//! HEVC (H.265) elementary stream parser.
//!
//! Extracts VPS, SPS, PPS NAL units for MKV codecPrivate.
//! Detects keyframes (IRAP pictures: IDR, CRA, BLA).
//! Each PES packet = one access unit = one frame.

use super::h264::{find_start_code, skip_start_code};
use super::{pts_to_ns, CodecParser, Frame, PesPacket};

// HEVC NAL unit types
const NAL_VPS: u8 = 32;
const NAL_SPS: u8 = 33;
const NAL_PPS: u8 = 34;
const NAL_AUD: u8 = 35;
// Dolby Vision RPU (Reference Processing Unit) — NAL type 62 (UNSPEC62).
// This is NOT filtered: all NAL types except VPS/SPS/PPS/AUD pass through
// to frame data, so DV enhancement layer RPU NALs are preserved automatically.
const _NAL_UNSPEC62_DV_RPU: u8 = 62;
// IRAP types (keyframes): BLA, IDR, CRA
const NAL_BLA_W_LP: u8 = 16;
const NAL_RSV_IRAP_VCL23: u8 = 23;

pub struct HevcParser {
    vps: Option<Vec<u8>>,
    sps: Option<Vec<u8>>,
    pps: Option<Vec<u8>>,
}

impl Default for HevcParser {
    fn default() -> Self {
        Self::new()
    }
}

impl HevcParser {
    pub fn new() -> Self {
        Self {
            vps: None,
            sps: None,
            pps: None,
        }
    }
}

impl CodecParser for HevcParser {
    fn parse(&mut self, pes: &PesPacket) -> Vec<Frame> {
        if pes.data.is_empty() {
            return Vec::new();
        }

        // Use DTS when available (monotonic for B-frame content), fall back to PTS
        let pts_ns = pes.dts.or(pes.pts).map(pts_to_ns).unwrap_or(0);
        let data = &pes.data;
        let mut keyframe = false;

        // Scan NAL units
        let mut pos = 0;
        while let Some(sc_pos) = find_start_code(data, pos) {
            if let Some(nal_start) = skip_start_code(data, sc_pos) {
                let next = find_start_code(data, nal_start).unwrap_or(data.len());
                let mut end = next;
                while end > nal_start && data[end - 1] == 0x00 {
                    end -= 1;
                }

                if nal_start < data.len() {
                    // HEVC NAL header: 2 bytes. Type is bits 1-6 of first byte.
                    let nal_type = (data[nal_start] >> 1) & 0x3F;

                    match nal_type {
                        NAL_VPS => self.vps = Some(data[nal_start..end].to_vec()),
                        NAL_SPS => self.sps = Some(data[nal_start..end].to_vec()),
                        NAL_PPS => self.pps = Some(data[nal_start..end].to_vec()),
                        t if (NAL_BLA_W_LP..=NAL_RSV_IRAP_VCL23).contains(&t) => {
                            keyframe = true;
                        }
                        _ => {}
                    }
                }
                pos = next;
            } else {
                break;
            }
        }

        // Convert Annex B to length-prefixed NALUs.
        // Skip VPS/SPS/PPS/AUD — they're in codecPrivate.
        let mut frame_data = Vec::new();
        let mut pos = 0;
        while let Some(sc_pos) = find_start_code(&pes.data, pos) {
            if let Some(nal_start) = skip_start_code(&pes.data, sc_pos) {
                let next = find_start_code(&pes.data, nal_start).unwrap_or(pes.data.len());
                let mut end = next;
                while end > nal_start && pes.data[end - 1] == 0x00 {
                    end -= 1;
                }

                if nal_start < pes.data.len() {
                    let nal_type = (pes.data[nal_start] >> 1) & 0x3F;
                    // Skip parameter sets and AUD
                    if nal_type != NAL_VPS
                        && nal_type != NAL_SPS
                        && nal_type != NAL_PPS
                        && nal_type != NAL_AUD
                    {
                        let nal = &pes.data[nal_start..end];
                        let len = nal.len() as u32;
                        frame_data.extend_from_slice(&len.to_be_bytes());
                        frame_data.extend_from_slice(nal);
                    }
                }
                pos = next;
            } else {
                break;
            }
        }

        if frame_data.is_empty() {
            return Vec::new();
        }

        vec![Frame {
            pts_ns,
            keyframe,
            data: frame_data,
        }]
    }

    fn codec_private(&self) -> Option<Vec<u8>> {
        // HEVCDecoderConfigurationRecord (ISO 14496-15)
        let vps = self.vps.as_ref()?;
        let sps = self.sps.as_ref()?;
        let pps = self.pps.as_ref()?;

        // Simplified: store as arrays in Annex B format
        // Full HEVCDecoderConfigurationRecord is complex — for now, concatenate
        let mut record = Vec::new();

        // Minimal HEVCDecoderConfigurationRecord header
        record.push(1); // configurationVersion
                        // General profile space, tier flag, profile IDC from SPS
        if sps.len() > 3 {
            record.push(sps[1]); // general_profile_space + general_tier_flag + general_profile_idc
        } else {
            record.push(0);
        }
        // general_profile_compatibility_flags (4 bytes) — from SPS bytes 2..6
        if sps.len() > 5 {
            record.extend_from_slice(&sps[2..6]);
        } else {
            record.extend_from_slice(&[0, 0, 0, 0]);
        }
        // general_constraint_indicator_flags (6 bytes) — from SPS bytes 6..12
        if sps.len() > 11 {
            record.extend_from_slice(&sps[6..12]);
        } else {
            let avail = sps.len().saturating_sub(6).min(6);
            if avail > 0 {
                record.extend_from_slice(&sps[6..6 + avail]);
                record.extend_from_slice(&vec![0u8; 6 - avail]);
            } else {
                record.extend_from_slice(&[0, 0, 0, 0, 0, 0]);
            }
        }
        // general_level_idc
        record.push(if sps.len() > 12 { sps[12] } else { 0 });
        // min_spatial_segmentation_idc (4 + 12 bits)
        record.extend_from_slice(&[0xF0, 0x00]);
        // parallelismType (6 + 2 bits)
        record.push(0xFC);
        // chromaFormat (6 + 2 bits)
        record.push(0xFC | 1); // 4:2:0
                               // bitDepthLumaMinus8 (5 + 3 bits)
        record.push(0xF8);
        // bitDepthChromaMinus8 (5 + 3 bits)
        record.push(0xF8);
        // avgFrameRate
        record.extend_from_slice(&[0, 0]);
        // constantFrameRate + numTemporalLayers + temporalIdNested + lengthSizeMinusOne
        record.push(0x03); // lengthSizeMinusOne = 3 (4 bytes)
                           // numOfArrays
        record.push(3); // VPS, SPS, PPS

        // VPS array
        record.push(0x20 | (NAL_VPS & 0x3F)); // array_completeness + NAL type
        record.extend_from_slice(&[0, 1]); // numNalus = 1
        record.push((vps.len() >> 8) as u8);
        record.push(vps.len() as u8);
        record.extend_from_slice(vps);

        // SPS array
        record.push(0x20 | (NAL_SPS & 0x3F));
        record.extend_from_slice(&[0, 1]);
        record.push((sps.len() >> 8) as u8);
        record.push(sps.len() as u8);
        record.extend_from_slice(sps);

        // PPS array
        record.push(0x20 | (NAL_PPS & 0x3F));
        record.extend_from_slice(&[0, 1]);
        record.push((pps.len() >> 8) as u8);
        record.push(pps.len() as u8);
        record.extend_from_slice(pps);

        Some(record)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::mux::ts::PesPacket;

    fn make_pes(data: Vec<u8>, pts: Option<i64>) -> PesPacket {
        PesPacket {
            pid: 0x1011,
            pts,
            dts: None,
            data,
        }
    }

    /// Build an HEVC NAL header (2 bytes). Type is bits 1-6 of first byte.
    /// Format: forbidden(1) | type(6) | layer_id_high(1) || layer_id_low(5) | tid(3)
    fn hevc_nal_header(nal_type: u8) -> [u8; 2] {
        [(nal_type & 0x3F) << 1, 0x01] // tid=1
    }

    // --- VPS+SPS+PPS → codec_private ---

    #[test]
    fn parse_vps_sps_pps() {
        let mut parser = HevcParser::new();

        let mut data = Vec::new();
        // VPS (type 32)
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        let vps_hdr = hevc_nal_header(32);
        data.extend_from_slice(&vps_hdr);
        data.extend_from_slice(&[0xAA, 0xBB, 0xCC]); // VPS payload

        // SPS (type 33)
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        let sps_hdr = hevc_nal_header(33);
        data.extend_from_slice(&sps_hdr);
        data.extend_from_slice(&[
            0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D,
        ]); // SPS payload (>12 bytes for level)

        // PPS (type 34)
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        let pps_hdr = hevc_nal_header(34);
        data.extend_from_slice(&pps_hdr);
        data.extend_from_slice(&[0xDD, 0xEE]); // PPS payload

        // IRAP slice (type 19 = IDR_W_RADL) so a frame is emitted
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        let idr_hdr = hevc_nal_header(19);
        data.extend_from_slice(&idr_hdr);
        data.extend_from_slice(&[0x10, 0x20, 0x30]);

        let pes = make_pes(data, Some(90000));
        let _frames = parser.parse(&pes);

        let cp = parser.codec_private();
        assert!(
            cp.is_some(),
            "codec_private should be Some after VPS+SPS+PPS"
        );

        let cp = cp.unwrap();
        // configurationVersion = 1
        assert_eq!(cp[0], 1);
        // numOfArrays = 3 (VPS, SPS, PPS)
        assert_eq!(cp[22], 3);
        // Should be longer than the minimal header (23 bytes) + array entries
        assert!(
            cp.len() > 23,
            "codec_private should contain VPS+SPS+PPS data"
        );
    }

    #[test]
    fn codec_private_none_before_params() {
        let parser = HevcParser::new();
        assert!(parser.codec_private().is_none());
    }

    #[test]
    fn codec_private_none_missing_pps() {
        let mut parser = HevcParser::new();

        // Only VPS + SPS, no PPS
        let mut data = Vec::new();
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        data.extend_from_slice(&hevc_nal_header(32));
        data.extend_from_slice(&[0xAA, 0xBB]);
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        data.extend_from_slice(&hevc_nal_header(33));
        data.extend_from_slice(&[0x01, 0x02, 0x03, 0x04]);
        // Add a slice so parse doesn't return empty
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        data.extend_from_slice(&hevc_nal_header(1)); // TRAIL_R
        data.extend_from_slice(&[0x10, 0x20]);

        let pes = make_pes(data, Some(0));
        parser.parse(&pes);
        assert!(
            parser.codec_private().is_none(),
            "should be None without PPS"
        );
    }

    // --- IRAP keyframe detection ---

    #[test]
    fn parse_irap_keyframe_idr_w_radl() {
        let mut parser = HevcParser::new();

        let mut data = Vec::new();
        // IDR_W_RADL = type 19
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        data.extend_from_slice(&hevc_nal_header(19));
        data.extend_from_slice(&[0x10, 0x20, 0x30]);

        let pes = make_pes(data, Some(90000));
        let frames = parser.parse(&pes);

        assert_eq!(frames.len(), 1);
        assert!(
            frames[0].keyframe,
            "IDR_W_RADL (type 19) should be keyframe"
        );
    }

    #[test]
    fn parse_irap_keyframe_bla() {
        let mut parser = HevcParser::new();

        // BLA_W_LP = type 16
        let mut data = Vec::new();
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        data.extend_from_slice(&hevc_nal_header(16));
        data.extend_from_slice(&[0x10, 0x20]);

        let pes = make_pes(data, Some(0));
        let frames = parser.parse(&pes);
        assert_eq!(frames.len(), 1);
        assert!(frames[0].keyframe, "BLA_W_LP (type 16) should be keyframe");
    }

    #[test]
    fn parse_irap_keyframe_cra() {
        let mut parser = HevcParser::new();

        // CRA_NUT = type 21
        let mut data = Vec::new();
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        data.extend_from_slice(&hevc_nal_header(21));
        data.extend_from_slice(&[0x10, 0x20]);

        let pes = make_pes(data, Some(0));
        let frames = parser.parse(&pes);
        assert_eq!(frames.len(), 1);
        assert!(frames[0].keyframe, "CRA (type 21) should be keyframe");
    }

    #[test]
    fn parse_irap_type_23() {
        let mut parser = HevcParser::new();

        // RSV_IRAP_VCL23 = type 23 (upper boundary)
        let mut data = Vec::new();
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        data.extend_from_slice(&hevc_nal_header(23));
        data.extend_from_slice(&[0x10, 0x20]);

        let pes = make_pes(data, Some(0));
        let frames = parser.parse(&pes);
        assert_eq!(frames.len(), 1);
        assert!(frames[0].keyframe, "type 23 should be keyframe");
    }

    // --- non-IRAP (trailing) → not keyframe ---

    #[test]
    fn parse_trailing_not_keyframe() {
        let mut parser = HevcParser::new();

        // TRAIL_R = type 1
        let mut data = Vec::new();
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        data.extend_from_slice(&hevc_nal_header(1));
        data.extend_from_slice(&[0x10, 0x20, 0x30]);

        let pes = make_pes(data, Some(180000));
        let frames = parser.parse(&pes);

        assert_eq!(frames.len(), 1);
        assert!(
            !frames[0].keyframe,
            "TRAIL_R (type 1) should not be keyframe"
        );
    }

    #[test]
    fn parse_tsa_not_keyframe() {
        let mut parser = HevcParser::new();

        // TSA_N = type 2
        let mut data = Vec::new();
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        data.extend_from_slice(&hevc_nal_header(2));
        data.extend_from_slice(&[0x10, 0x20]);

        let pes = make_pes(data, Some(0));
        let frames = parser.parse(&pes);
        assert_eq!(frames.len(), 1);
        assert!(!frames[0].keyframe, "TSA_N (type 2) should not be keyframe");
    }

    // --- VPS/SPS/PPS stripped from frame data ---

    #[test]
    fn param_sets_stripped_from_frame() {
        let mut parser = HevcParser::new();

        let mut data = Vec::new();
        // VPS
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        data.extend_from_slice(&hevc_nal_header(32));
        data.extend_from_slice(&[0xAA]);
        // SPS
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        data.extend_from_slice(&hevc_nal_header(33));
        data.extend_from_slice(&[0xBB]);
        // PPS
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        data.extend_from_slice(&hevc_nal_header(34));
        data.extend_from_slice(&[0xCC]);
        // IDR slice
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        let idr_hdr = hevc_nal_header(19);
        data.extend_from_slice(&idr_hdr);
        data.extend_from_slice(&[0x10, 0x20]);

        let pes = make_pes(data, Some(0));
        let frames = parser.parse(&pes);
        assert_eq!(frames.len(), 1);

        // Frame data should only have the IDR NAL (length-prefixed)
        let fd = &frames[0].data;
        let length = u32::from_be_bytes([fd[0], fd[1], fd[2], fd[3]]);
        // IDR NAL = 2 bytes header + 2 bytes payload = 4 bytes
        assert_eq!(
            length as usize + 4,
            fd.len(),
            "frame should contain exactly one length-prefixed NAL"
        );
    }

    // --- empty PES ---

    #[test]
    fn parse_empty_pes() {
        let mut parser = HevcParser::new();
        let pes = make_pes(Vec::new(), Some(0));
        let frames = parser.parse(&pes);
        assert!(frames.is_empty());
    }

    // --- PTS conversion ---

    #[test]
    fn pts_conversion() {
        let mut parser = HevcParser::new();

        let mut data = Vec::new();
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        data.extend_from_slice(&hevc_nal_header(1));
        data.extend_from_slice(&[0x10, 0x20]);

        let pes = make_pes(data, Some(90000));
        let frames = parser.parse(&pes);
        assert_eq!(frames.len(), 1);
        assert_eq!(frames[0].pts_ns, 1_000_000_000);
    }

    // --- Dolby Vision enhancement layer ---

    #[test]
    fn dv_rpu_nal_preserved() {
        // Dolby Vision enhancement layer streams contain RPU (Reference Processing
        // Unit) metadata as NAL type 62 (UNSPEC62). The HEVC parser must pass these
        // through to the frame data — only VPS/SPS/PPS/AUD are stripped.
        let mut parser = HevcParser::new();

        let mut data = Vec::new();

        // VPS (type 32) — should be stripped from frame data
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        data.extend_from_slice(&hevc_nal_header(32));
        data.extend_from_slice(&[0xAA, 0xBB]);

        // SPS (type 33) — should be stripped from frame data
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        data.extend_from_slice(&hevc_nal_header(33));
        data.extend_from_slice(&[0x01, 0x02, 0x03, 0x04]);

        // PPS (type 34) — should be stripped from frame data
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        data.extend_from_slice(&hevc_nal_header(34));
        data.extend_from_slice(&[0xDD, 0xEE]);

        // IDR_W_RADL slice (type 19) — should appear in frame data
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        let idr_hdr = hevc_nal_header(19);
        data.extend_from_slice(&idr_hdr);
        data.extend_from_slice(&[0x10, 0x20, 0x30]);

        // Dolby Vision RPU (type 62 = UNSPEC62) — MUST appear in frame data
        data.extend_from_slice(&[0x00, 0x00, 0x01]);
        let rpu_hdr = hevc_nal_header(62);
        data.extend_from_slice(&rpu_hdr);
        let rpu_payload = [0xF0, 0xF1, 0xF2, 0xF3, 0xF4];
        data.extend_from_slice(&rpu_payload);

        let pes = make_pes(data, Some(90000));
        let frames = parser.parse(&pes);

        assert_eq!(frames.len(), 1, "should produce one frame");
        assert!(frames[0].keyframe, "IDR should mark keyframe");

        // Verify the frame data contains both the IDR NAL and the RPU NAL.
        // Frame data is length-prefixed NALUs (4-byte big-endian length + NAL bytes).
        let fd = &frames[0].data;

        // Walk the length-prefixed NALUs and collect their types
        let mut nal_types = Vec::new();
        let mut offset = 0;
        while offset + 4 <= fd.len() {
            let length =
                u32::from_be_bytes([fd[offset], fd[offset + 1], fd[offset + 2], fd[offset + 3]])
                    as usize;
            offset += 4;
            assert!(offset + length <= fd.len(), "NAL length exceeds frame data");
            let nal_type = (fd[offset] >> 1) & 0x3F;
            nal_types.push(nal_type);
            offset += length;
        }

        assert!(
            nal_types.contains(&19),
            "frame data must contain IDR NAL (type 19), got: {:?}",
            nal_types
        );
        assert!(
            nal_types.contains(&62),
            "frame data must contain Dolby Vision RPU NAL (type 62), got: {:?}",
            nal_types
        );
        assert_eq!(
            nal_types.len(),
            2,
            "frame data should have exactly 2 NALs (IDR + RPU), got: {:?}",
            nal_types
        );

        // Verify RPU payload is intact
        let mut offset = 0;
        while offset + 4 <= fd.len() {
            let length =
                u32::from_be_bytes([fd[offset], fd[offset + 1], fd[offset + 2], fd[offset + 3]])
                    as usize;
            offset += 4;
            let nal_type = (fd[offset] >> 1) & 0x3F;
            if nal_type == 62 {
                // NAL = 2-byte header + payload
                let nal_payload = &fd[offset + 2..offset + length];
                assert_eq!(
                    nal_payload, &rpu_payload,
                    "RPU payload must be preserved verbatim"
                );
            }
            offset += length;
        }
    }
}