//! What counts as audio, and what the player can actually decode.
//!
//! These were seven separate hand-kept lists — the library scanner, the share
//! index, the row pruner, the loudness pass, and three in the frontend — and
//! they disagreed. The scanner indexed `.aiff`, the pruner did not recognise it
//! and DELETED the rows on the next startup. The share index knew `.ape`, the
//! scanner did not. Every list named `.opus`, which nothing here can decode.
//!
//! One table now, with a distinction the old lists could not express:
//!
//! - [`PLAYABLE`] — the decoder can turn this into sound. Derived from the
//!   codecs symphonia is actually built with (`all-codecs` + `all-formats`:
//!   aac, adpcm, alac, flac, mp1/2/3, pcm, vorbis; caf, isomp4, mkv, ogg,
//!   aiff, wav) and verified against real files by
//!   `cargo run -p player --example probe_formats`.
//! - [`RECOGNISED`] — audio we can index, share, download and show, but cannot
//!   play. Naming these is the point: a file the app can see and refuses to
//!   play with a clear reason is honest, whereas leaving it out of the tables
//!   makes it invisible, and claiming it plays makes the player fail at the
//!   moment the user presses play.
//!
//! Adding a codec means adding a decoder, not editing a list.

/// Extensions the player can decode. Verified, not assumed.
pub const PLAYABLE: &[&str] = &[
    // FLAC
    "flac",
    // MPEG audio — the bundle provides layers I, II and III
    "mp3", "mp2", "mp1",
    // ISO/MP4 container: AAC and ALAC live here
    "m4a", "m4b", "mp4", "m4r",
    // Raw AAC (ADTS)
    "aac",
    // Ogg container, Vorbis inside
    "ogg", "oga",
    // RIFF: PCM and ADPCM
    "wav", "wave",
    // AIFF / AIFF-C, also via the RIFF reader
    "aiff", "aif", "aifc",
    // Core Audio Format
    "caf",
    // Matroska — FLAC/Vorbis/AAC in a different wrapper
    "mka", "webm",
];

/// Audio we recognise but cannot decode. Indexed and shared; never played.
///
/// `wv` earns its place here more than any of them. A WavPack file that
/// carries the original RIFF header in its wrapper is probed as raw PCM, so
/// the decoder does not fail — it reads compressed bytes as samples and emits
/// NaN into the mixer. Refusing it by extension is the only thing that stops
/// that, because the decoder itself reports success.
pub const RECOGNISED: &[&str] = &[
    "opus", // no Opus decoder is built in
    "wma", "ape", "wv", "mpc", "tta", "shn", "dsf", "dff", "spx", "ra", "au", "amr",
];

/// Is this an audio file at all — playable or merely recognised?
///
/// The scanner, the share index and the row pruner must all answer this the
/// same way, or a file is indexed by one and deleted by another.
pub fn is_audio_ext(ext: &str) -> bool {
    let e = ext.to_ascii_lowercase();
    PLAYABLE.contains(&e.as_str()) || RECOGNISED.contains(&e.as_str())
}

/// Can the player turn this into sound?
pub fn is_playable_ext(ext: &str) -> bool {
    PLAYABLE.contains(&ext.to_ascii_lowercase().as_str())
}

/// Why this file will not play, in words that can go on screen.
pub fn unplayable_reason(ext: &str) -> Option<&'static str> {
    match ext.to_ascii_lowercase().as_str() {
        "opus" => Some("Opus isn't supported yet — this build has no Opus decoder"),
        "wv" => Some("WavPack isn't supported yet"),
        "ape" => Some("Monkey's Audio (APE) isn't supported yet"),
        "wma" => Some("Windows Media Audio isn't supported yet"),
        "mpc" => Some("Musepack isn't supported yet"),
        "tta" => Some("True Audio isn't supported yet"),
        "shn" => Some("Shorten isn't supported yet"),
        "dsf" | "dff" => Some("DSD isn't supported yet"),
        e if RECOGNISED.contains(&e) => Some("this format isn't supported yet"),
        _ => None,
    }
}

fn ext_of(path: &std::path::Path) -> Option<String> {
    path.extension()
        .and_then(|e| e.to_str())
        .map(|e| e.to_ascii_lowercase())
}

pub fn is_audio_path(path: &std::path::Path) -> bool {
    ext_of(path).is_some_and(|e| is_audio_ext(&e))
}

pub fn is_playable_path(path: &std::path::Path) -> bool {
    ext_of(path).is_some_and(|e| is_playable_ext(&e))
}

/// Why this path will not play. `None` means "go ahead and try".
pub fn unplayable_path_reason(path: &std::path::Path) -> Option<&'static str> {
    unplayable_reason(&ext_of(path)?)
}

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

    /// The bug the single table exists to prevent: the scanner indexed a
    /// format the pruner did not recognise, so importing an AIFF album put it
    /// in the library and the next startup silently deleted it.
    #[test]
    fn everything_indexed_survives_the_pruner() {
        for ext in PLAYABLE.iter().chain(RECOGNISED.iter()) {
            assert!(is_audio_ext(ext), "{ext} indexed but not recognised as audio");
        }
        // The extensions that were actually in the divergence.
        for ext in ["aiff", "aif", "ape", "wv", "opus"] {
            assert!(is_audio_ext(ext), "{ext} must be recognised");
        }
    }

    /// A format cannot be both — every entry has one answer.
    #[test]
    fn no_extension_is_in_both_tables() {
        for e in PLAYABLE {
            assert!(!RECOGNISED.contains(e), "{e} is in both tables");
        }
    }

    /// Recognised-but-not-playable must carry a reason, or the UI has nothing
    /// to say when it refuses.
    #[test]
    fn every_unplayable_format_can_explain_itself() {
        for e in RECOGNISED {
            assert!(unplayable_reason(e).is_some(), "{e} has no reason");
        }
        for e in PLAYABLE {
            assert!(unplayable_reason(e).is_none(), "{e} plays but claims it cannot");
        }
    }

    /// WavPack is the dangerous one: the decoder does NOT fail on it, so only
    /// an extension check keeps NaN out of the mixer.
    #[test]
    fn wavpack_is_refused_before_the_decoder_sees_it() {
        assert!(!is_playable_ext("wv"));
        assert!(is_audio_ext("wv"));
        assert_eq!(
            unplayable_path_reason(Path::new("C:\\m\\a.WV")),
            Some("WavPack isn't supported yet"),
            "case must not decide whether audio plays"
        );
    }

    #[test]
    fn case_and_paths() {
        assert!(is_playable_ext("FLAC"));
        assert!(is_playable_path(Path::new("C:\\m\\01 - Song.Mp3")));
        assert!(!is_audio_path(Path::new("C:\\m\\cover.jpg")));
        assert!(!is_audio_path(Path::new("C:\\m\\noext")));
    }
}