
            // EA, but bound-check against the next entry's offset
            // (or the table EA) so a malformed entry can't read past
            // the buffer / past the next entry.
            let entry_start = off as usize;
            let entry_hdr = buf
                .get(entry_start..entry_start + 8)
                .ok_or(Error::InvalidUdf("VMG_VTS_ATRT: entry header past buffer"))?;
            let entry_ea_rel =
                u32::from_be_bytes([entry_hdr[0], entry_hdr[1], entry_hdr[2], entry_hdr[3]])
                    as usize;
            let vts_category =
                u32::from_be_bytes([entry_hdr[4], entry_hdr[5], entry_hdr[6], entry_hdr[7]]);
            // The entry's "end_address" is inclusive of the last byte
            // of the entry (zero-based, relative to the entry start);
            // total entry length is therefore `entry_ea_rel + 1`. The
            // attribute blob runs from offset 8 through end-of-entry.
            let entry_total = entry_ea_rel
                .checked_add(1)
                .ok_or(Error::InvalidUdf("VMG_VTS_ATRT: entry EA overflow"))?;
            if entry_total < 8 {
                return Err(Error::InvalidUdf(
                    "VMG_VTS_ATRT: entry length shorter than 8-byte header",
                ));
            }
            // Bound against the next entry's offset (if any) so an
            // overlong EA can't pull bytes out of the following entry.
            let next_start = offsets
                .get(i + 1)
                .map(|&n| n as usize)
                .unwrap_or((end_address as usize).saturating_add(1));
            if entry_start.saturating_add(entry_total) > next_start {
                return Err(Error::InvalidUdf(
                    "VMG_VTS_ATRT: entry EA overlaps next entry",
                ));
            }
            let blob_end = entry_start
                .checked_add(entry_total)
                .ok_or(Error::InvalidUdf("VMG_VTS_ATRT: entry end overflow"))?;
            let blob = buf
                .get(entry_start + 8..blob_end)
                .ok_or(Error::InvalidUdf("VMG_VTS_ATRT: blob past buffer"))?
                .to_vec();
            entries.push(VmgVtsAtrtEntry {
                vts_number: (i as u8).saturating_add(1),
                vts_category,
                attributes_blob: blob,
            });
        }

        Ok(Self {
            number_of_title_sets,
            end_address,
            entries,
        })
    }

    /// Return the entry for the 1-based `vts_number`, or `None` when
    /// the index is past the table.
    pub fn entry(&self, vts_number: u8) -> Option<&VmgVtsAtrtEntry> {
        if vts_number == 0 {
            return None;
        }
        self.entries.get(usize::from(vts_number - 1))
    }
}

// ------------------------------------------------------------------
// VMG_PTL_MAIT — parental management table
// ------------------------------------------------------------------

/// One country-keyed sub-table of `VMG_PTL_MAIT`.
///
/// Each country gets one `PTL_MAIT` body — a flat array of
/// `Nts + 1` 16-bit masks per parental level. The spec describes
/// the body as 8 stacked level-blocks (level 8 first at body offset
/// 0, then level 7, …, level 1 at body offset `14 × (Nts + 1)`).
///
/// `masks[level_minus_one][title_set_index]` is the 16-bit mask for
/// the title set (where `title_set_index = 0` is the VMG itself and
/// `1..=nts` are the title sets in `1..=nts` order).
#[derive(Debug, Clone)]
pub struct PtlMait {
    /// 16-bit country code (BCD-packed ISO 3166 per `mpucoder-sprm.html`).
    pub country_code: u16,
    /// Eight per-level mask arrays. `masks[0]` = level 1, …,
    /// `masks[7]` = level 8 (level order surfaced ascending — easier
    /// to index by `parental_level - 1` than to invert the spec's
    /// descending storage order at every call site).
    ///
    /// Each inner `Vec` has `nts + 1` entries: index `0` = VMG mask,
    /// `1..=nts` = title-set 1..=nts mask. A set bit at position `i`
    /// in `masks[L-1][T]` means title-set `T` is blocked from level `L`
    /// in this country.
    pub masks: [Vec<u16>; 8],
}

impl PtlMait {
    /// Look up the mask for `parental_level` (1..=8) and
    /// `title_set` (0 = VMG, 1..=nts = title set).
    pub fn mask(&self, parental_level: u8, title_set: u8) -> Option<u16> {
        if !(1..=8).contains(&parental_level) {
            return None;
        }
        let level_idx = usize::from(parental_level - 1);
        self.masks[level_idx].get(usize::from(title_set)).copied()
    }
}

/// Parsed `VMG_PTL_MAIT` (parental management country/level table).
///
/// `mpucoder-ifo_vmg.html` documents one country-keyed entry per
/// supported region — each entry pointing at a sub-table of 8
/// parental-level mask arrays of length `nts + 1`. Strict literal
/// reading of the entry layout (8 cells of 16 bits each):
/// `country_code (u16) | reserved (u16) | ptl_mait_offset (u16) |
/// reserved (u16)`. The 16-bit offset bounds the per-country
/// sub-table to within the first 64 KB of `VMG_PTL_MAIT`, which is
/// the natural ceiling on DVD-Video discs (99 title sets × 16 bytes
/// per level × 8 levels = 12.7 KB per country, with up to ~100
/// countries fitting under the bound).
#[derive(Debug, Clone)]
pub struct VmgPtlMait {
    /// Number of countries (each gets one sub-table).
    pub number_of_countries: u16,
    /// Number of title sets (the body sub-tables carry `Nts + 1`
    /// masks per level — index 0 is the VMG-side mask).
    pub number_of_title_sets: u16,
    /// Last byte address of the last `PTL_MAIT` body, relative to
    /// the start of `VMG_PTL_MAIT`.
    pub end_address: u32,
    /// One sub-table per country.
    pub entries: Vec<PtlMait>,
}

impl VmgPtlMait {
    /// Parse `VMG_PTL_MAIT` from a buffer that starts at the
    /// table's first byte.
    pub fn parse(buf: &[u8]) -> Result<Self> {
        if buf.len() < 8 {
            return Err(Error::InvalidUdf("VMG_PTL_MAIT: header < 8 bytes"));
        }
        let number_of_countries = read_u16(buf, 0)?;
        let number_of_title_sets = read_u16(buf, 2)?;
        let end_address = read_u32(buf, 4)?;

        let nts = usize::from(number_of_title_sets);
        let masks_per_level = nts
            .checked_add(1)
            .ok_or(Error::InvalidUdf("VMG_PTL_MAIT: nts + 1 overflow"))?;
        let level_block_bytes = masks_per_level
            .checked_mul(2)
            .ok_or(Error::InvalidUdf("VMG_PTL_MAIT: level block size overflow"))?;
        let body_bytes = level_block_bytes
            .checked_mul(8)
            .ok_or(Error::InvalidUdf("VMG_PTL_MAIT: body size overflow"))?;

        let count = usize::from(number_of_countries);
        // Country entries are 8 bytes each starting at offset 8.
        let header_len = 8usize
            .checked_add(
                count
                    .checked_mul(8)
                    .ok_or(Error::InvalidUdf("VMG_PTL_MAIT: country list × 8 overflow"))?,
            )
            .ok_or(Error::InvalidUdf("VMG_PTL_MAIT: header length overflow"))?;
        if buf.len() < header_len {
            return Err(Error::InvalidUdf("VMG_PTL_MAIT: country list past end"));
        }

        let mut entries = Vec::with_capacity(count);
        for i in 0..count {
            let entry_base = 8 + i * 8;
            let country_code = read_u16(buf, entry_base)?;
            // bytes 2..4 reserved
            let body_offset = usize::from(read_u16(buf, entry_base + 4)?);
            // bytes 6..8 reserved
            let body_end = body_offset
                .checked_add(body_bytes)
                .ok_or(Error::InvalidUdf("VMG_PTL_MAIT: country body end overflow"))?;
            if body_end > buf.len() {
                return Err(Error::InvalidUdf(
                    "VMG_PTL_MAIT: country body past buffer end",
                ));
            }

            // The body stores level 8 first at body_offset, then level 7
            // at body_offset + level_block_bytes, … level 1 at
            // body_offset + 7 × level_block_bytes. Surface them in
            // ascending order so `masks[0]` = level 1.
            let mut masks: [Vec<u16>; 8] = Default::default();
            for level_storage_idx in 0..8 {
                // Storage idx 0 = level 8; storage idx 7 = level 1.
                let level_value = 8 - level_storage_idx; // 8..=1
                let block_start = body_offset + level_storage_idx * level_block_bytes;
                let mut row = Vec::with_capacity(masks_per_level);
                for slot in 0..masks_per_level {
                    row.push(read_u16(buf, block_start + slot * 2)?);
                }
                masks[level_value - 1] = row;
            }

            entries.push(PtlMait {
                country_code,
                masks,
            });
        }

        Ok(Self {
            number_of_countries,
            number_of_title_sets,
            end_address,
            entries,
        })
    }

    /// Look up the country-keyed sub-table for the given 16-bit
    /// country code.
    pub fn country(&self, country_code: u16) -> Option<&PtlMait> {
        self.entries.iter().find(|e| e.country_code == country_code)
    }
}

// ------------------------------------------------------------------
// Tests
// ------------------------------------------------------------------

#[cfg(test)]
mod tests {
    use super::*;

    // -------------------------------------------------------------
    // PgcTime decode
    // -------------------------------------------------------------

    #[test]
    fn pgc_time_decode_ntsc_30() {
        // 01:23:45.20 @ 30 fps → bytes 0x01 0x23 0x45 (0b11_10_0000 = 0xE0).
        // Frame field: bits 7+6 = 11 (30 fps), bits 5+4 = 0b10 = 2 in BCD
        // hi-nibble (frame tens), bits 3+0 = 0b0000 = 0 in BCD lo-nibble.
        // So frames = 2 * 10 + 0 = 20.
        let t = PgcTime::from_bytes([0x01, 0x23, 0x45, 0xE0]);
        assert_eq!(t.hours, 1);
        assert_eq!(t.minutes, 23);
        assert_eq!(t.seconds, 45);
        assert_eq!(t.frames, 20);
        assert_eq!(t.frame_rate, FrameRate::Ntsc30);
        assert_eq!(t.total_seconds(), 3600 + 23 * 60 + 45);
    }

    #[test]
    fn pgc_time_decode_pal_25() {
        // 00:00:01.00 @ 25 fps → bytes 0x00 0x00 0x01 (0b01_00_0000 = 0x40).
        let t = PgcTime::from_bytes([0x00, 0x00, 0x01, 0x40]);
        assert_eq!(t.frame_rate, FrameRate::Pal25);
        assert_eq!(t.frames, 0);
        assert_eq!(t.total_seconds(), 1);
    }

    // -------------------------------------------------------------
    // PgcTime::to_nanoseconds — exposes the per-rate fractional-frame
    // conversion that mkv_writer previously held privately.
    // -------------------------------------------------------------

    #[test]
    fn pgc_time_to_ns_ntsc_30_integer_seconds() {
        // 00:00:01.00 @ 30 fps → exactly 1 second, no frame fraction.
        let t = PgcTime::from_bytes([0x00, 0x00, 0x01, 0xC0]);
        assert_eq!(t.frame_rate, FrameRate::Ntsc30);
        assert_eq!(t.to_nanoseconds(), 1_000_000_000);
    }

    #[test]
    fn pgc_time_to_ns_ntsc_30_half_second() {
        // 00:00:01.15 @ 30 fps → 1 s + 15/30 s = 1.5 s exact.
        // Frame byte: rate=11, frames-tens=01 (bits 5+4), frames-units=0101
        //   = 0b11_01_0101 = 0xD5. BCD frames hi-nibble = 1, lo-nibble = 5
        //   → 15 frames.
        let t = PgcTime::from_bytes([0x00, 0x00, 0x01, 0xD5]);
        assert_eq!(t.frame_rate, FrameRate::Ntsc30);
        assert_eq!(t.frames, 15);
        assert_eq!(t.to_nanoseconds(), 1_500_000_000);
    }

    #[test]
    fn pgc_time_to_ns_pal_25_frame_period() {
        // 00:00:00.01 @ 25 fps → 1 frame × 40_000_000 ns/frame = 40 ms.
        // Frame byte: rate=01, frames=01 → 0b01_00_0001 = 0x41.
        let t = PgcTime::from_bytes([0x00, 0x00, 0x00, 0x41]);
        assert_eq!(t.frame_rate, FrameRate::Pal25);
        assert_eq!(t.frames, 1);
        assert_eq!(t.to_nanoseconds(), 40_000_000);
    }

    #[test]
    fn pgc_time_to_ns_illegal_rate_drops_frames() {
        // 00:00:02.07 with rate bits = 00 (illegal). Whole-seconds
        // portion survives; the 7-frame fraction is dropped because the
        // spec defines no rate to scale it by.
        let t = PgcTime::from_bytes([0x00, 0x00, 0x02, 0x07]);
        assert_eq!(t.frame_rate, FrameRate::Illegal);
        assert_eq!(t.frames, 7);
        assert_eq!(t.to_nanoseconds(), 2_000_000_000);
    }

    // -------------------------------------------------------------
    // VMGI MAT parse
    // -------------------------------------------------------------

    fn build_vmg_mat() -> Vec<u8> {
        let mut b = vec![0u8; 0x200];
        b[0..12].copy_from_slice(VMG_MAGIC);
        // 0x000C: last sector of VMG set = 1000
        b[0x000C..0x0010].copy_from_slice(&1000u32.to_be_bytes());
        // 0x001C: last sector of IFO = 4
        b[0x001C..0x0020].copy_from_slice(&4u32.to_be_bytes());
        // 0x0020: version 0x0011 (major 1, minor 1)
        b[0x0020..0x0022].copy_from_slice(&0x0011u16.to_be_bytes());
        // 0x0022: VMG category (region mask byte 1 = 0xFF "no region")
        b[0x0022..0x0026].copy_from_slice(&0x00FF_0000u32.to_be_bytes());
        // 0x0026: number of volumes = 1
        b[0x0026..0x0028].copy_from_slice(&1u16.to_be_bytes());
        // 0x0028: volume number = 1
        b[0x0028..0x002A].copy_from_slice(&1u16.to_be_bytes());
        // 0x002A: side ID = 0
        b[0x002A] = 0;
        // 0x003E: number of title sets = 2
        b[0x003E..0x0040].copy_from_slice(&2u16.to_be_bytes());
        // 0x0040: provider ID "OXIDEAV-TEST"
        let pid = b"OXIDEAV-TEST";
        b[0x0040..0x0040 + pid.len()].copy_from_slice(pid);
        // 0x0080: VMGI_MAT end
        b[0x0080..0x0084].copy_from_slice(&0x01FFu32.to_be_bytes());
        // 0x0084: FP_PGC start address = 0
        b[0x0084..0x0088].copy_from_slice(&0u32.to_be_bytes());
        // 0x00C0: menu VOB sector = 0 (no menu)
        // 0x00C4: TT_SRPT sector = 1
        b[0x00C4..0x00C8].copy_from_slice(&1u32.to_be_bytes());
        // 0x00C8: VMGM_PGCI_UT sector = 0
        // 0x00CC: VMG_PTL_MAIT sector = 0
        // 0x00D0: VMG_VTS_ATRT sector = 2
        b[0x00D0..0x00D4].copy_from_slice(&2u32.to_be_bytes());
        // 0x00D4: TXTDT_MG sector = 0
        // 0x00D8: VMGM_C_ADT sector = 0
        // 0x00DC: VMGM_VOBU_ADMAP sector = 0
        b
    }

    #[test]
    fn vmgi_mat_parse_roundtrip() {
        let buf = build_vmg_mat();
        let vmg = VmgIfo::parse(&buf).unwrap();
        assert_eq!(vmg.last_sector_vmg_set, 1000);
        assert_eq!(vmg.last_sector_ifo, 4);
        assert_eq!(vmg.version, 0x0011);
        assert_eq!(vmg.number_of_volumes, 1);
        assert_eq!(vmg.volume_number, 1);
        assert_eq!(vmg.side_id, 0);
        assert_eq!(vmg.number_of_title_sets, 2);
        assert_eq!(vmg.provider_id, "OXIDEAV-TEST");
        assert_eq!(vmg.tt_srpt_sector, 1);
        assert_eq!(vmg.vts_atrt_sector, 2);
        assert_eq!(vmg.menu_vob_sector, 0);
    }

    #[test]
    fn vmgi_mat_rejects_bad_magic() {
        let mut buf = build_vmg_mat();
        buf[0..12].copy_from_slice(b"DVDVIDEO-BAD");
        let err = VmgIfo::parse(&buf).unwrap_err();
        match err {
            Error::InvalidUdf(_) => {}
            other => panic!("expected InvalidUdf, got {other:?}"),
        }
    }

    // -------------------------------------------------------------
    // VTSI MAT parse
    // -------------------------------------------------------------

    fn build_vtsi_mat(
        ptt_srpt_sector: u32,
        pgci_sector: u32,
        c_adt_sector: u32,
        title_vob_sector: u32,
    ) -> Vec<u8> {
        let mut b = vec![0u8; 0x200];
        b[0..12].copy_from_slice(VTS_MAGIC);
        // last_sector_title_set
        b[0x000C..0x0010].copy_from_slice(&100_000u32.to_be_bytes());
        // last_sector_ifo
        b[0x001C..0x0020].copy_from_slice(&15u32.to_be_bytes());
        // version 0x0011
        b[0x0020..0x0022].copy_from_slice(&0x0011u16.to_be_bytes());
        // VTS category = 0
        // VTSI_MAT end
        b[0x0080..0x0084].copy_from_slice(&0x01FFu32.to_be_bytes());
        // menu VOB sector = 0
        // title VOB sector
        b[0x00C4..0x00C8].copy_from_slice(&title_vob_sector.to_be_bytes());
        // PTT_SRPT
        b[0x00C8..0x00CC].copy_from_slice(&ptt_srpt_sector.to_be_bytes());
        // PGCI
        b[0x00CC..0x00D0].copy_from_slice(&pgci_sector.to_be_bytes());
        // VTSM_PGCI_UT = 0
        // VTS_TMAPTI = 0
        // VTSM_C_ADT = 0
        // VTSM_VOBU_ADMAP = 0
        // VTS_C_ADT
        b[0x00E0..0x00E4].copy_from_slice(&c_adt_sector.to_be_bytes());
        // VTS_VOBU_ADMAP = 0
        b
    }

    #[test]
    fn vtsi_mat_parse_roundtrip() {
        let buf = build_vtsi_mat(1, 2, 3, 42);
        let mat = VtsiMat::parse(&buf).unwrap();
        assert_eq!(mat.last_sector_title_set, 100_000);
        assert_eq!(mat.last_sector_ifo, 15);
        assert_eq!(mat.version, 0x0011);
        assert_eq!(mat.title_vob_sector, 42);
        assert_eq!(mat.vts_ptt_srpt_sector, 1);
        assert_eq!(mat.vts_pgci_sector, 2);
        assert_eq!(mat.vts_c_adt_sector, 3);
    }

    // -------------------------------------------------------------
    // TT_SRPT
    // -------------------------------------------------------------

    fn build_tt_srpt(entries: &[(u8, u8, u16, u8, u8, u32)]) -> Vec<u8> {
        // 8-byte header + N * 12 entries.
        let n = entries.len();
        let len = 8 + n * 12;
        let mut b = vec![0u8; len];
        b[0..2].copy_from_slice(&(n as u16).to_be_bytes());
        // reserved at 2..4 = 0
        // end_address = last byte of last entry, relative to start
        let end_addr = (len - 1) as u32;
        b[4..8].copy_from_slice(&end_addr.to_be_bytes());
        for (i, e) in entries.iter().enumerate() {
            let base = 8 + i * 12;
            b[base] = e.0; // title_type
            b[base + 1] = e.1; // angle_count
            b[base + 2..base + 4].copy_from_slice(&e.2.to_be_bytes()); // chapter_count
            b[base + 4..base + 6].copy_from_slice(&0u16.to_be_bytes()); // parental_mask
            b[base + 6] = e.3; // vts_number
            b[base + 7] = e.4; // vts_title_number
            b[base + 8..base + 12].copy_from_slice(&e.5.to_be_bytes()); // vts_start_sector
            let _ = e; // suppress unused
        }
        b
    }

    #[test]
    fn tt_srpt_parses_titles() {
        // 3 titles: VTS1-title1 (15 chapters), VTS1-title2 (4 chapters),
        // VTS2-title1 (1 chapter).
        let entries = [
            (0x3F, 1u8, 15u16, 1u8, 1u8, 0x0000_0500u32),
            (0x3F, 1u8, 4u16, 1u8, 2u8, 0x0000_0500u32),
            (0x3F, 2u8, 1u16, 2u8, 1u8, 0x0000_8000u32),
        ];
        let buf = build_tt_srpt(&entries);
        let srpt = TtSrpt::parse(&buf).unwrap();
        assert_eq!(srpt.title_count, 3);
        assert_eq!(srpt.end_address, (8 + 3 * 12 - 1) as u32);
        assert_eq!(srpt.entries[0].chapter_count, 15);
        assert_eq!(srpt.entries[1].vts_title_number, 2);
        assert_eq!(srpt.entries[2].vts_number, 2);
        assert_eq!(srpt.entries[2].angle_count, 2);
        assert_eq!(srpt.entries[2].vts_start_sector, 0x0000_8000);
    }

    // -------------------------------------------------------------
    // VTS_C_ADT
    // -------------------------------------------------------------

    fn build_c_adt(rows: &[(u16, u8, u32, u32)]) -> Vec<u8> {
        let n = rows.len();
        let len = 8 + n * 12;
        let mut b = vec![0u8; len];
        // number_of_vob_ids — let's pick the distinct vob count
        let distinct = {
            let mut v: Vec<u16> = rows.iter().map(|r| r.0).collect();
            v.sort();
            v.dedup();
            v.len() as u16
        };
        b[0..2].copy_from_slice(&distinct.to_be_bytes());
        // end_address = last byte of last entry, relative to start
        let end_addr = (len - 1) as u32;
        b[4..8].copy_from_slice(&end_addr.to_be_bytes());
        for (i, r) in rows.iter().enumerate() {
            let base = 8 + i * 12;
            b[base..base + 2].copy_from_slice(&r.0.to_be_bytes());
            b[base + 2] = r.1;
            // reserved at +3 = 0
            b[base + 4..base + 8].copy_from_slice(&r.2.to_be_bytes());
            b[base + 8..base + 12].copy_from_slice(&r.3.to_be_bytes());
        }
        b
    }

    #[test]
    fn c_adt_parses_four_rows() {
        // 4 cells: VOB 1 → cells 1 + 2 + 3; VOB 2 → cell 1.
        let rows = [
            (1u16, 1u8, 100u32, 199u32),
            (1u16, 2u8, 200u32, 299u32),
            (1u16, 3u8, 300u32, 399u32),
            (2u16, 1u8, 1000u32, 1999u32),
        ];
        let buf = build_c_adt(&rows);
        let adt = VtsCAdt::parse(&buf).unwrap();
        assert_eq!(adt.number_of_vob_ids, 2);
        assert_eq!(adt.entries.len(), 4);
        assert_eq!(adt.lookup(1, 2), Some((200, 299)));
        assert_eq!(adt.lookup(2, 1), Some((1000, 1999)));
        assert_eq!(adt.lookup(3, 1), None);
    }

    // -------------------------------------------------------------
    // PGCI with 1 PGC + 3 cells
    // -------------------------------------------------------------

    fn build_pgc_with_cells(cells: &[CellPlaybackInfo], positions: &[CellPositionInfo]) -> Vec<u8> {
        assert_eq!(cells.len(), positions.len());
        let n = cells.len();
        // PGC header is 0xEC bytes. Then program map (1 program, 1
        // byte each, padded to word boundary). Then C_PBI (24*n). Then
        // C_POS (4*n).
        let header_size = 0xEC;
        let prog_count = 1u8;
        let prog_map_size = (usize::from(prog_count) + 1) & !1; // pad to word
        let pre_n = 1usize; // command table: 1 pre + 1 post + 2 cell = 4 words
        let post_n = 1usize;
        let cmd_cell_n = 2usize;
        let cmd_table_size = 8 + (pre_n + post_n + cmd_cell_n) * 8;
        let cpbi_size = n * 24;
        let cpos_size = n * 4;
        let mut b = vec![0u8; header_size + cmd_table_size + prog_map_size + cpbi_size + cpos_size];

        // number_of_programs at 0x0002
        b[0x0002] = prog_count;
        // number_of_cells at 0x0003
        b[0x0003] = n as u8;
        // playback time
        b[0x0004..0x0008].copy_from_slice(&[0x00, 0x05, 0x00, 0xE0]); // 00:05:00.00 @ 30fps
                                                                      // 0x0008..: prohibited UOPs = 0
                                                                      // next/prev/goup at 0x009C / 0x009E / 0x00A0 = 0
                                                                      // still time, playback mode = 0

        // Palette at 0x00A4: 16 × (0, Y, Cr, Cb). Fill entry i with a
        // deterministic (Y=0x10+i, Cr=0x80, Cb=0x80) so the round-trip
        // can assert the layout decode.
        for i in 0..16usize {
            let base = 0x00A4 + i * 4;
            b[base] = 0x00; // reserved
            b[base + 1] = 0x10 + i as u8; // Y
            b[base + 2] = 0x80; // Cr
            b[base + 3] = 0x80; // Cb
        }

        let off_cmd = header_size as u16; // command table right after header
        let off_pmap = (header_size + cmd_table_size) as u16;
        let off_cpbi = (header_size + cmd_table_size + prog_map_size) as u16;
        let off_cpos = (header_size + cmd_table_size + prog_map_size + cpbi_size) as u16;
        b[0x00E4..0x00E6].copy_from_slice(&off_cmd.to_be_bytes());
        b[0x00E6..0x00E8].copy_from_slice(&off_pmap.to_be_bytes());
        b[0x00E8..0x00EA].copy_from_slice(&off_cpbi.to_be_bytes());
        b[0x00EA..0x00EC].copy_from_slice(&off_cpos.to_be_bytes());

        // Command table header + words. Each word is tagged in byte 0
        // so the round-trip can tell pre/post/cell apart.
        let ct = header_size;
        b[ct..ct + 2].copy_from_slice(&(pre_n as u16).to_be_bytes());
        b[ct + 2..ct + 4].copy_from_slice(&(post_n as u16).to_be_bytes());
        b[ct + 4..ct + 6].copy_from_slice(&(cmd_cell_n as u16).to_be_bytes());
        b[ct + 6..ct + 8].copy_from_slice(&((cmd_table_size - 1) as u16).to_be_bytes());
        let mut w = ct + 8;
        b[w] = 0xA0; // pre[0]: command_type = 0b101
        b[w + 7] = 0x01;
        w += 8;
        b[w] = 0xB0; // post[0]
        b[w + 7] = 0x02;
        w += 8;
        b[w] = 0xC0; // cell[0]
        b[w + 7] = 0x03;
        w += 8;
        b[w] = 0xC1; // cell[1]
        b[w + 7] = 0x04;

        // program map: 1 program starting at cell 1
        b[off_pmap as usize] = 1;
        // (no padding needed since prog_map_size already includes pad)

        // C_PBI
        for (i, c) in cells.iter().enumerate() {
            let base = off_cpbi as usize + i * 24;
            b[base] = c.category_byte0;
            b[base + 1] = if c.restricted { 0x80 } else { 0 };
            b[base + 2] = c.still_time;
            b[base + 3] = c.cell_command;
            // playback time — synthesise a deterministic field
            b[base + 4] = 0x00;
            b[base + 5] = 0x01;
            b[base + 6] = 0x00;
            b[base + 7] = 0xE0;
            b[base + 8..base + 12].copy_from_slice(&c.first_vobu_start_sector.to_be_bytes());
            b[base + 12..base + 16].copy_from_slice(&c.first_ilvu_end_sector.to_be_bytes());
            b[base + 16..base + 20].copy_from_slice(&c.last_vobu_start_sector.to_be_bytes());
            b[base + 20..base + 24].copy_from_slice(&c.last_vobu_end_sector.to_be_bytes());
        }

        // C_POS
        for (i, p) in positions.iter().enumerate() {
            let base = off_cpos as usize + i * 4;
            b[base..base + 2].copy_from_slice(&p.vob_id.to_be_bytes());
            b[base + 3] = p.cell_id;
        }
        b
    }

    fn make_cell(start: u32, end: u32) -> CellPlaybackInfo {
        CellPlaybackInfo {
            category_byte0: 0,
            restricted: false,
            still_time: 0,
            cell_command: 0,
            playback_time: PgcTime::from_bytes([0, 1, 0, 0xE0]),
            first_vobu_start_sector: start,
            first_ilvu_end_sector: start + 5,
            last_vobu_start_sector: end - 5,
            last_vobu_end_sector: end,
        }
    }

    #[test]
    fn pgci_parses_one_pgc_with_three_cells() {
        let cells = [
            make_cell(1000, 1999),
            make_cell(2000, 2999),
            make_cell(3000, 3999),
        ];
        let positions = [
            CellPositionInfo {
                vob_id: 1,
                cell_id: 1,
            },
            CellPositionInfo {
                vob_id: 1,
                cell_id: 2,
            },
            CellPositionInfo {
                vob_id: 1,
                cell_id: 3,
            },
        ];
        let pgc_blob = build_pgc_with_cells(&cells, &positions);

        // Wrap that single PGC into a PGCI: 8-byte header + 1 SRP
        // entry (8 bytes) + the PGC body.
        let srp_size = 8usize;
        let body_off = 8 + srp_size; // PGC starts here
        let total = body_off + pgc_blob.len();
        let mut b = vec![0u8; total];
        // number_of_pgcs = 1
        b[0..2].copy_from_slice(&1u16.to_be_bytes());
        // reserved at 2..4 = 0
        // end_address = total - 1
        b[4..8].copy_from_slice(&((total - 1) as u32).to_be_bytes());
        // SRP[0]: category 0, offset = body_off
        b[8..12].copy_from_slice(&0u32.to_be_bytes());
        b[12..16].copy_from_slice(&(body_off as u32).to_be_bytes());
        // Copy PGC body
        b[body_off..body_off + pgc_blob.len()].copy_from_slice(&pgc_blob);

        let pgci = Pgci::parse(&b).unwrap();
        assert_eq!(pgci.number_of_pgcs, 1);
        assert_eq!(pgci.pgcs.len(), 1);
        let pgc = &pgci.pgcs[0];
        assert_eq!(pgc.number_of_programs, 1);
        assert_eq!(pgc.number_of_cells, 3);
        assert_eq!(pgc.cells.len(), 3);
        assert_eq!(pgc.cell_positions.len(), 3);
        assert_eq!(pgc.cells[0].first_vobu_start_sector, 1000);
        assert_eq!(pgc.cells[2].last_vobu_end_sector, 3999);
        assert_eq!(pgc.cell_positions[1].cell_id, 2);
        assert_eq!(pgc.playback_time.frame_rate, FrameRate::Ntsc30);

        // Palette decode: entry i carries (Y=0x10+i, Cr=0x80, Cb=0x80).
        assert_eq!(
            pgc.palette[0],
            PaletteEntry {
                y: 0x10,
                cr: 0x80,
                cb: 0x80
            }
        );
        assert_eq!(
            pgc.palette[15],
            PaletteEntry {
                y: 0x1F,
                cr: 0x80,
                cb: 0x80
            }
        );

        // Command table: 1 pre + 1 post + 2 cell, tagged in byte 0.
        let cmds = pgc.commands.as_ref().expect("command table present");
        assert_eq!(cmds.pre.len(), 1);
        assert_eq!(cmds.post.len(), 1);
        assert_eq!(cmds.cell.len(), 2);
        assert_eq!(cmds.pre[0].bytes[0], 0xA0);
        assert_eq!(cmds.pre[0].bytes[7], 0x01);
        assert_eq!(cmds.pre[0].command_type(), 0b101);
        assert_eq!(cmds.post[0].bytes[0], 0xB0);
        assert_eq!(cmds.post[0].bytes[7], 0x02);
        assert_eq!(cmds.cell[0].bytes[7], 0x03);
        assert_eq!(cmds.cell[1].bytes[7], 0x04);
    }

    // -------------------------------------------------------------
    // PGC palette + command table — focused unit tests
    // -------------------------------------------------------------

    #[test]
    fn palette_entry_skips_reserved_byte() {
        // (reserved, Y, Cr, Cb)
        let e = PaletteEntry::parse(&[0xFF, 0x42, 0x10, 0xC0]).unwrap();
        assert_eq!(
            e,
            PaletteEntry {
                y: 0x42,
                cr: 0x10,
                cb: 0xC0
            }
        );
        // Too short → error.
        assert!(PaletteEntry::parse(&[0x00, 0x01, 0x02]).is_err());
    }

    #[test]
    fn command_table_carves_three_lists() {
        // 2 pre + 1 post + 1 cell = 4 words.
        let pre = 2u16;
        let post = 1u16;
        let cell = 1u16;
        let total = (pre + post + cell) as usize;
        let size = 8 + total * 8;
        let mut b = vec![0u8; size];
        b[0..2].copy_from_slice(&pre.to_be_bytes());
        b[2..4].copy_from_slice(&post.to_be_bytes());
        b[4..6].copy_from_slice(&cell.to_be_bytes());
        b[6..8].copy_from_slice(&((size - 1) as u16).to_be_bytes());
        // Tag each word's last byte with its 1-based index.
        for i in 0..total {
            b[8 + i * 8 + 7] = (i + 1) as u8;
        }
        let t = PgcCommandTable::parse(&b).unwrap();
        assert_eq!(t.pre.len(), 2);
        assert_eq!(t.post.len(), 1);
        assert_eq!(t.cell.len(), 1);
        assert_eq!(t.end_address, (size - 1) as u16);
        // pre = words 1,2; post = word 3; cell = word 4.
        assert_eq!(t.pre[0].bytes[7], 1);
        assert_eq!(t.pre[1].bytes[7], 2);
        assert_eq!(t.post[0].bytes[7], 3);
        assert_eq!(t.cell[0].bytes[7], 4);
    }

    #[test]
    fn command_table_rejects_overlong_count() {
        // pre alone claims 129 words → > 128 invariant violated.
        let mut b = vec![0u8; 8];
        b[0..2].copy_from_slice(&129u16.to_be_bytes());
        assert!(PgcCommandTable::parse(&b).is_err());
    }

    #[test]
    fn command_table_rejects_truncated_list() {
        // Header claims 2 words but the buffer only holds one.
        let mut b = vec![0u8; 8 + 8];
        b[0..2].copy_from_slice(&2u16.to_be_bytes());
        assert!(PgcCommandTable::parse(&b).is_err());
    }

    // -------------------------------------------------------------
    // PgcCommandTable — typed-instruction iterator surface
    // -------------------------------------------------------------

    /// Build a synthetic `PgcCommandTable` with 1 pre + 1 post +
    /// 3 cell words covering distinct instruction types so the
    /// iterators below have something to discriminate on.
    fn synth_command_table() -> PgcCommandTable {
        let pre = 1u16;
        let post = 1u16;
        let cell = 3u16;
        let total = (pre + post + cell) as usize;
        let size = 8 + total * 8;
        let mut b = vec![0u8; size];
        b[0..2].copy_from_slice(&pre.to_be_bytes());
        b[2..4].copy_from_slice(&post.to_be_bytes());
        b[4..6].copy_from_slice(&cell.to_be_bytes());
        b[6..8].copy_from_slice(&((size - 1) as u16).to_be_bytes());
        // Word layout (per mpucoder-vmi.html "command word layout"):
        //   byte 0 = TTT D SSSS where TTT = type (bits 7..5),
        //     D = SET-direct flag (bit 4), SSSS = SET-op nibble.
        //   byte 1 = C HHH CCCC where C = CMP-direct (bit 7),
        //     HHH = CMP-op (bits 6..4), CCCC = cmd_nibble (bits 3..0).
        // pre[0] stays all-zero at offset 8 → Type 0 + cmd_nibble 0
        //   = NOP per `decode_type0`.
        // post[0]: Type 1 jumpcall + cmd_nibble 1 = Exit. Byte 0
        //   needs the SET-direct bit (D=1) so the dispatcher routes
        //   to `decode_type1_jumpcall`.
        let post_off = 8 + 8;
        b[post_off] = 0b0011_0000;
        b[post_off + 1] = 0x01;
        // cell[0]: same Type 1 Exit encoding as post[0].
        let cell0 = post_off + 8;
        b[cell0] = 0b0011_0000;
        b[cell0 + 1] = 0x01;
        // cell[1]: Type 0 Break — byte 0 = 0, cmd_nibble = 2.
        let cell1 = cell0 + 8;
        b[cell1] = 0x00;
        b[cell1 + 1] = 0x02;
        // cell[2]: Type 0 NOP — all zeros (already).
        PgcCommandTable::parse(&b).unwrap()
    }

    #[test]
    fn pgc_cmd_table_typed_iterators_walk_all_three_lists() {
        let t = synth_command_table();
        let pre: Vec<_> = t.pre_instructions().collect();
        let post: Vec<_> = t.post_instructions().collect();
        let cell: Vec<_> = t.cell_instructions().collect();
        assert_eq!(pre.len(), 1);
        assert_eq!(post.len(), 1);
        assert_eq!(cell.len(), 3);
        // pre[0] = NOP per the synth payload.
        assert!(matches!(pre[0], crate::nav::NavInstruction::Nop));
        // post[0] = Exit per the Type 1 / link-family `0x01` encoding.
        assert!(matches!(post[0], crate::nav::NavInstruction::Exit));
        // cell[0] = Exit; cell[1] = Break; cell[2] = NOP.
        assert!(matches!(cell[0], crate::nav::NavInstruction::Exit));
        assert!(matches!(cell[1], crate::nav::NavInstruction::Break));
        assert!(matches!(cell[2], crate::nav::NavInstruction::Nop));
    }

    #[test]
    fn pgc_cmd_table_cell_instruction_uses_one_based_index() {
        let t = synth_command_table();
        // Spec: cell_command = 0 means "no command associated"; the
        // accessor returns None.
        assert!(t.cell_instruction(0).is_none());
        // 1-based indexing — index 1 picks cell[0] = Exit.
        assert!(matches!(
            t.cell_instruction(1),
            Some(crate::nav::NavInstruction::Exit)
        ));
        // index 2 picks cell[1] = Break.
        assert!(matches!(
            t.cell_instruction(2),
            Some(crate::nav::NavInstruction::Break)
        ));
        // index 3 picks cell[2] = NOP.
        assert!(matches!(
            t.cell_instruction(3),
            Some(crate::nav::NavInstruction::Nop)
        ));
        // Out-of-range index returns None rather than panicking.
        assert!(t.cell_instruction(4).is_none());
        assert!(t.cell_instruction(u16::MAX).is_none());
    }

    #[test]
    fn nav_command_decode_instruction_matches_nav_decode() {
        // Same NavCommand word reached through the IFO-side
        // convenience and the explicit `nav` disassembler should
        // yield the same typed instruction.
        let mut bytes = [0u8; 8];
        bytes[0] = 0b0011_0000; // Type 1 + SET-direct → jumpcall family.
        bytes[1] = 0x01; // cmd_nibble = 1 → Exit.
        let raw = NavCommand { bytes };
        assert_eq!(raw.decode_instruction(), raw.decode());
        assert!(matches!(
            raw.decode_instruction(),
            crate::nav::NavInstruction::Exit
        ));
    }

    #[test]
    fn pgc_without_command_table_yields_none() {
        // build_pgc_with_cells always emits a command table; build a
        // minimal header-only PGC with offset_commands == 0.
        let mut b = vec![0u8; 0xEC];
        b[0x0002] = 0; // 0 programs
        b[0x0003] = 0; // 0 cells
        b[0x0004..0x0008].copy_from_slice(&[0x00, 0x00, 0x00, 0xC0]); // PAL 25 fps
                                                                      // all four table offsets stay 0
        let pgc = Pgc::parse(&b).unwrap();
        assert!(pgc.commands.is_none());
        // Palette defaults to all-zero when bytes are zero.
        assert_eq!(pgc.palette[7], PaletteEntry::default());
    }

    // -------------------------------------------------------------
    // VTS_PTT_SRPT walking 2 titles × 5 chapters
    // -------------------------------------------------------------

    #[test]
    fn ptt_srpt_walks_two_titles_five_chapters() {
        // 2 titles × 5 chapters each = 10 PTT entries × 4 bytes = 40 bytes
        // of chapter data. Plus 8-byte header + 2 × 4-byte offsets = 16
        // bytes of header. Total = 56 bytes.
        let n_titles = 2usize;
        let n_chaps = 5usize;
        let offsets_size = n_titles * 4;
        let header_size = 8 + offsets_size;
        let title_body_size = n_chaps * 4;
        let total = header_size + n_titles * title_body_size;
        let mut b = vec![0u8; total];
        // number_of_titles
        b[0..2].copy_from_slice(&(n_titles as u16).to_be_bytes());
        // end_address = total - 1
        b[4..8].copy_from_slice(&((total - 1) as u32).to_be_bytes());
        // offset_to_PTT[1] = header_size
        // offset_to_PTT[2] = header_size + title_body_size
        for ti in 0..n_titles {
            let off = (header_size + ti * title_body_size) as u32;
            b[8 + ti * 4..8 + ti * 4 + 4].copy_from_slice(&off.to_be_bytes());
        }
        // Fill chapter entries: PGCN = title_number, PGN = chapter_number
        for ti in 0..n_titles {
            for ci in 0..n_chaps {
                let base = header_size + ti * title_body_size + ci * 4;
                let pgcn = (ti + 1) as u16;
                let pgn = (ci + 1) as u16;
                b[base..base + 2].copy_from_slice(&pgcn.to_be_bytes());
                b[base + 2..base + 4].copy_from_slice(&pgn.to_be_bytes());
            }
        }

        let srpt = VtsPttSrpt::parse(&b).unwrap();
        assert_eq!(srpt.title_count, 2);
        assert_eq!(srpt.titles.len(), 2);
        for ti in 0..n_titles {
            assert_eq!(srpt.titles[ti].chapters.len(), 5);
            assert_eq!(srpt.titles[ti].chapters[0].pgcn, (ti + 1) as u16);
            assert_eq!(srpt.titles[ti].chapters[0].pgn, 1);
            assert_eq!(srpt.titles[ti].chapters[4].pgn, 5);
        }
    }

    // -------------------------------------------------------------
    // Round-trip composite: VTSI_MAT + PTT_SRPT + PGCI + C_ADT
    // -------------------------------------------------------------

    fn make_composite_vts() -> Vec<u8> {
        // We lay out a minimal IFO image:
        //   sector 0: VTSI_MAT
        //   sector 1: VTS_PTT_SRPT (1 title × 3 chapters)
        //   sector 2: VTS_PGCI (1 PGC with 5 cells; 3 programs)
        //   sector 3: VTS_C_ADT (5 cell entries)
        let mut img = vec![0u8; DVD_SECTOR * 4];

        // ---------- Sector 0: VTSI_MAT ----------
        let mat = build_vtsi_mat(1, 2, 3, 100);
        img[0..mat.len()].copy_from_slice(&mat);

        // ---------- Sector 2: VTS_PGCI ----------
        // 1 PGC with 5 cells (and 3 programs: cells 1, 3, 5 are
        // program entry points). Cells: 1, 2, 3, 4, 5 with disjoint
        // sector ranges.
        let cells: Vec<CellPlaybackInfo> = (0..5)
            .map(|i| make_cell(1000 + i * 1000, 1999 + i * 1000))
            .collect();
        let positions: Vec<CellPositionInfo> = (0..5)
            .map(|i| CellPositionInfo {
                vob_id: 1,
                cell_id: (i + 1) as u8,
            })
            .collect();
        // build_pgc_with_cells assumes 1 program; we extend manually
        // to 3 programs whose program_map = [1, 3, 5].
        let header_size = 0xEC;
        let prog_count = 3u8;
        let prog_map_size = (usize::from(prog_count) + 1) & !1; // 4
        let cpbi_size = 5 * 24;
        let cpos_size = 5 * 4;
        let pgc_blob_len = header_size + prog_map_size + cpbi_size + cpos_size;
        let mut pgc_blob = vec![0u8; pgc_blob_len];
        pgc_blob[0x0002] = prog_count;
        pgc_blob[0x0003] = 5; // number_of_cells
        pgc_blob[0x0004..0x0008].copy_from_slice(&[0x00, 0x15, 0x00, 0xE0]);
        let off_pmap = header_size as u16;
        let off_cpbi = (header_size + prog_map_size) as u16;
        let off_cpos = (header_size + prog_map_size + cpbi_size) as u16;
        pgc_blob[0x00E6..0x00E8].copy_from_slice(&off_pmap.to_be_bytes());
        pgc_blob[0x00E8..0x00EA].copy_from_slice(&off_cpbi.to_be_bytes());
        pgc_blob[0x00EA..0x00EC].copy_from_slice(&off_cpos.to_be_bytes());
        pgc_blob[header_size] = 1; // program 1 starts at cell 1
        pgc_blob[header_size + 1] = 3; // program 2 starts at cell 3
        pgc_blob[header_size + 2] = 5; // program 3 starts at cell 5
        for (i, c) in cells.iter().enumerate() {
            let base = header_size + prog_map_size + i * 24;
            pgc_blob[base + 4..base + 8].copy_from_slice(&[0, 1, 0, 0xE0]);
            pgc_blob[base + 8..base + 12].copy_from_slice(&c.first_vobu_start_sector.to_be_bytes());
            pgc_blob[base + 12..base + 16].copy_from_slice(&c.first_ilvu_end_sector.to_be_bytes());
            pgc_blob[base + 16..base + 20].copy_from_slice(&c.last_vobu_start_sector.to_be_bytes());
            pgc_blob[base + 20..base + 24].copy_from_slice(&c.last_vobu_end_sector.to_be_bytes());
        }
        for (i, p) in positions.iter().enumerate() {
            let base = header_size + prog_map_size + cpbi_size + i * 4;
            pgc_blob[base..base + 2].copy_from_slice(&p.vob_id.to_be_bytes());
            pgc_blob[base + 3] = p.cell_id;
        }
        // Wrap into PGCI
        let srp_size = 8usize;
        let body_off = 8 + srp_size;
        let pgci_total = body_off + pgc_blob.len();
        let mut pgci = vec![0u8; pgci_total];
        pgci[0..2].copy_from_slice(&1u16.to_be_bytes());
        pgci[4..8].copy_from_slice(&((pgci_total - 1) as u32).to_be_bytes());
        pgci[12..16].copy_from_slice(&(body_off as u32).to_be_bytes());
        pgci[body_off..body_off + pgc_blob.len()].copy_from_slice(&pgc_blob);
        img[2 * DVD_SECTOR..2 * DVD_SECTOR + pgci.len()].copy_from_slice(&pgci);

        // ---------- Sector 1: VTS_PTT_SRPT ----------
        // 1 title with 3 chapters at programs 1, 2, 3.
        let n_titles = 1usize;
        let n_chaps = 3usize;
        let header_sz = 8 + n_titles * 4;
        let title_body = n_chaps * 4;
        let total = header_sz + title_body;
        let mut ptt = vec![0u8; total];
        ptt[0..2].copy_from_slice(&(n_titles as u16).to_be_bytes());
        ptt[4..8].copy_from_slice(&((total - 1) as u32).to_be_bytes());
        ptt[8..12].copy_from_slice(&(header_sz as u32).to_be_bytes());
        for ci in 0..n_chaps {
            let base = header_sz + ci * 4;
            ptt[base..base + 2].copy_from_slice(&1u16.to_be_bytes()); // PGCN
            ptt[base + 2..base + 4].copy_from_slice(&((ci + 1) as u16).to_be_bytes());
            // PGN
        }
        img[DVD_SECTOR..DVD_SECTOR + ptt.len()].copy_from_slice(&ptt);

        // ---------- Sector 3: VTS_C_ADT ----------
        let cadt_rows: Vec<(u16, u8, u32, u32)> = (0..5)
            .map(|i| {
                (
                    1u16,
                    (i + 1) as u8,
                    1000 + i as u32 * 1000,
                    1999 + i as u32 * 1000,
                )
            })
            .collect();
        let cadt = build_c_adt(&cadt_rows);
        img[3 * DVD_SECTOR..3 * DVD_SECTOR + cadt.len()].copy_from_slice(&cadt);

        img
    }

    #[test]
    fn composite_vts_roundtrip() {
        let img = make_composite_vts();
        let vts = VtsIfo::parse(&img, 1).unwrap();
        assert_eq!(vts.vts_number, 1);
        assert_eq!(vts.title_count, 1);
        assert_eq!(vts.pgcs.len(), 1);
        // The PGC has 5 cells and 3 programs.
        assert_eq!(vts.pgcs[0].number_of_cells, 5);
        assert_eq!(vts.pgcs[0].number_of_programs, 3);
        // Chapter materialisation:
        let t = &vts.titles[0];
        assert_eq!(t.chapter_count, 3);
        // program_map = [1, 3, 5]; PTT[1] = (PGCN=1, PGN=1) →
        // start_cell=1, end_cell=2 (next program's start_cell - 1 = 3-1).
        assert_eq!(t.chapters[0].start_cell, 1);
        assert_eq!(t.chapters[0].end_cell, 2);
        // PTT[2] = (PGCN=1, PGN=2) → start_cell=3, end_cell=4.
        assert_eq!(t.chapters[1].start_cell, 3);
        assert_eq!(t.chapters[1].end_cell, 4);
        // PTT[3] = (PGCN=1, PGN=3) → start_cell=5, end_cell=5 (last PGC cell).
        assert_eq!(t.chapters[2].start_cell, 5);
        assert_eq!(t.chapters[2].end_cell, 5);
        // C_ADT must give us first cell's sector range.
        assert_eq!(vts.cell_adt.lookup(1, 1), Some((1000, 1999)));
        assert_eq!(vts.cell_adt.lookup(1, 5), Some((5000, 5999)));
        // The composite IFO was built without VOBU_ADMAP / TMAPTI
        // sector pointers — both materialised tables must be `None`.
        assert!(vts.vobu_admap.is_none());
        assert!(vts.time_map.is_none());
    }

    // -------------------------------------------------------------
    // VOBU_ADMAP
    // -------------------------------------------------------------

    fn build_vobu_admap(entries: &[u32]) -> Vec<u8> {
        // 4-byte end_address + N × 4-byte sector words.
        let n = entries.len();
        let len = 4 + n * 4;
        let mut b = vec![0u8; len];
        let end_addr = (len - 1) as u32;
        b[0..4].copy_from_slice(&end_addr.to_be_bytes());
        for (i, s) in entries.iter().enumerate() {
            b[4 + i * 4..4 + (i + 1) * 4].copy_from_slice(&s.to_be_bytes());
        }
        b
    }

    #[test]
    fn vobu_admap_parses_three_vobus() {
        let entries = [0u32, 200u32, 450u32];
        let buf = build_vobu_admap(&entries);
        let map = VobuAdmap::parse(&buf).unwrap();
        assert_eq!(map.vobu_count(), 3);
        assert_eq!(map.entries, entries);
        assert_eq!(map.end_address, (buf.len() - 1) as u32);
        // 1-based VOBU lookup.
        assert_eq!(map.vobu_start_sector(1), Some(0));
        assert_eq!(map.vobu_start_sector(2), Some(200));
        assert_eq!(map.vobu_start_sector(3), Some(450));
        assert_eq!(map.vobu_start_sector(4), None);
        assert_eq!(map.vobu_start_sector(0), None);
    }

    #[test]
    fn vobu_admap_partition_locates_containing_vobu() {
        // VOBUs start at sectors 0, 100, 300, 600.
        let buf = build_vobu_admap(&[0, 100, 300, 600]);
        let map = VobuAdmap::parse(&buf).unwrap();
        // Boundary-inclusive: a sector that matches an entry exactly
        // belongs to that VOBU.
        assert_eq!(map.vobu_containing(0), Some(1));
        assert_eq!(map.vobu_containing(99), Some(1));
        assert_eq!(map.vobu_containing(100), Some(2));
        assert_eq!(map.vobu_containing(299), Some(2));
        assert_eq!(map.vobu_containing(300), Some(3));
        assert_eq!(map.vobu_containing(599), Some(3));
        assert_eq!(map.vobu_containing(600), Some(4));
        // Far past — still maps to the last VOBU (its end is unknown
        // until the next entry, so the partition returns the last one).
        assert_eq!(map.vobu_containing(1_000_000), Some(4));
    }

    #[test]
    fn vobu_admap_first_entry_above_zero_returns_none_for_pre_sector() {
        // Map's first VOBU starts at sector 100; sector 50 falls
        // before it, so the lookup must return `None`.
        let buf = build_vobu_admap(&[100, 200, 300]);
        let map = VobuAdmap::parse(&buf).unwrap();
        assert_eq!(map.vobu_containing(0), None);
        assert_eq!(map.vobu_containing(99), None);
        assert_eq!(map.vobu_containing(100), Some(1));
    }

    #[test]
    fn vobu_admap_empty_map_lookups_return_none() {
        // end_address = 3 → body span = 0 bytes → zero entries.
        let mut b = vec![0u8; 4];
        b[0..4].copy_from_slice(&3u32.to_be_bytes());
        let map = VobuAdmap::parse(&b).unwrap();
        assert_eq!(map.vobu_count(), 0);
        assert_eq!(map.vobu_start_sector(1), None);
        assert_eq!(map.vobu_containing(0), None);
    }

    #[test]
    fn vobu_admap_rejects_non_multiple_end_address() {
        // end_address = 5 implies a 2-byte body span — not a
        // multiple of the 4-byte entry size.
        let mut b = vec![0u8; 8];
        b[0..4].copy_from_slice(&5u32.to_be_bytes());
        assert!(VobuAdmap::parse(&b).is_err());
    }

    #[test]
    fn vobu_admap_rejects_truncated_buffer() {
        // end_address = 11 implies 2 entries (8 body bytes), but
        // the buffer is only 4 + 4 = 8 bytes long, missing the
        // second entry.
        let mut b = vec![0u8; 4 + 4];
        b[0..4].copy_from_slice(&11u32.to_be_bytes());
        assert!(VobuAdmap::parse(&b).is_err());
    }

    // -------------------------------------------------------------
    // VTS_TMAP / VTS_TMAPTI
    // -------------------------------------------------------------

    fn build_tmap(time_unit: u8, entries: &[(u32, bool)]) -> Vec<u8> {
        let n = entries.len();
        let len = 4 + n * 4;
        let mut b = vec![0u8; len];
        b[0] = time_unit;
        // byte 1 reserved
        b[2..4].copy_from_slice(&(n as u16).to_be_bytes());
        for (i, (sector, disc)) in entries.iter().enumerate() {
            let mut raw = *sector & TmapEntry::SECTOR_MASK;
            if *disc {
                raw |= TmapEntry::DISCONTINUITY_BIT;
            }
            b[4 + i * 4..4 + (i + 1) * 4].copy_from_slice(&raw.to_be_bytes());
        }
        b
    }

    #[test]
    fn tmap_decodes_entries_and_discontinuity() {
        // Three 4-second steps, second entry flagged discontinuous.
        let buf = build_tmap(4, &[(100, false), (250, true), (400, false)]);
        let map = VtsTmap::parse(&buf).unwrap();
        assert_eq!(map.time_unit, 4);
        assert_eq!(map.entries.len(), 3);
        assert_eq!(
            map.entries[0],
            TmapEntry {
                sector: 100,
                discontinuous: false
            }
        );
        assert_eq!(
            map.entries[1],
            TmapEntry {
                sector: 250,
                discontinuous: true
            }
        );
        assert_eq!(map.total_seconds(), 12);
    }

    #[test]
    fn tmap_sector_at_brackets_seconds_per_time_unit() {
        // 5-second steps; first entry covers [0,5), second [5,10),
        // third [10,15).
        let buf = build_tmap(5, &[(10, false), (20, false), (30, false)]);
        let map = VtsTmap::parse(&buf).unwrap();
        assert_eq!(map.sector_at(0), Some(10));
        assert_eq!(map.sector_at(4), Some(10));
        assert_eq!(map.sector_at(5), Some(20));
        assert_eq!(map.sector_at(9), Some(20));
        assert_eq!(map.sector_at(10), Some(30));
        assert_eq!(map.sector_at(14), Some(30));
        // Past the last bracket: clamp to the last entry rather than
        // return `None` so playback engines that pass an inaccurate
        // wall-clock get a reasonable "seek to end" answer.
        assert_eq!(map.sector_at(15), Some(30));
        assert_eq!(map.sector_at(1_000_000), Some(30));
    }

    #[test]
    fn tmap_empty_map_yields_no_sector() {
        // number_of_entries = 0 → empty entry table → all lookups
        // return `None`.
        let buf = build_tmap(2, &[]);
        let map = VtsTmap::parse(&buf).unwrap();
        assert_eq!(map.time_unit, 2);
        assert!(map.entries.is_empty());
        assert_eq!(map.sector_at(0), None);
        assert_eq!(map.sector_at(60), None);
        assert_eq!(map.total_seconds(), 0);
    }

    #[test]
    fn tmap_zero_time_unit_yields_no_sector() {
        // time_unit = 0 with a populated entry table is a malformed
        // map — sector_at would divide by zero, so we explicitly
        // surface `None` instead.
        let buf = build_tmap(0, &[(1, false), (2, false)]);
        let map = VtsTmap::parse(&buf).unwrap();
        assert_eq!(map.sector_at(0), None);
    }

    #[test]
    fn tmap_rejects_truncated_buffer() {
        // number_of_entries = 2 (8 body bytes needed) but buffer
        // only carries 4 + 4 = 8 bytes — one entry missing.
        let mut b = vec![0u8; 4 + 4];
        b[0] = 1;
        b[2..4].copy_from_slice(&2u16.to_be_bytes());
        assert!(VtsTmap::parse(&b).is_err());
    }

    fn build_tmapti(maps: &[Vec<u8>]) -> Vec<u8> {
        // 8-byte header + N × 4-byte offsets + concatenated map bodies.
        let n = maps.len();
        let offsets_size = n * 4;
        let header_size = 8 + offsets_size;
        let body_size: usize = maps.iter().map(|m| m.len()).sum();
        let total = header_size + body_size;
        let mut b = vec![0u8; total];
        b[0..2].copy_from_slice(&(n as u16).to_be_bytes());
        // reserved at 2..4 = 0
        b[4..8].copy_from_slice(&((total - 1) as u32).to_be_bytes());
        let mut cursor = header_size;
        for (i, m) in maps.iter().enumerate() {
            let off = cursor as u32;
            b[8 + i * 4..8 + (i + 1) * 4].copy_from_slice(&off.to_be_bytes());
            b[cursor..cursor + m.len()].copy_from_slice(m);
            cursor += m.len();
        }
        b
    }

    #[test]
    fn tmapti_walks_two_pgc_maps() {
        let map_a = build_tmap(2, &[(0, false), (50, false), (100, false)]);
        let map_b = build_tmap(3, &[(200, false), (400, true)]);
        let buf = build_tmapti(&[map_a, map_b]);
        let table = VtsTmapti::parse(&buf).unwrap();
        assert_eq!(table.number_of_pgcs, 2);
        assert_eq!(table.maps.len(), 2);
        // PGCN lookups are 1-based.
        let m1 = table.get(1).unwrap();
        assert_eq!(m1.time_unit, 2);
        assert_eq!(m1.entries.len(), 3);
        let m2 = table.get(2).unwrap();
        assert_eq!(m2.time_unit, 3);
        assert!(m2.entries[1].discontinuous);
        assert_eq!(table.get(0), None);
        assert_eq!(table.get(3), None);
    }

    #[test]
    fn tmapti_carries_empty_map_per_spec_invariant() {
        // The spec mandates "each PGC MUST have a time map, even if
        // it is empty" — make sure an empty map decodes cleanly when
        // the offset list points at it.
        let empty = build_tmap(0, &[]);
        let buf = build_tmapti(&[empty]);
        let table = VtsTmapti::parse(&buf).unwrap();
        assert_eq!(table.number_of_pgcs, 1);
        let m = table.get(1).unwrap();
        assert!(m.entries.is_empty());
        assert_eq!(m.sector_at(0), None);
    }

    #[test]
    fn tmapti_rejects_short_offset_list() {
        // number_of_pgcs = 3 but only 8 bytes available — the offset
        // list runs past the buffer end.
        let mut b = vec![0u8; 8];
        b[0..2].copy_from_slice(&3u16.to_be_bytes());
        assert!(VtsTmapti::parse(&b).is_err());
    }

    // -------------------------------------------------------------
    // Composite VTS round-trip with VOBU_ADMAP + TMAPTI populated
    // -------------------------------------------------------------

    fn make_composite_vts_with_admap_and_tmap() -> Vec<u8> {
        // Sector layout:
        //   sector 0: VTSI_MAT
        //   sector 1: VTS_PTT_SRPT (1 title × 3 chapters)
        //   sector 2: VTS_PGCI (1 PGC, 5 cells, 3 programs)
        //   sector 3: VTS_C_ADT (5 cell entries)
        //   sector 4: VTS_VOBU_ADMAP (4 VOBUs)
        //   sector 5: VTS_TMAPTI (1 PGC × 3 steps)
        let mut img = vec![0u8; DVD_SECTOR * 6];

        // VTSI_MAT — populate the four sector pointers we exercise.
        // build_vtsi_mat zeroes the TMAPTI + VOBU_ADMAP pointers,
        // so patch them in manually after the base copy.
        let mat = build_vtsi_mat(1, 2, 3, 100);
        img[0..mat.len()].copy_from_slice(&mat);
        img[0x00D4..0x00D8].copy_from_slice(&5u32.to_be_bytes()); // TMAPTI sector
        img[0x00E4..0x00E8].copy_from_slice(&4u32.to_be_bytes()); // VOBU_ADMAP sector

        // PGCI — re-use the helper that already builds 1 PGC with 5
        // cells + 3 programs.
        let cells: Vec<CellPlaybackInfo> = (0..5)
            .map(|i| make_cell(1000 + i * 1000, 1999 + i * 1000))
            .collect();
        let positions: Vec<CellPositionInfo> = (0..5)
            .map(|i| CellPositionInfo {
                vob_id: 1,
                cell_id: (i + 1) as u8,
            })
            .collect();
        let header_size = 0xEC;
        let prog_count = 3u8;
        let prog_map_size = (usize::from(prog_count) + 1) & !1;
        let cpbi_size = 5 * 24;
        let cpos_size = 5 * 4;
        let pgc_blob_len = header_size + prog_map_size + cpbi_size + cpos_size;
        let mut pgc_blob = vec![0u8; pgc_blob_len];
        pgc_blob[0x0002] = prog_count;
        pgc_blob[0x0003] = 5;
        pgc_blob[0x0004..0x0008].copy_from_slice(&[0x00, 0x15, 0x00, 0xE0]);
        let off_pmap = header_size as u16;
        let off_cpbi = (header_size + prog_map_size) as u16;
        let off_cpos = (header_size + prog_map_size + cpbi_size) as u16;
        pgc_blob[0x00E6..0x00E8].copy_from_slice(&off_pmap.to_be_bytes());
        pgc_blob[0x00E8..0x00EA].copy_from_slice(&off_cpbi.to_be_bytes());
        pgc_blob[0x00EA..0x00EC].copy_from_slice(&off_cpos.to_be_bytes());
        pgc_blob[header_size] = 1;
        pgc_blob[header_size + 1] = 3;
        pgc_blob[header_size + 2] = 5;
        for (i, c) in cells.iter().enumerate() {
            let base = header_size + prog_map_size + i * 24;
            pgc_blob[base + 4..base + 8].copy_from_slice(&[0, 1, 0, 0xE0]);
            pgc_blob[base + 8..base + 12].copy_from_slice(&c.first_vobu_start_sector.to_be_bytes());
            pgc_blob[base + 12..base + 16].copy_from_slice(&c.first_ilvu_end_sector.to_be_bytes());
            pgc_blob[base + 16..base + 20].copy_from_slice(&c.last_vobu_start_sector.to_be_bytes());
            pgc_blob[base + 20..base + 24].copy_from_slice(&c.last_vobu_end_sector.to_be_bytes());
        }
        for (i, p) in positions.iter().enumerate() {
            let base = header_size + prog_map_size + cpbi_size + i * 4;
            pgc_blob[base..base + 2].copy_from_slice(&p.vob_id.to_be_bytes());
            pgc_blob[base + 3] = p.cell_id;
        }
        let srp_size = 8usize;
        let body_off = 8 + srp_size;
        let pgci_total = body_off + pgc_blob.len();
        let mut pgci = vec![0u8; pgci_total];
        pgci[0..2].copy_from_slice(&1u16.to_be_bytes());
        pgci[4..8].copy_from_slice(&((pgci_total - 1) as u32).to_be_bytes());
        pgci[12..16].copy_from_slice(&(body_off as u32).to_be_bytes());
        pgci[body_off..body_off + pgc_blob.len()].copy_from_slice(&pgc_blob);
        img[2 * DVD_SECTOR..2 * DVD_SECTOR + pgci.len()].copy_from_slice(&pgci);

        // PTT_SRPT
        let n_titles = 1usize;
        let n_chaps = 3usize;
        let header_sz = 8 + n_titles * 4;
        let title_body = n_chaps * 4;
        let total = header_sz + title_body;
        let mut ptt = vec![0u8; total];
        ptt[0..2].copy_from_slice(&(n_titles as u16).to_be_bytes());
        ptt[4..8].copy_from_slice(&((total - 1) as u32).to_be_bytes());
        ptt[8..12].copy_from_slice(&(header_sz as u32).to_be_bytes());
        for ci in 0..n_chaps {
            let base = header_sz + ci * 4;
            ptt[base..base + 2].copy_from_slice(&1u16.to_be_bytes());
            ptt[base + 2..base + 4].copy_from_slice(&((ci + 1) as u16).to_be_bytes());
        }
        img[DVD_SECTOR..DVD_SECTOR + ptt.len()].copy_from_slice(&ptt);

        // C_ADT
        let cadt_rows: Vec<(u16, u8, u32, u32)> = (0..5)
            .map(|i| {
                (
                    1u16,
                    (i + 1) as u8,
                    1000 + i as u32 * 1000,
                    1999 + i as u32 * 1000,
                )
            })
            .collect();
        let cadt = build_c_adt(&cadt_rows);
        img[3 * DVD_SECTOR..3 * DVD_SECTOR + cadt.len()].copy_from_slice(&cadt);

        // VTS_VOBU_ADMAP at sector 4 — 4 VOBUs at VOB-relative
        // sectors 0, 250, 600, 1100.
        let admap = build_vobu_admap(&[0, 250, 600, 1100]);
        img[4 * DVD_SECTOR..4 * DVD_SECTOR + admap.len()].copy_from_slice(&admap);

        // VTS_TMAPTI at sector 5 — one PGC, 4-second steps, three
        // entries pointing into the VOBU sector list.
        let tmap = build_tmap(4, &[(0, false), (250, false), (600, false)]);
        let tmapti = build_tmapti(&[tmap]);
        img[5 * DVD_SECTOR..5 * DVD_SECTOR + tmapti.len()].copy_from_slice(&tmapti);

        img
    }

    #[test]
    fn composite_vts_materialises_admap_and_tmap() {
        let img = make_composite_vts_with_admap_and_tmap();
        let vts = VtsIfo::parse(&img, 1).unwrap();
        let admap = vts.vobu_admap.as_ref().expect("VOBU_ADMAP materialised");
        assert_eq!(admap.vobu_count(), 4);
        assert_eq!(admap.vobu_start_sector(1), Some(0));
        assert_eq!(admap.vobu_start_sector(4), Some(1100));
        // Sector 700 falls inside VOBU 3's range [600, 1100).
        assert_eq!(admap.vobu_containing(700), Some(3));

        let tmapti = vts.time_map.as_ref().expect("VTS_TMAPTI materialised");
        assert_eq!(tmapti.number_of_pgcs, 1);
        let pgc_map = tmapti.get(1).unwrap();
        assert_eq!(pgc_map.time_unit, 4);
        assert_eq!(pgc_map.entries.len(), 3);

        // Time-based seek: 5 seconds in → step 2 (covers [4, 8)) →
        // VOBU at VOB-relative sector 250.
        assert_eq!(vts.vobu_sector_at_pgc_time(1, 5), Some(250));
        // 0 seconds → step 1 → sector 0.
        assert_eq!(vts.vobu_sector_at_pgc_time(1, 0), Some(0));
        // 9 seconds → step 3 → sector 600.
        assert_eq!(vts.vobu_sector_at_pgc_time(1, 9), Some(600));
        // Out-of-range PGCN → `None`.
        assert_eq!(vts.vobu_sector_at_pgc_time(2, 0), None);
    }

    // -------------------------------------------------------------
    // VTSI_MAT stream-attribute extension
    // -------------------------------------------------------------

    /// Build a single 8-byte audio-attribute slot covering the
    /// fields we exercise in the typed parse.
    #[allow(clippy::too_many_arguments)]
    fn pack_audio_attr(
        coding: u8,
        mc_ext: bool,
        lang_type: u8,
        app_mode: u8,
        quant: u8,
        sample_rate: u8,
        chans_minus_one: u8,
        lang: [u8; 2],
        code_ext: u8,
        app_info: u8,
    ) -> [u8; 8] {
        let mut b = [0u8; 8];
        b[0] = ((coding & 0b111) << 5)
            | (if mc_ext { 0b1_0000 } else { 0 })
            | ((lang_type & 0b11) << 2)
            | (app_mode & 0b11);
        b[1] = ((quant & 0b11) << 6) | ((sample_rate & 0b11) << 4) | (chans_minus_one & 0b111);
        b[2] = lang[0];
        b[3] = lang[1];
        b[5] = code_ext;
        b[7] = app_info;
        b
    }

    #[allow(clippy::too_many_arguments)]
    fn pack_video_attr(
        coding: u8,
        standard: u8,
        aspect: u8,
        pan_scan_disallowed: bool,
        letterbox_disallowed: bool,
        cc1: bool,
        cc2: bool,
        resolution: u8,
        letterbox_src: bool,
        film_pal: bool,
    ) -> [u8; 2] {
        let mut b = [0u8; 2];
        b[0] = ((coding & 0b11) << 6)
            | ((standard & 0b11) << 4)
            | ((aspect & 0b11) << 2)
            | (if pan_scan_disallowed { 0b10 } else { 0 })
            | (if letterbox_disallowed { 0b01 } else { 0 });
        b[1] = (if cc1 { 0b1000_0000 } else { 0 })
            | (if cc2 { 0b0100_0000 } else { 0 })
            | ((resolution & 0b111) << 3)
            | (if letterbox_src { 0b0000_0100 } else { 0 })
            | (if film_pal { 0b0000_0001 } else { 0 });
        b
    }

    fn pack_subp_attr(coding: u8, lang_type: u8, lang: [u8; 2], code_ext: u8) -> [u8; 6] {
        let mut b = [0u8; 6];
        b[0] = ((coding & 0b111) << 5) | (lang_type & 0b11);
        b[2] = lang[0];
        b[3] = lang[1];
        b[5] = code_ext;
        b
    }

    #[test]
    fn video_attributes_mpeg2_pal_16x9_full_d1() {
        let raw = pack_video_attr(1, 1, 3, false, false, false, false, 0, false, true);
        let v = VideoAttributes::parse(&raw);
        assert_eq!(v.coding_mode, VideoCodingMode::Mpeg2);
        assert_eq!(v.standard, VideoStandard::Pal);
        assert_eq!(v.aspect_ratio, VideoAspectRatio::Ratio16x9);
        assert_eq!(v.resolution, VideoResolution::FullD1);
        assert_eq!(
            v.resolution.dimensions(VideoStandard::Pal),
            Some((720, 576))
        );
        assert!(v.film_source_pal);
        assert!(!v.line21_field1_cc);
    }

    #[test]
    fn video_attributes_mpeg2_ntsc_4x3_sif_with_cc() {
        let raw = pack_video_attr(1, 0, 0, true, false, true, true, 3, true, false);
        let v = VideoAttributes::parse(&raw);
        assert_eq!(v.coding_mode, VideoCodingMode::Mpeg2);
        assert_eq!(v.standard, VideoStandard::Ntsc);
        assert_eq!(v.aspect_ratio, VideoAspectRatio::Ratio4x3);
        assert_eq!(v.resolution, VideoResolution::Sif);
        assert_eq!(
            v.resolution.dimensions(VideoStandard::Ntsc),
            Some((352, 240))
        );
        assert!(v.pan_scan_disallowed);
        assert!(v.line21_field1_cc);
        assert!(v.line21_field2_cc);
        assert!(v.letterboxed_source);
    }

    #[test]
    fn video_attributes_reserved_aspect_and_resolution() {
        let raw = pack_video_attr(1, 0, 1, false, false, false, false, 5, false, false);
        let v = VideoAttributes::parse(&raw);
        assert_eq!(v.aspect_ratio, VideoAspectRatio::Reserved(1));
        assert_eq!(v.resolution, VideoResolution::Reserved(5));
        assert_eq!(v.resolution.dimensions(VideoStandard::Ntsc), None);
    }

    #[test]
    fn audio_attributes_ac3_stereo_english() {
        // coding=0 (AC3), mc_ext=false, lang_type=1 (ISO), app=0 (unspec),
        // quant=0, sample=0 (48 kHz), chans-1=1 (stereo).
        let raw = pack_audio_attr(0, false, 1, 0, 0, 0, 1, *b"en", 0, 0);
        let a = AudioAttributes::parse(&raw);
        assert_eq!(a.coding_mode, AudioCodingMode::Ac3);
        assert!(!a.multichannel_extension_present);
        assert_eq!(a.language_type, AudioLanguageType::Iso639);
        assert_eq!(a.application_mode, AudioApplicationMode::Unspecified);
        assert_eq!(a.channel_count, 2);
        assert_eq!(a.sample_rate_hz(), Some(48_000));
        assert_eq!(&a.language_code, b"en");
        assert!(!a.dolby_surround_suitable());
    }

    #[test]
    fn audio_attributes_lpcm_24bit_six_channel() {
        // coding=4 (LPCM), quant=2 (24bps), chans-1=5 (6 channels).
        let raw = pack_audio_attr(4, false, 0, 0, 2, 0, 5, [0, 0], 0, 0);
        let a = AudioAttributes::parse(&raw);
        assert_eq!(a.coding_mode, AudioCodingMode::Lpcm);
        assert_eq!(a.quantization, AudioQuantizationDrc::Lpcm24);
        assert_eq!(a.channel_count, 6);
    }

    #[test]
    fn audio_attributes_mpeg2_drc_flag() {
        let raw = pack_audio_attr(3, false, 0, 0, 1, 0, 1, [0, 0], 0, 0);
        let a = AudioAttributes::parse(&raw);
        assert_eq!(a.coding_mode, AudioCodingMode::Mpeg2Ext);
        assert_eq!(a.quantization, AudioQuantizationDrc::Drc);
    }

    #[test]
    fn audio_attributes_surround_dolby_suitable_bit() {
        // surround app_mode + byte 7 bit 3 = Dolby-Surround-suitable.
        let raw = pack_audio_attr(0, false, 0, 2, 0, 0, 1, [0, 0], 0, 0b0000_1000);
        let a = AudioAttributes::parse(&raw);
        assert_eq!(a.application_mode, AudioApplicationMode::Surround);
        assert!(a.dolby_surround_suitable());
    }

    #[test]
    fn audio_attributes_karaoke_channel_assignment_3_0() {
        // karaoke app_mode + byte 7 bits 6..4 = 3 (= 3/0 L,M,R) + bit 1 set (MC intro).
        let raw = pack_audio_attr(0, true, 0, 1, 0, 0, 2, [0, 0], 0, 0b0011_0010);
        let a = AudioAttributes::parse(&raw);
        assert_eq!(a.application_mode, AudioApplicationMode::Karaoke);
        assert!(a.multichannel_extension_present);
        assert_eq!(a.karaoke_channel_assignment(), Some(3));
        assert_eq!(a.karaoke_mc_intro_present(), Some(true));
        assert_eq!(a.karaoke_duet(), Some(false));
    }

    #[test]
    fn subpicture_attributes_2bit_rle_japanese() {
        let raw = pack_subp_attr(0, 1, *b"ja", 0);
        let s = SubpictureAttributes::parse(&raw);
        assert_eq!(s.coding_mode, SubpictureCodingMode::Rle2Bit);
        assert_eq!(s.language_type, SubpictureLanguageType::Iso639);
        assert_eq!(&s.language_code, b"ja");
    }

    #[test]
    fn mc_extension_entry_decodes_per_channel_flags() {
        let raw = [
            0b0000_0001, // ACH0 guide melody
            0b0000_0000,
            0b0000_1010, // ACH2 GV1 + GM1
            0b0000_0101, // ACH3 GV2 + SE_A
            0b0000_1001, // ACH4 GV1 + SE_B
            0,
            0,
            0,
        ];
        let m = McExtensionEntry::parse(&raw);
        assert!(m.ach0_guide_melody);
        assert!(!m.ach1_guide_melody);
        assert!(m.ach2_guide_vocal_1);
        assert!(m.ach2_guide_melody_1);
        assert!(m.ach3_guide_vocal_2);
        assert!(m.ach3_sound_effect_a);
        assert!(m.ach4_guide_vocal_1);
        assert!(m.ach4_sound_effect_b);
        assert!(!m.ach4_guide_melody_b);
    }

    /// Build a full 0x03D8-byte VTSI_MAT carrying the menu + title
    /// attribute extension blocks. We populate enough fields to
    /// exercise the typed decoders end-to-end.
    fn build_vtsi_mat_with_attrs() -> Vec<u8> {
        let mut b = vec![0u8; 0x03D8];
        b[0..12].copy_from_slice(VTS_MAGIC);
        b[0x0080..0x0084].copy_from_slice(&(0x03D7u32).to_be_bytes());
        // Sector pointers we don't exercise stay zero.

        // Menu block at 0x0100..0x015C — MPEG-2 PAL 4:3 full-D1,
        // one MPEG-1 stereo audio stream, one Japanese sub-picture.
        let v_menu = pack_video_attr(1, 1, 0, false, false, false, false, 0, false, false);
        b[0x0100..0x0102].copy_from_slice(&v_menu);
        b[0x0102..0x0104].copy_from_slice(&1u16.to_be_bytes());
        let a_menu = pack_audio_attr(2, false, 1, 0, 0, 0, 1, *b"en", 1, 0);
        b[0x0104..0x010C].copy_from_slice(&a_menu);
        b[0x0154..0x0156].copy_from_slice(&1u16.to_be_bytes());
        let s_menu = pack_subp_attr(0, 1, *b"ja", 0);
        b[0x0156..0x015C].copy_from_slice(&s_menu);

        // Title block at 0x0200..0x03D8 — MPEG-2 NTSC 16:9 full-D1,
        // two AC-3 streams (en 5.1, fr stereo) + two sub-picture
        // streams (en + de).
        let v_title = pack_video_attr(1, 0, 3, false, false, false, false, 0, false, false);
        b[0x0200..0x0202].copy_from_slice(&v_title);
        b[0x0202..0x0204].copy_from_slice(&2u16.to_be_bytes());
        let a0 = pack_audio_attr(0, false, 1, 0, 0, 0, 5, *b"en", 1, 0);
        let a1 = pack_audio_attr(0, false, 1, 0, 0, 0, 1, *b"fr", 1, 0);
        b[0x0204..0x020C].copy_from_slice(&a0);
        b[0x020C..0x0214].copy_from_slice(&a1);
        b[0x0254..0x0256].copy_from_slice(&2u16.to_be_bytes());
        let s0 = pack_subp_attr(0, 1, *b"en", 0);
        let s1 = pack_subp_attr(0, 1, *b"de", 0);
        b[0x0256..0x025C].copy_from_slice(&s0);
        b[0x025C..0x0262].copy_from_slice(&s1);

        // MC extension slot at 0x0318 — leave 24 zeroed entries.
        b
    }

    #[test]
    fn vtsi_mat_decodes_menu_and_title_attribute_blocks() {
        let buf = build_vtsi_mat_with_attrs();
        let mat = VtsiMat::parse(&buf).unwrap();

        let menu_v = mat.menu_attributes.video.unwrap();
        assert_eq!(menu_v.standard, VideoStandard::Pal);
        assert_eq!(menu_v.aspect_ratio, VideoAspectRatio::Ratio4x3);
        assert_eq!(mat.menu_attributes.audio_streams.len(), 1);
        assert_eq!(
            mat.menu_attributes.audio_streams[0].coding_mode,
            AudioCodingMode::Mpeg1
        );
        assert_eq!(mat.menu_attributes.subpicture_streams.len(), 1);
        assert_eq!(
            &mat.menu_attributes.subpicture_streams[0].language_code,
            b"ja"
        );

        let title_v = mat.title_attributes.video.unwrap();
        assert_eq!(title_v.standard, VideoStandard::Ntsc);
        assert_eq!(title_v.aspect_ratio, VideoAspectRatio::Ratio16x9);
        assert_eq!(mat.title_attributes.audio_streams.len(), 2);
        assert_eq!(mat.title_attributes.audio_streams[0].channel_count, 6);
        assert_eq!(&mat.title_attributes.audio_streams[1].language_code, b"fr");
        assert_eq!(mat.title_attributes.subpicture_streams.len(), 2);
        assert_eq!(
            &mat.title_attributes.subpicture_streams[1].language_code,
            b"de"
        );
        assert_eq!(mat.title_attributes.multichannel_extension.len(), 24);
        assert!(!mat.title_attributes.multichannel_extension[0].ach0_guide_melody);
    }

    #[test]
    fn vtsi_mat_short_buffer_leaves_attributes_partial() {
        // The 0x200-byte buffer used by the legacy roundtrip test
        // covers the menu block but not the title block.
        let buf = build_vtsi_mat(1, 2, 3, 42);
        let mat = VtsiMat::parse(&buf).unwrap();
        // Menu block fits entirely within 0x200, so its video field
        // is parsed (all-zero → MPEG-1 NTSC 4:3).
        let menu_v = mat.menu_attributes.video.unwrap();
        assert_eq!(menu_v.coding_mode, VideoCodingMode::Mpeg1);
        // Title block starts at 0x0200 — buffer ends before that.
        assert!(mat.title_attributes.video.is_none());
        assert!(mat.title_attributes.audio_streams.is_empty());
        assert!(mat.title_attributes.multichannel_extension.is_empty());
    }

    // -------------------------------------------------------------
    // VMG_VTS_ATRT
    // -------------------------------------------------------------

    /// Build a synthetic `VMG_VTS_ATRT` with `entries.len()` entries,
    /// each carrying the supplied `(vts_category, blob)` pair.
    fn build_vts_atrt(entries: &[(u32, Vec<u8>)]) -> Vec<u8> {
        // Header is 8 bytes + 4 bytes per offset entry.
        let header = 8 + 4 * entries.len();
        // Each entry body = 8-byte header + blob.
        let mut offsets = Vec::with_capacity(entries.len());
        let mut bodies = Vec::with_capacity(entries.len());
        let mut cursor = header;
        for (cat, blob) in entries {
            offsets.push(cursor as u32);
            let entry_total = 8 + blob.len();
            let entry_ea = (entry_total - 1) as u32;
            let mut e = Vec::with_capacity(entry_total);
            e.extend_from_slice(&entry_ea.to_be_bytes());
            e.extend_from_slice(&cat.to_be_bytes());
            e.extend_from_slice(blob);
            bodies.push(e);
            cursor += entry_total;
        }
        let total = cursor;
        let mut out = vec![0u8; total];
        out[0..2].copy_from_slice(&(entries.len() as u16).to_be_bytes());
        // bytes 2..4 reserved
        out[4..8].copy_from_slice(&((total - 1) as u32).to_be_bytes());
        for (i, off) in offsets.iter().enumerate() {
            out[8 + i * 4..8 + (i + 1) * 4].copy_from_slice(&off.to_be_bytes());
        }
        for (i, body) in bodies.iter().enumerate() {
            let start = offsets[i] as usize;
            out[start..start + body.len()].copy_from_slice(body);
        }
        out
    }

    #[test]
    fn vts_atrt_walks_two_entries() {
        let blob_a = (0..0x300u32).map(|i| (i & 0xFF) as u8).collect::<Vec<_>>();
        let blob_b = vec![0x55u8; 0x300];
        let buf = build_vts_atrt(&[(0, blob_a.clone()), (1, blob_b.clone())]);
        let atrt = VmgVtsAtrt::parse(&buf).unwrap();
        assert_eq!(atrt.number_of_title_sets, 2);
        assert_eq!(atrt.entries.len(), 2);

        let e1 = atrt.entry(1).unwrap();
        assert_eq!(e1.vts_number, 1);
        assert_eq!(e1.vts_category, 0);
        assert_eq!(e1.attributes_blob, blob_a);

        let e2 = atrt.entry(2).unwrap();
        assert_eq!(e2.vts_number, 2);
        assert_eq!(e2.vts_category, 1); // Karaoke flag
        assert_eq!(e2.attributes_blob, blob_b);

        assert!(atrt.entry(0).is_none());
        assert!(atrt.entry(3).is_none());
    }

    #[test]
    fn vts_atrt_rejects_short_header() {
        let buf = vec![0u8; 4];
        assert!(VmgVtsAtrt::parse(&buf).is_err());
    }

    #[test]
    fn vts_atrt_rejects_offset_list_past_end() {
        let mut buf = vec![0u8; 8];
        buf[0..2].copy_from_slice(&5u16.to_be_bytes()); // claims 5 entries
                                                        // but the offset list (20 bytes) doesn't fit in the 8-byte buffer
        assert!(VmgVtsAtrt::parse(&buf).is_err());
    }

    #[test]
    fn vts_atrt_rejects_entry_ea_overlapping_next_entry() {
        // Build a valid 2-entry table, then corrupt entry 1's EA so it
        // claims more bytes than entry 2's offset allows.
        let blob = vec![0xAAu8; 0x100];
        let mut buf = build_vts_atrt(&[(0, blob.clone()), (0, blob.clone())]);
        // Entry 1 is at offset = read_u32(buf, 8). Bloat its EA field
        // (entry-local offset 0..4) so the entry would extend past
        // entry 2's start.
        let e1_off = u32::from_be_bytes([buf[8], buf[9], buf[10], buf[11]]) as usize;
        buf[e1_off..e1_off + 4].copy_from_slice(&0xFFFFu32.to_be_bytes());
        assert!(VmgVtsAtrt::parse(&buf).is_err());
    }

    // -------------------------------------------------------------
    // VMG_PTL_MAIT
    // -------------------------------------------------------------

    /// Build a synthetic `VMG_PTL_MAIT` with `entries.len()` countries
    /// and `nts` title sets. Each entry's `masks` are passed as
    /// `[level1..level8]` arrays of `nts + 1` u16s — they're stored on
    /// disc in descending level order (level 8 first).
    fn build_ptl_mait(
        country_codes: &[u16],
        nts: u16,
        masks_per_country: &[[Vec<u16>; 8]],
    ) -> Vec<u8> {
        assert_eq!(country_codes.len(), masks_per_country.len());
        let header_len = 8 + 8 * country_codes.len();
        let level_block_bytes = (usize::from(nts) + 1) * 2;
        let body_bytes = level_block_bytes * 8;
        let total = header_len + body_bytes * country_codes.len();

        let mut buf = vec![0u8; total];
        buf[0..2].copy_from_slice(&(country_codes.len() as u16).to_be_bytes());
        buf[2..4].copy_from_slice(&nts.to_be_bytes());
        buf[4..8].copy_from_slice(&((total - 1) as u32).to_be_bytes());

        for (i, (&cc, masks)) in country_codes
            .iter()
            .zip(masks_per_country.iter())
            .enumerate()
        {
            let body_offset = header_len + i * body_bytes;
            // Entry: cc(u16) | reserved(u16) | offset(u16) | reserved(u16)
            let entry_base = 8 + i * 8;
            buf[entry_base..entry_base + 2].copy_from_slice(&cc.to_be_bytes());
            // bytes 2..4 reserved
            buf[entry_base + 4..entry_base + 6]
                .copy_from_slice(&(body_offset as u16).to_be_bytes());
            // bytes 6..8 reserved
            // Body: 8 stacked blocks, level 8 first.
            for storage_idx in 0..8usize {
                let level_value = 8 - storage_idx; // 8..=1
                let row = &masks[level_value - 1]; // user passed ascending
                assert_eq!(row.len(), usize::from(nts) + 1);
                let block_start = body_offset + storage_idx * level_block_bytes;
                for (slot, &m) in row.iter().enumerate() {
                    buf[block_start + slot * 2..block_start + slot * 2 + 2]
                        .copy_from_slice(&m.to_be_bytes());
                }
            }
        }
        buf
    }

    #[test]
    fn ptl_mait_walks_two_countries() {
        // 2 countries × nts=2 (so masks_per_level = 3: VMG + 2 VTSs).
        let mut country_a_masks: [Vec<u16>; 8] = Default::default();
        let mut country_b_masks: [Vec<u16>; 8] = Default::default();
        for lvl_idx in 0..8 {
            // level 1..=8 stored ascending in the user-facing layout.
            let lvl = (lvl_idx + 1) as u16;
            country_a_masks[lvl_idx] = vec![lvl, lvl + 0x10, lvl + 0x20];
            country_b_masks[lvl_idx] =
                vec![0xF000 | lvl, 0xF000 | (lvl + 0x10), 0xF000 | (lvl + 0x20)];
        }
        // Country code 'us' = 0x7553; 'jp' = 0x6A70.
        let buf = build_ptl_mait(
            &[0x7553, 0x6A70],
            2,
            &[country_a_masks.clone(), country_b_masks.clone()],
        );

        let pm = VmgPtlMait::parse(&buf).unwrap();
        assert_eq!(pm.number_of_countries, 2);
        assert_eq!(pm.number_of_title_sets, 2);
        assert_eq!(pm.entries.len(), 2);

        let us = pm.country(0x7553).expect("US country present");
        // Level 1 mask for VMG (title_set=0) was 1.
        assert_eq!(us.mask(1, 0), Some(1));
        // Level 1 mask for VTS 1 was 0x11.
        assert_eq!(us.mask(1, 1), Some(0x11));
        // Level 1 mask for VTS 2 was 0x21.
        assert_eq!(us.mask(1, 2), Some(0x21));
        // Level 8 mask for VTS 2 was 8 + 0x20 = 0x28.
        assert_eq!(us.mask(8, 2), Some(0x28));

        let jp = pm.country(0x6A70).unwrap();
        assert_eq!(jp.mask(1, 0), Some(0xF001));
        assert_eq!(jp.mask(8, 2), Some(0xF028));

        assert!(pm.country(0x4242).is_none());
        // Out-of-range parental level.
        assert_eq!(us.mask(0, 0), None);
        assert_eq!(us.mask(9, 0), None);
        // Out-of-range title-set index.
        assert_eq!(us.mask(1, 3), None);
    }

    #[test]
    fn ptl_mait_zero_countries_decodes_empty() {
        let buf = build_ptl_mait(&[], 2, &[]);
        let pm = VmgPtlMait::parse(&buf).unwrap();
        assert_eq!(pm.number_of_countries, 0);
        assert!(pm.entries.is_empty());
    }

    #[test]
    fn ptl_mait_rejects_short_header() {
        let buf = vec![0u8; 4];
        assert!(VmgPtlMait::parse(&buf).is_err());
    }

    #[test]
    fn ptl_mait_rejects_country_list_past_end() {
        let mut buf = vec![0u8; 8];
        buf[0..2].copy_from_slice(&5u16.to_be_bytes()); // 5 countries
        buf[2..4].copy_from_slice(&2u16.to_be_bytes());
        // Truncated — no room for 5 × 8-byte entries after the header.
        assert!(VmgPtlMait::parse(&buf).is_err());
    }

    #[test]
    fn ptl_mait_rejects_body_offset_past_buffer() {
        // 1 country, nts=2 → body needs 8 × 6 = 48 bytes. Header
        // (8) + entry (8) = 16. Total valid buffer would be 16 + 48 = 64
        // bytes; truncate to 16 to trip the bound check.
        let mut buf = vec![0u8; 16];
        buf[0..2].copy_from_slice(&1u16.to_be_bytes());
        buf[2..4].copy_from_slice(&2u16.to_be_bytes());
        buf[4..8].copy_from_slice(&63u32.to_be_bytes());
        buf[8..10].copy_from_slice(&0x7553u16.to_be_bytes());
        buf[12..14].copy_from_slice(&16u16.to_be_bytes()); // body starts past buf end
        assert!(VmgPtlMait::parse(&buf).is_err());
    }

    // ----------------------------------------------------------------
    // VMGM_PGCI_UT / VTSM_PGCI_UT — Menu PGCI Unit Table
    // ----------------------------------------------------------------

    /// Minimal PGC body (236 bytes) — all sub-table offsets zero so
    /// `Pgc::parse` walks the header alone.
    fn empty_pgc_body() -> Vec<u8> {
        vec![0u8; 0xEC]
    }

    /// Build a synthetic PGCI_UT buffer from `(language_code,
    /// language_code_ext, menu_existence, pgc_categories)` tuples.
    /// Each language unit gets one PGC per `pgc_categories` entry,
    /// each PGC carries an empty 236-byte body.
    fn build_pgci_ut(units: &[(u16, u8, u8, Vec<u32>)]) -> Vec<u8> {
        let header_len = 8 + 8 * units.len();
        // Layout: outer header, outer SRP list, then back-to-back LUs.
        // Each LU has its own (8 + n_pgcs × 8) header + (n_pgcs × 236)
        // PGC bodies.
        let lu_lens: Vec<usize> = units
            .iter()
            .map(|(_, _, _, pgcs)| 8 + pgcs.len() * 8 + pgcs.len() * 0xEC)
            .collect();
        let total: usize = header_len + lu_lens.iter().sum::<usize>();
        let mut buf = vec![0u8; total];
        // Outer header: num LUs + end_address.
        buf[0..2].copy_from_slice(&(units.len() as u16).to_be_bytes());
        buf[4..8].copy_from_slice(&((total - 1) as u32).to_be_bytes());

        let mut lu_offset = header_len;
        for (i, ((lang, ext, exist, pgcs), &lu_len)) in units.iter().zip(lu_lens.iter()).enumerate()
        {
            // Outer SRP entry: lang(u16) | ext(u8) | exist(u8) | offset(u32)
            let srp_base = 8 + i * 8;
            buf[srp_base..srp_base + 2].copy_from_slice(&lang.to_be_bytes());
            buf[srp_base + 2] = *ext;
            buf[srp_base + 3] = *exist;
            buf[srp_base + 4..srp_base + 8].copy_from_slice(&(lu_offset as u32).to_be_bytes());

            // LU header at lu_offset: n_pgcs + end_address relative to LU.
            buf[lu_offset..lu_offset + 2].copy_from_slice(&(pgcs.len() as u16).to_be_bytes());
            buf[lu_offset + 4..lu_offset + 8].copy_from_slice(&((lu_len - 1) as u32).to_be_bytes());

            // Inner SRP entries + back-to-back PGC bodies.
            let inner_srp_end = 8 + pgcs.len() * 8;
            for (j, &cat) in pgcs.iter().enumerate() {
                let inner_base = lu_offset + 8 + j * 8;
                buf[inner_base..inner_base + 4].copy_from_slice(&cat.to_be_bytes());
                let pgc_offset_in_lu = (inner_srp_end + j * 0xEC) as u32;
                buf[inner_base + 4..inner_base + 8]
                    .copy_from_slice(&pgc_offset_in_lu.to_be_bytes());

                // Body is all zero from the vec init — that matches
                // empty_pgc_body() and parses fine.
                let pgc_global = lu_offset + pgc_offset_in_lu as usize;
                let empty = empty_pgc_body();
                buf[pgc_global..pgc_global + 0xEC].copy_from_slice(&empty);
            }

            lu_offset += lu_len;
        }
        buf
    }

    #[test]
    fn pgci_ut_walks_two_language_units() {
        // EN + JP, each with 2 PGCs. Categories encode entry-PGC flag
        // (bit 31) + menu-type nibble (low 4 bits of byte 0).
        // EN: PGC1 = entry-Root (0x83_00_00_00), PGC2 = non-entry (0x00_…).
        // JP: PGC1 = entry-Title (0x82_00_00_00), PGC2 = non-entry.
        let units = vec![
            (
                0x656E, // "en"
                0,
                menu_existence::ROOT | menu_existence::AUDIO,
                vec![0x83_00_00_00, 0x00_00_00_00],
            ),
            (
                0x6A70, // "jp"
                0,
                menu_existence::ROOT,
                vec![0x82_00_00_00, 0x00_00_00_00],
            ),
        ];
        let buf = build_pgci_ut(&units);
        let table = PgciUt::parse(&buf).unwrap();

        assert_eq!(table.number_of_language_units, 2);
        assert_eq!(table.srp.len(), 2);
        assert_eq!(table.language_units.len(), 2);

        // First LU: English, root + audio menus.
        let en_srp = &table.srp[0];
        assert_eq!(en_srp.language_code, 0x656E);
        assert!(en_srp.has_root_menu());
        assert!(en_srp.has_audio_menu());
        assert!(!en_srp.has_subpicture_menu());
        assert!(!en_srp.has_angle_menu());
        assert!(!en_srp.has_ptt_menu());

        let en_lu = &table.language_units[0];
        assert_eq!(en_lu.number_of_pgcs, 2);
        assert_eq!(en_lu.srp.len(), 2);
        assert_eq!(en_lu.pgcs.len(), 2);
        assert!(en_lu.srp[0].is_entry_pgc());
        assert_eq!(en_lu.srp[0].menu_type(), MenuType::Root);
        assert!(!en_lu.srp[1].is_entry_pgc());

        // Second LU: Japanese, title-menu entry.
        let jp_srp = &table.srp[1];
        assert_eq!(jp_srp.language_code, 0x6A70);
        let jp_lu = &table.language_units[1];
        assert_eq!(jp_lu.srp[0].menu_type(), MenuType::Title);

        // language_unit() lookup round-trips.
        assert_eq!(
            table.language_unit(0x656E).map(|lu| lu.number_of_pgcs),
            Some(2)
        );
        assert!(table.language_unit(0x4242).is_none());
    }

    #[test]
    fn pgci_ut_zero_language_units_decodes_empty() {
        let buf = build_pgci_ut(&[]);
        let table = PgciUt::parse(&buf).unwrap();
        assert_eq!(table.number_of_language_units, 0);
        assert!(table.srp.is_empty());
        assert!(table.language_units.is_empty());
    }

    #[test]
    fn pgci_ut_rejects_short_header() {
        let buf = vec![0u8; 4];
        assert!(PgciUt::parse(&buf).is_err());
    }

    #[test]
    fn pgci_ut_rejects_srp_list_past_buffer() {
        // Claim 5 LUs but truncate after the header.
        let mut buf = vec![0u8; 8];
        buf[0..2].copy_from_slice(&5u16.to_be_bytes());
        assert!(PgciUt::parse(&buf).is_err());
    }

    #[test]
    fn pgci_ut_rejects_lu_offset_zero() {
        // One LU with offset=0 — should be rejected per the in-range
        // check in `PgciUt::parse`.
        let mut buf = vec![0u8; 16];
        buf[0..2].copy_from_slice(&1u16.to_be_bytes());
        // outer SRP entry at offset 8: lang=0x656E, exist=0x80, off=0.
        buf[8..10].copy_from_slice(&0x656Eu16.to_be_bytes());
        buf[11] = menu_existence::ROOT;
        // offset bytes already zero.
        assert!(PgciUt::parse(&buf).is_err());
    }

    #[test]
    fn pgci_ut_rejects_lu_offset_past_buffer() {
        // One LU whose offset points beyond the buffer end.
        let mut buf = vec![0u8; 16];
        buf[0..2].copy_from_slice(&1u16.to_be_bytes());
        buf[8..10].copy_from_slice(&0x656Eu16.to_be_bytes());
        buf[11] = menu_existence::ROOT;
        buf[12..16].copy_from_slice(&64u32.to_be_bytes()); // beyond 16-byte buf
        assert!(PgciUt::parse(&buf).is_err());
    }

    #[test]
    fn pgci_lu_rejects_pgc_offset_past_buffer() {
        // A 16-byte LU body claiming 1 PGC whose offset points outside
        // the LU buffer.
        let mut buf = vec![0u8; 16];
        buf[0..2].copy_from_slice(&1u16.to_be_bytes());
        // Inner SRP at offset 8: category=0, offset=512 (way past 16).
        buf[12..16].copy_from_slice(&512u32.to_be_bytes());
        assert!(PgciLu::parse(&buf).is_err());
    }

    #[test]
    fn pgci_lu_srp_decodes_parental_mask() {
        // Build a single-LU table with one PGC whose category dword
        // is 0x83_00_00_FF — entry-Root menu, parental mask 0x00FF.
        let units = vec![(0x656E, 0, menu_existence::ROOT, vec![0x83_00_00_FF_u32])];
        let buf = build_pgci_ut(&units);
        let table = PgciUt::parse(&buf).unwrap();
        let lu = &table.language_units[0];
        assert!(lu.srp[0].is_entry_pgc());
        assert_eq!(lu.srp[0].menu_type(), MenuType::Root);
        assert_eq!(lu.srp[0].parental_mask(), 0x00FF);
    }

    #[test]
    fn menu_type_unknown_for_undefined_nibble() {
        // The spec defines 2..=7; 1 / 8..=15 fall through to Unknown.
        assert_eq!(MenuType::from_nibble(1), MenuType::Unknown(1));
        assert_eq!(MenuType::from_nibble(0), MenuType::Unknown(0));
        // High nibble is masked off — only low 4 bits matter.
        assert_eq!(MenuType::from_nibble(0xF3), MenuType::Root);
    }
}