libfreemkv/src/disc.rs

//! Disc structure — scan titles, streams, and sector ranges from a Blu-ray disc.
//!
//! This is the high-level API for disc content. The CLI calls this,
//! never parses MPLS/CLPI/UDF directly.
//!
//! Usage:
//!   let disc = Disc::scan(&mut session)?;
//!   for title in disc.titles() { ... }
//!   for stream in title.streams() { ... }

use crate::error::{Error, Result};
use crate::drive::DriveSession;
use crate::udf;
use crate::mpls;
use crate::clpi;


// ─── Public types ───────────────────────────────────────────────────────────

/// A scanned Blu-ray disc.
#[derive(Debug)]
pub struct Disc {
    /// UDF Volume Identifier from Primary Volume Descriptor (always present)
    pub volume_id: String,
    /// Disc title from META/DL/bdmt_eng.xml (None if disc has no metadata)
    pub meta_title: Option<String>,
    /// Disc format (BD, UHD, DVD)
    pub format: DiscFormat,
    /// Disc capacity in sectors
    pub capacity_sectors: u32,
    /// Disc capacity in bytes
    pub capacity_bytes: u64,
    /// Number of layers (1 = single, 2 = dual)
    pub layers: u8,
    /// Titles sorted by duration (longest first), then playlist name
    pub titles: Vec<Title>,
    /// Disc region
    pub region: DiscRegion,
    /// AACS state — None if disc is unencrypted or keys unavailable
    pub aacs: Option<AacsState>,
    /// Whether this disc requires AACS decryption
    pub encrypted: bool,
}

/// Disc format.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum DiscFormat {
    /// 4K UHD Blu-ray (HEVC 2160p)
    Uhd,
    /// Standard Blu-ray (1080p/1080i)
    BluRay,
    /// DVD
    Dvd,
    /// Unknown
    Unknown,
}

/// Disc playback region.
#[derive(Debug, Clone, PartialEq)]
pub enum DiscRegion {
    /// Region-free (all UHD discs, some BD/DVD)
    Free,
    /// Blu-ray regions (A/B/C or combination)
    BluRay(Vec<BdRegion>),
    /// DVD regions (1-8 or combination)
    Dvd(Vec<u8>),
}

/// Blu-ray region codes.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum BdRegion {
    /// Region A/1 — Americas, East Asia (Japan, Korea, Southeast Asia)
    A,
    /// Region B/2 — Europe, Africa, Australia, Middle East
    B,
    /// Region C/3 — Central/South Asia, China, Russia
    C,
}

/// A title (one MPLS playlist).
#[derive(Debug, Clone)]
pub struct Title {
    /// Playlist filename (e.g. "00800.mpls")
    pub playlist: String,
    /// Playlist number (e.g. 800)
    pub playlist_id: u16,
    /// Duration in seconds
    pub duration_secs: f64,
    /// Total size in bytes
    pub size_bytes: u64,
    /// Clip references in playback order
    pub clips: Vec<Clip>,
    /// All streams (video, audio, subtitle, etc.)
    pub streams: Vec<Stream>,
    /// Sector extents for ripping (clip LBA ranges)
    pub extents: Vec<Extent>,
}

/// A clip reference within a title.
#[derive(Debug, Clone)]
pub struct Clip {
    /// Clip filename without extension (e.g. "00001")
    pub clip_id: String,
    /// In-time in 45kHz ticks
    pub in_time: u32,
    /// Out-time in 45kHz ticks
    pub out_time: u32,
    /// Duration in seconds
    pub duration_secs: f64,
    /// Source packet count (from CLPI, 0 if unavailable)
    pub source_packets: u32,
}

/// A stream within a title.
#[derive(Debug, Clone)]
pub enum Stream {
    Video(VideoStream),
    Audio(AudioStream),
    Subtitle(SubtitleStream),
}

/// A video stream.
#[derive(Debug, Clone)]
pub struct VideoStream {
    /// MPEG-TS packet ID
    pub pid: u16,
    /// Codec (HEVC, H.264, VC-1, MPEG-2)
    pub codec: Codec,
    /// Resolution (e.g. "2160p", "1080p", "1080i")
    pub resolution: String,
    /// Frame rate (e.g. "23.976", "25")
    pub frame_rate: String,
    /// HDR format
    pub hdr: HdrFormat,
    /// Color space
    pub color_space: ColorSpace,
    /// Whether this is a secondary stream (PiP, Dolby Vision EL)
    pub secondary: bool,
    /// Extra label (e.g. "Dolby Vision EL")
    pub label: String,
}

/// An audio stream.
#[derive(Debug, Clone)]
pub struct AudioStream {
    /// MPEG-TS packet ID
    pub pid: u16,
    /// Codec (TrueHD, DTS-HD MA, DD, LPCM, etc.)
    pub codec: Codec,
    /// Channel layout (e.g. "5.1", "7.1", "stereo", "mono")
    pub channels: String,
    /// ISO 639-2 language code (e.g. "eng", "fra")
    pub language: String,
    /// Sample rate (e.g. "48kHz", "96kHz")
    pub sample_rate: String,
    /// Whether this is a secondary stream (commentary)
    pub secondary: bool,
    /// Extra label
    pub label: String,
}

/// A subtitle stream.
#[derive(Debug, Clone)]
pub struct SubtitleStream {
    /// MPEG-TS packet ID
    pub pid: u16,
    /// Codec (PGS)
    pub codec: Codec,
    /// ISO 639-2 language code (e.g. "eng", "fra")
    pub language: String,
    /// Whether this is a forced subtitle
    pub forced: bool,
}

/// Video/audio codec.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum Codec {
    // Video
    Hevc,
    H264,
    Vc1,
    Mpeg2,
    // Audio
    TrueHd,
    DtsHdMa,
    DtsHdHr,
    Dts,
    Ac3,
    Ac3Plus,
    Lpcm,
    // Subtitle
    Pgs,
    // Unknown
    Unknown(u8),
}

/// HDR format.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum HdrFormat {
    Sdr,
    Hdr10,
    DolbyVision,
}

/// Color space.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum ColorSpace {
    Bt709,
    Bt2020,
    Unknown,
}

/// A contiguous range of sectors on disc.
#[derive(Debug, Clone, Copy)]
pub struct Extent {
    pub start_lba: u32,
    pub sector_count: u32,
}

// ─── Display helpers ────────────────────────────────────────────────────────

impl Codec {
    pub fn name(&self) -> &'static str {
        match self {
            Codec::Hevc => "HEVC",
            Codec::H264 => "H.264",
            Codec::Vc1 => "VC-1",
            Codec::Mpeg2 => "MPEG-2",
            Codec::TrueHd => "TrueHD",
            Codec::DtsHdMa => "DTS-HD MA",
            Codec::DtsHdHr => "DTS-HD HR",
            Codec::Dts => "DTS",
            Codec::Ac3 => "AC-3",
            Codec::Ac3Plus => "AC-3+",
            Codec::Lpcm => "LPCM",
            Codec::Pgs => "PGS",
            Codec::Unknown(_) => "Unknown",
        }
    }

    fn from_coding_type(ct: u8) -> Self {
        match ct {
            0x24 => Codec::Hevc,
            0x1B => Codec::H264,
            0xEA => Codec::Vc1,
            0x02 => Codec::Mpeg2,
            0x83 => Codec::TrueHd,
            0x86 => Codec::DtsHdMa,
            0x85 => Codec::DtsHdHr,
            0x82 => Codec::Dts,
            0x81 => Codec::Ac3,
            0x84 | 0xA1 => Codec::Ac3Plus,
            0x80 => Codec::Lpcm,
            0xA2 => Codec::DtsHdHr,
            0x90 | 0x91 => Codec::Pgs,
            ct => Codec::Unknown(ct),
        }
    }
}

impl HdrFormat {
    pub fn name(&self) -> &'static str {
        match self {
            HdrFormat::Sdr => "SDR",
            HdrFormat::Hdr10 => "HDR10",
            HdrFormat::DolbyVision => "Dolby Vision",
        }
    }
}

impl ColorSpace {
    pub fn name(&self) -> &'static str {
        match self {
            ColorSpace::Bt709 => "BT.709",
            ColorSpace::Bt2020 => "BT.2020",
            ColorSpace::Unknown => "",
        }
    }
}

impl Title {
    /// Duration formatted as "Xh Ym"
    pub fn duration_display(&self) -> String {
        let hrs = (self.duration_secs / 3600.0) as u32;
        let mins = ((self.duration_secs % 3600.0) / 60.0) as u32;
        format!("{}h {:02}m", hrs, mins)
    }

    /// Size in GB
    pub fn size_gb(&self) -> f64 {
        self.size_bytes as f64 / (1024.0 * 1024.0 * 1024.0)
    }

    /// Total sectors across all extents
    pub fn total_sectors(&self) -> u64 {
        self.extents.iter().map(|e| e.sector_count as u64).sum()
    }
}


// ─── AACS state ─────────────────────────────────────────────────────────────

/// AACS decryption state for a disc.
#[derive(Debug)]
pub struct AacsState {
    /// AACS version (1 or 2)
    pub version: u8,
    /// Whether bus encryption is enabled (always true for AACS 2.0 / UHD)
    pub bus_encryption: bool,
    /// MKB version from disc (e.g. 68, 77)
    pub mkb_version: Option<u32>,
    /// Disc hash (SHA1 of Unit_Key_RO.inf) — hex string with 0x prefix
    pub disc_hash: String,
    /// How keys were resolved
    pub key_source: KeySource,
    /// Volume Unique Key (16 bytes)
    pub vuk: [u8; 16],
    /// Decrypted unit keys (CPS unit number, key)
    pub unit_keys: Vec<(u32, [u8; 16])>,
    /// Read data key for AACS 2.0 bus decryption — None for AACS 1.0
    pub read_data_key: Option<[u8; 16]>,
    /// Volume ID (16 bytes) — from SCSI handshake
    pub volume_id: [u8; 16],
}

/// How AACS keys were resolved.
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum KeySource {
    /// VUK found directly in KEYDB by disc hash
    KeyDb,
    /// Media key + Volume ID from KEYDB → derived VUK
    KeyDbDerived,
    /// MKB + processing keys → media key → VUK
    ProcessingKey,
    /// MKB + device keys → subset-difference tree → VUK
    DeviceKey,
}

impl KeySource {
    pub fn name(&self) -> &'static str {
        match self {
            KeySource::KeyDb => "KEYDB",
            KeySource::KeyDbDerived => "KEYDB (derived)",
            KeySource::ProcessingKey => "MKB + processing key",
            KeySource::DeviceKey => "MKB + device key",
        }
    }
}

// ─── Disc scanning ──────────────────────────────────────────────────────────

/// Standard KEYDB.cfg search locations (compatible with libaacs).
const KEYDB_SEARCH_PATHS: &[&str] = &[
    ".config/aacs/KEYDB.cfg",  // relative to $HOME
];
const KEYDB_SYSTEM_PATH: &str = "/etc/aacs/KEYDB.cfg";

/// Options for disc scanning.
pub struct ScanOptions {
    /// Path to KEYDB.cfg for AACS key lookup.
    /// If None, searches standard locations ($HOME/.config/aacs/ and /etc/aacs/).
    pub keydb_path: Option<std::path::PathBuf>,
}

impl Default for ScanOptions {
    fn default() -> Self {
        ScanOptions { keydb_path: None }
    }
}

impl ScanOptions {
    /// Create options with a specific KEYDB path.
    pub fn with_keydb(path: impl Into<std::path::PathBuf>) -> Self {
        ScanOptions { keydb_path: Some(path.into()) }
    }

    /// Resolve KEYDB path: explicit path first, then standard locations.
    fn resolve_keydb(&self) -> Option<std::path::PathBuf> {
        if let Some(p) = &self.keydb_path {
            if p.exists() { return Some(p.clone()); }
        }
        if let Some(home) = std::env::var_os("HOME") {
            for relative in KEYDB_SEARCH_PATHS {
                let p = std::path::PathBuf::from(&home).join(relative);
                if p.exists() { return Some(p); }
            }
        }
        let p = std::path::PathBuf::from(KEYDB_SYSTEM_PATH);
        if p.exists() { return Some(p); }
        None
    }
}

impl Disc {
    /// Disc capacity in GB
    pub fn capacity_gb(&self) -> f64 {
        self.capacity_sectors as f64 * 2048.0 / (1024.0 * 1024.0 * 1024.0)
    }

    /// Scan a disc — parse filesystem, playlists, streams, and set up AACS decryption.
    ///
    /// This is the main entry point. After scan(), the Disc is ready:
    ///   - titles are populated with streams
    ///   - AACS keys are derived (if KEYDB available)
    ///   - content can be read and decrypted transparently
    ///
    /// ```no_run
    /// use libfreemkv::{DriveSession, Disc};
    /// use libfreemkv::disc::ScanOptions;
    /// use std::path::Path;
    ///
    /// let mut session = DriveSession::open(Path::new("/dev/sr0")).unwrap();
    /// let disc = Disc::scan(&mut session, &ScanOptions::default()).unwrap();
    /// for title in &disc.titles {
    ///     println!("{} — {} streams", title.duration_display(), title.streams.len());
    /// }
    /// ```
    /// Scan a disc. One pipeline, one order:
    ///   1. Read capacity
    ///   2. Read UDF filesystem
    ///   3. Resolve AACS keys (all via UDF, no SCSI commands)
    ///   4. Parse playlists + streams
    ///   5. Apply labels
    ///
    /// The session must be open and unlocked (DriveSession::open handles this).
    /// All disc reads use standard READ(10) via UDF — no vendor SCSI commands.
    pub fn scan(session: &mut DriveSession, opts: &ScanOptions) -> Result<Self> {
        use crate::aacs::{self, KeyDb};

        // 1. Capacity
        let capacity = Self::read_capacity(session)?;

        // 2. UDF filesystem
        let udf_fs = udf::read_filesystem(session)?;

        // 3. AACS — read files from disc via UDF, resolve keys via KEYDB
        let encrypted = udf_fs.find_dir("/AACS").is_some()
            || udf_fs.find_dir("/BDMV/AACS").is_some();

        let aacs = if encrypted {
            if let Some(keydb_path) = opts.resolve_keydb() {
                Self::resolve_aacs(&udf_fs, session, &keydb_path).ok()
            } else {
                None
            }
        } else {
            None
        };

        // 4. Playlists
        let mut titles = Vec::new();
        if let Some(playlist_dir) = udf_fs.find_dir("/BDMV/PLAYLIST") {
            for entry in &playlist_dir.entries {
                if !entry.is_dir && entry.name.to_lowercase().ends_with(".mpls") {
                    let path = format!("/BDMV/PLAYLIST/{}", entry.name);
                    if let Ok(mpls_data) = udf_fs.read_file(session, &path) {
                        if let Some(title) = Self::parse_playlist(session, &udf_fs, &entry.name, &mpls_data) {
                            titles.push(title);
                        }
                    }
                }
            }
        }
        titles.sort_by(|a, b| b.duration_secs.partial_cmp(&a.duration_secs).unwrap_or(std::cmp::Ordering::Equal));

        // 5. Metadata + labels
        let meta_title = Self::read_meta_title(session, &udf_fs);
        crate::labels::apply(session, &udf_fs, &mut titles);

        // 6. Derive format, layers, region
        let format = Self::detect_format(&titles);
        let layers = if capacity > 24_000_000 { 2 } else { 1 };
        let region = if format == DiscFormat::Uhd { DiscRegion::Free } else { DiscRegion::Free };

        Ok(Disc {
            volume_id: udf_fs.volume_id.clone(),
            meta_title,
            format,
            capacity_sectors: capacity,
            capacity_bytes: capacity as u64 * 2048,
            layers,
            titles,
            region,
            aacs,
            encrypted,
        })
    }

    /// Resolve AACS keys from disc files + KEYDB. No SCSI commands.
    /// Reads Unit_Key_RO.inf, Content Certificate, and MKB from UDF.
    fn resolve_aacs(
        udf_fs: &udf::UdfFs,
        session: &mut DriveSession,
        keydb_path: &std::path::Path,
    ) -> Result<AacsState> {
        use crate::aacs::{self, KeyDb};

        let keydb = KeyDb::load(keydb_path).map_err(|e| Error::AacsError {
            detail: format!("failed to load KEYDB: {}", e),
        })?;

        // Read AACS files from disc via UDF (standard READ(10), no vendor commands)
        let uk_ro_data = udf_fs.read_file(session, "/AACS/Unit_Key_RO.inf")
            .or_else(|_| udf_fs.read_file(session, "/AACS/DUPLICATE/Unit_Key_RO.inf"))
            .map_err(|_| Error::AacsError {
                detail: "Unit_Key_RO.inf not found on disc".into(),
            })?;

        let cc_data = udf_fs.read_file(session, "/AACS/Content000.cer")
            .or_else(|_| udf_fs.read_file(session, "/AACS/Content001.cer"))
            .ok();

        let mkb_data = udf_fs.read_file(session, "/AACS/MKB_RW.inf")
            .or_else(|_| udf_fs.read_file(session, "/AACS/MKB_RO.inf"))
            .ok();
        let mkb_ver = mkb_data.as_deref().and_then(aacs::mkb_version);

        // Resolve: disc hash → KEYDB lookup → VUK → unit keys
        let vid_zero = [0u8; 16];
        let resolved = aacs::resolve_keys(
            &uk_ro_data,
            cc_data.as_deref(),
            &vid_zero,
            &keydb,
            mkb_data.as_deref(),
        ).ok_or_else(|| Error::AacsError {
            detail: "disc not in KEYDB".into(),
        })?;

        Ok(AacsState {
            version: if resolved.aacs2 { 2 } else { 1 },
            bus_encryption: resolved.bus_encryption,
            mkb_version: mkb_ver,
            disc_hash: aacs::disc_hash_hex(&resolved.disc_hash),
            key_source: match resolved.key_source {
                1 => KeySource::KeyDb,
                2 => KeySource::KeyDbDerived,
                3 => KeySource::ProcessingKey,
                4 => KeySource::DeviceKey,
                _ => KeySource::KeyDb,
            },
            vuk: resolved.vuk,
            unit_keys: resolved.unit_keys,
            read_data_key: None,
            volume_id: [0u8; 16],
        })
    }

    // ── Internal helpers ────────────────────────────────────────────────────

    /// Detect disc format from the main title's video streams.
    fn detect_format(titles: &[Title]) -> DiscFormat {
        for title in titles.iter().take(3) {
            for stream in &title.streams {
                if let Stream::Video(v) = stream {
                    if v.resolution.contains("2160") {
                        return DiscFormat::Uhd;
                    }
                    if v.resolution.contains("1080") || v.resolution.contains("720") {
                        return DiscFormat::BluRay;
                    }
                    if v.resolution.contains("480") || v.resolution.contains("576") {
                        return DiscFormat::Dvd;
                    }
                }
            }
        }
        DiscFormat::Unknown
    }

    /// Read disc title from META/DL/bdmt_eng.xml (Blu-ray Disc Meta Table).
    /// Prefers English, falls back to first available language.
    /// Returns None if META directory is empty or XML has no usable title.
    fn read_meta_title(session: &mut DriveSession, udf_fs: &udf::UdfFs) -> Option<String> {
        let meta_dir = udf_fs.find_dir("/BDMV/META")?;
        for sub in &meta_dir.entries {
            if !sub.is_dir { continue; }
            let dl_path = format!("/BDMV/META/{}", sub.name);
            if let Some(dl_dir) = udf_fs.find_dir(&dl_path) {
                let xml_files: Vec<_> = dl_dir.entries.iter()
                    .filter(|e| !e.is_dir && e.name.to_lowercase().ends_with(".xml"))
                    .collect();

                let eng = xml_files.iter().find(|e| e.name.to_lowercase().contains("eng"));
                let target = eng.or_else(|| xml_files.first());

                if let Some(entry) = target {
                    let path = format!("{}/{}", dl_path, entry.name);
                    if let Ok(data) = udf_fs.read_file(session, &path) {
                        let xml = String::from_utf8_lossy(&data);
                        if let Some(start) = xml.find("<di:name>") {
                            let s = start + "<di:name>".len();
                            if let Some(end) = xml[s..].find("</di:name>") {
                                let title = xml[s..s + end].trim().to_string();
                                if !title.is_empty() && title != "Blu-ray" {
                                    return Some(title);
                                }
                            }
                        }
                    }
                }
            }
        }
        None
    }

    fn read_capacity(session: &mut DriveSession) -> Result<u32> {
        let cdb = [0x25, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00];
        let mut buf = [0u8; 8];
        session.scsi_execute(&cdb, crate::scsi::DataDirection::FromDevice, &mut buf, 5_000)?;
        let lba = u32::from_be_bytes([buf[0], buf[1], buf[2], buf[3]]);
        Ok(lba + 1)
    }

    fn parse_playlist(
        session: &mut DriveSession,
        udf_fs: &udf::UdfFs,
        filename: &str,
        data: &[u8],
    ) -> Option<Title> {
        let parsed = mpls::parse(data).ok()?;

        // Calculate duration from play items
        let duration_ticks: u64 = parsed.play_items.iter()
            .map(|pi| (pi.out_time.saturating_sub(pi.in_time)) as u64)
            .sum();
        let duration_secs = duration_ticks as f64 / 45000.0;

        // Skip very short playlists (< 30 seconds)
        if duration_secs < 30.0 {
            return None;
        }

        // Parse each clip for size, duration, and sector extents
        let mut extents = Vec::new();
        let mut total_size: u64 = 0;
        let mut clips = Vec::with_capacity(parsed.play_items.len());

        for play_item in &parsed.play_items {
            let clip_dur = play_item.out_time.saturating_sub(play_item.in_time) as f64 / 45000.0;
            let mut pkt_count: u32 = 0;

            let clpi_path = format!("/BDMV/CLIPINF/{}.clpi", play_item.clip_id);
            if let Ok(clpi_data) = udf_fs.read_file(session, &clpi_path) {
                if let Ok(clip_info) = clpi::parse(&clpi_data) {
                    pkt_count = clip_info.source_packet_count;
                    total_size += pkt_count as u64 * 192;

                    // Get m2ts file start LBA and compute extent from packet count.
                    // BD-ROM m2ts files are contiguous on disc (mastering requirement).
                    let m2ts_path = format!("/BDMV/STREAM/{}.m2ts", play_item.clip_id);
                    let file_lba = udf_fs.file_start_lba(session, &m2ts_path).unwrap_or(0);
                    let total_bytes = pkt_count as u64 * 192;
                    let total_sectors = ((total_bytes + 2047) / 2048) as u32;
                    if total_sectors > 0 && file_lba > 0 {
                        extents.push(Extent {
                            start_lba: file_lba,
                            sector_count: total_sectors,
                        });
                    }
                }
            }

            clips.push(Clip {
                clip_id: play_item.clip_id.clone(),
                in_time: play_item.in_time,
                out_time: play_item.out_time,
                duration_secs: clip_dur,
                source_packets: pkt_count,
            });
        }

        // Build streams from STN table
        let streams: Vec<Stream> = parsed.streams.iter().filter_map(|s| {
            // Skip empty/padding entries (coding_type 0x00)
            if s.coding_type == 0 { return None; }
            let codec = Codec::from_coding_type(s.coding_type);
            match s.stream_type {
                1 | 6 | 7 => Some(Stream::Video(VideoStream {
                    pid: s.pid,
                    codec,
                    resolution: format_resolution(s.video_format, s.video_rate),
                    frame_rate: format_framerate(s.video_rate),
                    hdr: match s.dynamic_range {
                        1 => HdrFormat::Hdr10,
                        2 => HdrFormat::DolbyVision,
                        _ => HdrFormat::Sdr,
                    },
                    color_space: match s.color_space {
                        1 => ColorSpace::Bt709,
                        2 => ColorSpace::Bt2020,
                        _ => ColorSpace::Unknown,
                    },
                    secondary: s.secondary,
                    label: match s.stream_type {
                        7 => "Dolby Vision EL".to_string(),
                        _ => String::new(),
                    },
                })),
                2 | 5 => {
                    // Guard: if coding_type is a subtitle codec (PGS 0x90/0x91),
                    // this is a misaligned stream — treat as subtitle, not audio
                    if matches!(codec, Codec::Pgs) {
                        Some(Stream::Subtitle(SubtitleStream {
                            pid: s.pid,
                            codec,
                            language: s.language.clone(),
                            forced: false,
                        }))
                    } else {
                        Some(Stream::Audio(AudioStream {
                            pid: s.pid,
                            codec,
                            channels: format_channels(s.audio_format),
                            language: s.language.clone(),
                            sample_rate: format_samplerate(s.audio_rate),
                            secondary: s.stream_type == 5,
                            label: String::new(),
                        }))
                    }
                }
                3 => Some(Stream::Subtitle(SubtitleStream {
                    pid: s.pid,
                    codec,
                    language: s.language.clone(),
                    forced: false,
                })),
                // Stream type 4 = IG, unknown types — skip
                _ => None,
            }
        }).collect();

        let playlist_num = filename.trim_end_matches(".mpls").trim_end_matches(".MPLS");
        let playlist_id = playlist_num.parse::<u16>().unwrap_or(0);

        Some(Title {
            playlist: filename.to_string(),
            playlist_id,
            duration_secs,
            size_bytes: total_size,
            clips,
            streams,
            extents,
        })
    }
}

// ─── Decrypted reader ──────────────────────────────────────────────────────

/// A reader that reads m2ts content, decrypting transparently if needed.
///
/// Adaptive read strategy:
///   - Starts at max batch size (510 sectors ≈ 1MB) and full disc speed
///   - On read error: halves batch size, brief pause for drive recovery
///   - On repeated errors: reduces disc spin speed (scratched region)
///   - On success streak: ramps batch back up, then restores disc speed
///   - At minimum batch + still failing: retries once, then skips + zero-fills
pub struct ContentReader<'a> {
    session: &'a mut DriveSession,
    aacs: Option<&'a AacsState>,
    extents: Vec<Extent>,
    current_extent: usize,
    current_offset: u32,
    unit_key_idx: usize,
    read_buf: Vec<u8>,
    buf_pos: usize,
    buf_len: usize,
    /// Current batch size in sectors (adapts on errors)
    batch_sectors: u16,
    /// Maximum batch size detected from kernel limits
    max_batch_sectors: u16,
    /// Consecutive successful batch reads
    ok_streak: u32,
    /// Consecutive errors at current position
    error_streak: u32,
    /// Current speed tier index (0 = max, higher = slower)
    speed_tier: usize,
    /// Last time maintain_speed was called
    last_speed_maintain: std::time::Instant,
    /// Total read errors encountered
    pub errors: u32,
}

impl Disc {
    /// Open a title for reading. Decryption is automatic — if the disc
    /// is encrypted and keys were found during scan(), content is decrypted
    /// on the fly. Unencrypted discs pass through unchanged.
    ///
    /// ```no_run
    /// # use libfreemkv::{DriveSession, Disc};
    /// # use libfreemkv::disc::ScanOptions;
    /// # use std::path::Path;
    /// # let mut session = DriveSession::open(Path::new("/dev/sr0")).unwrap();
    /// let disc = Disc::scan(&mut session, &ScanOptions::default()).unwrap();
    /// let mut reader = disc.open_title(&mut session, 0).unwrap();
    /// while let Some(unit) = reader.read_unit().unwrap() {
    ///     // unit is 6144 bytes of decrypted content
    /// }
    /// ```
    pub fn open_title<'a>(&'a self, session: &'a mut DriveSession, title_idx: usize) -> Result<ContentReader<'a>> {
        let title = self.titles.get(title_idx).ok_or_else(|| Error::DiscError {
            detail: format!("title index {} out of range (have {})", title_idx, self.titles.len()),
        })?;

        // Let the drive manage its own read speed after init.
        // SET_CD_SPEED is only used reactively by the error handler to slow
        // down on read errors, then let the drive recover.

        // Detect kernel max transfer size for this device
        let max_batch = detect_max_batch_sectors(session.device_path());

        Ok(ContentReader {
            session,
            aacs: self.aacs.as_ref(),
            extents: title.extents.clone(),
            current_extent: 0,
            current_offset: 0,
            unit_key_idx: 0,
            read_buf: Vec::with_capacity(max_batch as usize * 2048),
            buf_pos: 0,
            buf_len: 0,
            batch_sectors: max_batch,
            max_batch_sectors: max_batch,
            ok_streak: 0,
            error_streak: 0,
            speed_tier: 0,
            last_speed_maintain: std::time::Instant::now(),
            errors: 0,
        })
    }
}

/// Detect the maximum transfer size in sectors for a device.
/// Reads /sys/block/<dev>/queue/max_hw_sectors_kb on Linux.
/// For sg devices, resolves the corresponding block device via sysfs.
/// Returns a value aligned to 3 sectors (one aligned unit).
fn detect_max_batch_sectors(device_path: &str) -> u16 {
    let dev_name = device_path.rsplit('/').next().unwrap_or("");
    if dev_name.is_empty() {
        return DEFAULT_BATCH_SECTORS;
    }

    // For sg devices, find the corresponding block device name
    let block_name = if dev_name.starts_with("sg") {
        let block_dir = format!("/sys/class/scsi_generic/{}/device/block", dev_name);
        std::fs::read_dir(&block_dir).ok()
            .and_then(|mut entries| entries.next())
            .and_then(|e| e.ok())
            .map(|e| e.file_name().to_string_lossy().to_string())
    } else {
        Some(dev_name.to_string())
    };

    if let Some(bname) = block_name {
        let sysfs_path = format!("/sys/block/{}/queue/max_hw_sectors_kb", bname);
        if let Ok(content) = std::fs::read_to_string(&sysfs_path) {
            if let Ok(kb) = content.trim().parse::<u32>() {
                // Convert KB to sectors (1 sector = 2 KB = 2048 bytes)
                let sectors = (kb / 2) as u16;
                // Stay well under kernel limit (80% of max) to avoid edge cases
                let safe = (sectors * 4 / 5).max(MIN_BATCH_SECTORS);
                // Align down to 3 (one aligned unit)
                let aligned = (safe / 3) * 3;
                if aligned >= MIN_BATCH_SECTORS {
                    return aligned.min(MAX_BATCH_SECTORS);
                }
            }
        }
    }
    // Fallback: safe default well under typical kernel limits
    DEFAULT_BATCH_SECTORS
}

/// Read strategy constants
const MAX_BATCH_SECTORS: u16 = 510;  // absolute max (170 aligned units ≈ 1MB)
const DEFAULT_BATCH_SECTORS: u16 = 48;  // safe fallback (96KB, under typical 120KB kernel limit)
const MIN_BATCH_SECTORS: u16 = 3;    // 1 aligned unit = 6KB (error recovery)
const RAMP_BATCH_AFTER: u32 = 5;     // successes before doubling batch size
const RAMP_SPEED_AFTER: u32 = 50;    // successes at max batch before restoring speed
const SLOW_SPEED_AFTER: u32 = 3;     // consecutive errors before reducing disc speed

/// Disc speed tiers (KB/s for SET CD SPEED).
/// Blu-ray: 1x=4500, 2x=9000, 4x=18000, 8x=36000, 12x=54000
const SPEED_TIERS: &[u16] = &[
    0xFFFF, // tier 0: max (drive decides, typically 8-12x)
    36000,  // tier 1: 8x BD (~36 MB/s)
    18000,  // tier 2: 4x BD (~18 MB/s)
    9000,   // tier 3: 2x BD (~9 MB/s)
    4500,   // tier 4: 1x BD (~4.5 MB/s) — last resort
];

impl<'a> ContentReader<'a> {
    /// Total bytes across all extents (for progress display).
    pub fn total_bytes(&self) -> u64 {
        self.extents.iter().map(|e| e.sector_count as u64 * 2048).sum()
    }

    /// Read the next aligned unit (6144 bytes).
    /// Automatically decrypted if AACS keys are available.
    /// Returns None when all extents are exhausted.
    pub fn read_unit(&mut self) -> Result<Option<Vec<u8>>> {
        // Refill buffer if empty
        if self.buf_pos >= self.buf_len {
            if !self.fill_buffer()? {
                return Ok(None);
            }
        }

        // Extract one aligned unit from buffer
        let start = self.buf_pos * crate::aacs::ALIGNED_UNIT_LEN;
        let end = start + crate::aacs::ALIGNED_UNIT_LEN;
        let mut unit = self.read_buf[start..end].to_vec();

        // Decrypt if needed
        self.decrypt_unit(&mut unit);
        self.buf_pos += 1;
        Ok(Some(unit))
    }

    /// Read the next batch of aligned units, decrypted in-place.
    /// Returns the decrypted data as a single contiguous slice.
    /// More efficient than read_unit() — one write_all() per batch instead of per unit.
    /// Returns None when all extents are exhausted.
    pub fn read_batch(&mut self) -> Result<Option<&[u8]>> {
        if !self.fill_buffer()? {
            return Ok(None);
        }

        // Decrypt all units in the buffer in-place
        let unit_len = crate::aacs::ALIGNED_UNIT_LEN;
        if let Some(aacs) = &self.aacs {
            let uk = aacs.unit_keys.get(self.unit_key_idx)
                .map(|(_, k)| *k)
                .unwrap_or([0u8; 16]);
            let rdk = aacs.read_data_key.as_ref();

            for i in 0..self.buf_len {
                let start = i * unit_len;
                let end = start + unit_len;
                let unit = &mut self.read_buf[start..end];
                if crate::aacs::is_unit_encrypted(unit) {
                    crate::aacs::decrypt_unit_full(unit, &uk, rdk);
                }
            }
        }

        let total_bytes = self.buf_len * unit_len;
        self.buf_pos = self.buf_len; // mark fully consumed
        Ok(Some(&self.read_buf[..total_bytes]))
    }

    /// Decrypt a single aligned unit in-place if needed.
    fn decrypt_unit(&self, unit: &mut [u8]) {
        if let Some(aacs) = &self.aacs {
            if crate::aacs::is_unit_encrypted(unit) {
                let uk = aacs.unit_keys.get(self.unit_key_idx)
                    .map(|(_, k)| *k)
                    .unwrap_or([0u8; 16]);

                crate::aacs::decrypt_unit_full(
                    unit,
                    &uk,
                    aacs.read_data_key.as_ref(),
                );
            }
        }
    }

    /// Read sectors via standard READ(10) 0x00.
    /// calibration primers. Standard reads are faster on most drives.
    fn read_sectors(&mut self, lba: u32, count: u16) -> Result<()> {
        self.session.read_content(lba, count, &mut self.read_buf)?;
        Ok(())
    }

    /// Set disc spin speed via SCSI SET CD SPEED.
    fn set_speed(&mut self, tier: usize) {
        let tier = tier.min(SPEED_TIERS.len() - 1);
        if tier != self.speed_tier {
            self.speed_tier = tier;
            let speed_kbs = SPEED_TIERS[tier];
            let cdb = crate::scsi::build_set_cd_speed(speed_kbs);
            let mut dummy = [0u8; 0];
            let _ = self.session.scsi_execute(
                &cdb, crate::scsi::DataDirection::None, &mut dummy, 5_000,
            );
        }
    }

    /// Read a batch of sectors into the internal buffer.
    ///
    /// Adaptive strategy:
    ///   1. Read at current batch size
    ///   2. On success: ramp batch up (double after 5 successes),
    ///      then restore disc speed (after 50 at max batch)
    ///   3. On error: halve batch, pause. After 3 consecutive errors,
    ///      also reduce disc spin speed (scratched/damaged region).
    ///   4. At min batch + still failing: retry once, then skip + zero-fill.
    fn fill_buffer(&mut self) -> Result<bool> {
        loop {
            if self.current_extent >= self.extents.len() {
                return Ok(false);
            }

            let ext_start = self.extents[self.current_extent].start_lba;
            let ext_sectors = self.extents[self.current_extent].sector_count;
            let remaining = ext_sectors - self.current_offset;

            // Align to 3 sectors (one aligned unit)
            let sectors_to_read = remaining.min(self.batch_sectors as u32) as u16;
            let sectors_to_read = sectors_to_read - (sectors_to_read % 3);
            if sectors_to_read == 0 {
                self.current_extent += 1;
                self.current_offset = 0;
                continue;
            }

            let lba = ext_start + self.current_offset;
            let byte_count = sectors_to_read as usize * 2048;
            self.read_buf.resize(byte_count, 0);

            match self.read_sectors(lba, sectors_to_read) {
                Ok(_) => {
                    self.buf_len = sectors_to_read as usize / 3;
                    self.buf_pos = 0;
                    self.current_offset += sectors_to_read as u32;
                    self.error_streak = 0;

                    if self.current_offset >= ext_sectors {
                        self.current_extent += 1;
                        self.current_offset = 0;
                    }

                    // Ramp up: batch size first, then disc speed
                    self.ok_streak += 1;
                    if self.batch_sectors < self.max_batch_sectors {
                        if self.ok_streak >= RAMP_BATCH_AFTER {
                            self.batch_sectors = (self.batch_sectors * 2).min(self.max_batch_sectors);
                            self.ok_streak = 0;
                        }
                    } else if self.speed_tier > 0 && self.ok_streak >= RAMP_SPEED_AFTER {
                        // At max batch for a while — try faster disc speed
                        self.set_speed(self.speed_tier - 1);
                        self.ok_streak = 0;
                    }

                    return Ok(true);
                }
                Err(_) => {
                    self.errors += 1;
                    self.error_streak += 1;
                    self.ok_streak = 0;

                    // Reduce disc speed after repeated errors (physical problem)
                    if self.error_streak >= SLOW_SPEED_AFTER
                        && self.speed_tier < SPEED_TIERS.len() - 1
                    {
                        self.set_speed(self.speed_tier + 1);
                        self.error_streak = 0; // reset — give new speed a chance
                    }

                    if self.batch_sectors > MIN_BATCH_SECTORS {
                        // Shrink batch and retry
                        self.batch_sectors = (self.batch_sectors / 2).max(MIN_BATCH_SECTORS);
                        std::thread::sleep(std::time::Duration::from_millis(100));
                    } else {
                        // At minimum batch — retry once with longer pause
                        std::thread::sleep(std::time::Duration::from_millis(500));
                        self.read_buf.resize(MIN_BATCH_SECTORS as usize * 2048, 0);
                        if self.read_sectors(lba, MIN_BATCH_SECTORS).is_ok() {
                            self.buf_len = 1;
                            self.buf_pos = 0;
                            self.error_streak = 0;
                            self.current_offset += MIN_BATCH_SECTORS as u32;
                            if self.current_offset >= ext_sectors {
                                self.current_extent += 1;
                                self.current_offset = 0;
                            }
                            return Ok(true);
                        }
                        // Still failing — skip this unit (zero-fill)
                        self.current_offset += 3;
                        if self.current_offset >= ext_sectors {
                            self.current_extent += 1;
                            self.current_offset = 0;
                        }
                        self.read_buf.resize(crate::aacs::ALIGNED_UNIT_LEN, 0);
                        self.read_buf.fill(0);
                        self.buf_len = 1;
                        self.buf_pos = 0;
                        return Ok(true);
                    }
                }
            }
        }
    }
}

// ─── Format helpers ────────────────────────────────────────────────────────

fn format_resolution(video_format: u8, _video_rate: u8) -> String {
    match video_format {
        1 => "480i".into(),
        2 => "576i".into(),
        3 => "480p".into(),
        4 => "1080i".into(),
        5 => "720p".into(),
        6 => "1080p".into(),
        7 => "576p".into(),
        8 => "2160p".into(),
        _ => String::new(),
    }
}

fn format_framerate(video_rate: u8) -> String {
    match video_rate {
        1 => "23.976".into(),
        2 => "24".into(),
        3 => "25".into(),
        4 => "29.97".into(),
        6 => "50".into(),
        7 => "59.94".into(),
        _ => String::new(),
    }
}

fn format_channels(audio_format: u8) -> String {
    match audio_format {
        1 => "mono".into(),
        3 => "stereo".into(),
        6 => "5.1".into(),
        12 => "7.1".into(),
        _ if audio_format > 0 => format!("{}ch", audio_format),
        _ => String::new(),
    }
}

fn format_samplerate(audio_rate: u8) -> String {
    match audio_rate {
        1 => "48kHz".into(),
        4 => "96kHz".into(),
        5 => "192kHz".into(),
        12 => "48/192kHz".into(),
        14 => "48/96kHz".into(),
        _ => String::new(),
    }
}