# bilibili-merge

Merge bilibili downloaded videos with audio files.

## Install

```bash
cargo install bilibili-merge
```

## Usage

```bash
bilibili-merge [OPTIONS] [PATH]
```

### Arguments

- `PATH` - Path to the directory containing video and audio files (default: current directory)

### Options

- `-n, --dry-run` - Dry run mode: show what would be done without actually doing it
- `-f, --force` - Force overwrite existing files
- `-h, --help` - Print help information

## How It Works

1. **Video File Selection**: The tool automatically finds the **largest file** (by file size) in the specified directory and uses it as the video file. This means:
   - If there's only one video file, it will be selected
   - If there are multiple files, the largest one (by size) will be selected
   - Only files (not directories) are considered
   - The selection is based on file size, not file name

2. **Audio File Matching**: The tool looks for an audio file with the same base name as the video file, but with `.m4a` extension. For example:
   - Video: `video.mp4` → Audio: `video.m4a`
   - Video: `episode_01.flv` → Audio: `episode_01.m4a`

3. **Processing Steps**:
   - Converts the audio file from M4A to AAC format
   - Renames the original video file to `original.<extension>` as a backup
   - Merges the video and audio into a single file
   - The merged file is saved as `<original_name>.mp4` (always MP4 format, regardless of input format)

## Examples

```bash
# Merge video and audio in current directory
bilibili-merge

# Merge video and audio in a specific directory
bilibili-merge /path/to/video/directory

# Dry run to see what would be done
bilibili-merge -n

# Force overwrite existing files
bilibili-merge -f

# Combine options
bilibili-merge -n -f /path/to/directory
```

## Notes

- The tool requires `ffmpeg` to be installed and available in your PATH
- By default, the tool will **not** overwrite existing files (use `-f` to force)
- The original video file is automatically backed up as `original.<extension>`
- The output file is always in MP4 format, regardless of the input video format
- In dry-run mode, you'll get a shell script that you can review or execute manually