# Feature Request: Advanced Playlist Parsing & Mix Handling

## Context
We are upgrading the **StreamCapture** application. Currently, the app only supports parsing standard single video URLs.
We need to implement robust support for **Standard Playlists** and **YouTube Mixes (Radio)**, while solving performance issues and thumbnail loading errors.

## Problem Statement
1.  **Playlists (`/playlist?list=...`)**: Fails to parse entries or hangs because it attempts to resolve full metadata for every video. Thumbnails are missing.
2.  **Mixes (`/watch?v=...&list=RD...`)**: Currently fails or behaves unpredictably.
3.  **UI/UX**: Users need a specific choice when encountering a "Mix" link:
    * **Option A (Default):** Treat it as a single video (ignore the list).
    * **Option B:** Parse the Mix as a playlist (limit to top 20 items).

## Technical Requirements

### 1. Rust Backend Refactoring (`src-tauri/src/ytdlp.rs`)

Refactor the `fetch_metadata` command to use a unified, efficient parsing strategy.

#### A. Command Construction
For **ALL** metadata fetching, use the `--flat-playlist` flag to prevent deep extraction (which causes the hang).

**Base Command:**
```bash
yt-dlp --dump-single-json --flat-playlist --no-warnings [URL]
```

#### B. Handling Different URL Types
1. Single Video:
    - `yt-dlp` returns a single JSON object with `_type: "video"` (or no type).
    - Action: Wrap it in a list of 1.

2. Standard Playlist:
    - `yt-dlp` returns `_type: "playlist"` with an `entries` array.
    - Action: Map the `entries` to our `Video` struct.

3. Mix / Radio (Infinite List):
    - Condition: If the frontend flags this request as a "Mix Playlist scan".
    - Modification: Add flag --playlist-end 20 to the command.
    - Reason: Mixes are infinite; we must cap them.

#### C. Data Normalization & Thumbnail Fallback

When using `--flat-playlist`, the `entries` often lack full `thumbnail` URLs or return webp formats that might not render immediately.

- Logic: If the `thumbnail` field is missing or empty in an entry, construct it manually using the ID:
    - https://i.ytimg.com/vi/{video_id}/mqdefault.jpg

### 2. Frontend Logic (`src/views/Home.vue` & Stores)

#### A. URL Detection & User Choice

Before sending the URL to Rust, analyze the string:

1. Regex Check: Detect if the URL contains both `v=` AND `list=` (typical for Mixes).

2. New UI Element:
    - If a Mix link is detected, show a **Checkbox** or **Toggle** near the "Analyze" button.
    - Label: "Scan Playlist (Max 20)"
    - Default State: Unchecked (Off).

3. Submission Logic:
    - If Unchecked (Default): Strip the `&list=...` parameter from the URL string before calling Rust. Treat it as a pure single video.
    - If Checked: Keep the full URL and pass a flag (e.g., `is_mix: true`) to the Rust backend (or handle the logic to request the top 20).

#### B. Displaying Results

- Ensure the "Selection Area" can render a list of cards whether it contains 1 video or 20 videos.
- If it's a playlist, show a "Select All" / "Deselect All" control.

## Implementation Plan

### Step 1: Rust Structs Update

Update the Serde structs in `ytdlp.rs` to handle the `flat-playlist` JSON structure.

```rust
// Example structure hint
struct YtDlpResponse {
    _type: Option<String>,
    entries: Option<Vec<VideoEntry>>,
    // ... fields for single video fallback
    id: Option<String>,
    title: Option<String>,
}

struct VideoEntry {
    id: String,
    title: String,
    duration: Option<f64>,
    thumbnail: Option<String>, // Might be missing
}
```

### Step 2: Rust Logic Update

Modify `command::fetch_metadata`.

- Accept an optional argument `parse_mix_playlist: bool`.
- If `true`, append `--playlist-end 20`.
- Implement the thumbnail fallback logic (if `thumbnail` is None, use `i.ytimg.com`).

### Step 3: Frontend Update

- Add the "Mix Detected" logic in `Home.vue`.
- Add the toggle UI.
- Update the `analyze` function to handle URL stripping vs. passing through based on the toggle.

## Deliverables

Please rewrite the necessary parts of `src-tauri/src/ytdlp.rs`, `src-tauri/src/commands.rs`, and `src/views/Home.vue` to implement this logic.