dvc-cli/src/packaging.ts

import { join } from 'node:path';
import { execMP4Box } from './utils';
import type { VideoProfile } from './types';

/**
 * Package MP4 files into DASH format using MP4Box
 * Stage 2: Light work - just packaging, no encoding
 * Creates one master MPD manifest with all profiles
 */
export async function packageToDash(
  mp4Files: Map<string, string>,
  outputDir: string,
  profiles: VideoProfile[],
  segmentDuration: number
): Promise<string> {
  const manifestPath = join(outputDir, 'manifest.mpd');
  
  // Build MP4Box command
  const args = [
    '-dash', String(segmentDuration * 1000), // MP4Box expects milliseconds
    '-frag', String(segmentDuration * 1000),
    '-rap', // Force segments to start with random access points
    '-segment-name', '$RepresentationID$_$Number$',
    '-out', manifestPath
  ];

  // Add all MP4 files with their profile IDs
  for (const profile of profiles) {
    const mp4Path = mp4Files.get(profile.name);
    if (!mp4Path) {
      throw new Error(`MP4 file not found for profile: ${profile.name}`);
    }
    
    // Add video track with representation ID
    args.push(`${mp4Path}#video:id=${profile.name}`);
    // Add audio track (shared across all profiles)
    if (profile === profiles[0]) {
      args.push(`${mp4Path}#audio:id=audio`);
    }
  }

  // Execute MP4Box
  await execMP4Box(args);

  // MP4Box creates files in the same directory as output MPD
  // Move segment files to profile subdirectories for clean structure
  await organizeSegments(outputDir, profiles);

  // Update MPD to reflect new file structure with subdirectories
  await updateManifestPaths(manifestPath, profiles);

  return manifestPath;
}

/**
 * Organize segments into profile subdirectories
 * MP4Box creates all files in one directory, we organize them
 */
async function organizeSegments(
  outputDir: string,
  profiles: VideoProfile[]
): Promise<void> {
  const { readdir, rename, mkdir } = await import('node:fs/promises');
  
  // Create profile subdirectories
  for (const profile of profiles) {
    const profileDir = join(outputDir, profile.name);
    await mkdir(profileDir, { recursive: true });
  }
  
  // Create audio subdirectory
  const audioDir = join(outputDir, 'audio');
  await mkdir(audioDir, { recursive: true });
  
  // Get all files in output directory
  const files = await readdir(outputDir);
  
  // Move segment files to their respective directories
  for (const file of files) {
    // Skip manifest
    if (file === 'manifest.mpd') {
      continue;
    }
    
    // Move audio files to audio/ directory
    if (file.startsWith('audio_') || file === 'audio_init.m4s') {
      const oldPath = join(outputDir, file);
      const newPath = join(audioDir, file);
      await rename(oldPath, newPath);
      continue;
    }
    
    // Move video segment files to their profile directories
    for (const profile of profiles) {
      if (file.startsWith(`${profile.name}_`)) {
        const oldPath = join(outputDir, file);
        const newPath = join(outputDir, profile.name, file);
        await rename(oldPath, newPath);
        break;
      }
    }
  }
}

/**
 * Update MPD manifest to reflect subdirectory structure
 */
async function updateManifestPaths(
  manifestPath: string,
  profiles: VideoProfile[]
): Promise<void> {
  const { readFile, writeFile } = await import('node:fs/promises');
  
  let mpd = await readFile(manifestPath, 'utf-8');
  
  // MP4Box uses $RepresentationID$ template variable
  // Replace: media="$RepresentationID$_$Number$.m4s" 
  // With:    media="$RepresentationID$/$RepresentationID$_$Number$.m4s"
  
  mpd = mpd.replace(
    /media="\$RepresentationID\$_\$Number\$\.m4s"/g,
    'media="$RepresentationID$/$RepresentationID$_$Number$.m4s"'
  );
  
  // Replace: initialization="$RepresentationID$_.mp4"
  // With:    initialization="$RepresentationID$/$RepresentationID$_.mp4"
  
  mpd = mpd.replace(
    /initialization="\$RepresentationID\$_\.mp4"/g,
    'initialization="$RepresentationID$/$RepresentationID$_.mp4"'
  );
  
  await writeFile(manifestPath, mpd, 'utf-8');
}