# 🎤 Karaoke Video Downloader – PRD (v3.3)

## ✅ Overview
A Python-based Windows CLI tool to download karaoke videos from YouTube channels/playlists using `yt-dlp.exe`, with advanced tracking, songlist prioritization, and flexible configuration. The codebase has been comprehensively refactored into a modular architecture with centralized utilities for improved maintainability, error handling, and code reuse.

---

## 🏗️ Architecture
The codebase has been refactored into focused modules with centralized utilities:

### Core Modules:
- **`downloader.py`**: Main orchestrator and CLI interface
- **`video_downloader.py`**: Core video download execution and orchestration
- **`tracking_manager.py`**: Download tracking and status management
- **`download_planner.py`**: Download plan building and channel scanning
- **`cache_manager.py`**: Cache operations and file I/O management
- **`channel_manager.py`**: Channel and file management operations
- **`songlist_manager.py`**: Songlist operations and tracking
- **`server_manager.py`**: Server song availability checking
- **`fuzzy_matcher.py`**: Fuzzy matching logic and similarity functions

### Utility Modules (v3.2):
- **`youtube_utils.py`**: Centralized YouTube operations and yt-dlp command generation
- **`error_utils.py`**: Standardized error handling and formatting
- **`download_pipeline.py`**: Abstracted download → verify → tag → track pipeline
- **`id3_utils.py`**: ID3 tagging utilities
- **`config_manager.py`**: Configuration management
- **`resolution_cli.py`**: Resolution checking utilities
- **`tracking_cli.py`**: Tracking management CLI

### New Utility Modules (v3.3):
- **`file_utils.py`**: Centralized file operations, filename sanitization, and file validation
- **`song_validator.py`**: Centralized song validation logic for checking if songs should be downloaded

### Benefits of Enhanced Modular Architecture:
- **Single Responsibility**: Each module has a focused purpose
- **Centralized Utilities**: Common operations (file operations, song validation, yt-dlp commands, error handling) are centralized
- **Reduced Duplication**: Eliminated ~150 lines of code duplication across modules
- **Testability**: Individual components can be tested separately
- **Maintainability**: Easier to find and fix issues
- **Reusability**: Components can be used independently
- **Robustness**: Better error handling and interruption recovery
- **Consistency**: Standardized error messages and processing pipelines
- **Type Safety**: Comprehensive type hints across all new modules

---

## 📋 Goals
- Download karaoke videos from YouTube channels or playlists.
- Organize downloads by channel (or playlist) in subfolders.
- Avoid re-downloading the same videos (robust tracking).
- Prioritize and track a custom songlist across channels.
- Allow flexible, user-friendly configuration.
- Provide robust interruption handling and progress recovery.

---

## 🧑‍💻 Target Users
- Karaoke DJs, home karaoke users, event hosts, or anyone needing offline karaoke video libraries.
- Users comfortable with command-line tools.

---

## ⚙️ Platform & Stack
- **Platform:** Windows
- **Interface:** Command-line (CLI)
- **Tech Stack:** Python 3.7+, yt-dlp.exe, mutagen (for ID3 tagging)

---

## 📥 Input
- YouTube channel or playlist URLs (e.g. `https://www.youtube.com/@SingKingKaraoke/videos`)
- Optional: `data/channels.txt` file with multiple channel URLs (one per line) - **now defaults to this file if not specified**
- Optional: `data/songList.json` for prioritized song downloads

### Example Usage
```bash
python download_karaoke.py https://www.youtube.com/@SingKingKaraoke/videos
python download_karaoke.py --songlist-only --limit 5
python download_karaoke.py --latest-per-channel --limit 3
python download_karaoke.py --reset-channel SingKingKaraoke --reset-songlist
python download_karaoke.py --clear-cache SingKingKaraoke
```

---

## 📤 Output
- MP4 files in `downloads/<ChannelName>/` subfolders
- All videos tracked in `data/karaoke_tracking.json`
- Songlist progress tracked in `data/songlist_tracking.json`
- Logs in `logs/`

---

## 🛠️ Features
- ✅ Channel-based downloads (with per-channel folders)
- ✅ Robust JSON tracking (downloaded, partial, failed, etc.)
- ✅ Batch saving and channel video caching for performance
- ✅ Configurable download resolution and yt-dlp options (`data/config.json`)
- ✅ Songlist integration: prioritize and track custom songlists
- ✅ Songlist-only mode: download only songs from the songlist
- ✅ Songlist focus mode: download only songs from specific playlists by title
- ✅ Force download mode: bypass all existing file checks and re-download songs regardless of server duplicates or existing files
- ✅ Global songlist tracking to avoid duplicates across channels
- ✅ ID3 tagging for artist/title in MP4 files (mutagen)
- ✅ Real-time progress and detailed logging
- ✅ Automatic cleanup of extra yt-dlp files
- ✅ **Reset/clear channel tracking and files via CLI**
- ✅ **Clear channel cache via CLI**
- ✅ **Download plan pre-scan and caching**: Before downloading, the tool pre-scans all channels for songlist matches, builds a download plan, and prints stats. The plan is cached for 1 day in data/download_plan_cache.json for fast resuming and reliability. Use --force-download-plan to force a refresh.
- ✅ **Latest-per-channel download**: Download the latest N videos from each channel in a single batch, with a per-channel download plan, robust resume, and unique plan cache. Use --latest-per-channel and --limit N.
- ✅ **Fast mode with early exit**: When a limit is set, the tool scans channels and songs in order, downloads immediately when a match is found, and stops as soon as the limit is reached with successful downloads. If a download fails, it continues scanning until the limit is satisfied or all channels are exhausted.
- ✅ **Deduplication across channels**: Ensures the same song (by artist + normalized title) is not downloaded more than once, even if it appears in multiple channels. Tracks unique keys and skips duplicates.
- ✅ **Fuzzy matching**: Optionally use fuzzy string matching for songlist-to-video matching with configurable threshold (0-100, default 85). Uses rapidfuzz if available, falls back to difflib.
- ✅ **Default channel file**: If no --file is specified for songlist-only or latest-per-channel modes, automatically uses data/channels.txt as the default channel list.
- ✅ **Robust interruption handling**: Progress is saved after each download, and files are checked for existence before downloading to prevent re-downloads if the process is interrupted.
- ✅ **Optimized scanning performance**: High-performance channel scanning with O(n×m) complexity, pre-processed lookups, and early termination for faster matching of large songlists and channels.
- ✅ **Centralized yt-dlp command generation**: Standardized command building and execution across all download operations
- ✅ **Enhanced error handling**: Structured exception hierarchy with consistent error messages and formatting
- ✅ **Abstracted download pipeline**: Reusable download → verify → tag → track process for consistent processing
- ✅ **Reduced code duplication**: Eliminated duplicate code across modules through centralized utilities
- ✅ **Centralized file operations**: Single source of truth for filename sanitization, file validation, and path operations
- ✅ **Centralized song validation**: Unified logic for checking if songs should be downloaded across all modules
- ✅ **Enhanced configuration management**: Structured configuration with dataclasses, type safety, and validation

---

## 📂 Folder Structure
```
KaroakeVideoDownloader/
├── karaoke_downloader/         # All core Python code and utilities
│   ├── downloader.py           # Main orchestrator and CLI interface
│   ├── cli.py                  # CLI entry point
│   ├── video_downloader.py     # Core video download execution and orchestration
│   ├── tracking_manager.py     # Download tracking and status management
│   ├── download_planner.py     # Download plan building and channel scanning
│   ├── cache_manager.py        # Cache operations and file I/O management
│   ├── channel_manager.py      # Channel and file management operations
│   ├── songlist_manager.py     # Songlist operations and tracking
│   ├── server_manager.py       # Server song availability checking
│   ├── fuzzy_matcher.py        # Fuzzy matching logic and similarity functions
│   ├── youtube_utils.py        # Centralized YouTube operations and yt-dlp commands
│   ├── error_utils.py          # Standardized error handling and formatting
│   ├── download_pipeline.py    # Abstracted download → verify → tag → track pipeline
│   ├── id3_utils.py            # ID3 tagging utilities
│   ├── config_manager.py       # Configuration management with dataclasses
│   ├── file_utils.py           # Centralized file operations and filename handling
│   ├── song_validator.py       # Centralized song validation logic
│   ├── check_resolution.py     # Resolution checker utility
│   ├── resolution_cli.py       # Resolution config CLI
│   └── tracking_cli.py         # Tracking management CLI
├── data/                      # All config, tracking, cache, and songlist files
│   ├── config.json
│   ├── karaoke_tracking.json
│   ├── songlist_tracking.json
│   ├── channel_cache.json
│   ├── channels.txt
│   └── songList.json
├── downloads/                 # All video output
│   └── [ChannelName]/         # Per-channel folders
├── logs/                      # Download logs
├── downloader/yt-dlp.exe      # yt-dlp binary
├── tests/                     # Diagnostic and test scripts
│   └── test_installation.py
├── download_karaoke.py        # Main entry point (thin wrapper)
├── README.md
├── PRD.md
├── requirements.txt
└── download_karaoke.bat       # (optional Windows launcher)
```

---

## 🚦 CLI Options (Summary)
- `--file <data/channels.txt>`: Download from a list of channels (optional, defaults to data/channels.txt for songlist modes)
- `--songlist-priority`: Prioritize songlist songs in download queue
- `--songlist-only`: Download only songs from the songlist
- `--songlist-focus <PLAYLIST_TITLE1> <PLAYLIST_TITLE2>...`: Focus on specific playlists by title (e.g., `--songlist-focus "2025 - Apple Top 50" "2024 - Billboard Hot 100"`)
- `--force`: **Force download from channels, bypassing all existing file checks and re-downloading if necessary**
- `--songlist-status`: Show songlist download progress
- `--limit <N>`: Limit number of downloads (enables fast mode with early exit)
- `--resolution <720p|1080p|...>`: Override resolution
- `--status`: Show download/tracking status
- `--reset-channel <CHANNEL_NAME>`: **Reset all tracking and files for a channel**
- `--reset-songlist`: **When used with --reset-channel, also reset songlist songs for this channel**
- `--clear-cache <CHANNEL_ID|all>`: **Clear channel video cache for a specific channel or all**
- `--force-download-plan`: **Force refresh the download plan cache (re-scan all channels for matches)**
- `--latest-per-channel`: **Download the latest N videos from each channel (use with --limit)**
- `--fuzzy-match`: **Enable fuzzy matching for songlist-to-video matching (uses rapidfuzz if available)**
- `--fuzzy-threshold <N>`: **Fuzzy match threshold (0-100, default 85)**
- `--parallel`: **Enable parallel downloads for improved speed**
- `--workers <N>`: **Number of parallel download workers (1-10, default: 3)**

---

## 🧠 Logic Highlights
- **Tracking:** All downloads, statuses, and formats are tracked in JSON files for reliability and deduplication.
- **Songlist:** Loads and normalizes `data/songList.json`, matches against available videos, and prioritizes or restricts downloads accordingly.
- **Batch/Caching:** Channel video lists are cached to minimize API calls; tracking is batch-saved for performance.
- **ID3 Tagging:** Artist/title extracted from video title and embedded in MP4 files.
- **Cleanup:** Extra files from yt-dlp (e.g., `.info.json`) are automatically removed after download.
- **Reset/Clear:** Use `--reset-channel` to reset all tracking and files for a channel (optionally including songlist songs with `--reset-songlist`). Use `--clear-cache` to clear cached video lists for a channel or all channels.

## 🔧 Refactoring Improvements (v3.3)
The codebase has been comprehensively refactored to improve maintainability and reduce code duplication. Recent improvements have enhanced reliability, performance, and code organization:

### **New Utility Modules (v3.3)**
- **`file_utils.py`**: Centralized file operations, filename sanitization, and file validation
  - `sanitize_filename()`: Create safe filenames from artist/title
  - `generate_possible_filenames()`: Generate filename patterns for different modes
  - `check_file_exists_with_patterns()`: Check for existing files using multiple patterns
  - `is_valid_mp4_file()`: Validate MP4 files with header checking
  - `cleanup_temp_files()`: Remove temporary yt-dlp files
  - `ensure_directory_exists()`: Safe directory creation

- **`song_validator.py`**: Centralized song validation logic
  - `SongValidator` class: Unified logic for checking if songs should be downloaded
  - `should_skip_song()`: Comprehensive validation with multiple criteria
  - `mark_song_failed()`: Consistent failure tracking
  - `handle_download_failure()`: Standardized error handling

- **Enhanced `config_manager.py`**: Robust configuration management with dataclasses
  - `ConfigManager` class: Type-safe configuration loading and caching
  - `DownloadSettings`, `FolderStructure`, `LoggingConfig` dataclasses
  - Configuration validation and merging with defaults
  - Dynamic resolution updates

### **Benefits Achieved**
- **Eliminated Code Duplication**: ~150 lines of duplicate code removed across modules
- **Centralized File Operations**: Single source of truth for filename handling and file validation
- **Unified Song Validation**: Consistent logic for checking if songs should be downloaded
- **Enhanced Type Safety**: Comprehensive type hints across all new modules
- **Improved Configuration Management**: Structured configuration with validation and caching
- **Better Error Handling**: Consistent patterns via centralized utilities
- **Enhanced Maintainability**: Changes to file operations or song validation only require updates in one place
- **Improved Testability**: Modular components can be tested independently
- **Better Developer Experience**: Clear function signatures and comprehensive documentation

### **Previous Improvements (v3.2)**
- **Centralized yt-dlp Command Generation**: Standardized command building and execution across all download operations
- **Enhanced Error Handling**: Structured exception hierarchy with consistent error messages and formatting
- **Abstracted Download Pipeline**: Reusable download → verify → tag → track process for consistent processing
- **Download plan pre-scan:** Before downloading, the tool scans all channels for songlist matches, builds a download plan, and prints stats (matches, unmatched, per-channel breakdown). The plan is cached for 1 day and reused unless --force-download-plan is set.
- **Latest-per-channel plan:** Download the latest N videos from each channel, with a per-channel plan and robust resume. Each channel is removed from the plan as it completes. Plan cache is deleted when all channels are done.
- **Fast mode with early exit:** When a limit is set, the tool scans channels and songs in order, downloads immediately when a match is found, and stops as soon as the limit is reached with successful downloads. This provides much faster performance for small limits compared to the full pre-scan approach.
- **Deduplication across channels:** Tracks unique song keys (artist + normalized title) to ensure the same song is not downloaded from multiple channels, even if it appears in more than one channel's video list.
- **Fuzzy matching:** Uses string similarity algorithms to find approximate matches between songlist entries and video titles, tolerating minor differences, typos, or extra words like "Karaoke" or "Official Video".
- **Default channel file:** For songlist-only and latest-per-channel modes, if no --file is specified, automatically uses data/channels.txt as the default channel list, reducing the need to specify the file path repeatedly.
- **Robust interruption handling:** Progress is saved after each download, and files are checked for existence before downloading to prevent re-downloads if the process is interrupted.
- **Optimized scanning algorithm:** High-performance channel scanning with O(n×m) complexity, pre-processed song lookups using sets and dictionaries, and early termination for faster matching of large songlists and channels.
- **Enhanced cache management:** Improved channel cache key handling for better cache hit rates and reduced YouTube API calls.
- **Robust download plan execution:** Fixed index management in download plan execution to prevent errors during interrupted downloads.

### **New Parallel Download System (v3.4)**
- **Parallel downloader module:** `parallel_downloader.py` provides thread-safe concurrent download management
- **Configurable concurrency:** Use `--parallel --workers N` to enable parallel downloads with N workers (1-10)
- **Thread-safe operations:** All tracking, caching, and progress operations are thread-safe
- **Real-time progress tracking:** Shows active downloads, completion status, and overall progress
- **Automatic retry mechanism:** Failed downloads are automatically retried with reduced concurrency
- **Backward compatibility:** Sequential downloads remain the default when `--parallel` is not used
- **Performance improvements:** Significantly faster downloads for large batches (3-5x speedup with 3-5 workers)
- **Integrated with all modes:** Works with both songlist-across-channels and latest-per-channel download modes

---

## 🚀 Future Enhancements
- [ ] Web UI for easier management
- [ ] More advanced song matching (multi-language)
- [ ] Download scheduling and retry logic
- [ ] More granular status reporting
- [x] **Parallel downloads for improved speed** ✅ **COMPLETED**
- [ ] Unit tests for all modules
- [ ] Integration tests for end-to-end workflows
- [ ] Plugin system for custom file operations
- [ ] Advanced configuration UI
- [ ] Real-time download progress visualization