Syplheed-Reborn/crates/sylpheed-formats/src/slb.rs

//! `.slb` XACT sound banks → a decodable XMA1 `RIFF`.
//!
//! `dat/sound.pak` (9519 entries across `sound.p00..p04`) is the game's audio
//! bank. Each entry is an XACT `.slb` wrapping **XMA1** (`fmt ` tag `0x0165`,
//! 48 kHz). Files are named `<lang>\Voice\…`, `<lang>\Movie\VOICE_<movie>.slb`,
//! `BGM_###.slb`, etc. (see `docs/re/structures/sound-slb.md`); look them up by
//! [`crate::hash::name_hash`]. Movie cutscene voice = one continuous
//! `<eng|jpn>\Movie\VOICE_<movie>.slb` track meant to play from the video start.
//!
//! Two on-disc layouts, both reversed statically:
//! - **RIFF present** — a standard `RIFF/WAVE` sits inside the bank; its 32-byte
//!   `fmt ` is the real `XMAWAVEFORMAT` and the XMA packets are everything after
//!   that RIFF's `data` chunk header (the declared `data` size is unreliable, so
//!   we take to end and let the caller clamp to the known media length).
//! - **Headerless** — no RIFF at all; a fixed **1392-byte** header precedes raw
//!   XMA1 packets (48 kHz, 2 channels).
//!
//! [`to_xma_riff`] rebuilds a standalone `RIFF/WAVE` (XMA1) for either layout,
//! ready to hand to an XMA decoder (e.g. FFmpeg's `xma1`). The content is always
//! mono (some clips put it in the left channel only, others duplicate L=R), so
//! the decode step should downmix to mono (take the left channel).

/// Fixed offset of the raw XMA1 stream in a headerless `.slb` (no `RIFF`).
pub const HEADERLESS_DATA_OFFSET: usize = 1392;

/// XMA1 packet size. A headerless stream is always a whole number of these, which
/// is how a leading stream is told apart from arbitrary bytes before a `RIFF`.
pub const XMA1_PACKET: usize = 2048;

/// Voice language for cutscene audio. Only English and Japanese voice exist on
/// the disc (subtitles cover more languages, voice does not).
#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
pub enum VoiceLang {
    /// The default only because the disc's own default audio track is English;
    /// nothing else about the code should assume it.
    #[default]
    English,
    Japanese,
}

impl VoiceLang {
    pub const ALL: [VoiceLang; 2] = [VoiceLang::English, VoiceLang::Japanese];

    pub fn label(self) -> &'static str {
        match self {
            VoiceLang::English => "English",
            VoiceLang::Japanese => "Japanese",
        }
    }

    fn code(self) -> &'static str {
        match self {
            VoiceLang::English => "eng",
            VoiceLang::Japanese => "jpn",
        }
    }

    /// `eng` / `jpn` — the `sound.pak` path prefix for this voice language.
    pub fn code_pub(self) -> &'static str {
        self.code()
    }
}

/// The `sound.pak` entry name for a movie's continuous voice track, e.g.
/// `eng\Movie\VOICE_RT07A.slb`. Hash it with [`crate::hash::name_hash`] to get
/// the `sound.pak` TOC key.
pub fn movie_voice_name(movie_basename: &str, lang: VoiceLang) -> String {
    format!("{}\\Movie\\VOICE_{}.slb", lang.code(), movie_basename)
}

/// One playable voice clip discovered in `sounds.tbl`.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct VoiceClip {
    /// Full `sound.pak` entry name, e.g. `eng\Voice\VOICE_ADAN_010.slb`.
    pub name: String,
    /// Speaker/category code, e.g. `ADAN`, `TCAF`, `A`, `RT07A`.
    pub speaker: String,
    /// Short UI label, e.g. `ADAN 010`.
    pub display: String,
}

/// What kind of audio a `sounds.tbl` entry names.
///
/// The split is the on-disc path shape, not a guess: the 36 language-independent
/// banks sit at the table root (`BGM_###.slb`, `JNGL_00#.slb`, `Static.slb`),
/// while everything else is under `<lang>\<dir>\`.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum AudioCategory {
    /// `BGM_###.slb` — 32 music tracks, language-independent.
    Music,
    /// `JNGL_00#.slb` — 3 short jingles (mission clear / fail stings).
    Jingle,
    /// `Static.slb` — the sound-effect bank, one 9 MB multi-wave bank.
    Sfx,
    /// `<lang>\Voice\` — in-mission radio chatter, by speaker.
    Radio,
    /// `<lang>\etc\` — the other spoken lines (cutscene dialogue, system).
    Dialogue,
    /// `<lang>\Movie\VOICE_<movie>.slb` — a cutscene's continuous voice track.
    MovieVoice,
    /// `<lang>\Briefing\BR<NN>_<MM>.slb` — mission briefing lines.
    Briefing,
    /// A `.slb` whose path matched no known shape.
    Other,
}

impl AudioCategory {
    pub const ALL: [AudioCategory; 8] = [
        AudioCategory::Music,
        AudioCategory::Jingle,
        AudioCategory::Sfx,
        AudioCategory::Radio,
        AudioCategory::Dialogue,
        AudioCategory::MovieVoice,
        AudioCategory::Briefing,
        AudioCategory::Other,
    ];

    pub fn label(self) -> &'static str {
        match self {
            AudioCategory::Music => "Music",
            AudioCategory::Jingle => "Jingles",
            AudioCategory::Sfx => "Sound effects",
            AudioCategory::Radio => "Radio",
            AudioCategory::Dialogue => "Dialogue",
            AudioCategory::MovieVoice => "Movie voice",
            AudioCategory::Briefing => "Briefing",
            AudioCategory::Other => "Other",
        }
    }

    /// True for the categories that are spoken lines — the set
    /// [`list_voice_clips`] returns.
    pub fn is_voice(self) -> bool {
        matches!(
            self,
            AudioCategory::Radio
                | AudioCategory::Dialogue
                | AudioCategory::MovieVoice
                | AudioCategory::Briefing
        )
    }

    /// True when the bank is language-independent, so it appears whichever
    /// `<lang>\sounds.tbl` is read.
    pub fn is_shared(self) -> bool {
        matches!(
            self,
            AudioCategory::Music | AudioCategory::Jingle | AudioCategory::Sfx
        )
    }

    fn classify(name: &str) -> AudioCategory {
        let leaf = name.rsplit('\\').next().unwrap_or(name);
        if !name.contains('\\') {
            return if leaf.starts_with("BGM_") {
                AudioCategory::Music
            } else if leaf.starts_with("JNGL_") {
                AudioCategory::Jingle
            } else if leaf.eq_ignore_ascii_case("Static.slb") {
                AudioCategory::Sfx
            } else {
                AudioCategory::Other
            };
        }
        match name.rsplit('\\').nth(1) {
            Some("Voice") => AudioCategory::Radio,
            Some("etc") => AudioCategory::Dialogue,
            Some("Movie") => AudioCategory::MovieVoice,
            Some("Briefing") => AudioCategory::Briefing,
            _ => AudioCategory::Other,
        }
    }
}

/// One playable bank named in `sounds.tbl`, with the category its path implies.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct AudioEntry {
    pub clip: VoiceClip,
    pub category: AudioCategory,
}

/// Enumerate **every** `.slb` bank named in a decompressed `sounds.tbl` (the
/// IDXD in `tables.pak`): the language-independent music/jingle/SFX banks at
/// the table root, plus every `<lang>\…` spoken line.
///
/// Measured on the retail disc: `eng\sounds.tbl` names 4 418 banks (36 shared +
/// 2 382 Radio + 1 821 Dialogue + 101 Briefing + 78 Movie voice) and
/// `jpn\sounds.tbl` names 5 136 (the same 36 shared + 5 100 Japanese lines).
/// Every one of the 36 shared names resolves to a `sound.pak` TOC entry under
/// [`crate::hash::name_hash`], which is the check that they are real banks and
/// not stale table text.
pub fn list_audio_entries(sounds_tbl: &[u8], lang: VoiceLang) -> Vec<AudioEntry> {
    let prefix = format!("{}\\", lang.code());
    let mut seen = std::collections::BTreeSet::new();
    let mut out = Vec::new();
    // Scan for printable-ASCII runs; keep those that name a `.slb`.
    let mut i = 0;
    while i < sounds_tbl.len() {
        let start = i;
        while i < sounds_tbl.len() && (0x20..=0x7e).contains(&sounds_tbl[i]) {
            i += 1;
        }
        if i - start >= 6 {
            if let Ok(s) = std::str::from_utf8(&sounds_tbl[start..i]) {
                // Take this language's entries plus the root (shared) banks; a
                // path under the OTHER language would be a table artefact.
                let mine = s.starts_with(&prefix) || !s.contains('\\');
                if mine && s.ends_with(".slb") && seen.insert(s.to_string()) {
                    out.push(AudioEntry {
                        category: AudioCategory::classify(s),
                        clip: parse_voice_clip(s),
                    });
                }
            }
        }
        i += 1;
    }
    out
}

/// Enumerate just the spoken-line clips — [`list_audio_entries`] restricted to
/// [`AudioCategory::is_voice`].
///
/// In-mission radio (`\Voice\`, `\etc\`) and bound movie voices (`\Movie\`) all
/// carry `VOICE_`; mission-briefing lines live in `\Briefing\` as
/// `BR<NN>_<MM>.slb` and carry no `VOICE` at all, which is why the category —
/// i.e. the directory — decides this and not the filename.
pub fn list_voice_clips(sounds_tbl: &[u8], lang: VoiceLang) -> Vec<VoiceClip> {
    list_audio_entries(sounds_tbl, lang)
        .into_iter()
        .filter(|e| e.category.is_voice())
        .map(|e| e.clip)
        .collect()
}

fn parse_voice_clip(name: &str) -> VoiceClip {
    // `<lang>\<cat>\VOICE_<SPK>_<NNN>.slb` or `..\VOICE_<movie>.slb`.
    let stem = name
        .rsplit('\\')
        .next()
        .unwrap_or(name)
        .strip_suffix(".slb")
        .unwrap_or(name);
    let body = stem.strip_prefix("VOICE_").unwrap_or(stem);
    let (speaker, display) = match body.rsplit_once('_') {
        Some((spk, num)) if num.chars().all(|c| c.is_ascii_digit()) => {
            (spk.to_string(), format!("{spk} {num}"))
        }
        _ => (body.to_string(), body.to_string()),
    };
    VoiceClip {
        name: name.to_string(),
        speaker,
        display,
    }
}

/// Build one standalone XMA1 `RIFF/WAVE` **per sub-wave** in a `.slb` bank, in
/// on-disc order. A `.slb` is an XACT bank of one or more sub-waves; the sub-waves
/// are EITHER alternate takes (the first is the whole track — e.g. `VOICE_S01A`,
/// `VOICE_ADV`: sub0 ≈ the movie length) OR sequential segments that must be
/// concatenated (e.g. `VOICE_RT07A`: 24s + 14s + 11s ≈ the 50s movie). The caller
/// decodes each to PCM, concatenates in order, and clamps to the movie length —
/// that yields the full track for segment banks while the clamp drops the
/// duplicate takes for alternate-take banks. (Dynamic RE via Canary file-I/O
/// tracing confirmed the movie→voice binding; this fixes the *decode* of `RT*`.)
/// A bank's channel count, read from its first `RIFF` sub-wave.
///
/// `XMASTREAMFORMAT.Channels` sits at `RIFF + 49`. **2.12 % of banks are stereo**
/// (170 of 8 021), and decoding one of those as mono yields a single frame and
/// stops — the same signature already recorded for the leading segment. So the
/// channel count has to be read, not assumed. Returns `None` when there is no
/// `RIFF` to read it from.
fn riff_channels(slb: &[u8]) -> Option<u8> {
    let ri = find(slb, b"RIFF", 0)?;
    slb.get(ri + 49).copied().filter(|c| *c == 1 || *c == 2)
}

/// The four data offsets that occur on the disc, in ascending order.
///
/// Measured over all 7 358 banks whose offset is *known* (they carry a `RIFF`,
/// so the offset is forced to `first_riff % XMA1_PACKET`): no other value
/// occurs. They are all of the form `1392 + 4k`.
pub const DATA_OFFSET_CANDIDATES: [usize; 4] = [1392, 1468, 1600, 1728];

/// How plausible a candidate offset is, judged by XMA1 packet headers alone.
///
/// Each 2048-byte packet opens with a big-endian header: 6 bits frame count,
/// 15 bits frame-offset-in-bits, 3 bits metadata, 8 bits packet-skip. At the
/// true offset those fields stay in range packet after packet; one byte off and
/// they do not. Returns the fraction of the first `LIMIT` packets that look
/// sane, so 1.0 is a clean stream.
fn packet_plausibility(slb: &[u8], start: usize) -> f32 {
    const LIMIT: usize = 24;
    let (mut seen, mut ok, mut pos) = (0usize, 0usize, start);
    while pos + XMA1_PACKET <= slb.len() && seen < LIMIT {
        let h = u32::from_be_bytes([slb[pos], slb[pos + 1], slb[pos + 2], slb[pos + 3]]);
        let frame_offset_bits = (h >> 11) & 0x7FFF;
        let metadata = (h >> 8) & 0x7;
        let packet_skip = h & 0xFF;
        if frame_offset_bits as usize <= XMA1_PACKET * 8 && metadata <= 1 && packet_skip <= 8 {
            ok += 1;
        }
        seen += 1;
        pos += XMA1_PACKET;
    }
    if seen == 0 {
        0.0
    } else {
        ok as f32 / seen as f32
    }
}

/// The data offset implied by the bank's `seek` chunk, if it has one.
///
/// A bank's `seek` chunk lands on a packet boundary, so `seek_pos % XMA1_PACKET`
/// *is* the data offset. Measured on the 6 033 labelled banks that have a
/// `seek` before their first `RIFF`: **6 031 agree (99.97 %)**, 2 disagree.
/// This is structural rather than statistical, which is why it is tried first.
fn seek_chunk_offset(slb: &[u8]) -> Option<usize> {
    let pos = find(slb, b"seek", 0)?;
    let residue = pos % XMA1_PACKET;
    DATA_OFFSET_CANDIDATES.contains(&residue).then_some(residue)
}

/// Recover a bank's data offset when there is no `RIFF` to derive it from.
///
/// Two independent signals, tried in order of how well each is evidenced:
///
/// 1. **the `seek` chunk's position** mod the packet size — 99.97 % on the
///    labelled set, and structural rather than statistical;
/// 2. **packet-header plausibility** — pick the candidate whose XMA1 headers
///    stay in range over the first 24 packets. Alone this is 99.62 %, and all
///    28 of its misses are ties rather than wrong unique winners.
///
/// Together, on the 7 358 banks where the answer *is* known from the `RIFF`
/// position: **7 354 correct (99.95 %)**. The `seek` residue resolves 26 of the
/// scan's 28 ties correctly and none of them wrongly; the other 2 have no
/// usable `seek`. Falls back to [`HEADERLESS_DATA_OFFSET`] when neither signal
/// decides.
pub fn scan_data_offset(slb: &[u8]) -> usize {
    if let Some(off) = seek_chunk_offset(slb) {
        return off;
    }
    let mut best = (HEADERLESS_DATA_OFFSET, -1.0f32);
    let mut tied = false;
    for &c in &DATA_OFFSET_CANDIDATES {
        if c >= slb.len() {
            continue;
        }
        let score = packet_plausibility(slb, c);
        if score > best.1 {
            best = (c, score);
            tied = false;
        } else if (score - best.1).abs() < f32::EPSILON {
            tied = true;
        }
    }
    if tied {
        HEADERLESS_DATA_OFFSET
    } else {
        best.0
    }
}

/// Where a bank's leading headerless packet stream starts.
///
/// The stream is a whole number of 2048-byte XMA1 packets ending at the first
/// `RIFF`, so its start is simply `first_riff % XMA1_PACKET`. Disc-wide that
/// lands on 1392, 1468, 1600 or 1728 depending on language and subdirectory —
/// [`HEADERLESS_DATA_OFFSET`] is just the `<lang>\etc\` case. Measured over a
/// 140-bank sample, deriving the offset instead of assuming 1392 recovers a
/// median **70×** more decoded audio and never less except in one bank where
/// neither offset decodes (see `docs/re/structures/slb-data-offset.md`).
pub fn leading_data_offset(first_riff: usize) -> usize {
    first_riff % XMA1_PACKET
}

pub fn to_xma_riffs(slb: &[u8]) -> Vec<Vec<u8>> {
    let mut out = Vec::new();
    let first_riff = find(slb, b"RIFF", 0);
    if first_riff.is_none() {
        // Headerless single-stream bank. Two things here were wrong, and the
        // corrections are measured (docs/re/structures/slb-data-offset.md):
        //
        //   * the offset is not the constant — with no `RIFF` to derive it from,
        //     scan the four candidates by packet plausibility;
        //   * the stream is **mono**. At two channels a 48-bank sample yielded
        //     0..4 816 bytes; at one, 180 000..380 000. There was not one bank
        //     where the old stereo/1392 pair beat the scanned mono pair, and the
        //     median gain was 184x.
        let start = scan_data_offset(slb);
        if let Some(data) = slb.get(start..) {
            if !data.is_empty() {
                out.push(build_riff(&synth_xma1_fmt(1, 0, 48000), data));
            }
        }
        return out;
    }
    // HYBRID banks: a headerless packet stream followed by RIFF sub-waves, two
    // SEQUENTIAL SEGMENTS of one clip. The branch above only fires when there is
    // no `RIFF` at all, so the leading segment used to be dropped — which is why
    // `VOICE_D_453` decoded to 0.14 s: its line is in that segment and only the
    // trailing fragment survived.
    //
    // The boundary is arithmetic, not a magic: XMA1 packets are 2048 bytes, so a
    // leading stream is a whole number of packets ending at the first `RIFF`.
    // Its START is therefore `first_riff % XMA1_PACKET` — **not** the constant
    // `HEADERLESS_DATA_OFFSET`, which is only the value that offset happens to
    // take in `<lang>\etc\`. Disc-wide it takes four values (1392, 1468, 1600,
    // 1728), varying by language and subdirectory, and assuming 1392 starts the
    // decode mid-packet everywhere else. See docs/re/structures/slb-data-offset.md.
    // It decodes as **mono** — at two channels every bank yields exactly 1792
    // bytes, one frame, whatever its size.
    //
    // An earlier version of this was withdrawn for two good reasons, both now
    // answered: it recovered no audio (it used the stereo format), and it
    // matched 1524 of the 8021 RIFF-bearing entries. The byte-level reach is
    // still 1524, but the *audible* reach is not: across the 84 movie-bound
    // banks the segment adds >1 s to exactly **7** — the `hokyu_*_H` tankers
    // bound to `VOICE_D_453`/`454`, i.e. precisely the broken ones — and
    // ≤0.25 s to 66 of the rest. Callers clamp to the movie length anyway.
    if let Some(ri) = first_riff {
        let start = leading_data_offset(ri);
        if ri > start {
            if let Some(data) = slb.get(start..ri) {
                if data.iter().any(|b| *b != 0) {
                    // Channels come from the bank's own `fmt `, not a constant:
                    // 170 of 8 021 banks are stereo and decode to one frame if
                    // forced to mono.
                    let ch = riff_channels(slb).unwrap_or(1);
                    let mask = if ch == 2 { 2 } else { 0 };
                    out.push(build_riff(&synth_xma1_fmt(ch, mask, 48000), data));
                }
            }
        }
    }
    let mut pos = 0usize;
    while let Some(ri) = find(slb, b"RIFF", pos) {
        // Parse this sub-wave's fmt + data. The declared `data` size is an
        // UPPER bound, not an exact one: 5 296 of 7 586 banks declare more than
        // the entry holds and none declares exactly what it holds, so the clamp
        // below is load-bearing (docs/re/structures/slb-data-offset.md).
        let Some(fi) = find(slb, b"fmt ", ri) else { break };
        let Some(fsz) = le32(slb, fi + 4) else { break };
        let Some(fmt_end) = fi.checked_add(8).and_then(|v| v.checked_add(fsz as usize)) else {
            break;
        };
        if fmt_end > slb.len() {
            break;
        }
        let Some(di) = find(slb, b"data", fi) else { break };
        let Some(dsz) = le32(slb, di + 4) else { break };
        let Some(ds) = di.checked_add(8) else { break };
        let de = ds
            .checked_add(dsz as usize)
            .unwrap_or(slb.len())
            .min(slb.len());
        if let Some(data) = slb.get(ds..de) {
            if !data.is_empty() {
                out.push(build_riff(&slb[fi..fmt_end], data));
            }
        }
        // Advance past this sub-wave's data to find the next RIFF.
        pos = de.max(ri + 4);
    }
    out
}

/// Build a standalone XMA1 `RIFF/WAVE` from a `.slb` bank, decodable by FFmpeg's
/// `xma1`. Returns `None` if the bank is too small / malformed. This is the
/// FIRST sub-wave only; prefer [`to_xma_riffs`] for correct multi-segment banks.
pub fn to_xma_riff(slb: &[u8]) -> Option<Vec<u8>> {
    if let Some(ri) = find(slb, b"RIFF", 0) {
        // RIFF layout: a `.slb` is an XACT bank of one or more sub-waves, each
        // `[seek][RIFF: fmt + Dmmy pad + data][declared_size XMA bytes]`. Take the
        // FIRST sub-wave, bounded by its **declared `data` size** — which is an
        // upper bound only (69.8 % of banks over-declare it, so the clamp
        // matters), but still the right boundary to cut at. Decoding to
        // end-of-file instead would append the later sub-waves — for multi-take
        // story movies those are ALTERNATE takes, which is what made S10–S16
        // play the wrong audio.
        let fi = find(slb, b"fmt ", ri)?;
        let fsz = le32(slb, fi + 4)? as usize;
        let fmt_end = fi.checked_add(8)?.checked_add(fsz)?;
        if fmt_end > slb.len() {
            return None;
        }
        let fmt_chunk = &slb[fi..fmt_end];
        let di = find(slb, b"data", fi)?;
        let dsz = le32(slb, di + 4)? as usize;
        let end = di.checked_add(8)?.checked_add(dsz)?.min(slb.len());
        let data = slb.get(di + 8..end)?;
        Some(build_riff(fmt_chunk, data))
    } else {
        // Headerless: 1392-byte header, then raw XMA1 (48 kHz, 2 channels).
        let data = slb.get(HEADERLESS_DATA_OFFSET..)?;
        if data.is_empty() {
            return None;
        }
        Some(build_riff(&synth_xma1_fmt(2, 2, 48000), data))
    }
}

/// Rebuild a standalone XMA1 `RIFF/WAVE` from a single-stream `.slb`, robust to
/// the layout variants seen in `<lang>\etc\` radio clips. Unlike [`to_xma_riff`]
/// (which assumes `RIFF → fmt → data` in order), this picks the **largest `data`
/// chunk anywhere** in the bank — some radio banks store the audio *before* the
/// trailing `RIFF`/`fmt` metadata (an empty post-`RIFF` `data` chunk), which the
/// ordered scan misses. Pairs it with the first `fmt ` chunk; falls back to the
/// headerless layout. Returns `None` only when no usable audio can be found.
pub fn to_xma_riff_best(slb: &[u8]) -> Option<Vec<u8>> {
    // Largest usable `data` chunk (bounded by its declared size and the buffer).
    let mut best: Option<(usize, usize)> = None; // (data offset, usable payload len)
    let mut i = 0;
    while let Some(di) = find(slb, b"data", i) {
        let declared = le32(slb, di + 4).unwrap_or(0) as usize;
        let usable = declared.min(slb.len().saturating_sub(di + 8));
        if best.map_or(true, |(_, b)| usable > b) {
            best = Some((di, usable));
        }
        i = di + 4;
    }
    if let (Some(fi), Some((di, sz))) = (find(slb, b"fmt ", 0), best) {
        if sz > 512 {
            let fsz = le32(slb, fi + 4)? as usize;
            let fmt_end = (fi + 8 + fsz).min(slb.len());
            let data = slb.get(di + 8..di + 8 + sz)?;
            return Some(build_riff(slb.get(fi..fmt_end)?, data));
        }
    }
    // Headerless fallback: fixed data offset, synthesized XMA1 stereo/48k fmt.
    let data = slb.get(HEADERLESS_DATA_OFFSET..)?;
    (!data.is_empty()).then(|| build_riff(&synth_xma1_fmt(2, 2, 48000), data))
}

/// A minimal `fmt ` chunk carrying an XMA1 `XMAWAVEFORMAT` (one stream).
fn synth_xma1_fmt(channels: u8, channel_mask: u16, rate: u32) -> Vec<u8> {
    let mut fmt = Vec::with_capacity(40);
    fmt.extend_from_slice(b"fmt ");
    fmt.extend_from_slice(&32u32.to_le_bytes());
    // XMAWAVEFORMAT header
    fmt.extend_from_slice(&0x0165u16.to_le_bytes()); // wFormatTag = XMA1
    fmt.extend_from_slice(&16u16.to_le_bytes()); // BitsPerSample
    fmt.extend_from_slice(&0u16.to_le_bytes()); // EncodeOptions
    fmt.extend_from_slice(&0u16.to_le_bytes()); // LargestSkip
    fmt.extend_from_slice(&1u16.to_le_bytes()); // NumStreams
    fmt.push(0); // LoopCount
    fmt.push(3); // Version
    // XMASTREAMFORMAT[0]
    fmt.extend_from_slice(&(rate * channels as u32 * 2).to_le_bytes()); // PsuedoBytesPerSec
    fmt.extend_from_slice(&rate.to_le_bytes()); // SampleRate
    fmt.extend_from_slice(&0u32.to_le_bytes()); // LoopStart
    fmt.extend_from_slice(&0u32.to_le_bytes()); // LoopEnd
    fmt.push(4); // SubframeData
    fmt.push(channels); // Channels
    fmt.extend_from_slice(&channel_mask.to_le_bytes()); // ChannelMask
    fmt
}

fn build_riff(fmt_chunk: &[u8], data: &[u8]) -> Vec<u8> {
    let mut body = Vec::with_capacity(4 + fmt_chunk.len() + 8 + data.len());
    body.extend_from_slice(b"WAVE");
    body.extend_from_slice(fmt_chunk);
    body.extend_from_slice(b"data");
    body.extend_from_slice(&(data.len() as u32).to_le_bytes());
    body.extend_from_slice(data);
    let mut out = Vec::with_capacity(8 + body.len());
    out.extend_from_slice(b"RIFF");
    out.extend_from_slice(&(body.len() as u32).to_le_bytes());
    out.extend_from_slice(&body);
    out
}

fn find(hay: &[u8], needle: &[u8], from: usize) -> Option<usize> {
    if from >= hay.len() {
        return None;
    }
    hay[from..]
        .windows(needle.len())
        .position(|w| w == needle)
        .map(|p| p + from)
}

fn le32(b: &[u8], o: usize) -> Option<u32> {
    let s = b.get(o..o + 4)?;
    Some(u32::from_le_bytes([s[0], s[1], s[2], s[3]]))
}

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

    #[test]
    fn movie_voice_names_and_hashes() {
        assert_eq!(
            movie_voice_name("RT07A", VoiceLang::English),
            "eng\\Movie\\VOICE_RT07A.slb"
        );
        // Verified present in dat/sound.pak (VOICE_S00A == TOC entry 0x2A4F97D3).
        assert_eq!(name_hash("eng\\Movie\\VOICE_RT07A.slb"), 0xA44A_EA1C);
        assert_eq!(name_hash("eng\\Movie\\VOICE_S00A.slb"), 0x2A4F_97D3);
    }

    #[test]
    fn takes_only_first_subwave() {
        // Bank of TWO sub-waves; only the FIRST must be extracted (bounded by its
        // declared `data` size), not everything to end-of-file.
        let fmt = synth_xma1_fmt(2, 2, 48000);
        let mut slb = vec![0xAB; 16];
        slb.extend_from_slice(b"RIFF");
        slb.extend_from_slice(&999u32.to_le_bytes()); // riff size (ignored)
        slb.extend_from_slice(b"WAVE");
        slb.extend_from_slice(&fmt);
        slb.extend_from_slice(b"data");
        slb.extend_from_slice(&4u32.to_le_bytes()); // declared: 4 bytes
        slb.extend_from_slice(&[1, 2, 3, 4]); // sub-wave 1 XMA
        slb.extend_from_slice(&[9, 9, 9, 9]); // a second sub-wave's bytes — excluded
        let riff = to_xma_riff(&slb).unwrap();
        assert_eq!(&riff[0..4], b"RIFF");
        let dpos = find(&riff, b"data", 0).unwrap();
        assert_eq!(le32(&riff, dpos + 4), Some(4));
        assert_eq!(&riff[dpos + 8..], &[1, 2, 3, 4]);
    }

    #[test]
    fn list_voice_clips_covers_movie_radio_and_briefing() {
        // The standalone player must enumerate every spoken-line category: bound
        // movie voices, in-mission radio (\etc\ + \Voice\), and briefing (\Briefing\,
        // whose BR<NN>_<MM> names lack "VOICE"). Music (BGM_*) must stay excluded.
        let mut tbl = Vec::new();
        for s in [
            "eng\\Movie\\VOICE_S13A.slb",
            "eng\\etc\\VOICE_D_450.slb",
            "eng\\Voice\\VOICE_ADAN_010.slb",
            "eng\\Briefing\\BR01_01.slb",
            "eng\\bgm\\BGM_001.slb",
        ] {
            tbl.extend_from_slice(s.as_bytes());
            tbl.push(0);
        }
        let names: Vec<String> = list_voice_clips(&tbl, VoiceLang::English)
            .into_iter()
            .map(|c| c.name)
            .collect();
        for want in [
            "eng\\Movie\\VOICE_S13A.slb",
            "eng\\etc\\VOICE_D_450.slb",
            "eng\\Voice\\VOICE_ADAN_010.slb",
            "eng\\Briefing\\BR01_01.slb",
        ] {
            assert!(names.iter().any(|n| n == want), "missing {want}");
        }
        assert!(
            !names.iter().any(|n| n.contains("BGM_")),
            "music must not be listed as a voice clip"
        );
    }

    #[test]
    fn list_audio_entries_categorises_root_banks_and_keeps_them_language_shared() {
        // The three root banks carry no language component, so BOTH sounds.tbl
        // files name them; a language filter that only accepted `<lang>\` would
        // silently drop all the music, which is what it used to do.
        let mut tbl = Vec::new();
        for s in [
            "BGM_001.slb",
            "JNGL_002.slb",
            "Static.slb",
            "eng\\Voice\\VOICE_ADAN_010.slb",
            "eng\\etc\\VOICE_D_450.slb",
            "eng\\Movie\\VOICE_S13A.slb",
            "eng\\Briefing\\BR01_01.slb",
        ] {
            tbl.extend_from_slice(s.as_bytes());
            tbl.push(0);
        }
        let by = |lang| {
            list_audio_entries(&tbl, lang)
                .into_iter()
                .map(|e| (e.clip.name, e.category))
                .collect::<Vec<_>>()
        };
        let eng = by(VoiceLang::English);
        let want = [
            ("BGM_001.slb", AudioCategory::Music),
            ("JNGL_002.slb", AudioCategory::Jingle),
            ("Static.slb", AudioCategory::Sfx),
            ("eng\\Voice\\VOICE_ADAN_010.slb", AudioCategory::Radio),
            ("eng\\etc\\VOICE_D_450.slb", AudioCategory::Dialogue),
            ("eng\\Movie\\VOICE_S13A.slb", AudioCategory::MovieVoice),
            ("eng\\Briefing\\BR01_01.slb", AudioCategory::Briefing),
        ];
        assert_eq!(eng.len(), want.len());
        for (n, c) in want {
            assert!(
                eng.iter().any(|(en, ec)| en == n && *ec == c),
                "{n} not categorised as {c:?}"
            );
        }
        // Reading the Japanese table yields the shared banks and none of the
        // English lines.
        let jpn = by(VoiceLang::Japanese);
        assert_eq!(jpn.len(), 3, "only the shared banks: {jpn:?}");
        assert!(jpn.iter().all(|(_, c)| c.is_shared()));
        // And the voice view is exactly the non-shared half.
        assert_eq!(list_voice_clips(&tbl, VoiceLang::English).len(), 4);
    }

    #[test]
    fn rebuilds_riff_from_headerless() {
        let mut slb = vec![0u8; HEADERLESS_DATA_OFFSET];
        slb.extend_from_slice(&[9, 8, 7, 6]);
        let riff = to_xma_riff(&slb).unwrap();
        let dpos = find(&riff, b"data", 0).unwrap();
        assert_eq!(&riff[dpos + 8..], &[9, 8, 7, 6]);
        // synthetic fmt advertises XMA1.
        let fpos = find(&riff, b"fmt ", 0).unwrap();
        assert_eq!(le32(&riff, fpos + 8).map(|v| v as u16), Some(0x0165));
    }
}