libfreemkv 0.4.0

//! AACS decryption — Volume Unique Key lookup and title key derivation.
//!
//! Two paths:
//!   1. VUK lookup: disc_hash → KEYDB.cfg → VUK (fast, 99% of discs)
//!   2. Full handshake: device_keys + MKB → Media Key → + Volume ID → VUK (fallback)
//!
//! KEYDB.cfg format:
//!   | DK | DEVICE_KEY 0x... | DEVICE_NODE 0x... | KEY_UV 0x... | KEY_U_MASK_SHIFT 0x...
//!   | PK | 0x...
//!   | HC | HOST_PRIV_KEY 0x... | HOST_CERT 0x...
//!   0x<disc_hash> = <title> | D | <date> | M | 0x<media_key> | I | 0x<disc_id> | V | 0x<vuk> | U | <unit_keys>
//!
//! The VUK decrypts title keys from AACS/Unit_Key_RO.inf on disc.
//! Title keys decrypt m2ts stream content (AES-128-CBC).

pub mod handshake;

use std::collections::HashMap;
use aes::Aes128;
use aes::cipher::{BlockEncrypt, BlockDecrypt, KeyInit, generic_array::GenericArray};

/// Parsed AACS key database.
#[derive(Debug)]
pub struct KeyDb {
    /// Device keys for MKB processing
    pub device_keys: Vec<DeviceKey>,
    /// Processing keys (pre-computed media keys for specific MKB versions)
    pub processing_keys: Vec<[u8; 16]>,
    /// Host certificate + private key for SCSI authentication
    pub host_cert: Option<HostCert>,
    /// Per-disc VUK entries indexed by disc hash (hex lowercase)
    pub disc_entries: HashMap<String, DiscEntry>,
}

/// A device key for MKB subset-difference tree processing.
#[derive(Debug, Clone)]
pub struct DeviceKey {
    pub key: [u8; 16],
    pub node: u16,
    pub uv: u32,
    pub u_mask_shift: u8,
}

/// Host certificate + private key for AACS SCSI authentication.
#[derive(Debug, Clone)]
pub struct HostCert {
    pub private_key: [u8; 20],
    pub certificate: Vec<u8>, // 92 bytes
}

/// A per-disc entry from the key database.
#[derive(Debug, Clone)]
pub struct DiscEntry {
    /// Disc hash (20 bytes, hex)
    pub disc_hash: String,
    /// Disc title
    pub title: String,
    /// Media Key (16 bytes) — from MKB processing
    pub media_key: Option<[u8; 16]>,
    /// Disc ID (16 bytes)
    pub disc_id: Option<[u8; 16]>,
    /// Volume Unique Key (16 bytes) — decrypts title keys
    pub vuk: Option<[u8; 16]>,
    /// Unit keys (title keys) indexed by CPS unit number
    pub unit_keys: Vec<(u32, [u8; 16])>,
}

/// Parse a hex string like "0xABCD..." into bytes.
fn parse_hex(s: &str) -> Option<Vec<u8>> {
    let s = s.trim().trim_start_matches("0x").trim_start_matches("0X");
    if s.len() % 2 != 0 { return None; }
    let mut out = Vec::with_capacity(s.len() / 2);
    for i in (0..s.len()).step_by(2) {
        out.push(u8::from_str_radix(&s[i..i+2], 16).ok()?);
    }
    Some(out)
}

/// Parse hex into a fixed-size array.
fn parse_hex16(s: &str) -> Option<[u8; 16]> {
    let v = parse_hex(s)?;
    if v.len() != 16 { return None; }
    let mut out = [0u8; 16];
    out.copy_from_slice(&v);
    Some(out)
}

fn parse_hex20(s: &str) -> Option<[u8; 20]> {
    let v = parse_hex(s)?;
    if v.len() != 20 { return None; }
    let mut out = [0u8; 20];
    out.copy_from_slice(&v);
    Some(out)
}

impl KeyDb {
    /// Parse a KEYDB.cfg file from a string.
    pub fn parse(data: &str) -> Self {
        let mut db = KeyDb {
            device_keys: Vec::new(),
            processing_keys: Vec::new(),
            host_cert: None,
            disc_entries: HashMap::new(),
        };

        for line in data.lines() {
            let line = line.trim();

            // Skip comments and empty lines
            if line.is_empty() || line.starts_with(';') || line.starts_with('#') {
                continue;
            }

            // Device Key
            if line.starts_with("| DK") {
                if let Some(dk) = Self::parse_device_key(line) {
                    db.device_keys.push(dk);
                }
                continue;
            }

            // Processing Key
            if line.starts_with("| PK") {
                if let Some(pk) = Self::parse_processing_key(line) {
                    db.processing_keys.push(pk);
                }
                continue;
            }

            // Host Certificate
            if line.starts_with("| HC") {
                db.host_cert = Self::parse_host_cert(line);
                continue;
            }

            // Disc entry: starts with 0x
            if line.starts_with("0x") && line.contains(" = ") {
                if let Some(entry) = Self::parse_disc_entry(line) {
                    db.disc_entries.insert(entry.disc_hash.clone(), entry);
                }
            }
        }

        db
    }

    /// Load KEYDB.cfg from a file path.
    pub fn load(path: &std::path::Path) -> std::io::Result<Self> {
        let data = std::fs::read_to_string(path)?;
        Ok(Self::parse(&data))
    }

    /// Look up a disc by its hash. Returns the VUK if found.
    pub fn find_vuk(&self, disc_hash: &str) -> Option<[u8; 16]> {
        let hash = disc_hash.trim().to_lowercase().trim_start_matches("0x").to_string();
        // Try with 0x prefix and without
        self.disc_entries.get(&format!("0x{}", hash))
            .or_else(|| self.disc_entries.get(&hash))
            .and_then(|e| e.vuk)
    }

    /// Look up a disc by its hash. Returns the full entry.
    pub fn find_disc(&self, disc_hash: &str) -> Option<&DiscEntry> {
        let hash = disc_hash.trim().to_lowercase().trim_start_matches("0x").to_string();
        self.disc_entries.get(&format!("0x{}", hash))
            .or_else(|| self.disc_entries.get(&hash))
    }

    // ── Parsers ─────────────────────────────────────────────────────────────

    fn parse_device_key(line: &str) -> Option<DeviceKey> {
        // | DK | DEVICE_KEY 0x... | DEVICE_NODE 0x... | KEY_UV 0x... | KEY_U_MASK_SHIFT 0x...
        let key_str = line.split("DEVICE_KEY").nth(1)?.split('|').next()?.trim();
        let node_str = line.split("DEVICE_NODE").nth(1)?.split('|').next()?.trim();
        let uv_str = line.split("KEY_UV").nth(1)?.split('|').next()?.trim();
        let shift_str = line.split("KEY_U_MASK_SHIFT").nth(1)?.split(';').next()?.split('|').next()?.trim();

        Some(DeviceKey {
            key: parse_hex16(key_str)?,
            node: u16::from_str_radix(node_str.trim_start_matches("0x"), 16).ok()?,
            uv: u32::from_str_radix(uv_str.trim_start_matches("0x"), 16).ok()?,
            u_mask_shift: u8::from_str_radix(shift_str.trim_start_matches("0x"), 16).ok()?,
        })
    }

    fn parse_processing_key(line: &str) -> Option<[u8; 16]> {
        // | PK | 0x...
        let parts: Vec<&str> = line.split('|').collect();
        if parts.len() >= 3 {
            let key_str = parts[2].split(';').next()?.trim();
            return parse_hex16(key_str);
        }
        None
    }

    fn parse_host_cert(line: &str) -> Option<HostCert> {
        // | HC | HOST_PRIV_KEY 0x... | HOST_CERT 0x...
        let priv_str = line.split("HOST_PRIV_KEY").nth(1)?.split('|').next()?.trim();
        let cert_str = line.split("HOST_CERT").nth(1)?.split(';').next()?.split('|').next()?.trim();

        Some(HostCert {
            private_key: parse_hex20(priv_str)?,
            certificate: parse_hex(cert_str)?,
        })
    }

    fn parse_disc_entry(line: &str) -> Option<DiscEntry> {
        // 0x<hash> = <title> | D | <date> | M | 0x<mk> | I | 0x<id> | V | 0x<vuk> | U | <unit_keys>
        let (hash_part, rest) = line.split_once(" = ")?;
        let disc_hash = hash_part.trim().to_lowercase();

        // Extract title (before first |)
        let title_part = rest.split(" | ").next().unwrap_or("").trim();
        // Clean title: "TITLE_NAME (Display Title)" → use display title if present
        let title = if let Some(start) = title_part.find('(') {
            if let Some(end) = title_part.rfind(')') {
                title_part[start+1..end].to_string()
            } else {
                title_part.to_string()
            }
        } else {
            title_part.to_string()
        };

        // Parse fields by tag
        let mut media_key = None;
        let mut disc_id = None;
        let mut vuk = None;
        let mut unit_keys = Vec::new();

        let parts: Vec<&str> = rest.split(" | ").collect();
        let mut i = 0;
        while i < parts.len() {
            match parts[i].trim() {
                "M" => {
                    if i + 1 < parts.len() {
                        media_key = parse_hex16(parts[i+1].trim());
                        i += 1;
                    }
                }
                "I" => {
                    if i + 1 < parts.len() {
                        disc_id = parse_hex16(parts[i+1].trim());
                        i += 1;
                    }
                }
                "V" => {
                    if i + 1 < parts.len() {
                        vuk = parse_hex16(parts[i+1].trim());
                        i += 1;
                    }
                }
                "U" => {
                    if i + 1 < parts.len() {
                        // Unit keys: "1-0xKEY" or "1-0xKEY ; comment"
                        let uk_str = parts[i+1].split(';').next().unwrap_or("").trim();
                        for uk in uk_str.split(' ') {
                            let uk = uk.trim();
                            if let Some((num, key)) = uk.split_once('-') {
                                if let Ok(n) = num.parse::<u32>() {
                                    if let Some(k) = parse_hex16(key) {
                                        unit_keys.push((n, k));
                                    }
                                }
                            }
                        }
                        i += 1;
                    }
                }
                _ => {}
            }
            i += 1;
        }

        Some(DiscEntry {
            disc_hash,
            title,
            media_key,
            disc_id,
            vuk,
            unit_keys,
        })
    }
}

// ── AACS constants ──────────────────────────────────────────────────────────

/// Fixed IV used by AACS for all AES-CBC operations.
const AACS_IV: [u8; 16] = [
    0x0B, 0xA0, 0xF8, 0xDD, 0xFE, 0xA6, 0x1F, 0xB3,
    0xD8, 0xDF, 0x9F, 0x56, 0x6A, 0x05, 0x0F, 0x78,
];

/// Size of an AACS aligned unit (3 × 2048-byte sectors).
pub const ALIGNED_UNIT_LEN: usize = 6144;

/// Size of one sector.
const SECTOR_LEN: usize = 2048;

/// Transport stream packet spacing in Blu-ray m2ts (192 bytes = 4 TP_extra + 188 TS).
const TS_PACKET_LEN: usize = 192;

/// TS sync byte.
const TS_SYNC: u8 = 0x47;

// ── AES primitives ──────────────────────────────────────────────────────────

/// AES-128-ECB encrypt a single 16-byte block.
fn aes_ecb_encrypt(key: &[u8; 16], data: &[u8; 16]) -> [u8; 16] {
    let cipher = Aes128::new(GenericArray::from_slice(key));
    let mut block = GenericArray::clone_from_slice(data);
    cipher.encrypt_block(&mut block);
    let mut out = [0u8; 16];
    out.copy_from_slice(&block);
    out
}

/// AES-128-ECB decrypt a single 16-byte block.
pub fn aes_ecb_decrypt(key: &[u8; 16], data: &[u8; 16]) -> [u8; 16] {
    let cipher = Aes128::new(GenericArray::from_slice(key));
    let mut block = GenericArray::clone_from_slice(data);
    cipher.decrypt_block(&mut block);
    let mut out = [0u8; 16];
    out.copy_from_slice(&block);
    out
}

/// AES-128-CBC decrypt in-place with the fixed AACS IV.
/// AES-128-CBC decrypt in-place with the fixed AACS IV.
fn aes_cbc_decrypt(key: &[u8; 16], data: &mut [u8]) {
    let cipher = Aes128::new(GenericArray::from_slice(key));
    let num_blocks = data.len() / 16;
    // Process blocks in reverse to avoid clobbering ciphertext needed for XOR
    for i in (0..num_blocks).rev() {
        let offset = i * 16;
        let prev = if i == 0 {
            AACS_IV
        } else {
            let mut p = [0u8; 16];
            p.copy_from_slice(&data[(i - 1) * 16..i * 16]);
            p
        };
        let mut block = GenericArray::clone_from_slice(&data[offset..offset + 16]);
        cipher.decrypt_block(&mut block);
        for j in 0..16 {
            data[offset + j] = block[j] ^ prev[j];
        }
    }
}

// ── VUK derivation ──────────────────────────────────────────────────────────

/// Derive VUK from Media Key and Volume ID.
/// VUK = AES-128-ECB-DECRYPT(media_key, volume_id) XOR volume_id
pub fn derive_vuk(media_key: &[u8; 16], volume_id: &[u8; 16]) -> [u8; 16] {
    let mut vuk = aes_ecb_decrypt(media_key, volume_id);
    for i in 0..16 {
        vuk[i] ^= volume_id[i];
    }
    vuk
}

/// Decrypt an encrypted unit key using the VUK (AES-128-ECB).
pub fn decrypt_unit_key(vuk: &[u8; 16], encrypted_uk: &[u8; 16]) -> [u8; 16] {
    aes_ecb_decrypt(vuk, encrypted_uk)
}

// ── Unit_Key_RO.inf parsing ─────────────────────────────────────────────────

/// Parsed Unit_Key_RO.inf file.
#[derive(Debug)]
pub struct UnitKeyFile {
    /// Disc hash (SHA1 of the entire file) — used as KEYDB lookup key
    pub disc_hash: [u8; 20],
    /// Application type (1 = BD-ROM)
    pub app_type: u8,
    /// Number of BDMV directories
    pub num_bdmv_dir: u8,
    /// Whether SKB MKB is used
    pub use_skb_mkb: bool,
    /// Whether this is AACS 2.0
    pub aacs2: bool,
    /// Encrypted unit keys (CPS unit number, encrypted key)
    pub encrypted_keys: Vec<(u32, [u8; 16])>,
    /// Title → CPS unit index mapping (title_idx → unit_key_idx)
    pub title_cps_unit: Vec<u16>,
}

/// Compute disc hash (SHA1 of Unit_Key_RO.inf content).
pub fn disc_hash(data: &[u8]) -> [u8; 20] {
    use sha1::{Sha1, Digest};
    let hash = Sha1::digest(data);
    let mut out = [0u8; 20];
    out.copy_from_slice(&hash);
    out
}

/// Format disc hash as hex string with 0x prefix (for KEYDB lookup).
pub fn disc_hash_hex(hash: &[u8; 20]) -> String {
    let mut s = String::with_capacity(42);
    s.push_str("0x");
    for b in hash {
        s.push_str(&format!("{:02X}", b));
    }
    s
}

/// Parse Unit_Key_RO.inf from raw bytes.
///
/// Format (from AACS spec):
///   [0..4]   BE32: offset to key storage area (uk_pos)
///   [16]     app_type (1 = BD-ROM)
///   [17]     num_bdmv_dir
///   [18]     bit 7: use_skb_mkb
///   [20..22] BE16: first_play CPS unit
///   [22..24] BE16: top_menu CPS unit
///   [24..26] BE16: num_titles
///   [26..]   title entries: 2 bytes padding + 2 bytes CPS unit, × num_titles
///
///   Key storage at uk_pos:
///   [uk_pos..uk_pos+2]   BE16: num_unit_keys
///   [uk_pos+48..]        encrypted keys, 16 bytes each
///                         AACS 1.0: 48-byte stride
///                         AACS 2.0: 64-byte stride (48 + 16 extra)
pub fn parse_unit_key_ro(data: &[u8], aacs2: bool) -> Option<UnitKeyFile> {
    if data.len() < 20 {
        return None;
    }

    let hash = disc_hash(data);

    // Header
    let app_type = data[16];
    let num_bdmv_dir = data[17];
    let use_skb_mkb = (data[18] >> 7) & 1 == 1;

    // Key storage offset
    let uk_pos = u32::from_be_bytes([data[0], data[1], data[2], data[3]]) as usize;
    if uk_pos + 2 > data.len() {
        return None;
    }

    // Number of unit keys
    let num_uk = u16::from_be_bytes([data[uk_pos], data[uk_pos + 1]]) as usize;
    if num_uk == 0 {
        return Some(UnitKeyFile {
            disc_hash: hash, app_type, num_bdmv_dir, use_skb_mkb,
            aacs2, encrypted_keys: Vec::new(), title_cps_unit: Vec::new(),
        });
    }

    // Stride between keys
    let stride = if aacs2 { 64 } else { 48 };

    // Validate size
    let keys_start = uk_pos + 48; // first key at uk_pos + 48
    if keys_start + 16 > data.len() {
        return None;
    }

    // Extract encrypted keys
    let mut encrypted_keys = Vec::with_capacity(num_uk);
    let mut pos = keys_start;
    for i in 0..num_uk {
        if pos + 16 > data.len() {
            break;
        }
        let mut key = [0u8; 16];
        key.copy_from_slice(&data[pos..pos + 16]);
        encrypted_keys.push(((i + 1) as u32, key));
        pos += stride;
    }

    // Title → CPS unit mapping
    let mut title_cps_unit = Vec::new();
    if data.len() >= 26 {
        let first_play = u16::from_be_bytes([data[20], data[21]]);
        let top_menu = u16::from_be_bytes([data[22], data[23]]);
        let num_titles = u16::from_be_bytes([data[24], data[25]]) as usize;

        title_cps_unit.push(first_play);
        title_cps_unit.push(top_menu);

        for i in 0..num_titles {
            let off = 26 + i * 4 + 2; // 2 bytes padding + 2 bytes CPS unit
            if off + 2 <= data.len() {
                let cps = u16::from_be_bytes([data[off], data[off + 1]]);
                title_cps_unit.push(cps);
            }
        }
    }

    Some(UnitKeyFile {
        disc_hash: hash,
        app_type,
        num_bdmv_dir,
        use_skb_mkb,
        aacs2,
        encrypted_keys,
        title_cps_unit,
    })
}

// ── MKB processing ──────────────────────────────────────────────────────────

/// Derive Media Key from MKB data using processing keys.
///
/// Processing keys are pre-computed keys that work for specific MKB versions.
/// This is the fast path — no subset-difference tree traversal needed.
///
/// MKB format:
///   Record type 0x10 = Verify Media Key Record (has mk_dv)
///   Record type 0x81 = Type and Version Record (has MKB version)
///   Record type 0x04 = Subset-Difference Index (has UVS entries)
///   Record type 0x07 = Explicit Subset-Difference Record (has cvalues)
pub fn derive_media_key_from_pk(mkb: &[u8], processing_keys: &[[u8; 16]]) -> Option<[u8; 16]> {
    // Parse MKB records
    let mk_dv = mkb_find_mk_dv(mkb)?;
    let uvs = mkb_find_subdiff_records(mkb)?;
    let cvalues = mkb_find_cvalues(mkb)?;

    // Count UV entries (each 5 bytes, stop when high bits set)
    let num_uvs = uvs.chunks(5).take_while(|c| c.len() == 5 && (c[0] & 0xC0) == 0).count();

    // Try each processing key against each UV/cvalue pair
    for pk in processing_keys {
        for i in 0..num_uvs {
            let uv = &uvs[1 + i * 5..]; // skip first byte
            let cv = &cvalues[i * 16..(i + 1) * 16];
            if let Some(mk) = validate_processing_key(pk, cv, uv, &mk_dv) {
                return Some(mk);
            }
        }
    }
    None
}

/// Validate a processing key against a cvalue/UV pair.
/// Returns the Media Key if valid.
fn validate_processing_key(pk: &[u8; 16], cvalue: &[u8], _uv: &[u8], mk_dv: &[u8; 16]) -> Option<[u8; 16]> {
    if cvalue.len() < 16 {
        return None;
    }
    // mk = AES-DEC(pk, cvalue) XOR cvalue
    let mut cv = [0u8; 16];
    cv.copy_from_slice(&cvalue[..16]);
    let mut mk = aes_ecb_decrypt(pk, &cv);
    for i in 0..16 {
        mk[i] ^= cv[i];
    }

    // Verify: AES-ECB(mk, mk_dv) should produce a specific pattern
    let _verify = aes_ecb_encrypt(&mk, mk_dv);
    // mk_dv verification: the first 12 bytes of AES(mk, mk_dv) should be all 0xDEADBEEF...
    // Actually per AACS spec: verify record value is AES(mk, all_zeros)
    // No — the mk_dv IS the verification value. We compute AES-ECB(mk, verify_data)
    // and check it matches.
    // From libaacs _validate_pk:
    //   crypto_aes128d(pk, rec + a*16, mk) → decrypt cvalue with PK
    //   mk[i] ^= rec[i]  → XOR with cvalue
    //   crypto_aes128e(mk, mk_dv, test) → encrypt mk_dv with derived mk
    //   if first 12 bytes of test are zero → valid media key
    let test = aes_ecb_encrypt(&mk, mk_dv);
    // AACS spec: Verify Media Key record — first 12 bytes must be zero
    if test[..12] == [0u8; 12] {
        return Some(mk);
    }
    None
}

/// Find Verify Media Key Record (type 0x10) in MKB.
fn mkb_find_mk_dv(mkb: &[u8]) -> Option<[u8; 16]> {
    let mut pos = 0;
    while pos + 4 <= mkb.len() {
        let rec_type = mkb[pos];
        let rec_len = u32::from_be_bytes([0, mkb[pos + 1], mkb[pos + 2], mkb[pos + 3]]) as usize;
        if rec_len < 4 || pos + rec_len > mkb.len() { break; }

        if rec_type == 0x10 && rec_len >= 20 {
            // mk_dv is at offset 4 (after record header)
            let mut dv = [0u8; 16];
            dv.copy_from_slice(&mkb[pos + 4..pos + 20]);
            return Some(dv);
        }
        pos += rec_len;
    }
    None
}

/// Find Subset-Difference records (type 0x04) in MKB.
fn mkb_find_subdiff_records(mkb: &[u8]) -> Option<Vec<u8>> {
    let mut pos = 0;
    while pos + 4 <= mkb.len() {
        let rec_type = mkb[pos];
        let rec_len = u32::from_be_bytes([0, mkb[pos + 1], mkb[pos + 2], mkb[pos + 3]]) as usize;
        if rec_len < 4 || pos + rec_len > mkb.len() { break; }

        if rec_type == 0x04 && rec_len > 4 {
            return Some(mkb[pos + 4..pos + rec_len].to_vec());
        }
        pos += rec_len;
    }
    None
}

/// Find Conditional Values (cvalues) record (type 0x07) in MKB.
fn mkb_find_cvalues(mkb: &[u8]) -> Option<Vec<u8>> {
    let mut pos = 0;
    while pos + 4 <= mkb.len() {
        let rec_type = mkb[pos];
        let rec_len = u32::from_be_bytes([0, mkb[pos + 1], mkb[pos + 2], mkb[pos + 3]]) as usize;
        if rec_len < 4 || pos + rec_len > mkb.len() { break; }

        if rec_type == 0x07 && rec_len > 4 {
            return Some(mkb[pos + 4..pos + rec_len].to_vec());
        }
        pos += rec_len;
    }
    None
}

/// Get MKB version from Type and Version Record (type 0x81).
pub fn mkb_version(mkb: &[u8]) -> Option<u32> {
    let mut pos = 0;
    while pos + 4 <= mkb.len() {
        let rec_type = mkb[pos];
        let rec_len = u32::from_be_bytes([0, mkb[pos + 1], mkb[pos + 2], mkb[pos + 3]]) as usize;
        if rec_len < 4 || pos + rec_len > mkb.len() { break; }

        if rec_type == 0x81 && rec_len >= 8 {
            return Some(u32::from_be_bytes([mkb[pos + 4], mkb[pos + 5], mkb[pos + 6], mkb[pos + 7]]));
        }
        pos += rec_len;
    }
    None
}

// ── AACS-G3 key derivation (subset-difference tree) ─────────────────────────

/// AACS-G3 seed constant.
const AESG3_SEED: [u8; 16] = [
    0x7B, 0x10, 0x3C, 0x5D, 0xCB, 0x08, 0xC4, 0xE5,
    0x1A, 0x27, 0xB0, 0x17, 0x99, 0x05, 0x3B, 0xD9,
];

/// AACS-G3: derive a subkey from a parent key.
/// seed[15] += inc, then AES-DEC(key, seed) XOR seed.
fn aesg3(key: &[u8; 16], inc: u8) -> [u8; 16] {
    let mut seed = AESG3_SEED;
    seed[15] = seed[15].wrapping_add(inc);
    let mut out = aes_ecb_decrypt(key, &seed);
    for i in 0..16 {
        out[i] ^= seed[i];
    }
    out
}

/// Compute v_mask from a UV value.
fn calc_v_mask(uv: u32) -> u32 {
    let mut v_mask: u32 = 0xFFFFFFFF;
    while (uv & !v_mask) == 0 && v_mask != 0 {
        v_mask <<= 1;
    }
    v_mask
}

/// Derive processing key from device key using subset-difference tree traversal.
fn calc_pk_from_dk(dk: &[u8; 16], uv: u32, v_mask: u32, dev_key_v_mask: u32) -> [u8; 16] {
    // Initial derivation: left_child = aesg3(dk, 0), pk = aesg3(dk, 1), right_child = aesg3(dk, 2)
    let mut left_child = aesg3(dk, 0);
    let mut pk = aesg3(dk, 1);
    let mut right_child = aesg3(dk, 2);
    let mut current_v_mask = dev_key_v_mask;

    while current_v_mask != v_mask {
        // Find the highest unset bit in current_v_mask
        let mut bit_pos: i32 = -1;
        for i in (0..32).rev() {
            if (current_v_mask & (1u32 << i)) == 0 {
                bit_pos = i as i32;
                break;
            }
        }

        let curr_key = if bit_pos < 0 || (uv & (1u32 << bit_pos as u32)) == 0 {
            left_child
        } else {
            right_child
        };

        left_child = aesg3(&curr_key, 0);
        pk = aesg3(&curr_key, 1);
        right_child = aesg3(&curr_key, 2);

        current_v_mask = ((current_v_mask as i32) >> 1) as u32;
    }

    pk
}

/// Derive Media Key from MKB using device keys (subset-difference tree).
pub fn derive_media_key_from_dk(
    mkb: &[u8],
    device_keys: &[DeviceKey],
) -> Option<[u8; 16]> {
    let mk_dv = mkb_find_mk_dv(mkb)?;
    let uvs = mkb_find_subdiff_records(mkb)?;
    let cvalues = mkb_find_cvalues(mkb)?;

    // Count UV entries
    let num_uvs = uvs.chunks(5).take_while(|c| c.len() == 5 && (c[0] & 0xC0) == 0).count();

    for dk in device_keys {
        let device_number = dk.node as u32;

        // Find applying subset-difference for this device
        for uvs_idx in 0..num_uvs {
            let p_uv = &uvs[1 + 5 * uvs_idx..];
            let u_mask_shift = uvs[5 * uvs_idx]; // byte before the UV value

            if u_mask_shift & 0xC0 != 0 {
                break; // device revoked
            }

            let uv = u32::from_be_bytes([p_uv[0], p_uv[1], p_uv[2], p_uv[3]]);
            if uv == 0 { continue; }

            let u_mask: u32 = 0xFFFFFFFF << u_mask_shift;
            let v_mask = calc_v_mask(uv);

            if ((device_number & u_mask) == (uv & u_mask)) &&
               ((device_number & v_mask) != (uv & v_mask))
            {
                // Found matching subset-difference — find the right device key
                let dev_key_v_mask = calc_v_mask(dk.uv);
                let dev_key_u_mask: u32 = 0xFFFFFFFF << dk.u_mask_shift;

                if u_mask == dev_key_u_mask &&
                   (uv & dev_key_v_mask) == (dk.uv & dev_key_v_mask)
                {
                    // Derive processing key via tree traversal
                    let pk = calc_pk_from_dk(&dk.key, uv, v_mask, dev_key_v_mask);

                    // Validate and derive media key
                    if uvs_idx < cvalues.len() / 16 {
                        let cv = &cvalues[uvs_idx * 16..(uvs_idx + 1) * 16];
                        if let Some(mk) = validate_processing_key(&pk, cv, &uvs[1 + uvs_idx * 5..], &mk_dv) {
                            return Some(mk);
                        }
                    }
                }
            }
        }
    }
    None
}

/// MKB disc structure format code.
const MKB_DISC_STRUCTURE_FORMAT: u8 = 0x83;
/// MKB pack buffer size.
const MKB_PACK_SIZE: usize = 32772;

/// Read MKB from drive via SCSI (REPORT DISC STRUCTURE format 0x83).
/// Returns the concatenated MKB data from all packs.
pub fn read_mkb_from_drive(session: &mut crate::drive::DriveSession) -> crate::error::Result<Vec<u8>> {
    use crate::scsi::{DataDirection, SCSI_READ_DISC_STRUCTURE};

    let cdb = [
        SCSI_READ_DISC_STRUCTURE, 0x01,
        0x00, 0x00, 0x00, 0x00,
        0x00, MKB_DISC_STRUCTURE_FORMAT,
        (MKB_PACK_SIZE >> 8) as u8, (MKB_PACK_SIZE & 0xFF) as u8,
        0x00, 0x00,
    ];
    let mut buf = vec![0u8; 32772];
    session.scsi_execute(&cdb, DataDirection::FromDevice, &mut buf, 10_000)?;

    let data_len = u16::from_be_bytes([buf[0], buf[1]]) as usize;
    if data_len < 2 { return Ok(Vec::new()); }
    let len = data_len - 2;
    let num_packs = buf[3] as usize;

    let mut mkb = Vec::with_capacity(32768 * num_packs.max(1));
    if len > 0 && len <= 32768 {
        mkb.extend_from_slice(&buf[4..4 + len]);
    }

    // Read remaining packs
    for pack in 1..num_packs {
        let mut cdb = [
            SCSI_READ_DISC_STRUCTURE, 0x01,
            0x00, 0x00, 0x00, 0x00,
            0x00, MKB_DISC_STRUCTURE_FORMAT,
            (MKB_PACK_SIZE >> 8) as u8, (MKB_PACK_SIZE & 0xFF) as u8,
            0x00, 0x00,
        ];
        // Pack number goes in address field
        cdb[2] = ((pack >> 24) & 0xFF) as u8;
        cdb[3] = ((pack >> 16) & 0xFF) as u8;
        cdb[4] = ((pack >> 8) & 0xFF) as u8;
        cdb[5] = (pack & 0xFF) as u8;

        let mut buf = vec![0u8; 32772];
        if session.scsi_execute(&cdb, DataDirection::FromDevice, &mut buf, 10_000).is_ok() {
            let len = u16::from_be_bytes([buf[0], buf[1]]) as usize;
            if len > 2 && len - 2 <= 32768 {
                mkb.extend_from_slice(&buf[4..4 + len - 2]);
            }
        }
    }

    Ok(mkb)
}

// ── Content Certificate parsing ─────────────────────────────────────────────

/// AACS Content Certificate — identifies disc AACS version and features.
#[derive(Debug)]
pub struct ContentCert {
    /// Bus encryption enabled flag
    pub bus_encryption: bool,
    /// Content Certificate ID (6 bytes)
    pub cc_id: [u8; 6],
    /// AACS version: false = AACS 1.0, true = AACS 2.0
    pub aacs2: bool,
}

/// Parse a Content Certificate (ContentXXX.cer) file.
pub fn parse_content_cert(data: &[u8]) -> Option<ContentCert> {
    if data.len() < 8 {
        return None;
    }

    // Content Certificate format:
    //   [0] certificate type (0x00 = AACS1, 0x01 = AACS2)
    //   [1] bus_encryption_enabled (bit 0)
    //   [2..8] cc_id (6 bytes)
    let aacs2 = data[0] != 0x00;
    let bus_encryption = (data[1] & 0x01) != 0;
    let mut cc_id = [0u8; 6];
    cc_id.copy_from_slice(&data[2..8]);

    Some(ContentCert {
        bus_encryption,
        cc_id,
        aacs2,
    })
}

// ── Full VUK resolution chain ───────────────────────────────────────────────

/// Result of resolving a disc's VUK.
#[derive(Debug)]
pub struct ResolvedKeys {
    /// Disc hash (SHA1 of Unit_Key_RO.inf)
    pub disc_hash: [u8; 20],
    /// Volume Unique Key
    pub vuk: [u8; 16],
    /// Decrypted unit keys (CPS unit number, key)
    pub unit_keys: Vec<(u32, [u8; 16])>,
    /// Title → CPS unit index mapping
    pub title_cps_unit: Vec<u16>,
    /// Whether AACS 2.0
    pub aacs2: bool,
    /// Whether bus encryption is enabled (from Content Certificate)
    pub bus_encryption: bool,
    /// Which resolution path succeeded (1=KEYDB, 2=KEYDB derived, 3=PK, 4=DK)
    pub key_source: u8,
}

/// Resolve all AACS keys for a disc given:
///   - Unit_Key_RO.inf raw data
///   - Content Certificate raw data (optional, for AACS version detection)
///   - Volume ID (from SCSI handshake)
///   - KEYDB
///
/// Tries in order:
///   1. Disc hash → KEYDB → VUK (fast path)
///   2. KEYDB media key + volume ID → VUK (if disc hash not in KEYDB but MK is)
///   3. MKB + processing keys → media key → VUK (full derivation)
pub fn resolve_keys(
    unit_key_ro_data: &[u8],
    content_cert_data: Option<&[u8]>,
    volume_id: &[u8; 16],
    keydb: &KeyDb,
    mkb_data: Option<&[u8]>,
) -> Option<ResolvedKeys> {
    // Detect AACS version
    let aacs2 = content_cert_data
        .and_then(|d| parse_content_cert(d))
        .map(|cc| cc.aacs2)
        .unwrap_or(false);

    let bus_encryption = content_cert_data
        .and_then(|d| parse_content_cert(d))
        .map(|cc| cc.bus_encryption)
        .unwrap_or(false);

    // Parse Unit_Key_RO.inf
    let uk_file = parse_unit_key_ro(unit_key_ro_data, aacs2)?;

    let hash_hex = disc_hash_hex(&uk_file.disc_hash);

    // Helper to build result
    let build = |vuk: [u8; 16], key_source: u8| -> ResolvedKeys {
        let unit_keys: Vec<(u32, [u8; 16])> = uk_file.encrypted_keys.iter()
            .map(|(num, enc_key)| (*num, decrypt_unit_key(&vuk, enc_key)))
            .collect();
        ResolvedKeys {
            disc_hash: uk_file.disc_hash,
            vuk,
            unit_keys,
            title_cps_unit: uk_file.title_cps_unit.clone(),
            aacs2,
            bus_encryption,
            key_source,
        }
    };

    // Path 1: Look up VUK by disc hash in KEYDB
    if let Some(entry) = keydb.find_disc(&hash_hex) {
        if let Some(vuk) = entry.vuk {
            return Some(build(vuk, 1));
        }
    }

    // Path 2: Find entry with matching VID → derive VUK from MK + VID
    for entry in keydb.disc_entries.values() {
        if let (Some(mk), Some(did)) = (entry.media_key, entry.disc_id) {
            if did == *volume_id {
                return Some(build(derive_vuk(&mk, volume_id), 2));
            }
        }
    }

    // Path 3: MKB + processing keys → media key → VUK
    if let Some(mkb) = mkb_data {
        if let Some(mk) = derive_media_key_from_pk(mkb, &keydb.processing_keys) {
            return Some(build(derive_vuk(&mk, volume_id), 3));
        }

        // Path 4: MKB + device keys → processing key → media key → VUK
        if let Some(mk) = derive_media_key_from_dk(mkb, &keydb.device_keys) {
            return Some(build(derive_vuk(&mk, volume_id), 4));
        }
    }

    None
}

// ── Content decryption ──────────────────────────────────────────────────────

/// Check if a 6144-byte aligned unit is encrypted (copy_permission_indicator bits).
pub fn is_unit_encrypted(unit: &[u8]) -> bool {
    unit.len() >= ALIGNED_UNIT_LEN && (unit[0] & 0xC0) != 0
}

/// Verify decrypted unit by checking TS sync bytes at expected offsets.
fn verify_ts(unit: &[u8]) -> bool {
    // In a 6144-byte unit, TS packets start at byte 0 with 4-byte TP_extra_header
    // then 188-byte TS packet, repeating every 192 bytes.
    // Sync byte 0x47 should appear at offset 4, 196, 388, ...
    let mut count = 0;
    let mut offset = 4;
    while offset < unit.len() {
        if unit[offset] == TS_SYNC {
            count += 1;
        }
        offset += TS_PACKET_LEN;
    }
    // Expect at least most packets to have sync bytes
    let total = (unit.len() - 4) / TS_PACKET_LEN + 1;
    count > total / 2
}

/// Decrypt one AACS aligned unit (6144 bytes) in-place.
/// Returns true if decryption succeeded (verified by TS sync bytes).
///
/// Algorithm:
/// 1. AES-128-ECB encrypt first 16 bytes with unit_key → derived
/// 2. XOR derived with original 16 bytes → unit_decrypt_key
/// 3. AES-128-CBC decrypt bytes 16..6143 with unit_decrypt_key and AACS IV
/// 4. Clear encryption flag bits
pub fn decrypt_unit(unit: &mut [u8], unit_key: &[u8; 16]) -> bool {
    if unit.len() < ALIGNED_UNIT_LEN {
        return false;
    }
    if !is_unit_encrypted(unit) {
        return true; // not encrypted
    }

    // Save original first 16 bytes (they're plaintext TP_extra_header)
    let mut header = [0u8; 16];
    header.copy_from_slice(&unit[..16]);

    // Step 1: Encrypt header with unit key to derive per-unit key
    let derived = aes_ecb_encrypt(unit_key, &header);

    // Step 2: XOR to get the actual decryption key
    let mut decrypt_key = [0u8; 16];
    for i in 0..16 {
        decrypt_key[i] = derived[i] ^ header[i];
    }

    // Step 3: Decrypt bytes 16..6143 with AES-CBC
    aes_cbc_decrypt(&decrypt_key, &mut unit[16..ALIGNED_UNIT_LEN]);

    // Step 4: Clear encryption flag
    unit[0] &= !0xC0;

    // Verify
    verify_ts(unit)
}

/// Decrypt one aligned unit trying multiple unit keys. Returns the key index that worked.
pub fn decrypt_unit_try_keys(unit: &mut [u8], unit_keys: &[[u8; 16]]) -> Option<usize> {
    if !is_unit_encrypted(unit) {
        return Some(0);
    }

    // Save original for retry
    let original = unit[..ALIGNED_UNIT_LEN].to_vec();

    for (i, key) in unit_keys.iter().enumerate() {
        unit[..ALIGNED_UNIT_LEN].copy_from_slice(&original);
        if decrypt_unit(unit, key) {
            return Some(i);
        }
    }

    // Restore original on failure
    unit[..ALIGNED_UNIT_LEN].copy_from_slice(&original);
    None
}

/// Remove bus encryption from an aligned unit (AACS 2.0 / UHD).
/// Bus encryption uses read_data_key, decrypting bytes 16..2047 of each 2048-byte sector.
pub fn decrypt_bus(unit: &mut [u8], read_data_key: &[u8; 16]) {
    for sector_start in (0..ALIGNED_UNIT_LEN).step_by(SECTOR_LEN) {
        if sector_start + SECTOR_LEN > unit.len() {
            break;
        }
        // First 16 bytes of each sector are plaintext
        aes_cbc_decrypt(read_data_key, &mut unit[sector_start + 16..sector_start + SECTOR_LEN]);
    }
}

/// Full decrypt of an aligned unit: bus decrypt (if needed) then AACS decrypt.
pub fn decrypt_unit_full(
    unit: &mut [u8],
    unit_key: &[u8; 16],
    read_data_key: Option<&[u8; 16]>,
) -> bool {
    if !is_unit_encrypted(unit) {
        return true;
    }
    if let Some(rdk) = read_data_key {
        decrypt_bus(unit, rdk);
    }
    decrypt_unit(unit, unit_key)
}

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

    /// Get KEYDB path from KEYDB_PATH environment variable. Returns None if not set or not found.
    fn keydb_path() -> Option<std::path::PathBuf> {
        let path = std::path::PathBuf::from(std::env::var("KEYDB_PATH").ok()?);
        if path.exists() { Some(path) } else { None }
    }

    #[test]
    fn test_parse_disc_entry() {
        let line = r#"0x1C620AB48AEA23F3440F1189D268F3D24F61C007 = DUNE_PART_TWO (Dune: Part Two) | D | 2024-04-02 | M | 0x252FB636E883529E119AB715F4EB1640 | I | 0xA13CBE2CE40565D104B53E768C700E30 | V | 0x1114360B10EE6EAC78AA4AC0B752EAEB | U | 1-0x9E5D1310337443E811A52EBBEAE0470F ; MKBv77"#;
        let entry = KeyDb::parse_disc_entry(line).unwrap();
        assert_eq!(entry.title, "Dune: Part Two");
        assert!(entry.media_key.is_some());
        assert!(entry.vuk.is_some());
        assert_eq!(entry.unit_keys.len(), 1);
        assert_eq!(entry.unit_keys[0].0, 1);
    }

    #[test]
    fn test_parse_device_key() {
        let line = "| DK | DEVICE_KEY 0x5FB86EF127C19C171E799F61C27BDC2A | DEVICE_NODE 0x0800 | KEY_UV 0x00000400 | KEY_U_MASK_SHIFT 0x17 ; MKBv01-MKBv48";
        let dk = KeyDb::parse_device_key(line).unwrap();
        assert_eq!(dk.node, 0x0800);
        assert_eq!(dk.u_mask_shift, 0x17);
    }

    #[test]
    fn test_parse_host_cert() {
        let line = "| HC | HOST_PRIV_KEY 0x909250D0C7FC2EE0F0383409D896993B723FA965 | HOST_CERT 0x0203005CFFFF800001C100003A5907E685E4CBA2A8CD5616665DFAA74421A14F6020D4CFC9847C23107697C39F9D109C8B2D5B93280499661AAE588AD3BF887C48DE144D48226ABC2C7ADAD0030893D1F3F1832B61B8D82D1FAFFF81 ; Revoked";
        let hc = KeyDb::parse_host_cert(line).unwrap();
        assert_eq!(hc.private_key[0], 0x90);
        assert_eq!(hc.certificate.len(), 92);
    }

    #[test]
    fn test_vuk_derivation() {
        // Civil War UHD: known MK, VID, VUK from KEYDB
        // MK = 15665F98..., VID (disc_id) = from entry, VUK = F96D7908...
        // VUK = AES-DEC(MK, VID) XOR VID
        let path = match keydb_path() { Some(p) => p, None => return };

        let db = KeyDb::load(&path).unwrap();

        // Find a disc with both MK, disc_id, and VUK so we can verify derivation
        let entry = db.disc_entries.values()
            .find(|e| e.media_key.is_some() && e.disc_id.is_some() && e.vuk.is_some())
            .expect("No disc with MK + VID + VUK");

        let mk = entry.media_key.unwrap();
        let vid = entry.disc_id.unwrap();
        let expected_vuk = entry.vuk.unwrap();

        let derived = derive_vuk(&mk, &vid);
        assert_eq!(derived, expected_vuk,
            "VUK derivation failed for disc: {} (hash {})", entry.title, entry.disc_hash);
        eprintln!("VUK derivation verified for: {}", entry.title);
    }

    #[test]
    fn test_aes_ecb_roundtrip() {
        let key = [0x15u8, 0x66, 0x5F, 0x98, 0x01, 0x02, 0x03, 0x04,
                   0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C];
        let plain = [0x41u8; 16];
        let enc = aes_ecb_encrypt(&key, &plain);
        let dec = aes_ecb_decrypt(&key, &enc);
        assert_eq!(dec, plain);
    }

    #[test]
    fn test_decrypt_unit_unencrypted() {
        // Unit with 0xC0 bits clear should pass through unchanged
        let mut unit = vec![0u8; ALIGNED_UNIT_LEN];
        unit[0] = 0x00; // not encrypted
        let key = [0u8; 16];
        assert!(decrypt_unit(&mut unit, &key));
    }

    #[test]
    fn test_aes_cbc_roundtrip() {
        let key = [0x11u8, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88,
                   0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF, 0x00];
        let original = vec![0x42u8; 128]; // 8 blocks
        let mut data = original.clone();

        // Encrypt with CBC manually (forward direction)
        fn aes_cbc_encrypt(key: &[u8; 16], data: &mut [u8]) {
            let cipher = Aes128::new(GenericArray::from_slice(key));
            let mut prev = super::AACS_IV;
            let num_blocks = data.len() / 16;
            for i in 0..num_blocks {
                let offset = i * 16;
                for j in 0..16 {
                    data[offset + j] ^= prev[j];
                }
                let mut block = GenericArray::clone_from_slice(&data[offset..offset + 16]);
                cipher.encrypt_block(&mut block);
                data[offset..offset + 16].copy_from_slice(&block);
                prev.copy_from_slice(&data[offset..offset + 16]);
            }
        }

        aes_cbc_encrypt(&key, &mut data);
        assert_ne!(data, original); // should be different after encrypt

        super::aes_cbc_decrypt(&key, &mut data);
        assert_eq!(data, original); // should match after roundtrip
    }

    #[test]
    fn test_decrypt_unit_synthetic() {
        // Build a fake 6144-byte aligned unit with known TS sync pattern,
        // encrypt it with the AACS algorithm, then decrypt and verify.
        let unit_key = [0xAAu8; 16];

        // Build plaintext unit with TS sync bytes every 192 bytes starting at offset 4
        let mut plain = vec![0u8; ALIGNED_UNIT_LEN];
        let mut offset = 4;
        while offset < ALIGNED_UNIT_LEN {
            plain[offset] = TS_SYNC;
            offset += TS_PACKET_LEN;
        }
        // Set encryption flag
        plain[0] |= 0xC0;

        // Now encrypt bytes 16..6143 using the AACS algorithm (reverse of decrypt)
        let header: [u8; 16] = plain[..16].try_into().unwrap();
        let derived = super::aes_ecb_encrypt(&unit_key, &header);
        let mut encrypt_key = [0u8; 16];
        for i in 0..16 {
            encrypt_key[i] = derived[i] ^ header[i];
        }

        // CBC encrypt bytes 16..6143
        let cipher = Aes128::new(GenericArray::from_slice(&encrypt_key));
        let mut prev = super::AACS_IV;
        let num_blocks = (ALIGNED_UNIT_LEN - 16) / 16;
        for i in 0..num_blocks {
            let off = 16 + i * 16;
            for j in 0..16 {
                plain[off + j] ^= prev[j];
            }
            let mut block = GenericArray::clone_from_slice(&plain[off..off + 16]);
            cipher.encrypt_block(&mut block);
            plain[off..off + 16].copy_from_slice(&block);
            prev.copy_from_slice(&plain[off..off + 16]);
        }

        // Now plain contains encrypted data. Decrypt it.
        let mut unit = plain;
        assert!(is_unit_encrypted(&unit));
        assert!(decrypt_unit(&mut unit, &unit_key));
        assert!(!is_unit_encrypted(&unit)); // flag should be cleared

        // Verify TS sync bytes
        let mut count = 0;
        let mut off = 4;
        while off < ALIGNED_UNIT_LEN {
            if unit[off] == TS_SYNC {
                count += 1;
            }
            off += TS_PACKET_LEN;
        }
        assert_eq!(count, (ALIGNED_UNIT_LEN - 4) / TS_PACKET_LEN + 1);
    }

    #[test]
    fn test_decrypt_unit_key_from_vuk() {
        // Test the full chain: VUK → decrypt encrypted unit key → unit key
        // Use a known disc from KEYDB that has both VUK and unit keys
        let path = match keydb_path() { Some(p) => p, None => return };

        let db = KeyDb::load(&path).unwrap();

        // Find a disc with VUK and unit keys
        let entry = db.disc_entries.values()
            .find(|e| e.vuk.is_some() && !e.unit_keys.is_empty())
            .expect("No disc with VUK + unit keys");

        eprintln!("Testing unit key decrypt for: {} ({})", entry.title, entry.disc_hash);
        eprintln!("  VUK: {:02X?}", entry.vuk.unwrap());
        for (num, key) in &entry.unit_keys {
            eprintln!("  Unit key {}: {:02X?}", num, key);
        }

        // The unit keys in KEYDB are already decrypted — we can verify the chain
        // by encrypting with VUK and then decrypting
        let vuk = entry.vuk.unwrap();
        for (num, expected_uk) in &entry.unit_keys {
            let encrypted = aes_ecb_encrypt(&vuk, expected_uk);
            let decrypted = decrypt_unit_key(&vuk, &encrypted);
            assert_eq!(&decrypted, expected_uk,
                "Unit key {} roundtrip failed for {}", num, entry.title);
        }
        eprintln!("  All {} unit key roundtrips passed", entry.unit_keys.len());
    }

    #[test]
    fn test_decrypt_real_unit() {
        // Try decrypting a real encrypted aligned unit from Civil War UHD
        // This disc is AACS 2.0 (BEE) so unit key alone won't work —
        // we need bus decryption first. But this verifies the pipeline.
        let unit_path = std::path::Path::new("/tmp/encrypted_unit.bin");
        if !unit_path.exists() { return; }

        let original = std::fs::read(unit_path).unwrap();
        assert_eq!(original.len(), ALIGNED_UNIT_LEN);
        assert!(is_unit_encrypted(&original), "Unit should be encrypted");

        let kp = match keydb_path() { Some(p) => p, None => return };
        let db = KeyDb::load(&kp).unwrap();

        // Civil War UHD entries
        let civil_war_entries: Vec<&DiscEntry> = db.disc_entries.values()
            .filter(|e| e.title.contains("CIVIL WAR") && !e.unit_keys.is_empty())
            .collect();

        eprintln!("Found {} Civil War entries with unit keys", civil_war_entries.len());

        // Try each entry's unit keys
        for entry in &civil_war_entries {
            let keys: Vec<[u8; 16]> = entry.unit_keys.iter().map(|(_, k)| *k).collect();
            let mut unit = original.clone();

            if let Some(idx) = decrypt_unit_try_keys(&mut unit, &keys) {
                eprintln!("SUCCESS: Decrypted with entry {} key {}", entry.disc_hash, idx);
                // Count TS sync bytes
                let ts = (0..32).filter(|&i| unit[4 + i * 192] == 0x47).count();
                eprintln!("  TS sync bytes: {}/32", ts);
                return;
            }
        }

        // Expected: none work because this is AACS 2.0 and needs bus decryption first
        eprintln!("No unit key worked (expected for AACS 2.0 BEE disc — needs read_data_key)");
    }

    #[test]
    fn test_parse_full_keydb() {
        let path = match keydb_path() { Some(p) => p, None => return }; // skip if not available

        let db = KeyDb::load(&path).unwrap();

        assert_eq!(db.device_keys.len(), 4);
        assert_eq!(db.processing_keys.len(), 3);
        assert!(db.host_cert.is_some());
        assert!(db.disc_entries.len() > 170000);

        // Look up Dune: Part Two
        let dune = db.disc_entries.values()
            .find(|e| e.title.contains("Dune: Part Two") && e.vuk.is_some())
            .expect("Dune: Part Two not found");
        assert!(dune.media_key.is_some());
        assert!(dune.vuk.is_some());
        assert!(!dune.unit_keys.is_empty());

        eprintln!("Parsed {} disc entries, {} DK, {} PK",
            db.disc_entries.len(), db.device_keys.len(), db.processing_keys.len());
    }

    #[test]
    fn test_disc_hash() {
        // SHA1 of a known byte sequence
        let data = b"test unit key ro inf data";
        let hash = disc_hash(data);
        assert_ne!(hash, [0u8; 20]);
        // Same input → same hash
        assert_eq!(hash, disc_hash(data));
    }

    #[test]
    fn test_disc_hash_hex() {
        let hash = [0x55, 0xBF, 0xD0, 0x51, 0xD1, 0xF8, 0x2C, 0xBB, 0x67, 0x76,
                    0x46, 0x3B, 0x6D, 0x70, 0x09, 0x12, 0x47, 0xBA, 0x61, 0x5D];
        let hex = disc_hash_hex(&hash);
        assert_eq!(hex, "0x55BFD051D1F82CBB6776463B6D70091247BA615D");
    }

    #[test]
    fn test_parse_unit_key_ro_synthetic() {
        // Build a synthetic Unit_Key_RO.inf
        // Header: uk_pos at offset 0 (BE32), points to key storage
        // Keys at uk_pos + 48 (16 bytes each, 48-byte stride for AACS 1.0)
        let mut data = vec![0u8; 256];

        // uk_pos = 0x60 (96)
        data[0] = 0x00; data[1] = 0x00; data[2] = 0x00; data[3] = 0x60;

        // Header fields at 16-18
        data[16] = 1; // app_type = BD-ROM
        data[17] = 1; // num_bdmv_dir
        data[18] = 0; // no SKB

        // Title mapping at 20-25
        data[20] = 0; data[21] = 1; // first_play = CPS unit 1
        data[22] = 0; data[23] = 1; // top_menu = CPS unit 1
        data[24] = 0; data[25] = 1; // num_titles = 1
        // Title 0 entry: 2 bytes pad + CPS unit
        data[28] = 0; data[29] = 1; // CPS unit 1

        // Key storage at offset 0x60
        let uk_pos = 0x60usize;
        data[uk_pos] = 0; data[uk_pos + 1] = 2; // 2 unit keys

        // Key 1 at uk_pos + 48
        let key1_pos = uk_pos + 48;
        for i in 0..16 { data[key1_pos + i] = 0xAA; }

        // Key 2 at uk_pos + 48 + 48
        let key2_pos = key1_pos + 48;
        for i in 0..16 { data[key2_pos + i] = 0xBB; }

        let parsed = parse_unit_key_ro(&data, false).unwrap();
        assert_eq!(parsed.app_type, 1);
        assert_eq!(parsed.num_bdmv_dir, 1);
        assert!(!parsed.aacs2);
        assert_eq!(parsed.encrypted_keys.len(), 2);
        assert_eq!(parsed.encrypted_keys[0].0, 1); // CPS unit 1
        assert_eq!(parsed.encrypted_keys[0].1, [0xAA; 16]);
        assert_eq!(parsed.encrypted_keys[1].0, 2); // CPS unit 2
        assert_eq!(parsed.encrypted_keys[1].1, [0xBB; 16]);
    }

    #[test]
    fn test_mkb_version_parse() {
        // Synthetic MKB with Type and Version record (0x81)
        let mut mkb = vec![0u8; 32];
        // Record: type=0x81, length=12 (BE24)
        mkb[0] = 0x81;
        mkb[1] = 0x00; mkb[2] = 0x00; mkb[3] = 0x0C;
        // Version = 77
        mkb[4] = 0x00; mkb[5] = 0x00; mkb[6] = 0x00; mkb[7] = 77;

        assert_eq!(mkb_version(&mkb), Some(77));
    }

    #[test]
    fn test_resolve_keys_vuk_path() {
        // Test the full resolve chain using VUK path
        let path = match keydb_path() { Some(p) => p, None => return };
        let db = KeyDb::load(&path).unwrap();

        // Find V for Vendetta BD — has VUK and unit keys
        // hash: 0x55BFD051D1F82CBB6776463B6D70091247BA615D
        let entry = db.find_disc("0x55BFD051D1F82CBB6776463B6D70091247BA615D");
        if entry.is_none() { return; }
        let entry = entry.unwrap();
        let vuk = entry.vuk.unwrap();
        let vid = entry.disc_id.unwrap();

        // We need the actual Unit_Key_RO.inf from the disc to compute disc hash.
        // Since we don't have it, we can at least test that the KEYDB lookup
        // works with a known hash.
        let hash_hex = "0x55BFD051D1F82CBB6776463B6D70091247BA615D";
        let found = db.find_disc(hash_hex);
        assert!(found.is_some());
        assert_eq!(found.unwrap().vuk, Some(vuk));

        // Verify VUK derivation if we have MK + VID
        if let Some(mk) = entry.media_key {
            let derived = derive_vuk(&mk, &vid);
            assert_eq!(derived, vuk, "VUK derivation mismatch for V for Vendetta");
            eprintln!("V for Vendetta VUK derivation verified");
        }
    }

    #[test]
    fn test_content_cert_parse() {
        // AACS 1.0 cert
        let mut data = vec![0u8; 16];
        data[0] = 0x00; // AACS 1.0
        data[1] = 0x00; // no bus encryption
        let cc = parse_content_cert(&data).unwrap();
        assert!(!cc.aacs2);
        assert!(!cc.bus_encryption);

        // AACS 2.0 with bus encryption
        data[0] = 0x01; // AACS 2.0
        data[1] = 0x01; // bus encryption enabled
        let cc = parse_content_cert(&data).unwrap();
        assert!(cc.aacs2);
        assert!(cc.bus_encryption);
    }
}