oximedia_distributed/

segment.rs

//! Video segmentation and reassembly for distributed encoding.
//!
//! This module handles:
//! - Video segmentation strategies (time-based, tile-based, GOP-based)
//! - GOP (Group of Pictures) detection
//! - Segment overlap handling
//! - Reassembly and concatenation
//! - Bitrate normalization

#![allow(dead_code)]

use crate::{Result, SplitStrategy};
use std::path::{Path, PathBuf};
use std::time::Duration;
use tracing::{debug, info, warn};

/// Video segment representation
#[derive(Debug, Clone)]
pub struct VideoSegment {
    /// Segment identifier
    pub id: String,

    /// Segment index
    pub index: usize,

    /// Start time in seconds
    pub start_time: f64,

    /// End time in seconds
    pub end_time: f64,

    /// Duration
    pub duration: f64,

    /// Overlap with next segment
    pub overlap: f64,

    /// Source file path
    pub source_path: PathBuf,

    /// Output file path
    pub output_path: Option<PathBuf>,

    /// Segment type
    pub segment_type: SegmentType,
}

/// Segment type
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum SegmentType {
    /// Time-based segment
    Time,
    /// Spatial tile
    Tile,
    /// GOP-aligned segment
    GOP,
}

/// Video segmenter
pub struct VideoSegmenter {
    /// Strategy for splitting
    strategy: SplitStrategy,

    /// Segment duration (for time-based)
    segment_duration: Duration,

    /// Overlap duration
    overlap_duration: Duration,

    /// GOP size hint
    gop_size: usize,

    /// Tile grid (width, height)
    tile_grid: (u32, u32),
}

impl VideoSegmenter {
    /// Create a new video segmenter
    #[must_use]
    pub fn new(strategy: SplitStrategy) -> Self {
        Self {
            strategy,
            segment_duration: Duration::from_secs(60),
            overlap_duration: Duration::from_millis(500),
            gop_size: 30,
            tile_grid: (2, 2),
        }
    }

    /// Set segment duration for time-based splitting
    #[must_use]
    pub fn with_duration(mut self, duration: Duration) -> Self {
        self.segment_duration = duration;
        self
    }

    /// Set overlap duration
    #[must_use]
    pub fn with_overlap(mut self, overlap: Duration) -> Self {
        self.overlap_duration = overlap;
        self
    }

    /// Set GOP size hint
    #[must_use]
    pub fn with_gop_size(mut self, gop_size: usize) -> Self {
        self.gop_size = gop_size;
        self
    }

    /// Set tile grid for spatial splitting
    #[must_use]
    pub fn with_tile_grid(mut self, width: u32, height: u32) -> Self {
        self.tile_grid = (width, height);
        self
    }

    /// Split video into segments
    pub async fn split_video(
        &self,
        source: &Path,
        video_info: &VideoInfo,
    ) -> Result<Vec<VideoSegment>> {
        match self.strategy {
            SplitStrategy::SegmentBased => self.split_by_time(source, video_info).await,
            SplitStrategy::TileBased => self.split_by_tiles(source, video_info).await,
            SplitStrategy::GopBased => self.split_by_gop(source, video_info).await,
        }
    }

    /// Split video by time segments
    async fn split_by_time(
        &self,
        source: &Path,
        video_info: &VideoInfo,
    ) -> Result<Vec<VideoSegment>> {
        info!("Splitting video by time segments");

        let mut segments = Vec::new();
        let total_duration = video_info.duration;
        let segment_duration = self.segment_duration.as_secs_f64();
        let overlap = self.overlap_duration.as_secs_f64();

        let num_segments = (total_duration / segment_duration).ceil() as usize;

        for i in 0..num_segments {
            let start_time = i as f64 * segment_duration;
            let mut end_time = (i + 1) as f64 * segment_duration;

            // Adjust last segment
            if end_time > total_duration {
                end_time = total_duration;
            }

            // Add overlap
            let actual_end_time = if i < num_segments - 1 {
                (end_time + overlap).min(total_duration)
            } else {
                end_time
            };

            let segment = VideoSegment {
                id: format!("seg_{i:04}"),
                index: i,
                start_time,
                end_time: actual_end_time,
                duration: actual_end_time - start_time,
                overlap,
                source_path: source.to_path_buf(),
                output_path: None,
                segment_type: SegmentType::Time,
            };

            segments.push(segment);
        }

        info!("Created {} time-based segments", segments.len());
        Ok(segments)
    }

    /// Split video by spatial tiles
    async fn split_by_tiles(
        &self,
        source: &Path,
        video_info: &VideoInfo,
    ) -> Result<Vec<VideoSegment>> {
        info!("Splitting video by spatial tiles");

        let mut segments = Vec::new();
        let (tile_cols, tile_rows) = self.tile_grid;

        let _tile_width = video_info.width / tile_cols;
        let _tile_height = video_info.height / tile_rows;

        for row in 0..tile_rows {
            for col in 0..tile_cols {
                let index = (row * tile_cols + col) as usize;

                // Tiles span the entire video duration
                let segment = VideoSegment {
                    id: format!("tile_{row}_{col}"),
                    index,
                    start_time: 0.0,
                    end_time: video_info.duration,
                    duration: video_info.duration,
                    overlap: 0.0,
                    source_path: source.to_path_buf(),
                    output_path: None,
                    segment_type: SegmentType::Tile,
                };

                segments.push(segment);
            }
        }

        info!(
            "Created {} tile-based segments ({}x{})",
            segments.len(),
            tile_cols,
            tile_rows
        );
        Ok(segments)
    }

    /// Split video by GOP boundaries
    async fn split_by_gop(
        &self,
        source: &Path,
        video_info: &VideoInfo,
    ) -> Result<Vec<VideoSegment>> {
        info!("Splitting video by GOP boundaries");

        // Detect GOP boundaries
        let gop_boundaries = self.detect_gop_boundaries(source, video_info).await?;

        let mut segments = Vec::new();
        let frame_rate = video_info.frame_rate;

        for (i, window) in gop_boundaries.windows(2).enumerate() {
            let start_frame = window[0];
            let end_frame = window[1];

            let start_time = start_frame as f64 / frame_rate;
            let end_time = end_frame as f64 / frame_rate;

            let segment = VideoSegment {
                id: format!("gop_{i:04}"),
                index: i,
                start_time,
                end_time,
                duration: end_time - start_time,
                overlap: 0.0,
                source_path: source.to_path_buf(),
                output_path: None,
                segment_type: SegmentType::GOP,
            };

            segments.push(segment);
        }

        info!("Created {} GOP-based segments", segments.len());
        Ok(segments)
    }

    /// Detect GOP boundaries in video
    async fn detect_gop_boundaries(
        &self,
        _source: &Path,
        video_info: &VideoInfo,
    ) -> Result<Vec<u64>> {
        debug!("Detecting GOP boundaries");

        // Simplified GOP detection - assume regular GOP structure
        let total_frames = (video_info.duration * video_info.frame_rate) as u64;
        let gop_size = self.gop_size as u64;

        let mut boundaries = vec![0];
        let mut current_frame = gop_size;

        while current_frame < total_frames {
            boundaries.push(current_frame);
            current_frame += gop_size;
        }

        boundaries.push(total_frames);

        debug!("Detected {} GOP boundaries", boundaries.len());
        Ok(boundaries)
    }
}

/// Video information
#[derive(Debug, Clone)]
pub struct VideoInfo {
    /// Video width
    pub width: u32,

    /// Video height
    pub height: u32,

    /// Duration in seconds
    pub duration: f64,

    /// Frame rate
    pub frame_rate: f64,

    /// Bitrate
    pub bitrate: u64,

    /// Codec
    pub codec: String,

    /// Total frames
    pub total_frames: u64,
}

impl VideoInfo {
    /// Create video info from basic parameters
    #[must_use]
    pub fn new(width: u32, height: u32, duration: f64, frame_rate: f64) -> Self {
        Self {
            width,
            height,
            duration,
            frame_rate,
            bitrate: 5_000_000, // Default 5 Mbps
            codec: "h264".to_string(),
            total_frames: (duration * frame_rate) as u64,
        }
    }

    /// Probe video file to get information
    pub async fn probe(_path: &Path) -> Result<Self> {
        // In production, would use FFprobe or similar
        // For now, return mock data
        Ok(Self {
            width: 1920,
            height: 1080,
            duration: 600.0, // 10 minutes
            frame_rate: 30.0,
            bitrate: 5_000_000,
            codec: "h264".to_string(),
            total_frames: 18000,
        })
    }
}

/// Segment reassembler for combining encoded segments
pub struct SegmentReassembler {
    /// Concatenation strategy
    strategy: ConcatenationStrategy,

    /// Bitrate normalization
    normalize_bitrate: bool,

    /// Target bitrate for normalization
    target_bitrate: Option<u64>,
}

impl SegmentReassembler {
    /// Create a new segment reassembler
    #[must_use]
    pub fn new() -> Self {
        Self {
            strategy: ConcatenationStrategy::Concat,
            normalize_bitrate: true,
            target_bitrate: None,
        }
    }

    /// Set concatenation strategy
    #[must_use]
    pub fn with_strategy(mut self, strategy: ConcatenationStrategy) -> Self {
        self.strategy = strategy;
        self
    }

    /// Enable bitrate normalization
    #[must_use]
    pub fn with_normalization(mut self, enable: bool) -> Self {
        self.normalize_bitrate = enable;
        self
    }

    /// Set target bitrate
    #[must_use]
    pub fn with_target_bitrate(mut self, bitrate: u64) -> Self {
        self.target_bitrate = Some(bitrate);
        self
    }

    /// Reassemble segments into final output
    pub async fn reassemble(
        &self,
        segments: &[VideoSegment],
        output: &Path,
    ) -> Result<ReassemblyResult> {
        info!("Reassembling {} segments", segments.len());

        match self.strategy {
            ConcatenationStrategy::Concat => self.concat_segments(segments, output).await,
            ConcatenationStrategy::Blend => self.blend_segments(segments, output).await,
            ConcatenationStrategy::Stitch => self.stitch_tiles(segments, output).await,
        }
    }

    /// Concatenate time-based segments
    async fn concat_segments(
        &self,
        segments: &[VideoSegment],
        output: &Path,
    ) -> Result<ReassemblyResult> {
        info!("Concatenating segments");

        // Sort segments by index
        let mut sorted_segments = segments.to_vec();
        sorted_segments.sort_by_key(|s| s.index);

        // Handle overlaps
        let processed_segments = if sorted_segments.iter().any(|s| s.overlap > 0.0) {
            self.trim_overlaps(&sorted_segments)?
        } else {
            sorted_segments
        };

        // In production, would use FFmpeg concat demuxer
        debug!(
            "Concatenating {} segments to {:?}",
            processed_segments.len(),
            output
        );

        Ok(ReassemblyResult {
            output_path: output.to_path_buf(),
            total_duration: processed_segments.iter().map(|s| s.duration).sum(),
            num_segments: processed_segments.len(),
            final_bitrate: self.target_bitrate.unwrap_or(5_000_000),
        })
    }

    /// Blend segments with overlaps
    async fn blend_segments(
        &self,
        segments: &[VideoSegment],
        output: &Path,
    ) -> Result<ReassemblyResult> {
        info!("Blending segments with overlaps");

        // Sort segments
        let mut sorted_segments = segments.to_vec();
        sorted_segments.sort_by_key(|s| s.index);

        // Process overlapping regions with cross-fade
        for window in sorted_segments.windows(2) {
            let seg1 = &window[0];
            let seg2 = &window[1];

            if seg1.overlap > 0.0 {
                debug!(
                    "Blending overlap between {} and {} ({:.2}s)",
                    seg1.id, seg2.id, seg1.overlap
                );
                // In production, apply cross-fade filter
            }
        }

        Ok(ReassemblyResult {
            output_path: output.to_path_buf(),
            total_duration: segments.iter().map(|s| s.duration - s.overlap).sum::<f64>()
                + segments.last().map_or(0.0, |s| s.overlap),
            num_segments: segments.len(),
            final_bitrate: self.target_bitrate.unwrap_or(5_000_000),
        })
    }

    /// Stitch spatial tiles back together
    async fn stitch_tiles(
        &self,
        segments: &[VideoSegment],
        output: &Path,
    ) -> Result<ReassemblyResult> {
        info!("Stitching {} tiles", segments.len());

        // In production, would use FFmpeg xstack filter
        debug!("Stitching tiles to {:?}", output);

        Ok(ReassemblyResult {
            output_path: output.to_path_buf(),
            total_duration: segments.first().map_or(0.0, |s| s.duration),
            num_segments: segments.len(),
            final_bitrate: self.target_bitrate.unwrap_or(5_000_000),
        })
    }

    /// Trim overlapping regions from segments
    fn trim_overlaps(&self, segments: &[VideoSegment]) -> Result<Vec<VideoSegment>> {
        let mut trimmed = Vec::new();

        for (i, segment) in segments.iter().enumerate() {
            let mut seg = segment.clone();

            // Trim the overlap from the end (except last segment)
            if i < segments.len() - 1 {
                seg.duration -= seg.overlap;
                seg.end_time -= seg.overlap;
            }

            trimmed.push(seg);
        }

        Ok(trimmed)
    }

    /// Normalize bitrates across segments
    pub fn normalize_bitrates(&self, segments: &[VideoSegment]) -> Result<Vec<BitrateAdjustment>> {
        if !self.normalize_bitrate {
            return Ok(Vec::new());
        }

        let target = self.target_bitrate.unwrap_or(5_000_000);
        info!("Normalizing bitrates to {} bps", target);

        // Create adjustments for each segment
        let adjustments: Vec<BitrateAdjustment> = segments
            .iter()
            .map(|s| BitrateAdjustment {
                segment_id: s.id.clone(),
                original_bitrate: 5_000_000, // Would be detected from encoded file
                target_bitrate: target,
                adjustment_factor: target as f64 / 5_000_000.0,
            })
            .collect();

        Ok(adjustments)
    }
}

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

/// Concatenation strategy
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ConcatenationStrategy {
    /// Simple concatenation
    Concat,
    /// Blend overlapping regions
    Blend,
    /// Stitch spatial tiles
    Stitch,
}

/// Reassembly result
#[derive(Debug, Clone)]
pub struct ReassemblyResult {
    /// Output file path
    pub output_path: PathBuf,

    /// Total duration
    pub total_duration: f64,

    /// Number of segments
    pub num_segments: usize,

    /// Final bitrate
    pub final_bitrate: u64,
}

/// Bitrate adjustment information
#[derive(Debug, Clone)]
pub struct BitrateAdjustment {
    pub segment_id: String,
    pub original_bitrate: u64,
    pub target_bitrate: u64,
    pub adjustment_factor: f64,
}

/// GOP (Group of Pictures) detector
pub struct GOPDetector {
    /// Minimum GOP size
    min_gop_size: usize,

    /// Maximum GOP size
    max_gop_size: usize,

    /// Scene change threshold
    scene_threshold: f64,
}

impl GOPDetector {
    /// Create a new GOP detector
    #[must_use]
    pub fn new() -> Self {
        Self {
            min_gop_size: 10,
            max_gop_size: 300,
            scene_threshold: 0.3,
        }
    }

    /// Set GOP size constraints
    #[must_use]
    pub fn with_gop_range(mut self, min: usize, max: usize) -> Self {
        self.min_gop_size = min;
        self.max_gop_size = max;
        self
    }

    /// Set scene change threshold
    #[must_use]
    pub fn with_scene_threshold(mut self, threshold: f64) -> Self {
        self.scene_threshold = threshold;
        self
    }

    /// Detect GOP structure in video
    pub async fn detect_gops(&self, _video_path: &Path) -> Result<Vec<GOPInfo>> {
        // In production, would analyze video frames
        // For now, return mock data
        let gops = vec![
            GOPInfo {
                start_frame: 0,
                end_frame: 30,
                keyframe_positions: vec![0],
                num_p_frames: 29,
                num_b_frames: 0,
            },
            GOPInfo {
                start_frame: 30,
                end_frame: 60,
                keyframe_positions: vec![30],
                num_p_frames: 29,
                num_b_frames: 0,
            },
        ];

        Ok(gops)
    }

    /// Validate GOP alignment for segments
    pub fn validate_alignment(&self, segments: &[VideoSegment], gops: &[GOPInfo]) -> Result<bool> {
        for segment in segments {
            if segment.segment_type != SegmentType::GOP {
                continue;
            }

            // Check if segment boundaries align with GOPs
            let start_aligned = gops
                .iter()
                .any(|g| (g.start_frame as f64 - segment.start_time * 30.0).abs() < 0.1);

            let end_aligned = gops
                .iter()
                .any(|g| (g.end_frame as f64 - segment.end_time * 30.0).abs() < 0.1);

            if !start_aligned || !end_aligned {
                warn!("Segment {} not aligned with GOP boundaries", segment.id);
                return Ok(false);
            }
        }

        Ok(true)
    }
}

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

/// GOP information
#[derive(Debug, Clone)]
pub struct GOPInfo {
    /// Start frame
    pub start_frame: u64,

    /// End frame
    pub end_frame: u64,

    /// Keyframe positions
    pub keyframe_positions: Vec<u64>,

    /// Number of P-frames
    pub num_p_frames: usize,

    /// Number of B-frames
    pub num_b_frames: usize,
}

impl GOPInfo {
    /// Get GOP size
    #[must_use]
    pub fn size(&self) -> u64 {
        self.end_frame - self.start_frame
    }

    /// Check if frame is a keyframe
    #[must_use]
    pub fn is_keyframe(&self, frame: u64) -> bool {
        self.keyframe_positions.contains(&frame)
    }
}

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

    #[test]
    fn test_time_based_segmentation() {
        let segmenter = VideoSegmenter::new(SplitStrategy::SegmentBased)
            .with_duration(Duration::from_secs(60))
            .with_overlap(Duration::from_millis(500));

        assert_eq!(segmenter.segment_duration.as_secs(), 60);
        assert_eq!(segmenter.overlap_duration.as_millis(), 500);
    }

    #[test]
    fn test_video_info_creation() {
        let info = VideoInfo::new(1920, 1080, 600.0, 30.0);
        assert_eq!(info.width, 1920);
        assert_eq!(info.height, 1080);
        assert_eq!(info.duration, 600.0);
        assert_eq!(info.total_frames, 18000);
    }

    #[test]
    fn test_segment_reassembler() {
        let reassembler = SegmentReassembler::new()
            .with_normalization(true)
            .with_target_bitrate(5_000_000);

        assert!(reassembler.normalize_bitrate);
        assert_eq!(reassembler.target_bitrate, Some(5_000_000));
    }

    #[test]
    fn test_gop_detector() {
        let detector = GOPDetector::new().with_gop_range(10, 300);

        assert_eq!(detector.min_gop_size, 10);
        assert_eq!(detector.max_gop_size, 300);
    }

    #[test]
    fn test_gop_info() {
        let gop = GOPInfo {
            start_frame: 0,
            end_frame: 30,
            keyframe_positions: vec![0, 15, 30],
            num_p_frames: 27,
            num_b_frames: 0,
        };

        assert_eq!(gop.size(), 30);
        assert!(gop.is_keyframe(0));
        assert!(gop.is_keyframe(15));
        assert!(!gop.is_keyframe(10));
    }

    #[test]
    fn test_concatenation_strategies() {
        assert_eq!(ConcatenationStrategy::Concat, ConcatenationStrategy::Concat);
        assert_ne!(ConcatenationStrategy::Concat, ConcatenationStrategy::Blend);
    }
}