implement video download

needs check, if converted files can be run on device

Signed-off-by: Peter Siegmund <developer@mars3142.org>

server/cinema/lib/common/video_downloader.dart

@@ -0,0 +1,112 @@
+import 'dart:io';
+
+import 'package:injectable/injectable.dart';
+
+@singleton
+class VideoDownloader {
+  static const cacheDir = 'cache/video';
+  static const int maxWidth = 480;
+  static const int maxHeight = 320;
+
+  /// Downloads and resizes a YouTube video
+  /// Returns the path to the resized video file, or null on failure
+  Future<String?> downloadAndResize(String videoId) async {
+    final videoDir = Directory('$cacheDir/$videoId');
+    final originalVideoFile = File('${videoDir.path}/video_original.mp4');
+    final resizedVideoFile = File('${videoDir.path}/video.mp4');
+
+    // Check if resized video already exists in cache
+    if (await resizedVideoFile.exists()) {
+      return resizedVideoFile.path;
+    }
+
+    // Create cache directory if it doesn't exist
+    if (!await videoDir.exists()) {
+      await videoDir.create(recursive: true);
+    }
+
+    final youtubeUrl = 'https://www.youtube.com/watch?v=$videoId';
+
+    try {
+      // Use yt-dlp to download the video
+      final downloadResult = await Process.run(
+        'yt-dlp',
+        [
+          '-f', 'bestvideo[ext=mp4]+bestaudio[ext=m4a]/best[ext=mp4]/best',
+          '-o', originalVideoFile.path,
+          '--merge-output-format', 'mp4',
+          youtubeUrl,
+        ],
+      );
+
+      if (downloadResult.exitCode != 0) {
+        print('Failed to download video $videoId: ${downloadResult.stderr}');
+        await _cleanup(videoDir);
+        return null;
+      }
+
+      // Resize video to fit within maxWidth x maxHeight using ffmpeg
+      final resizeResult = await Process.run(
+        'ffmpeg',
+        [
+          '-i', originalVideoFile.path,
+          '-vf', 'scale=w=$maxWidth:h=$maxHeight:force_original_aspect_ratio=decrease',
+          '-c:v', 'libx264',
+          '-preset', 'medium',
+          '-crf', '23',
+          '-c:a', 'aac',
+          '-b:a', '128k',
+          '-movflags', '+faststart',
+          '-y',
+          resizedVideoFile.path,
+        ],
+      );
+
+      if (resizeResult.exitCode != 0) {
+        print('Failed to resize video $videoId: ${resizeResult.stderr}');
+        await _cleanup(videoDir);
+        return null;
+      }
+
+      // Delete original video to save space
+      if (await originalVideoFile.exists()) {
+        await originalVideoFile.delete();
+      }
+
+      return resizedVideoFile.path;
+    } catch (e) {
+      print('Error processing video $videoId: $e');
+      await _cleanup(videoDir);
+      return null;
+    }
+  }
+
+  /// Check if video is already cached
+  Future<bool> isCached(String videoId) async {
+    final resizedVideoFile = File('$cacheDir/$videoId/video.mp4');
+    return resizedVideoFile.exists();
+  }
+
+  /// Get all cached video IDs
+  Future<List<String>> getCachedVideos() async {
+    final dir = Directory(cacheDir);
+    if (!await dir.exists()) {
+      return [];
+    }
+
+    final videos = <String>[];
+    await for (final entity in dir.list()) {
+      if (entity is Directory) {
+        final videoId = entity.path.split('/').last;
+        videos.add(videoId);
+      }
+    }
+    return videos;
+  }
+
+  Future<void> _cleanup(Directory videoDir) async {
+    if (await videoDir.exists()) {
+      await videoDir.delete(recursive: true);
+    }
+  }
+}