sharkyflac 0.2.0

// TODO: rewrite parsers to use `BitReader` properly

use bitflags::bitflags;
use byteorder::{BE, LE, ReadBytesExt, WriteBytesExt};
use std::io;
use std::io::{Read, Seek};
use std::num::{NonZero, NonZeroU32};
use std::ops::Deref;
use strum::Display;

use crate::ascii_str::{self, ArrayList, AsciiArray, AsciiStr};
use crate::bit_io::{BitRead, BitReader, BitWrite};
use crate::bits::Bitset;
use crate::num::*;
use crate::{Decode, Encode};

#[derive(Debug, thiserror::Error)]
pub enum Error {
    #[error("IO: {0}")]
    Io(#[from] io::Error),

    #[error("The metadata block type is 127, which is forbidden")]
    ForbiddenBlockType,

    #[error("Block size {1} is invalid for block type {0}")]
    InvalidBlockSize(BlockType, U24),

    #[error("A reserved block type was used")]
    ReservedBlockType,

    #[error("The picture's type is reserved")]
    ReservedPictureType,

    #[error(
        "{0} is not contained within the valid range `4..=32`: The streaminfo block indicated an invalid bits_per_channel"
    )]
    InvalidBitsPerSample(U5),

    #[error("{0} is an invalid maximum block size")]
    InvalidMaxBlockSize(u16),

    #[error("{0} is an invalid minimum block size")]
    InvalidMinBlockSize(u16),

    #[error("{0}")]
    InvalidUtf8String(#[from] std::string::FromUtf8Error),

    #[error("{0}")]
    InvalidUtf8(#[from] std::str::Utf8Error),

    #[error("{0}")]
    ParseInt(#[from] std::num::ParseIntError),

    #[error("Invalid vorbis comment")]
    InvalidVorbisComment,

    #[error("Vorbis comment key contains invalid ASCII")]
    CommentKeyNotAscii,

    #[error("Invalid cuesheet")]
    InvalidCuesheet,

    #[error("Invalid cuesheet track")]
    InvalidCuesheetTrack,

    #[error("Invalid cuesheet track index points")]
    InvalidCuesheetIndexPoints,

    #[error("Invalid cuesheet track index point")]
    InvalidCuesheetIndexPoint,

    #[error("Invalid channel mask")]
    InvalidChannelMask,

    #[error("Non-ASCII ISRC in cuesheet track")]
    NonAscii(#[from] ascii_str::NonAscii),

    #[error("The lengths coded within the metadata block exceed the block length")]
    BlockExceededLength,

    #[error("The vendor string is too long for a vorbis comment block")]
    VendorTooLong,

    #[error("The number of user comments is too long for a vorbis comment block")]
    UserCommentsTooLong,

    #[error("The user comment string is too long for a vorbis comment block")]
    UserComment,

    #[error("There are too many cuesheet tracks (must be less than u8::MAX)")]
    CuesheetTrackCount,

    #[error("Picture description is too large (was > u32::MAX)")]
    OverlongDescription,

    #[error("Picture data is too large (was > u32::MAX)")]
    OverlongPictureData,
}

/// See <https://www.ietf.org/rfc/rfc9639.html#section-8.1-1>
#[derive(Debug, Clone, Copy, Eq, Display, PartialEq)]
#[repr(u8)]
pub enum BlockType {
    Streaminfo = 0,
    Padding,
    Application,
    SeekTable,
    VorbisComment,
    Cuesheet,
    Picture,
}

impl TryFrom<u8> for BlockType {
    type Error = Error;

    #[inline]
    fn try_from(value: u8) -> Result<Self, Self::Error> {
        Ok(match value {
            0 => Self::Streaminfo,
            1 => Self::Padding,
            2 => Self::Application,
            3 => Self::SeekTable,
            4 => Self::VorbisComment,
            5 => Self::Cuesheet,
            6 => Self::Picture,
            127 => return Err(Error::ForbiddenBlockType),
            _ => return Err(Error::ReservedBlockType),
        })
    }
}

impl From<BlockType> for u8 {
    #[inline]
    fn from(value: BlockType) -> Self {
        match value {
            BlockType::Streaminfo => 0,
            BlockType::Padding => 1,
            BlockType::Application => 2,
            BlockType::SeekTable => 3,
            BlockType::VorbisComment => 4,
            BlockType::Cuesheet => 5,
            BlockType::Picture => 6,
        }
    }
}

impl Encode for BlockType {
    type Error = Error;

    fn encode<W: BitWrite>(&self, writer: &mut W, _opt: ()) -> Result<(), Self::Error> {
        writer.write_bits(u8::from(*self).into(), 7)?;
        Ok(())
    }
}

#[derive(Debug, Clone, Copy)]
pub struct BlockHeader {
    /// Whether this is the final metadata block
    pub is_final: bool,
    pub kind:     BlockType,
    /// The size of the metadata block in bytes
    pub size:     U24,
}

impl BlockHeader {
    /// Get the metadata block type
    #[inline]
    pub fn block_type_num_from_u8(byte: u8) -> Result<BlockType, Error> {
        BlockType::try_from(byte.get_bit_range_msb(1, 7))
    }
}

impl Decode<()> for BlockHeader {
    type Error = Error;

    fn decode<R: BitRead + Seek>(reader: &mut R, _opt: ()) -> Result<Self, Error> {
        let kind = reader.read_u8()?;
        let size = U24::new(reader.read_u24::<BE>()?).expect("this is a valid u24");

        let is_final = kind.get_bit_msb(0);
        let kind = Self::block_type_num_from_u8(kind)?;

        Ok(Self {
            is_final,
            kind,
            size,
        })
    }
}

impl Encode for BlockHeader {
    type Error = Error;

    fn encode<W: BitWrite>(&self, writer: &mut W, _opt: ()) -> Result<(), Self::Error> {
        debug_assert!(writer.is_byte_aligned());

        writer.write_bit(self.is_final)?;
        self.kind.encode(writer, ())?;
        writer.write_bits(self.size.inner().into(), 24)?;

        debug_assert!(writer.is_byte_aligned());
        Ok(())
    }
}

#[derive(Clone)]
pub struct ReservedData(pub Vec<u8>);

impl std::fmt::Debug for ReservedData {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("ReservedData").finish_non_exhaustive()
    }
}

#[derive(Debug, Clone)]
pub enum BlockData {
    Streaminfo(Streaminfo),
    /// Padding hasn't any data.
    Padding,
    Application(Application),
    SeekTable(SeekTable),
    VorbisComment(VorbisComment),
    Cuesheet(Cuesheet),
    Picture(Picture),
}

#[derive(Debug)]
pub struct Block {
    pub header: BlockHeader,
    pub data:   BlockData,
}

impl Decode<()> for Block {
    type Error = Error;

    fn decode<R: BitRead + Seek>(reader: &mut R, _opt: ()) -> Result<Self, Error> {
        let header = BlockHeader::decode(reader, ())?;

        let invalid_block_size = Err(Error::InvalidBlockSize(header.kind, header.size));

        let data = match header.kind {
            // error states
            BlockType::Streaminfo if header.size != 34 => return invalid_block_size,
            BlockType::VorbisComment if header.size < 8 => return invalid_block_size,
            BlockType::Cuesheet if header.size < 432 => return invalid_block_size,
            BlockType::Picture if header.size < 32 => return invalid_block_size,
            BlockType::Padding if header.size == 0 => BlockData::Padding,

            BlockType::Padding => {
                reader.seek_relative(i64::from(header.size.inner()))?;
                BlockData::Padding
            }

            BlockType::Streaminfo => BlockData::Streaminfo(Streaminfo::decode(reader, ())?),
            BlockType::Application => {
                BlockData::Application(Application::decode(reader, header.size)?)
            }
            BlockType::SeekTable => BlockData::SeekTable(SeekTable::decode(reader, header.size)?),
            BlockType::VorbisComment => {
                BlockData::VorbisComment(VorbisComment::decode(reader, ())?)
            }
            BlockType::Cuesheet => BlockData::Cuesheet(Cuesheet::decode(reader, ())?),
            BlockType::Picture => BlockData::Picture(Picture::decode(reader, header.size.inner())?),
        };

        Ok(Self { header, data })
    }
}

impl Encode for Block {
    type Error = Error;

    fn encode<W: BitWrite>(&self, writer: &mut W, _opt: ()) -> Result<(), Self::Error> {
        self.header.encode(writer, ())?;

        let invalid_block_size = Err(Error::InvalidBlockSize(self.header.kind, self.header.size));
        match &self.data {
            // error states
            BlockData::Streaminfo(_) if self.header.size != 34 => return invalid_block_size,
            BlockData::VorbisComment(_) if self.header.size < 8 => return invalid_block_size,
            BlockData::Cuesheet(_) if self.header.size < 432 => return invalid_block_size,
            BlockData::Picture(_) if self.header.size < 32 => return invalid_block_size,

            BlockData::Padding => {
                for _ in 0..self.header.size.inner() {
                    writer.write_u8(0)?;
                }
            }
            BlockData::Streaminfo(d) => d.encode(writer, ())?,
            BlockData::Application(d) => d.encode(writer, ())?,
            BlockData::SeekTable(d) => d.encode(writer, ())?,
            BlockData::VorbisComment(d) => d.encode(writer, ())?,
            BlockData::Cuesheet(d) => d.encode(writer, ())?,
            BlockData::Picture(d) => d.encode(writer, ())?,
        }

        Ok(())
    }
}

/// Iteratively read [`Block`]s.
pub struct BlockIter<'a, R: Read + Seek> {
    reader: &'a mut BitReader<R>,
    ended:  bool,
}

impl<'a, R: Read + Seek> BlockIter<'a, R> {
    pub fn new(reader: &'a mut BitReader<R>) -> Self {
        Self {
            reader,
            ended: false,
        }
    }
}

impl<R: Read + Seek> Iterator for BlockIter<'_, R> {
    type Item = Result<Block, Error>;

    /// Parse the next [`Block`]. In the event of an error, this will
    /// return that error and return [`None`] on any subsequent calls.
    fn next(&mut self) -> Option<Self::Item> {
        if self.ended {
            return None;
        }

        match Block::decode(self.reader, ()) {
            Err(e) => {
                self.ended = true;
                Some(Err(e))
            }
            Ok(block) => {
                if block.header.is_final {
                    self.ended = true;
                }

                Some(Ok(block))
            }
        }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct Streaminfo {
    /// The minimum block size (in samples) used in the stream, excluding the
    /// last block.
    pub min_block_size: u16,

    /// The maximum block size (in samples) used in the stream.
    pub max_block_size: u16,

    /// The minimum frame size (in bytes) used in the stream. A value of `0`
    /// signifies that the value is not known.
    pub min_frame_size: U24,

    // The maximum frame size (in bytes) used in the stream. A value of `0` signifies that the
    // value is not known.
    pub max_frame_size: U24,

    /// Sample rate in Hz.
    pub sample_rate: U20,

    /// (number of channels) - 1. FLAC supports from `1` to `8` channels. Use
    /// [`Streaminfo::num_channels()`] to get the actual value.
    pub num_channels: U3,

    /// Bits per sample - 1. FLAC supports from `4` to `32` bits per sample. Use
    /// [`Streaminfo::bits_per_sample()`] to get the actual value.
    pub bits_per_sample: U5,

    /// Total number of *interchannel* samples in the stream. A value of `0`
    /// here means the number of total samples is unknown.
    pub num_samples: Option<NonZeroU36>,

    /// MD5 checksum of the unencoded audio data. This allows the decoder to
    /// determine if an error exists in the audio data even when, despite the
    /// error, the bitstream itself is valid. A value of [`None`] signifies that
    /// the value is not known.
    pub md5sum: Option<NonZero<u128>>,
}

impl Streaminfo {
    pub const LARGEST_POSSIBLE_BLOCK_SIZE: u16 = u16::MAX;

    #[inline]
    pub const fn num_channels(&self) -> usize {
        self.num_channels.inner() as usize + 1
    }

    #[inline]
    pub const fn bits_per_sample(&self) -> u8 {
        self.bits_per_sample.inner() + 1
    }
}

impl Decode<()> for Streaminfo {
    type Error = Error;

    fn decode<R: BitRead + Seek>(reader: &mut R, _opt: ()) -> Result<Self, Self::Error> {
        // https://www.ietf.org/rfc/rfc9639.html#name-streaminfo\

        let min_block_size = reader.read_u16::<BE>()?;
        let max_block_size = reader.read_u16::<BE>()?;
        let min_frame_size = U24::new(reader.read_u24::<BE>()?).expect("Should be valid u24");
        let max_frame_size = U24::new(reader.read_u24::<BE>()?).expect("Should be valid u24");
        let (sample_rate, num_channels, bits_per_sample, num_samples) = {
            let bytes = reader.read_u64::<BE>()?;
            let sample_rate =
                U20::new(bytes.get_bit_range_msb(0, 20) as u32).expect("Should be a valid u20");
            let num_channels =
                U3::new(bytes.get_bit_range_msb(20, 3) as u8).expect("Should be a valid u3");
            let bits_per_sample =
                U5::new(bytes.get_bit_range_msb(23, 5) as u8).expect("Should be a valid u5");
            let num_samples = NonZeroU36::new(
                U36::new(bytes.get_bit_range_msb(28, 36)).expect("Should be a valid u36"),
            );

            (sample_rate, num_channels, bits_per_sample, num_samples)
        };
        let md5sum = NonZero::new(reader.read_u128::<BE>()?);

        if min_block_size < 16 {
            return Err(Error::InvalidMinBlockSize(min_block_size));
        }
        if max_block_size < 16 {
            return Err(Error::InvalidMaxBlockSize(max_block_size));
        }
        if !(4..=32).contains(&bits_per_sample.inner()) {
            return Err(Error::InvalidBitsPerSample(bits_per_sample));
        }

        Ok(Self {
            min_block_size,
            max_block_size,
            min_frame_size,
            max_frame_size,
            sample_rate,
            num_channels,
            bits_per_sample,
            num_samples,
            md5sum,
        })
    }
}

impl Encode for Streaminfo {
    type Error = Error;

    fn encode<W: BitWrite>(&self, writer: &mut W, _opt: ()) -> Result<(), Self::Error> {
        debug_assert!(writer.is_byte_aligned());

        writer.write_u16::<BE>(self.min_block_size)?;
        writer.write_u16::<BE>(self.max_block_size)?;

        writer.write_uint::<BE>(self.min_frame_size.inner().into(), 3)?;
        writer.write_uint::<BE>(self.max_frame_size.inner().into(), 3)?;

        writer.write_bits(self.sample_rate.inner().into(), 20)?;
        writer.write_bits(self.num_channels.inner().into(), 3)?;
        writer.write_bits(self.bits_per_sample.inner().into(), 5)?;
        writer.write_bits(
            self.num_samples
                .map_or_else(Default::default, |x| x.get().inner()),
            36,
        )?;
        writer.write_u128::<BE>(
            self.md5sum
                .map_or_else(u128::default, std::num::NonZero::get),
        )?;

        debug_assert!(writer.is_byte_aligned());
        Ok(())
    }
}

#[derive(Debug, Clone)]
pub struct Application {
    /// A registered application ID.
    ///
    /// Application IDs are registered in the [IANA "FLAC Application Metadata
    /// Block IDs registry"](https://www.iana.org/assignments/flac/flac.xhtml).
    pub id: u32,

    /// This is `MetadataBlock::size() - 4` bytes in length and is big-endian.
    pub data: Vec<u8>,
}

impl Decode<U24> for Application {
    type Error = Error;

    fn decode<R: BitRead + Seek>(reader: &mut R, block_size: U24) -> Result<Self, Self::Error> {
        let mut data = vec![0u8; block_size.inner().saturating_sub(4) as usize];
        let id = reader.read_u32::<BE>()?;
        reader.read_exact(&mut data)?;

        Ok(Self { id, data })
    }
}

impl Encode for Application {
    type Error = Error;

    fn encode<W: BitWrite>(&self, writer: &mut W, _opt: ()) -> Result<(), Self::Error> {
        debug_assert!(writer.is_byte_aligned());
        writer.write_u32::<BE>(self.id)?;
        writer.write_all(&self.data)?;
        Ok(())
    }
}

/// [`SeekPoint`]s are sorted in ascending order by sample number and have
/// unique sample numbers. All placehoder points occur at the end of the table.
#[derive(Debug, Clone)]
pub struct SeekTable(pub Vec<SeekPoint>);

impl Decode<U24> for SeekTable {
    type Error = Error;

    fn decode<R: BitRead + Seek>(reader: &mut R, block_size: U24) -> Result<Self, Error> {
        let n_seek_points = block_size.inner() / 18;

        let mut seek_points = Vec::with_capacity(n_seek_points as usize);
        for _ in 0..n_seek_points {
            seek_points.push(SeekPoint::decode(reader, ())?);
        }

        Ok(Self(seek_points))
    }
}

impl Encode for SeekTable {
    type Error = Error;

    fn encode<W: BitWrite>(&self, writer: &mut W, _opt: ()) -> Result<(), Self::Error> {
        for seek_point in &self.0 {
            seek_point.encode(writer, ())?;
        }

        Ok(())
    }
}

/// ## Notes
/// - For placeholder points, the second and third field values are undefined.
/// - The sample offsets are those of an unmuxed FLAC stream. The offsets MUST
///   NOT be updated on muxing to reflect the new offsets of FLAC frames in a
///   container.
#[derive(Debug, Clone, Copy)]
pub struct SeekPoint {
    /// Sample number of the first sample in the target frame or [`u64::MAX`]
    /// for a placeholder point.
    pub sample_idx:   u64,
    /// Offset (in bytes) from the first byte of the first frame header to the
    /// first byte of the target frame's header.
    pub offset:       u64,
    /// Number of samples in the target frame.
    pub sample_count: u16,
}

impl SeekPoint {
    pub const fn is_placeholder(self) -> bool {
        self.sample_idx == u64::MAX
    }
}

impl Decode<()> for SeekPoint {
    type Error = Error;

    fn decode<R: BitRead + Seek>(reader: &mut R, _opt: ()) -> Result<Self, Error> {
        let sample_idx = reader.read_u64::<BE>()?;
        let offset = reader.read_u64::<BE>()?;
        let sample_count = reader.read_u16::<BE>()?;

        Ok(Self {
            sample_idx,
            offset,
            sample_count,
        })
    }
}

impl Encode for SeekPoint {
    type Error = Error;

    fn encode<W: BitWrite>(&self, writer: &mut W, _opt: ()) -> Result<(), Self::Error> {
        writer.write_u64::<BE>(self.sample_idx)?;
        writer.write_u64::<BE>(self.offset)?;
        writer.write_u16::<BE>(self.sample_count)?;
        Ok(())
    }
}

bitflags! {
    /// The channel mask indicates which channels are present. The flags *only*
    /// signal which channels are present, not in which order, so if a file to be
    /// encoded has channels that are ordered differently, they have to be
    /// reordered.
    #[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
    pub struct ChannelMask: u32 {
        const FRONT_LEFT = 0x1;
        const FRONT_RIGHT = 0x2;
        const FRONT_CENTER = 0x4;
        const LOW_FREQUENCY_EFFECTS = 0x8;
        const BACK_LEFT = 0x10;
        const BACK_RIGHT = 0x20;
        const FRONT_LEFT_OF_CENTER = 0x40;
        const FRONT_RIGHT_OF_CENTER = 0x80;
        const BACK_CENTER = 0x100;
        const SIDE_LEFT = 0x200;
        const SIDE_RIGHT = 0x400;
        const TOP_CENTER = 0x800;
        const TOP_FRONT_LEFT = 0x1000;
        const TOP_FRONT_CENTER = 0x2000;
        const TOP_FRONT_RIGHT = 0x4000;
        const TOP_REAR_LEFT = 0x8000;
        const TOP_REAR_CENTER = 0x10_000;
        const TOP_REAR_RIGHT = 0x20_000;
    }
}

impl ChannelMask {
    /// Parse a [`ChannelMask`] from a hexadecimal string.
    pub fn from_hex(hex: &str) -> Result<Self, std::num::ParseIntError> {
        Ok(Self::from_bits_truncate(u32::from_str_radix(hex, 16)?))
    }
}

#[derive(Debug, Clone)]
#[must_use]
pub struct VorbisComment {
    pub vendor:            String,
    pub user_comment_list: Vec<VorbisUserComment>,
}

impl VorbisComment {
    pub fn get_channel_mask(&self) -> Option<Result<ChannelMask, Error>> {
        self.user_comment_list
            .iter()
            .find(|c| c.key.as_str() == "WAVEFORMATEXTENSIBLE_CHANNEL_MASK")
            .map(|c| {
                // skip the `0x` prefix
                let value = c.value.get(2..).ok_or(Error::InvalidChannelMask);
                value.and_then(|x| ChannelMask::from_hex(x).map_err(Error::from))
            })
    }
}

impl Decode<()> for VorbisComment {
    type Error = Error;

    // NOTE: Vorbis comments are Little Endian!
    // See: https://xiph.org/vorbis/doc/v-comment.html
    fn decode<R: BitRead + Seek>(reader: &mut R, _opt: ()) -> Result<Self, Error> {
        let vendor_length = reader.read_u32::<LE>()?;
        let vendor = {
            let mut buf = vec![0u8; vendor_length as usize];
            reader.read_exact(&mut buf)?;
            String::from_utf8(buf)?
        };

        let user_comment_count = reader.read_u32::<LE>()?;
        let mut user_comment_list = Vec::with_capacity(user_comment_count as usize);

        for _ in 0..user_comment_count {
            // TODO: perhaps ignore invalid fields? Perhaps have this behavior be
            // configurable.
            user_comment_list.push(VorbisUserComment::decode(reader, ())?);
        }

        Ok(Self {
            vendor,
            user_comment_list,
        })
    }
}

impl Encode for VorbisComment {
    type Error = Error;

    fn encode<W: BitWrite>(&self, writer: &mut W, _opt: ()) -> Result<(), Self::Error> {
        debug_assert!(writer.is_byte_aligned());

        writer.write_u32::<LE>(
            self.vendor
                .len()
                .try_into()
                .map_err(|_| Error::VendorTooLong)?,
        )?;
        writer.write_all(self.vendor.as_bytes())?;

        writer.write_u32::<LE>(
            self.user_comment_list
                .len()
                .try_into()
                .map_err(|_| Error::UserCommentsTooLong)?,
        )?;

        for comment in &self.user_comment_list {
            comment.encode(writer, ())?;
        }

        Ok(())
    }
}

#[derive(Debug, Clone)]
pub struct VorbisUserComment {
    pub key:   Box<AsciiStr>,
    pub value: String,
}

impl VorbisUserComment {
    pub fn new(key: &AsciiStr, value: impl Into<String>) -> Option<Self> {
        let key: Box<_> = key.into();
        let value = value.into();

        Self::key_is_valid(&key).then_some(Self { key, value })
    }

    /// `key` can contain all printable ASCII characters except `=`.
    #[inline]
    pub fn key_is_valid(key: &AsciiStr) -> bool {
        key.bytes().all(|byte| byte != b'=')
    }
}

impl Decode<()> for VorbisUserComment {
    type Error = Error;

    // NOTE: Vorbis comments are Little Endian!
    // See: https://xiph.org/vorbis/doc/v-comment.html
    fn decode<R: BitRead + Seek>(reader: &mut R, _opt: ()) -> Result<Self, Error> {
        let length = reader.read_u32::<LE>()?;

        let mut buf = vec![0u8; length as usize];
        reader.read_exact(&mut buf)?;

        let (key, value) = buf
            .iter()
            .position(|&x| x == b'=')
            .map(|pos| buf.split_at(pos))
            .map(|(key, value)| (key, &value[1..]))
            .ok_or(Error::InvalidVorbisComment)?;
        let key = Box::from(AsciiStr::from_bytes(key).ok_or(Error::CommentKeyNotAscii)?);
        let value = str::from_utf8(value)?.to_string();

        Ok(Self { key, value })
    }
}

impl Encode for VorbisUserComment {
    type Error = Error;

    fn encode<W: BitWrite>(&self, writer: &mut W, _opt: ()) -> Result<(), Self::Error> {
        let length: u32 = (self.key.len() + self.value.len() + 1)
            .try_into()
            .map_err(|_| Error::VendorTooLong)?;

        writer.write_u32::<LE>(length)?;

        writer.write_all(self.key.as_bytes())?;
        writer.write_u8(b'=')?;
        writer.write_all(self.value.as_bytes())?;

        Ok(())
    }
}

#[derive(Debug, Clone)]
pub struct Cuesheet {
    /// Media catalog number in ASCII printable characters (`0x20..=0x7E`). If
    /// the media catalog number is less than 128 bytes long, it is right-padded
    /// with `0x00` bytes.
    pub media_catalog_number: AsciiArray<128>,

    /// Number of lead-in samples.
    ///
    /// The number of lead-in samples has meaning only for CD-DA cuesheets; for
    /// other uses, it should be 0.
    pub lead_in_samples: u64,

    /// The cuesheet corresponds to a CD-DA.
    pub is_cdda: bool,

    // u(7+258*8) 	Reserved. All bits MUST be set to zero.
    pub tracks: Vec<CuesheetTrack>,
}

impl Cuesheet {
    #[inline]
    pub const fn is_valid(&self) -> bool {
        if let Some(x) = self.tracks.as_slice().last() {
            x.is_lead_out(self.is_cdda)
        } else {
            false
        }
    }
}

impl Decode<()> for Cuesheet {
    type Error = Error;

    fn decode<R: BitRead + Seek>(reader: &mut R, _opt: ()) -> Result<Self, Error> {
        let media_catalog_number = {
            let mut n = [0u8; 128];
            reader.read_exact(&mut n)?;
            let mut n = AsciiArray::try_from(n)?;
            // If the media catalog number is less than 128 bytes long, it is right-padded
            // with 0x00 bytes
            n.rtrim(b"\0");

            n
        };

        let lead_in_samples = reader.read_u64::<BE>()?;
        let is_cdda = {
            // NOTE: there are 7 reserved bits after the cdda bool.
            let cdda = reader.read_u8()?;
            cdda.get_bit_msb(0)
        };

        // NOTE: There are 258 reserved bytes after `is_cdda`
        reader.seek_relative(258)?;

        let track_count = reader.read_u8()?;

        let mut tracks = Vec::with_capacity(track_count.into());
        for _ in 0..track_count {
            tracks.push(CuesheetTrack::decode(reader, is_cdda)?);
        }

        let cuesheet = Self {
            media_catalog_number,
            lead_in_samples,
            is_cdda,
            tracks,
        };

        cuesheet
            .is_valid()
            .then_some(cuesheet)
            .ok_or(Error::InvalidCuesheet)
    }
}

impl Encode for Cuesheet {
    type Error = Error;

    fn encode<W: BitWrite>(&self, writer: &mut W, _opt: ()) -> Result<(), Self::Error> {
        let mut cat_num = self.media_catalog_number;
        cat_num.fill_rest(0u8);

        writer.write_all(&cat_num)?;
        writer.write_u64::<BE>(self.lead_in_samples)?;
        writer.write_bit(self.is_cdda)?;

        // reserved
        writer.flush_bits()?;
        writer.write_all(&[0u8; 258])?;

        writer.write_u8(
            self.tracks
                .len()
                .try_into()
                .map_err(|_| Error::CuesheetTrackCount)?,
        )?;

        for track in &self.tracks {
            track.encode(writer, self.is_cdda)?;
        }

        Ok(())
    }
}

#[derive(Debug, Clone, PartialEq)]
pub struct CuesheetTrack {
    /// Track offset of the first index point in samples, relative to the
    /// beginning of the FLAC audio stream.
    ///
    /// Note that the track offset differs from the one in CD-DA, where the
    /// track's offset in the table of contents (TOC) is that of the track's
    /// INDEX 01 even if there is an INDEX 00. For CD-DA, the track offset MUST
    /// be evenly divisible by `588` samples (`588 samples == 44100 samples/s *
    /// 1/75 s`).
    pub offset:       u64,
    /// Track number.
    pub number:       NonZero<u8>,
    /// Track a 12-digit, alphanumeric ASCII ISRC code.
    pub isrc:         Option<AsciiArray<12>>,
    /// Whether the track type is 'audio'.  This corresponds to the CD-DA
    /// Q-channel control bit 3.
    pub is_audio:     bool,
    /// The pre-emphasis flag: `false` for no pre-emphasis, `true` for
    /// pre-emphasis. This corresponds to the CD-DA Q-channel control bit 5.
    pub pre_emphasis: bool,
    // 6 + 8*13 of reserved space
    pub index_points: CuesheetTrackIndexPoints,
}

impl CuesheetTrack {
    #[inline]
    pub const fn is_lead_out(&self, cdda: bool) -> bool {
        !cdda && self.number.get() == 255 || self.number.get() == 170
    }

    #[inline]
    pub fn is_valid(&self, cdda: bool) -> bool {
        // https://www.ietf.org/rfc/rfc9639.html#section-8.7.1

        let is_number_valid = match (cdda, self.number.get()) {
            (true, 1..=99 | 170) // CD-DA: tracks 1-99 + lead-out 170
            | (false, 1..=255) => true, // non-CD-DA: any track 1-254 + lead-out 255
            _ => false,
        };
        let is_offset_valid = !cdda || (self.offset.is_multiple_of(588));
        let is_index_point_count_valid = if cdda {
            // CD-DA: at most 100 index points per track (except the lead-out)
            self.index_points.len <= 100 || self.is_lead_out(cdda)
        } else {
            // non-CD-DA: no limit at all
            true
        };
        let is_isrc_valid = match self.isrc {
            None => true,
            Some(isrc) => {
                let mut valid = true;
                let mut i = 0usize;
                while valid && i < 12 {
                    valid = valid && isrc.get(i) != 0 && isrc.get(i).is_ascii_alphanumeric();
                    i += 1;
                }
                valid
            }
        };

        is_offset_valid
            && is_number_valid
            && is_index_point_count_valid
            && is_isrc_valid
            && self.index_points.is_valid(cdda)
    }
}

impl Decode<bool> for CuesheetTrack {
    type Error = Error;

    fn decode<R: BitRead + Seek>(reader: &mut R, is_cdda: bool) -> Result<Self, Error> {
        let offset = reader.read_u64::<BE>()?;
        let number = NonZero::new(reader.read_u8()?).ok_or(Error::InvalidCuesheetTrack)?;
        let isrc = {
            let mut isrc = [0u8; 12];
            reader.read_exact(&mut isrc)?;
            if isrc.iter().all(|&x| x == 0) {
                None
            } else {
                Some(AsciiArray::try_from(isrc)?)
            }
        };
        let (is_audio, pre_emphasis) = {
            let flags = reader.read_u8()?;
            let is_audio = !flags.get_bit_msb(0);
            let pre_emphasis = flags.get_bit_msb(1);
            // NOTE: The remaining 6 bits are reserved.
            (is_audio, pre_emphasis)
        };
        // Skip the 13 reserved bytes.
        reader.seek_relative(13)?;

        let index_points = CuesheetTrackIndexPoints::decode(reader, is_cdda)?;

        let x = Self {
            offset,
            number,
            isrc,
            is_audio,
            pre_emphasis,
            index_points,
        };

        if x.is_valid(is_cdda) {
            Ok(x)
        } else {
            Err(Error::InvalidCuesheetTrack)
        }
    }
}

impl Encode<bool> for CuesheetTrack {
    type Error = Error;

    fn encode<W: BitWrite>(&self, writer: &mut W, is_cdda: bool) -> Result<(), Self::Error> {
        if cfg!(debug_assertions) && !self.is_valid(is_cdda) {
            return Err(Error::InvalidCuesheetTrack);
        }

        let mut isrc = self.isrc.unwrap_or_default();
        isrc.fill_rest(0);
        debug_assert_eq!(isrc.len(), 12);

        writer.write_u64::<BE>(self.offset)?;
        writer.write_u8(self.number.get())?;
        writer.write_all(&isrc)?;
        writer.write_bit(!self.is_audio)?;
        writer.write_bit(self.pre_emphasis)?;

        // reserved
        writer.flush_bits()?;
        writer.write_all(&[0; 13])?;

        self.index_points.encode(writer, is_cdda)?;

        Ok(())
    }
}

#[derive(Debug, Clone, Copy, PartialEq)]
pub struct CuesheetTrackIndexPoints {
    /// The number of track index points.
    pub len:          u8,
    pub index_points: ArrayList<CuesheetTrackIndexPoint, 255>,
}

impl Deref for CuesheetTrackIndexPoints {
    type Target = [CuesheetTrackIndexPoint];

    #[inline]
    fn deref(&self) -> &Self::Target {
        self.index_points
            .split_at_checked(self.len as usize)
            .unwrap()
            .0
    }
}

impl CuesheetTrackIndexPoints {
    pub fn is_valid_cdda(&self) -> bool {
        // > For CD-DA, a track index point number of 0 corresponds to the track
        // > pre-gap.
        // > The first index point in a track MUST have a number of 0 or 1, and
        // > subsequently, index point numbers MUST increase by 1.

        let mut valid = true;
        let mut i = 0usize;

        while valid && i < self.len as usize {
            let point = self.index_points[i];
            if i == 0 {
                valid = valid && matches!(point.number, 0 | 1);
            } else {
                let prev = self.index_points[i - 1];
                valid = valid && point.number > prev.number;
            }

            valid = valid && point.is_valid_cdda();

            i += 1;
        }

        valid
    }

    pub fn is_valid(&self, cdda: bool) -> bool {
        let is_unique = {
            let mut valid = true;
            let mut i = 1usize;

            while valid && i < self.len as usize {
                let point = self.index_points[i];
                let prev = self.index_points[i - 1];
                valid = valid && point.number != prev.number;
                i += 1;
            }

            valid
        };

        (!cdda || self.is_valid_cdda()) && is_unique
    }
}

impl Decode<bool> for CuesheetTrackIndexPoints {
    type Error = Error;

    fn decode<R: BitRead + Seek>(reader: &mut R, is_cdda: bool) -> Result<Self, Error> {
        let len = reader.read_u8()?;
        let mut index_points = ArrayList::default();

        for _ in 0..len {
            index_points.push(CuesheetTrackIndexPoint::decode(reader, is_cdda)?);
        }

        let x = Self { len, index_points };
        if x.is_valid(is_cdda) {
            Ok(x)
        } else {
            Err(Error::InvalidCuesheetIndexPoints)
        }
    }
}

impl Encode<bool> for CuesheetTrackIndexPoints {
    type Error = Error;

    fn encode<W: BitWrite>(&self, writer: &mut W, is_cdda: bool) -> Result<(), Self::Error> {
        debug_assert!(writer.is_byte_aligned());

        if cfg!(debug_assertions) && !self.is_valid(is_cdda) {
            return Err(Error::InvalidCuesheetIndexPoints);
        }

        writer.write_u8(self.len)?;
        for point in &*self.index_points {
            point.encode(writer, is_cdda)?;
        }

        Ok(())
    }
}

#[derive(Debug, PartialEq, Clone, Copy, Eq, Default)]
pub struct CuesheetTrackIndexPoint {
    /// Offset in samples, relative to the track offset, of the index point.
    pub offset: u64,
    /// The track index point number.
    pub number: u8,
    // [u8;3] of reserved bytes
}

impl CuesheetTrackIndexPoint {
    #[inline]
    pub const fn is_valid(self, is_cdda: bool) -> bool {
        !is_cdda || self.is_valid_cdda()
    }

    #[inline]
    pub const fn is_valid_cdda(self) -> bool {
        // NOTE: the track index point offset MUST be evenly divisible by 588 samples
        // (588 samples = 44100 samples/s * 1/75 s). Note that the offset is from the
        // beginning of the track, not the beginning of the audio data.
        self.offset.is_multiple_of(588)
    }
}

impl Decode<bool> for CuesheetTrackIndexPoint {
    type Error = Error;

    fn decode<R: BitRead + Seek>(reader: &mut R, is_cdda: bool) -> Result<Self, Error> {
        let offset = reader.read_u64::<BE>()?;
        let number = reader.read_u8()?;

        // Skip reserved bytes
        reader.seek_relative(3)?;

        let x = Self { offset, number };
        let is_valid = x.is_valid(is_cdda);

        if is_valid {
            Ok(x)
        } else {
            Err(Error::InvalidCuesheetIndexPoint)
        }
    }
}

impl Encode<bool> for CuesheetTrackIndexPoint {
    type Error = Error;

    fn encode<W: BitWrite>(&self, writer: &mut W, is_cdda: bool) -> Result<(), Self::Error> {
        if cfg!(debug_assertions) && !self.is_valid(is_cdda) {
            return Err(Error::InvalidCuesheetIndexPoints);
        }

        writer.write_u64::<BE>(self.offset)?;
        writer.write_u8(self.number)?;

        writer.write_all(&[0; 3])?; // reserved

        Ok(())
    }
}

/// See table from RFC9639: <https://www.ietf.org/rfc/rfc9639.html#table-13>
#[derive(Debug, Clone, Copy)]
#[repr(u32)]
pub enum PictureType {
    Other = 0,
    /// PNG file icon of 32x32 pixels (see [RFC2083](https://www.rfc-editor.org/info/rfc2083))
    PngFileIcon,
    /// General file icon
    FileIcon,
    FrontCover,
    BackCover,
    /// Liner notes page
    LinerNotes,
    /// Media label (e.g., CD, Vinyl or Cassette label)
    MediaLabel,
    /// Lead artist, lead performer, or soloist
    LeadArtist,
    /// Artist or performer
    Artist,
    Conductor,
    /// Band or orchestra
    Band,
    Composer,
    /// Lyricist or text writer
    Lyricist,
    RecordingLocation,
    /// During recording
    Recording,
    /// During performance
    Performance,
    /// Movie or video screen capture
    Movie,
    /// A bright colored fish
    ///
    /// > The origin and use of
    /// > [`BrightColoredFish`][PictureType::BrightColoredFish] is unclear.
    /// > This was copied to maintain compatibility with ID3v2. Applications are
    /// > discouraged from offering this value to users when embedding a picture
    ///
    /// <!-- Rust ANALyzer can't parse blockquotes correctly if there's no
    /// newline after -->
    BrightColoredFish,
    Illustration,
    /// Band or artist logotype
    ArtistLogotype,
    /// Publisher or studio logotype
    Publisher,
}

impl TryFrom<u32> for PictureType {
    type Error = Error;

    #[inline]
    fn try_from(value: u32) -> Result<Self, Self::Error> {
        use PictureType::*;
        Ok(match value {
            0 => Other,
            1 => PngFileIcon,
            2 => FileIcon,
            3 => FrontCover,
            4 => BackCover,
            5 => LinerNotes,
            6 => MediaLabel,
            7 => LeadArtist,
            8 => Artist,
            9 => Conductor,
            10 => Band,
            11 => Composer,
            12 => Lyricist,
            13 => RecordingLocation,
            14 => Recording,
            15 => Performance,
            16 => Movie,
            17 => BrightColoredFish,
            18 => Illustration,
            19 => ArtistLogotype,
            20 => Publisher,
            21.. => return Err(Error::ReservedPictureType),
        })
    }
}

impl From<PictureType> for u32 {
    fn from(value: PictureType) -> Self {
        use PictureType::*;
        match value {
            Other => 0,
            PngFileIcon => 1,
            FileIcon => 2,
            FrontCover => 3,
            BackCover => 4,
            LinerNotes => 5,
            MediaLabel => 6,
            LeadArtist => 7,
            Artist => 8,
            Conductor => 9,
            Band => 10,
            Composer => 11,
            Lyricist => 12,
            RecordingLocation => 13,
            Recording => 14,
            Performance => 15,
            Movie => 16,
            BrightColoredFish => 17,
            Illustration => 18,
            ArtistLogotype => 19,
            Publisher => 20,
        }
    }
}

#[derive(Clone)]
pub enum PictureData {
    Bytes {
        /// The media type string as specified by [RFC2046](https://www.rfc-editor.org/rfc/rfc2046.html)
        media_type: Box<AsciiArray<255>>,
        data:       Vec<u8>,
    },
    /// A URI pointing to the picture data. The character encoding of the URI is
    /// left unspecified by RFC 9639.
    Uri(Vec<u8>),
}

impl std::fmt::Debug for PictureData {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::Bytes { media_type, .. } => f
                .debug_struct("Bytes")
                .field("media_type", media_type)
                .finish_non_exhaustive(),
            Self::Uri(_) => f.debug_tuple("Uri").finish_non_exhaustive(),
        }
    }
}

/// The `height`, `width`, and `color_depth`, and `color_count` fields are for
/// informational purposes only. Applications MUST NOT use them in decoding the
/// picture or deciding how to display it, but applications MAY use them to
/// decide whether or not to process a block and MAY show them to the user.
#[derive(Debug, Clone)]
pub struct Picture {
    pub kind: PictureType,

    // TODO: Parse Media Types
    /// Description of the picture
    pub description: String,

    /// The width of the picture in pixels. For informational purposes only (See
    /// [`Picture`]).
    pub width: u32,

    /// The height of the picture in pixels. For informational purposes only
    /// (See [`Picture`]).
    pub height: u32,

    /// The color depth of the picture in bits per pixel. For informational
    /// purposes only (See [`Picture`]).
    pub color_depth: u32,

    /// For indexed-color pictures (e.g., GIF), the number of colors used;
    /// [`None`] for non-indexed pictures.
    pub color_count: Option<NonZero<u32>>,

    /// The binary picture data.
    pub data: PictureData,
}

impl Decode<u32> for Picture {
    type Error = Error;

    fn decode<R: BitRead + Seek>(reader: &mut R, max_length: u32) -> Result<Self, Error> {
        let mut total_length = 0u32;

        let mut inc_total_length = |len: u32| -> Result<(), Error> {
            total_length += len;
            if total_length > max_length {
                Err(Error::BlockExceededLength)
            } else {
                Ok(())
            }
        };

        let kind = PictureType::try_from(reader.read_u32::<BE>()?)?;

        let media_type = {
            let length = reader.read_u32::<BE>()?;
            inc_total_length(length)?;

            let mut media_type = [0u8; 255];
            reader.read_exact(&mut media_type[..length as usize])?;
            Box::new(AsciiArray::from_array(media_type, length as usize)?)
        };

        let description = {
            let length = reader.read_u32::<BE>()?;
            inc_total_length(length)?;

            let mut description = vec![0u8; length as usize];
            reader.read_exact(&mut description)?;
            String::from_utf8(description)?
        };

        let width = reader.read_u32::<BE>()?;
        let height = reader.read_u32::<BE>()?;
        let color_depth = reader.read_u32::<BE>()?;
        let color_count = NonZero::new(reader.read_u32::<BE>()?);

        let data = {
            let length = reader.read_u32::<BE>()?;
            inc_total_length(length)?;

            let mut data = vec![0u8; length as usize];
            reader.read_exact(&mut data)?;

            match media_type.as_str() {
                "-->" => PictureData::Uri(data),
                _ => PictureData::Bytes { media_type, data },
            }
        };

        Ok(Self {
            kind,
            description,
            width,
            height,
            color_depth,
            color_count,
            data,
        })
    }
}

impl Encode for Picture {
    type Error = Error;

    fn encode<W: BitWrite>(&self, writer: &mut W, _opt: ()) -> Result<(), Self::Error> {
        let (media_type, data) = match &self.data {
            PictureData::Bytes { media_type, data } => (**media_type, data),
            PictureData::Uri(data) => (AsciiArray::from_bytes(b"-->").unwrap(), data),
        };
        writer.write_u32::<BE>(u32::from(self.kind))?;
        writer.write_u32::<BE>(media_type.len() as u32)?;
        writer.write_all(&media_type)?;
        writer.write_u32::<BE>(
            self.description
                .len()
                .try_into()
                .map_err(|_| Error::OverlongDescription)?,
        )?;
        writer.write_all(self.description.as_bytes())?;
        writer.write_u32::<BE>(self.width)?;
        writer.write_u32::<BE>(self.height)?;
        writer.write_u32::<BE>(self.color_depth)?;
        writer.write_u32::<BE>(self.color_count.map(NonZeroU32::get).unwrap_or_default())?;
        writer.write_u32::<BE>(
            data.len()
                .try_into()
                .map_err(|_| Error::OverlongPictureData)?,
        )?;
        writer.write_all(data)?;

        Ok(())
    }
}

#[allow(clippy::dbg_macro)]
#[cfg(test)]
mod tests {
    use crate::MAGIC;

    use super::*;

    const FLAC_BIN: &[u8] = include_bytes!("../tests/audio/binaural-with-picture.flac");

    #[test]
    fn new_vorbis_user_comment() {
        let _mask = VorbisUserComment::new(
            AsciiStr::from_str("WAVEFORMATEXTENSIBLE_CHANNEL_MASK").unwrap(),
            "0x8",
        )
        .unwrap();
    }

    #[test]
    fn get_channel_mask() {
        let mask = VorbisUserComment::new(
            AsciiStr::from_str("WAVEFORMATEXTENSIBLE_CHANNEL_MASK").unwrap(),
            "0x8",
        )
        .unwrap();
        let block = VorbisComment {
            vendor:            String::from("Tgirl hooters"),
            user_comment_list: vec![mask],
        };
        let channel_mask = block.get_channel_mask().unwrap().unwrap();
        assert_eq!(channel_mask, ChannelMask::LOW_FREQUENCY_EFFECTS);
    }

    #[test]
    fn block_header_is_final() {
        // Example: A 'VorbisComment' (Type 4) that is NOT the last block.
        // Binary: 0 (last flag) 0000100 (type 4) -> 00000100 -> 0x04
        // Let's assume this is the start of a 4-byte u32 header: 0x04000006
        let header = dbg!(BlockHeader::decode_bytes(&[0b1000_0000, 0x00, 0x00, 0x00], ()).unwrap());

        assert!(header.is_final);
        let header = dbg!(BlockHeader::decode_bytes(&[0b0000_0000, 0x00, 0x00, 0x00], ()).unwrap());

        assert!(!header.is_final);
    }

    #[test]
    fn block_header_kind() {
        // Example: A 'VorbisComment' (Type 4) that is NOT the last block.
        // Binary: 0 (last flag) 0000100 (type 4) -> 00000100 -> 0x04
        // Let's assume this is the start of a 4-byte u32 header: 0x04000006
        let bytes = [
            0b0000_0100, // is_last=0, block_type=0 (STREAMINFO)
            0x00,
            0x00,
            0x22, // length = 34
        ];
        let header = BlockHeader::decode_bytes(&bytes, ()).unwrap();

        assert_eq!(header.kind, BlockType::VorbisComment);

        // let header = dbg!(BlockHeader::decode_bytes(
        //     &0x0CAFEBABE_u32.to_ne_bytes()
        // )?);
        // assert_eq!(header.kind, BlockType::Reserved(0x4A));
    }

    fn parse_block<R: BitRead + Seek>(reader: &mut R, mut cb: impl FnMut(Block)) {
        loop {
            let block = Block::decode(reader, ()).unwrap();
            let is_final = block.header.is_final;
            println!("{block:#?}");

            cb(block);

            if is_final {
                break;
            }
        }
    }

    #[test]
    fn test_parse_block() {
        let mut flac = BitReader::new(io::Cursor::new(FLAC_BIN));

        let mut magic = [0u8; size_of_val(&MAGIC)];
        flac.read_exact(&mut magic).unwrap();
        assert_eq!(magic, MAGIC);

        parse_block(&mut flac, |_block| {});
    }
}

#[cfg(test)]
mod streaminfo_encode {
    use super::*;
    use crate::Encode;
    use crate::bit_io::{BitReader, BitWriter};
    use std::io::Cursor;

    // The test FLAC file is already embedded by the existing metadata tests.
    const FLAC_BIN: &[u8] = include_bytes!("../tests/audio/binaural-with-picture.flac");

    fn streaminfo_from_file() -> &'static [u8] {
        // NOTE: STREAMINFO is always exactly 34 bytes.
        &FLAC_BIN[8..42] // Skip magic and block header.
    }

    fn parse_streaminfo(raw: &[u8]) -> Streaminfo {
        Streaminfo::decode(&mut BitReader::new(Cursor::new(raw)), ()).unwrap()
    }

    #[test]
    fn round_trip_encode_streaminfo() {
        let original_bytes = streaminfo_from_file();
        let parsed = parse_streaminfo(original_bytes);

        let mut w = BitWriter::new(Vec::new());
        parsed.encode(&mut w, ()).unwrap();
        let encoded = w.into_inner();

        assert_eq!(
            encoded, original_bytes,
            "re-encoded STREAMINFO does not match original bytes from file"
        );
    }

    #[test]
    fn round_trip_encode_streaminfo_parsed() {
        let original_bytes = streaminfo_from_file();
        let original = parse_streaminfo(original_bytes);

        let mut w = BitWriter::new(Vec::new());
        original.encode(&mut w, ()).unwrap();
        let encoded = w.into_inner();

        let decoded = parse_streaminfo(&encoded);
        assert_eq!(original, decoded);
    }

    #[test]
    fn test_block_header_bytes_are_valid() {
        let header_bytes = &FLAC_BIN[4..8];

        let block_type = header_bytes[0] & 0x7F;
        assert_eq!(block_type, 0, "first metadata block must be STREAMINFO");

        let length = u32::from_be_bytes([0, header_bytes[1], header_bytes[2], header_bytes[3]]);
        assert_eq!(length, 34, "STREAMINFO block length must be 34");
    }

    #[test]
    fn round_trip_encode_block_header() {
        let original_header_bytes = &FLAC_BIN[4..8];
        let header =
            BlockHeader::decode(&mut BitReader::new(Cursor::new(original_header_bytes)), ())
                .unwrap();

        let mut w = BitWriter::new(Vec::new());
        header.encode(&mut w, ()).unwrap();
        let encoded = w.into_inner();

        assert_eq!(
            encoded.as_slice(),
            original_header_bytes,
            "re-encoded block header does not match original"
        );
    }
}