# Core API Fix Request: Video Range Requests Support

## Issue

Video player in Studio cannot seek (跳轉) because Core API video endpoint does not support HTTP Range requests.

## Current Behavior

```bash
$ curl -I "http://localhost:3002/api/v1/file/{uuid}/video?start_time=0&end_time=5"
HTTP/1.1 200 OK
content-type: video/mp4
content-length: 1918410
# Missing: Accept-Ranges header
# Missing: 206 Partial Content support
```

## Expected Behavior

```bash
$ curl -I "http://localhost:3002/api/v1/file/{uuid}/video" -H "Range: bytes=0-1000"
HTTP/1.1 206 Partial Content
content-type: video/mp4
content-range: bytes 0-1000/1918410
accept-ranges: bytes
content-length: 1001
```

## Why This Matters

1. **Browser seeking requires Range support** - HTML5 `<video>` element uses Range requests to seek to different timestamps
2. **Current workaround is inefficient** - Users must download entire video or use `start_time` param (re-downloads video)
3. **High bitrate videos suffer most** - 4K/10Mbps videos cannot be quickly navigated

## Implementation Requirements

### 1. Add `Accept-Ranges: bytes` header to video endpoint

```
GET /api/v1/file/{uuid}/video
Response Headers:
  Accept-Ranges: bytes
```

### 2. Handle Range requests with 206 Partial Content

```rust
// Pseudo-code for Rust implementation
if let Some(range_header) = request.headers().get("Range") {
    let (start, end) = parse_range(range_header)?;
    let file_chunk = read_file_range(file_path, start, end)?;
    
    Response::builder()
        .status(206)
        .header("Content-Range", format!("bytes {}-{}/{}", start, end, file_size))
        .header("Accept-Ranges", "bytes")
        .header("Content-Length", end - start + 1)
        .body(file_chunk)
} else {
    // Full file response
    Response::builder()
        .status(200)
        .header("Accept-Ranges", "bytes")
        .body(full_file)
}
```

### 3. Support multiple Range formats

- `Range: bytes=0-999` (first 1000 bytes)
- `Range: bytes=1000-` (from byte 1000 to end)
- `Range: bytes=-500` (last 500 bytes)

## Affected Files (Core API)

- `src/api/files.rs` - Video streaming endpoint
- Possibly `src/api/video.rs` if exists

## Testing

```bash
# Test 1: Initial request should include Accept-Ranges
curl -I "http://localhost:3002/api/v1/file/{uuid}/video"
# Expect: Accept-Ranges: bytes

# Test 2: Range request should return 206
curl -I "http://localhost:3002/api/v1/file/{uuid}/video" -H "Range: bytes=0-1000"
# Expect: HTTP/1.1 206 Partial Content
# Expect: Content-Range: bytes 0-1000/{total}

# Test 3: Browser seeking should work
# Open Studio, play video, click on timeline
# Video should seek without re-downloading
```

## Priority

**High** - Critical for user experience when navigating long videos

## Related Studio Files

- `src/components/VideoPlayer.vue` - Uses `<video>` element with native controls
- `src-tauri/src/proxy.rs` - Already streams video, will pass through Range headers

## Notes

- Studio proxy already supports streaming (lines 325-367 in proxy.rs)
- Just need Core API to handle Range requests properly
- This is standard HTTP behavior for video streaming

---

## Additional Request: Adaptive Bitrate / Resolution Selection

### Problem

High bitrate videos (4K, 10+ Mbps) cause playback lag in browser due to software decoding limitations.

### Solution Options

#### Option A: Resolution Parameter

```bash
GET /api/v1/file/{uuid}/video?start_time=0&end_time=60&resolution=720p
GET /api/v1/file/{uuid}/video?start_time=0&end_time=60&resolution=480p
```

**Implementation:**
- Use FFmpeg to transcode on-the-fly or pre-generate proxy versions
- Store proxy videos at lower bitrates (720p @ 2Mbps, 480p @ 1Mbps)

#### Option B: Quality Parameter (1-100)

```bash
GET /api/v1/file/{uuid}//video?start_time=0&end_time=60&quality=50
```

#### Option C: Max Bitrate Parameter

```bash
GET /api/v1/file/{uuid}/video?start_time=0&end_time=60&max_bitrate=2000
```

### Recommended Approach

**Pre-generate proxy videos during processing:**

```rust
// During file processing, generate multiple versions:
// - Original: {uuid}_original.mp4 (preserve original quality)
// - 720p: {uuid}_720p.mp4 (2 Mbps)
// - 480p: {uuid}_480p.mp4 (1 Mbps)
```

**Storage Impact:**
- Original 100MB video → ~105MB total (5% overhead for proxies)

**API Changes:**

```rust
pub fn get_video_stream(
    file_uuid: String,
    start_time: f64,
    end_time: f64,
    resolution: Option<String>,  // "original" | "720p" | "480p"
) -> Result<VideoStream, Error>
```

### Frontend Integration

Studio VideoPlayer can add quality selector:

```vue
<select v-model="selectedResolution">
  <option value="original">Original (1080p)</option>
  <option value="720p">HD (720p)</option>
  <option value="480p">SD (480p)</option>
</select>
```

### Benefits

1. **Eliminates lag** on high bitrate videos
2. **Faster loading** with smaller file sizes
3. **Bandwidth savings** for remote access
4. **Better UX** - smooth playback on all devices