# HTTP API Documentation

This document describes the available endpoints and their usage. All endpoints return JSON responses (unless otherwise specified) and may require certain parameters (query, body, or path). Some endpoints serve static or streaming content (e.g., `.ts`, `.m3u8`, `.vtt` files).

> **Note**: If Basic Authentication is configured (via `auth_username` and `auth_password` in your configuration), you must include an `Authorization: Basic <urlsafe-base64-encoded-credentials>` header or use `?apikey=<urlsafe-base64-encoded-credentials>` query parameter (fallback) in every request.

- All responses use standard HTTP status codes to indicate success or error conditions.
- Endpoints support an `OPTIONS` request for CORS.

---

## Table of Contents

- [HTTP API Documentation](#http-api-documentation)
  - [Table of Contents](#table-of-contents)
  - [Authentication](#authentication)
  - [Global Notes](#global-notes)
  - [Endpoints](#endpoints)
    - [GET /api/ping](#get-apiping)
    - [POST /api/yt-dlp/convert](#post-apiyt-dlpconvert)
    - [POST /api/yt-dlp/command/](#post-apiyt-dlpcommand)
    - [GET /api/yt-dlp/url/info](#get-apiyt-dlpurlinfo)
    - [GET /api/history/add](#get-apihistoryadd)
    - [POST /api/history](#post-apihistory)
    - [DELETE /api/history](#delete-apihistory)
    - [POST /api/history/{id}](#post-apihistoryid)
    - [GET /api/history/{id}](#get-apihistoryid)
    - [GET /api/history](#get-apihistory)
    - [DELETE /api/history/{id}/archive](#delete-apihistoryidarchive)
    - [POST /api/history/{id}/archive](#post-apihistoryidarchive)
    - [GET /api/archiver](#get-apiarchiver)
    - [POST /api/archiver](#post-apiarchiver)
    - [DELETE /api/archiver](#delete-apiarchiver)
    - [GET /api/tasks](#get-apitasks)
    - [PUT /api/tasks](#put-apitasks)
    - [POST /api/tasks/inspect](#post-apitasksinspect)
    - [POST /api/tasks/{id}/mark](#post-apitasksidmark)
    - [DELETE /api/tasks/{id}/mark](#delete-apitasksidmark)
    - [POST /api/tasks/{id}/metadata](#post-apitasksidmetadata)
    - [PATCH /api/tasks/{id}](#patch-apitasksid)
    - [GET /api/task\_definitions/](#get-apitask_definitions)
    - [GET /api/task\_definitions/{identifier}](#get-apitask_definitionsidentifier)
    - [POST /api/task\_definitions/](#post-apitask_definitions)
    - [PUT /api/task\_definitions/{identifier}](#put-apitask_definitionsidentifier)
    - [DELETE /api/task\_definitions/{identifier}](#delete-apitask_definitionsidentifier)
    - [GET /api/player/playlist/{file:.\*}.m3u8](#get-apiplayerplaylistfilem3u8)
    - [GET /api/player/m3u8/{mode}/{file:.\*}.m3u8](#get-apiplayerm3u8modefilem3u8)
    - [GET /api/player/segments/{segment}/{file:.\*}.ts](#get-apiplayersegmentssegmentfilets)
    - [GET /api/player/subtitle/{file:.\*}.vtt](#get-apiplayersubtitlefilevtt)
    - [GET /api/thumbnail](#get-apithumbnail)
    - [GET /api/file/ffprobe/{file:.\*}](#get-apifileffprobefile)
    - [GET /api/file/info/{file:.\*}](#get-apifileinfofile)
    - [GET /api/file/browser/{path:.\*}](#get-apifilebrowserpath)
    - [POST /api/file/actions](#post-apifileactions)
    - [POST /api/file/download](#post-apifiledownload)
    - [GET /api/file/download/{token}](#get-apifiledownloadtoken)
    - [GET /api/download/{filename}](#get-apidownloadfilename)
    - [GET /api/random/background](#get-apirandombackground)
    - [GET /api/presets](#get-apipresets)
    - [GET /api/dl\_fields](#get-apidl_fields)
    - [PUT /api/dl\_fields](#put-apidl_fields)
    - [PUT /api/presets](#put-apipresets)
    - [GET /api/conditions](#get-apiconditions)
    - [PUT /api/conditions](#put-apiconditions)
    - [POST /api/conditions/test](#post-apiconditionstest)
    - [GET /api/logs](#get-apilogs)
    - [GET /api/notifications](#get-apinotifications)
    - [PUT /api/notifications](#put-apinotifications)
    - [POST /api/yt-dlp/archive\_id/](#post-apiyt-dlparchive_id)
    - [POST /api/notifications/test](#post-apinotificationstest)
    - [GET /api/yt-dlp/options](#get-apiyt-dlpoptions)
    - [POST /api/system/pause](#post-apisystempause)
    - [POST /api/system/resume](#post-apisystemresume)
    - [POST /api/system/shutdown](#post-apisystemshutdown)
    - [POST /api/system/check-updates](#post-apisystemcheck-updates)
    - [GET /api/dev/loop](#get-apidevloop)
    - [GET /api/dev/pip](#get-apidevpip)
    - [GET /api/docs/{file}](#get-apidocsfile)
  - [WebSocket API](#websocket-api)
    - [Connection](#connection)
    - [Authentication](#authentication-1)
    - [Message Format](#message-format)
    - [Core Events](#core-events)
      - [Connection Events](#connection-events)
        - [`connect` (Built-in)](#connect-built-in)
        - [`disconnect` (Built-in)](#disconnect-built-in)
        - [`configuration` (Server → Client)](#configuration-server--client)
        - [`connected` (Server → Client)](#connected-server--client)
      - [Logging Events](#logging-events)
        - [`log_info` (Server → Client)](#log_info-server--client)
        - [`log_success` (Server → Client)](#log_success-server--client)
        - [`log_warning` (Server → Client)](#log_warning-server--client)
        - [`log_error` (Server → Client)](#log_error-server--client)
        - [`log_lines` (Server → Client)](#log_lines-server--client)
    - [Download Queue Events](#download-queue-events)
      - [`item_added` (Server → Client)](#item_added-server--client)
      - [`item_updated` (Server → Client)](#item_updated-server--client)
      - [`item_completed` (Server → Client)](#item_completed-server--client)
      - [`item_cancelled` (Server → Client)](#item_cancelled-server--client)
      - [`item_deleted` (Server → Client)](#item_deleted-server--client)
      - [`item_moved` (Server → Client)](#item_moved-server--client)
    - [Terminal/CLI Events](#terminalcli-events)
      - [`cli_post` (Client → Server)](#cli_post-client--server)
      - [`cli_output` (Server → Client)](#cli_output-server--client)
      - [`cli_close` (Server → Client)](#cli_close-server--client)
  - [Error Responses](#error-responses)

---

## Authentication

If `YTP_AUTH_USERNAME` and `YTP_AUTH_PASSWORD` are set, all API requests must include a valid credential using one of the following:

1. HTTP Basic Auth header:

   ```
   Authorization: Basic base64("<username>:<password>")
   ```

2. Query Parameter fallback:

   ```
   ?apikey=<base64_urlsafe("<username>:<password>")>
   ```

If you fail to provide valid credentials, a `401 Unauthorized` response is returned.

---

## Global Notes

- **Content-Type**  
  - Requests expecting a JSON body should include `Content-Type: application/json`.  
  - Responses typically include `Content-Type: application/json`, unless returning a file or streaming resource.

- **Status Codes**  
  - `200 OK` on success.  
  - `4xx` on client errors (e.g., missing parameters).  
  - `5xx` on server errors (e.g., unexpected failures).

- **Error Responses**  
  When an error occurs, responses follow a structure similar to:
  ```json
  {
    "error": "Description of the error",
  }
  ```
  with an appropriate HTTP status code.

---

## Endpoints

### GET /api/ping
**Purpose**: Health-check endpoint.  
**Response**:
```json
{
  "status": "pong"
}
```

---

### POST /api/yt-dlp/convert
**Purpose**: Convert a string of yt-dlp options into a JSON-friendly structure.

**Body**:
```json
{
  "args": "<string>"
}
```
**Example**:
```json
{
  "args": "--write-sub --embed-subs"
}
```
**Response**:  
```json
{
    "opts": { ... },
    "output_template": "...",
    "download_path": "...",
    "removed_options": ["option1", "option2"]  // optional, only if options were removed
}
```
or an error:
```json
{
  "error": "Failed to parse command options for yt-dlp. '<reason>'."
}
```

---

### POST /api/yt-dlp/command/
**Purpose**: Build a complete yt-dlp CLI command string with priority-based argument merging from user input, presets, and defaults.

**Requires**: Console must be enabled (`YTP_CONSOLE_ENABLED=true` env).

**Body**: JSON object:
```json
{
  "url": "https://example.com/video",// required - item url
  "preset": "preset_name",           // optional - preset name to apply
  "folder": "subfolder",             // optional - output folder (relative to download_path)
  "template": "%(title)s.%(ext)s",   // optional - output filename template
  "cli": "--write-sub --embed-subs", // optional - additional yt-dlp CLI arguments
  "cookies": "cookie_string"         // optional - authentication cookies as string
}
```

If cookies are given, they will be stored in a temporary file and the appropriate `--cookies <file>` argument 
will be added to the command.

**Priority System** (User > Preset > Default):
1. **User fields** take highest priority (from request body)
2. **Preset fields** used only if user didn't provide them
3. **Default fields** used as final fallback (from configuration)

**Response**:
```json
{
  "command": "--output-path /downloads/subfolder --output %(title)s.%(ext)s --write-sub --embed-subs https://example.com/video"
}
```

**Error Responses**:
- `403 Forbidden` if console is disabled
- `400 Bad Request` if body is invalid JSON or Item format validation fails
- `400 Bad Request` if CLI command building fails

---

### GET /api/yt-dlp/url/info
**Purpose**: Retrieves metadata (info) for a provided URL without adding it to the download queue.

**Query Parameters**:
- `url=<video-url>` (required)
- `preset=<preset-name>` (optional) - The preset to use for extracting info.
- `force=true` (optional) - Force fetch new info instead of using cache.
- `args=<yt-dlp-command-opts>` (optional) - The yt-dlp command options to apply to the info extraction.

**Response** (example):
```json
{
  "title": "...",
  "duration": 123.4,
  "extractor": "youtube",
  "_cached": {
    "status": "miss|hit",
    "preset": "<preset-name>",
    "cli_args": "<yt-dlp-command-opts>",
    "key": "<hash>",
    "ttl": 300,
    "ttl_left": 299.82,
    "expires": 1690430096.429
  },
  ...
}
```
or an error:
```json
{
  "error": "text"
}
```
- If the URL is invalid or missing, returns `400 Bad Request`.
- If the preset is specified and not found, returns `404 Not Found`.

---

### GET /api/history/add
**Purpose**: **(Quick Add)** Add a single URL to the download queue via GET.  

**Query Parameters**:
- `url=<video-url>`
- `preset=<preset-name>`

**Response**:
```json
{
  "status": true|false, # true if added to the queue. false otherwise.
  "message": "..." # the response message.
}
```

- If `url` is missing, returns `400 Bad Request`.
- If `preset` is set and not found, returns `404 Not Found`.

> [!NOTE]
> This endpoint is a quick way to add a single item to the queue without needing to format a full JSON body. It is primarily for convenience and may not support all options available in the full POST `/api/history` endpoint.
> Also note, that the endpoint uses different error format compared to the other endpoints, returning a simple JSON object with `status` and `message` fields.
> This is to make easier to script bookmarklets or simple API requests.

---

### POST /api/history
**Purpose**: Add one or multiple items (URLs) to the download queue via JSON body.  

**Body**:
```json5
// Single item
{
  "url": "https://youtube.com/watch?v=...", // -- required. The video URL to download.
  "preset": "default", // -- optional. The preset to use for this item.
  "folder": "my_channel/foo", // -- optional. The folder to save the item in, relative to the `download_path`.
  "cookies": "...", // -- optional. If provided, it MUST BE in Netscape HTTP Cookie format.
  "template": "%(title)s.%(ext)s", // -- optional. The filename template to use for this item.
  "cli": "--write-subs --embed-subs", // -- optional. Additional command options for yt-dlp to apply to this item.
  "auto_start": true // -- optional. Whether to auto-start the download after adding it. Defaults to true.
}

// Or multiple items (array of objects)
[
  {
    "url": "...",
    "preset": "default",
    ...
  },
  {
    "url": "...",
    ...
  }
]
```
**Response**:
```json
[
  {
    "status": "queued",
  },
  ...
]
```
- If any item is invalid (e.g., missing `url`), returns `400 Bad Request`.

---

### DELETE /api/history
**Purpose**: Delete items from either the "queue" or the "done" history.

**Body Parameters**:
- `type` (string, required): Type of items - `"queue"` or `"done"`
- `ids` (array, optional): List of specific item IDs to delete. If provided, `status` filter is ignored
- `status` (string, optional): Filter by status (e.g., `"finished"`, `"!finished"`). Required if `ids` not provided
- `remove_file` (boolean, optional): Whether to delete files from disk. Default: `true`.

> [!NOTE]
> `remove_file` is only considered if `YTP_REMOVE_FILES=true` is set. otherwise, files will not be deleted from disk even if `remove_file` is `true`.

**Request Examples**:

**Delete specific items by IDs:**
```json
{
  "type": "done",
  "ids": ["<id1>", "<id2>"],
  "remove_file": true
}
```

**Delete all finished items (filter mode):**
```json
{
  "type": "done",
  "status": "finished",
  "remove_file": true
}
```

**Delete all non-finished items (exclusion filter):**
```json
{
  "type": "done",
  "status": "!finished",
  "remove_file": false
}
```

**Response**:
```json
{
  "<id1>": "status",
  "<id2>": "status",
  ...
}
```

**Response (Filter mode with deleted count)**:
```json
{
  "items":{
    "<id1>": "status",
    "<id2>": "status",
    ...
  },
  "deleted": 5
}
```

**Error Responses**:
- `400 Bad Request` if parameters are invalid:
  ```json
  { "error": "type is required." }
  { "error": "either 'ids' or 'status' filter is required." }
  { "error": "type must be 'queue' or 'done'." }
  ```

**Notes**:
- When using filter mode, all matching items will be deleted.
- Filter mode with `{ "status": "!finished" }` is useful for cleaning up failed/pending downloads.
- Filter mode returns a `deleted` count indicating how many items were removed.

---

### POST /api/history/{id}
**Purpose**: Update an item in the `completed` history.

**Path Parameter**:
- `id` = Unique item ID.

**Body** (example):
```json
{
  "title": "My Custom Title",
  "someOtherField": "new-value"
}
```
**Response**:
```json
{
  "title": "My Custom Title",
  ....
}
```
or an error:
```json
{
  "error": "text"
}
```

- `200 OK` with updated item if successful.
- `304 Not Modified` if nothing changed.
- `404 Not Found` if the item doesn’t exist.
- `400 Bad Request` if id is missing or the body is empty.

---

### GET /api/history/{id}
**Purpose**: View details of a specific item in the database.

**Path Parameter**:
- `id` = Unique item ID.

**Response**:
```json
{
  "_id": "<uuid>",
  "title": "Video Title",
  "url": "https://youtube.com/watch?v=...",
  ....
}
```
or an error:
```json
{
  "error": "text"
}
```

- `200 OK` If the item exists and is returned.
- `404 Not Found` if the item doesn’t exist.
- `400 Bad Request` if id is missing.

---

### GET /api/history
**Purpose**: Returns the download queue and/or download history with optional pagination support.

**Query Parameters**:
- `type` (optional): Type of items to return. Default: `all`
  - `all` (default): Returns both queue and history (legacy behavior, no pagination)
  - `queue`: Returns only queue items (with pagination)
  - `done`: Returns only history items (with pagination)
- `page` (optional): Page number (1-indexed). Default: `1`. Only used when `type != all`
- `per_page` (optional): Items per page. Default: `config.default_pagination`, Max: `200`. Only used when `type != all`
- `order` (optional): Sort order. Default: `DESC`. Only used when `type != all`
  - `DESC`: Newest items first (descending by creation date)
  - `ASC`: Oldest items first (ascending by creation date)
- `status` (optional): Filter items by status. Only used when `type != all`
  - Use status value to include only items with that status (e.g., `status=finished`)
  - Prefix with `!` to exclude items with that status (e.g., `status=!finished`)
  - Common status values: `finished`, `downloading`, `pending`, `error`

**Response (when `type=all` or no type set)** - Legacy format:
```json
{
  "queue": [
    { 
      "id": "abc123",
      "url": "https://example.com/video",
      "title": "Video Title",
      "status": "downloading",
      ...
    },
    ...
  ],
  "history": [
    {
      "id": "def456", 
      "url": "https://example.com/video2",
      "title": "Completed Video",
      "status": "finished",
      ...
    },
    ...
  ]
}
```

**Response (when `type=queue` or `type=done`)** - Paginated format:
```json
{
  "pagination": {
    "page": 1,
    "per_page": 50,
    "total": 1234,
    "total_pages": 25,
    "has_next": true,
    "has_prev": false
  },
  "items": [
    {
      "id": "abc123",
      "url": "https://example.com/video",
      "title": "Video Title",
      "status": "finished",
      ...
    },
    ...
  ]
}
```

**Error Responses**:
- `400 Bad Request` if parameters are invalid:
  ```json
  { "error": "type must be one of all, queue, done." }
  { "error": "page must be >= 1." }
  { "error": "per_page must be between 1 and 1000." }
  { "error": "order must be ASC or DESC." }
  { "error": "page and per_page must be valid integers." }
  ```

**Notes**:
- The `type=all` behavior is considered legacy and will be removed in future versions
- For large datasets, use paginated requests (`type=queue` or `type=done`) for better performance
- The `items` array contains ItemDTO objects serialized to JSON

**Examples**:
```bash
# Get all finished items from history
GET /api/history?type=done&status=finished

# Get all items except finished ones
GET /api/history?type=done&status=!finished

# Get only downloading items from queue
GET /api/history?type=queue&status=downloading

# Get all items except errors, with pagination
GET /api/history?type=done&status=!error&page=2&per_page=50

# Combine with sorting - oldest pending items first
GET /api/history?type=queue&status=pending&order=ASC
```

---

### DELETE /api/history/{id}/archive
**Purpose**: Remove an item from archive file, allowing it to be re-downloaded.

**Path Parameter**:
- `id`: Item ID from the history.

**Response**:
```json
{ "message": "item '<title>' removed from '<archive_file>' archive." }
```
or an error:
```json
{ "error": "text" }
```

- `400 Bad Request` if archive is not configured or parameters are invalid.
- `404 Not Found` if the item or archive entry is not found.

---

### POST /api/history/{id}/archive
**Purpose**: Add item to the archive file preventing it from being downloaded.

**Path Parameter**:
- `id`: Item ID from the history.

**Response**:
```json
{ "message": "item '<archive_id>' archived in file '<archive_file>'." }
```
or an error:
```json
{ "error": "text" }
```

- `404 Not Found` if the item or archive file does not exist.
- `409 Conflict` if the item is already archived.

---

### GET /api/archiver
**Purpose**: Read entries from the download archive associated with a preset.

**Query Parameters**:
- `preset` (required): Preset name.
- `ids` (optional): Comma-separated list of archive IDs to filter. If omitted, returns all entries.

**Response**:
```json
{
  "file": "/path/to/archive.log",
  "items": ["youtube ABC123", "vimeo XYZ789"],
  "count": 2
}
```
or an error:
```json
{ "error": "Preset '<name>' does not provide a download_archive." }
```

- `400 Bad Request` if `preset` is missing/invalid or the preset has no `download_archive`.

---

### POST /api/archiver
**Purpose**: Append archive IDs to the download archive resolved by a preset.

**Body**:
```json
{
  "preset": "<preset-name>",
  "items": ["youtube ABC123", "vimeo XYZ789"],
  "skip_check": false
}
```

**Response**:
```json
{
  "file": "/path/to/archive.log",
  "status": true,
  "items": ["youtube ABC123", "vimeo XYZ789"]
}
```
Notes:
- Returns `200 OK` if any new entries were added, `304 Not Modified` if no-op (all already present or invalid).
- `400 Bad Request` if `preset` is missing/invalid, the preset has no `download_archive`, or `items` is empty.

---

### DELETE /api/archiver
**Purpose**: Remove archive IDs from the download archive resolved by a preset.

**Body**:
```json
{
  "preset": "<preset-name>",
  "items": ["youtube ABC123", "vimeo XYZ789"]
}
```

**Response**:
```json
{
  "file": "/path/to/archive.log",
  "status": true,
  "items": ["youtube ABC123", "vimeo XYZ789"]
}
```
Notes:
- Returns `200 OK` if the archive file changed, `304 Not Modified` if it was unchanged.
- `400 Bad Request` if `preset` is missing/invalid, the preset has no `download_archive`, or `items` is empty.

---

### GET /api/tasks
**Purpose**: Retrieves the scheduled tasks from the internal `Tasks` manager.  

**Response**:
```json
[
  {
    "id": "<uuid>",
    "name": "...",
    "url": "...",
    "folder": "...",
    "preset": "...",
    "timer": "<cron-expression>",
    "template": "...",
    "cookies": "...",
    "config": { ... },
  },
  ...
]
```

---

### PUT /api/tasks
**Purpose**: Overwrites the entire scheduled tasks list (Cron tasks).  

**Body**: An array of task objects. Example:
```json
[
  {
    "id": "a2ae3f18-4428-4e32-9d4c-0cc45af8bb48",
    "name": "My Task",
    "url": "https://youtube.com/...",
    "timer": "5 */2 * * *",
    "cookies": "",
    "config": {},
    "template": "...",
    "folder": "...",
    "auto_start": true,
    "handler_enabled": true,
    "enabled": true
  },
  {
    "url": "https://youtube.com/...",
    "timer": "*/15 * * * *"
  }
]
```
If `id` or other fields are missing, they may be auto-generated or defaulted (e.g., a random ID, a default cron, etc.).

**Response**:
```json
[
  {
    "id": "<uuid>",
    "name": "...",
    "url": "...",
    "timer": "...",
    "cookies": "...",
    "config": { ... },
    "template": "...",
    "folder": "...",
    "auto_start": true,
    "handler_enabled": true,
    "enabled": true
  }
  ...
]
```
or on error
```json
{
  "error": "text"
}
```

---

### POST /api/tasks/inspect
**Purpose**: Preview which handler matches a URL and review the items it would queue without dispatching downloads.

**Body**:
```json
{
  "url": "https://example.com/feed",            // required, validated URL
  "preset": "news-preset",                     // optional preset override - In real scenarios, the preset come from the task.
  "handler": "GenericTaskHandler",              // optional explicit handler class name, in real scenarios, the handler is resolved automatically.
  "static_only": false                          // optional, if true performs only can_handle check without extracting items (faster, lightweight)
}
```

**Notes**:
- When `static_only` is `true`, the endpoint only checks if a handler can process the URL using the `can_handle` method
- This is much faster and lighter than the full inspection which calls the handler's `extract` method
- Use `static_only: true` for quick validation checks (e.g., UI indicators)
- Use `static_only: false` (default) for full inspection with item extraction

**Response (success with static_only: true)**:
```json
{
  "items": [],
  "metadata": {
    "matched": true,
    "handler": "GenericTaskHandler"
  }
}
```

**Response (success with static_only: false)**:
```json
{
  "matched": true,
  "handler": "GenericTaskHandler",
  "supported": true,
  "items": [
    {
      "url": "https://example.com/video/1",
      "title": "Example title",
      "archive_id": "generic 1",
      "metadata": {
        "source_id": "...",
        "source_name": "...",
        "source_handler": "GenericTaskHandler"
      }
    }
  ],
  "metadata": {
    "raw_count": 3
  }
}
```

- Returns `200 OK` when inspection succeeds.
- The `metadata` object is optional and may contain handler-specific keys.

**Response (failure)**:
```json
{
  "matched": false,
  "handler": null,
  "error": "No handler matched the supplied URL.",
  "message": "No handler matched the supplied URL.",
  "metadata": {
    "supported": true
  }
}
```

- Returns `400 Bad Request` when the handler cannot process the URL or inspection fails.
- When a handler is specified but does not support manual inspection, `supported` is `false` and the `message` explains the limitation.

---

### POST /api/tasks/{id}/mark
**Purpose**: Mark all entries associated with a scheduled task as downloaded.

**Path Parameter**:
- `id`: Task ID.

**Response**:
```json
{ "message": "..." }
```
or
```json
{ "error": "..." }
```

- `400 Bad Request` if id is missing or invalid.
- `404 Not Found` if the task does not exist.

---

### DELETE /api/tasks/{id}/mark
**Purpose**: Remove all entries associated with a scheduled task from the download archive, allowing them to be re-downloaded.

**Path Parameter**:
- `id`: Task ID.

**Response**:
```json
{ "message": "..." }
```
or
```json
{ "error": "..." }
```

- `400 Bad Request` if id is missing or invalid.
- `404 Not Found` if the task does not exist.

---

### POST /api/tasks/{id}/metadata
**Purpose**: Generate metadata files for a scheduled task, including NFO files, thumbnails, and JSON metadata compatible with media centers.

**Path Parameter**:
- `id`: Task ID.

**Response**:
```json
{
  "id": "channel_or_playlist_id",
  "id_type": "youtube|twitch|...",
  "title": "Channel/Playlist Title",
  "description": "Description text...",
  "uploader": "Uploader name",
  "tags": ["tag1", "tag2"],
  "year": 2024,
  "json_file": "path/to/Title [id].info.json",
  "nfo_file": "path/to/tvshow.nfo",
  "thumbnails": {
    "poster": "path/to/poster.jpg",
    "fanart": "path/to/fanart.jpg",
    "thumb": "path/to/thumb.jpg",
    "banner": "path/to/banner.jpg",
    "icon": "path/to/icon.jpg",
    "landscape": "path/to/landscape.jpg"
  }
}
```
or
```json
{ "error": "..." }
```

**Files Generated**:
- `tvshow.nfo` - NFO file for media center compatibility (Kodi, Jellyfin, Emby, etc.)
- `Title [id].info.json` - yt-dlp metadata file.
- `poster.jpg`, `fanart.jpg`, `thumb.jpg`, `banner.jpg`, `icon.jpg`, `landscape.jpg` - Thumbnail images (if available from the source)

**Notes**:
- This endpoint fetches metadata from the URL associated with the task
- Files are saved to the task's configured folder (or default download path)
- Existing files will be overwritten.
- Thumbnail images are only downloaded if available from the source.
- The NFO file follows the Kodi tvshow.nfo format

**Status Codes**:
- `200 OK` - Metadata generated successfully
- `400 Bad Request` - Missing task ID, invalid folder path, or failed to fetch metadata
- `404 Not Found` - Task does not exist

---

### PATCH /api/tasks/{id}
**Purpose**: Update specific fields of a scheduled task.

**Path Parameter**:
- `id`: Task ID.

**Request Body**:
JSON object with fields to update:
```json
{
  "enabled": false,
  "handler_enabled": true,
  "timer": "0 */6 * * *",
  "preset": "audio",
  "folder": "downloads/music",
  "template": "%(title)s.%(ext)s",
  "cli": "--extract-audio",
  "auto_start": true
}
```

**Notes**:
- Only include fields you want to update
- All fields are optional

**Response**:
Returns the updated task
```json
{
  "id": "task_id",
  "name": "Task Name",
  "url": "https://example.com/playlist",
  "preset": "audio",
  "folder": "downloads/music",
  "template": "%(title)s.%(ext)s",
  "cli": "--extract-audio",
  "timer": "0 */6 * * *",
  "auto_start": true,
  "handler_enabled": true,
  "enabled": false
}
```

**Error Responses**:
```json
{ "error": "Task 'task_id' does not exist." }
{ "error": "Invalid JSON in request body.", "message": "..." }
{ "error": "Request body must be a JSON object." }
{ "error": "No valid fields to update." }
{ "error": "Validation failed: Invalid timer format." }
```

**Status Codes**:
- `200 OK` - Task updated successfully
- `400 Bad Request` - Missing task ID, invalid JSON, no valid fields, or validation error
- `404 Not Found` - Task does not exist
- `500 Internal Server Error` - Failed to update task

---

### GET /api/task_definitions/
**Purpose**: Retrieve all task definitions.

**Query Parameters**:
- `include=definition` (optional) - Include the full definition object in response.

**Response**:
```json
[
  {
    "id": "<uuid>",
    "name": "Task Definition Name",
    "description": "...",
    "enabled": true,
    "definition": { ... }  // only if include=definition
  },
  ...
]
```

---

### GET /api/task_definitions/{identifier}
**Purpose**: Retrieve a specific task definition by ID or name.

**Path Parameter**:
- `identifier`: Task definition ID or name.

**Response**:
```json
{
  "id": "<uuid>",
  "name": "Task Definition Name",
  "description": "...",
  "enabled": true,
  "definition": {
    "handler": "GenericTaskHandler",
    "config": { ... }
  }
}
```

- `400 Bad Request` if identifier is missing.
- `404 Not Found` if the task definition doesn't exist.

---

### POST /api/task_definitions/
**Purpose**: Create a new task definition.

**Body**:
```json
{
  "name": "My Task Definition",
  "description": "...",
  "enabled": true,
  "definition": {
    "handler": "GenericTaskHandler",
    "config": { ... }
  }
}
```

Or wrap in a definition object:
```json
{
  "definition": {
    "name": "My Task Definition",
    "handler": "GenericTaskHandler",
    ...
  }
}
```

**Response**:
```json
{
  "id": "<uuid>",
  "name": "My Task Definition",
  "description": "...",
  "enabled": true,
  "definition": { ... }
}
```

- `201 Created` if successful.
- `400 Bad Request` if validation fails.

---

### PUT /api/task_definitions/{identifier}
**Purpose**: Update an existing task definition.

**Path Parameter**:
- `identifier`: Task definition ID or name.

**Body**:
```json
{
  "name": "Updated Name",
  "description": "...",
  "enabled": false,
  "definition": {
    "handler": "GenericTaskHandler",
    "config": { ... }
  }
}
```

**Response**:
```json
{
  "id": "<uuid>",
  "name": "Updated Name",
  "description": "...",
  "enabled": false,
  "definition": { ... }
}
```

- `200 OK` if successful.
- `400 Bad Request` if identifier is missing or validation fails.

---

### DELETE /api/task_definitions/{identifier}
**Purpose**: Delete a task definition.

**Path Parameter**:
- `identifier`: Task definition ID or name.

**Response**:
```json
{ "status": "deleted" }
```

- `200 OK` if successful.
- `400 Bad Request` if identifier is missing or task definition doesn't exist.

---

### GET /api/player/playlist/{file:.*}.m3u8
**Purpose**: Generate a playlist for a given local media file.

**Path Parameter**:
- `file` = Relative path of the media file within the `download_path`.

**Response**:  
An `.m3u8` playlist.

---

### GET /api/player/m3u8/{mode}/{file:.*}.m3u8
**Purpose**: Dynamically generate an M3U8 playlist for video or subtitles.  

**Path Parameters**:
- `mode`: either `video` or `subtitle`.
- `file`: relative path of the file.

**Query Parameters (when `mode=subtitle`)**:
- `duration`: The total duration of the subtitle track

**Response**:
- `Content-Type: application/x-mpegURL` containing the `.m3u8` text.

---

### GET /api/player/segments/{segment}/{file:.*}.ts
**Purpose**: Streams a single TS segment for adaptive HLS playback.  

**Path Parameters**:
- `segment` = Numeric segment index.
- `file` = Relative file path.

**Query Parameters**:
- `sd` = The segment duration (float).  
- `vc` = `1` or `0` (whether to convert video).  
- `ac` = `1` or `0` (whether to convert audio).

**Response**:  
Binary TS data (`Content-Type: video/mpegts`).

---

### GET /api/player/subtitle/{file:.*}.vtt
**Purpose**: Provides a `.vtt` (WebVTT) subtitle file for playback.  

**Path Parameter**:
- `file` = Relative path of the subtitle file.

**Response**:  
`Content-Type: text/vtt; charset=UTF-8`.

---

### GET /api/thumbnail
**Purpose**: Proxy/fetch a remote thumbnail image.  

**Query Parameter**:
- `?url=<remote-thumbnail-url>`

**Response**:  
Binary image data with the appropriate `Content-Type`.

---

### GET /api/file/ffprobe/{file:.*}
**Purpose**: Return the `ffprobe` data for a local file.  

**Path Parameter**:
- `file` = Relative path to the file inside `download_path`.

**Response**:
```json
{
  "streams": [...],
  "format": { ... },
  ...
}
```

### GET /api/file/info/{file:.*}
**Purpose**: Get comprehensive file information including ffprobe data, MIME type, and sidecar files.  

**Path Parameter**:
- `file` = Relative path to the file inside `download_path`.

**Response**:
```json
{
  "title": "filename",
  "ffprobe": {
    "streams": [...],
    "format": { ... },
    ...
  },
  "mimetype": "video/mp4",
  "sidecar": {
    "subtitles": [
      {
        "file": "filename.xxx.vtt",
        "lang": "xxx",
        "name": "VTT 0 - XXX|end",
      },
      ...
      }
    ],
    "video": [],
    "audio": [],
    "image": [],
    "text": [],
    "metadata": [],
    ...
  }
}
```

---

### GET /api/file/browser/{path:.*}
**Purpose**: Browse files and directories within the download path (if browser is enabled).  

**Path Parameter**:
- `path` = Relative path within the download directory (URL-encoded).

**Response**:
```json
{
  "path": "/some/path",
  "contents": [
    {
      "type": "file",
      "content_type": "video|subtitle|audio|image|text|metadata|dir|download",
      "name": "filename.mp4",
      "path": "/filename.mp4",
      "size": 123456789,
      "mimetype": "mime/type",
      "mtime": "2023-01-01T12:00:00Z",
      "ctime": "2023-01-01T12:00:00Z",
      "is_dir": true|false,
      "is_file": true|false,
      ...
    },
    {
      "type": "dir",
      "content_type": "dir",
      "name": "Season 2025",
      "path": "/Season 2025",
      ...
    }
  ]
}
```
- Returns `403 Forbidden` if file browser is disabled.
- Returns `404 Not Found` if the path doesn't exist.

---

### POST /api/file/actions
**Purpose**: Perform file browser actions on files or directories.

**Body**:
```json
[
  { "action": "rename", "path": "relative/path/file.ext", "new_name": "new_name.ext" },
  { "action": "delete", "path": "relative/path/file.ext" },
  { "action": "move", "path": "relative/path/file.ext", "new_path": "new/relative/path" },
  { "action": "directory", "path": "relative/path", "new_dir": "subdirectory" }
]
```

Actions and required fields:
- `rename`: `{ "action": "rename", "path": "...", "new_name": "<name>" }`
- `delete`: `{ "action": "delete", "path": "..." }`
- `move`: `{ "action": "move", "path": "...", "new_path": "<dir-relative-to-download_path>" }`
- `directory`: `{ "action": "directory", "path": "...", "new_dir": "<subdir/to/create>" }`

**Response**: 
```json
[
  { "path": "relative/path", "action": "rename", "ok": true },
  { "path": "relative/path", "action": "delete", "ok": true },
  ...
]
```

or an error:
```json
{ "error": "text" }
```

- `403 Forbidden` if browser actions are disabled.
- `400 Bad Request` for invalid actions or parameters.

---

### POST /api/file/download
**Purpose**: Prepare a ZIP download of selected files (and detected sidecars). Returns a short-lived token.

**Body**:
```json
[ "relative/path/file1.ext", "relative/path/file2.ext" ]
```

**Response**:
```json
{ "token": "<uuid>", "files": ["relative/path/file1.ext", "..."] }
```

- `400 Bad Request` if the body is not a JSON array or contains no valid files.

---

### GET /api/file/download/{token}
**Purpose**: Stream a ZIP file for the previously prepared download token.

**Path Parameter**:
- `token`: Token returned by POST `/api/file/download`.

**Response**:
- `200 OK` streaming response with `Content-Type: application/zip` and `Content-Disposition: attachment`.
- JSON error with `400 Bad Request` if the token is invalid/expired or no files available.

---

### GET /api/download/{filename}
**Purpose**: Serve downloaded files directly from the download path.

**Path Parameter**:
- `filename`: Relative path to the file within the download directory (URL-encoded).

**Response**:
- `200 OK` with file content and appropriate headers
- `302 Found` redirect if the file path needs normalization
- `404 Not Found` if the file doesn't exist

- **Error Responses**  

When an error occurs, responses follow a structure similar to:
```json
{ "error": "Description of the error"  }
```
with an appropriate HTTP status code.

---

### GET /api/random/background
**Purpose**: Get a random background image from configured backends.  

**Query Parameters**:
- `force=true` (optional) - Force fetch a new image instead of using cache.

**Response**:
Binary image data with appropriate headers

---

### GET /api/presets
**Purpose**: Retrieve all available download presets.  

**Query Parameters**:
- `filter=<field1,field2>` (optional) - Comma-separated list of fields to include in response.

**Response**:
```json5
[
  {
    "id": "<uuid>",
    "name": "preset_name",
    "description": "...",
    "folder": "my_channel/foo",
    "template": "%(title)s.%(ext)s",
    "cookies": "...",
    "cli": "--write-subs --embed-subs",
    "default": true|false, // optional, indicates if this is the default preset.
    ...
  },
  ...
]
```

---

### GET /api/dl_fields
**Purpose**: Retrieve the list of configured download fields.

**Query Parameters (optional)**:
- `filter`: Comma-separated list of field names to include in each object.

**Response**:
```json
[
  { "id": "<uuid>", "name": "...", ... },
  ...
]
```

---

### PUT /api/dl_fields
**Purpose**: Save the list of download fields. Replaces existing entries.

**Body**: Array of objects. Required per-item fields: `name`. `id` is auto-generated if missing or invalid.
```json
[
  { "name": "...", "id": "<uuid>", ... },
  { "name": "..." }
]
```

**Response**:
```json
[
  { "id": "<uuid>", "name": "...", ... },
  ...
]
```
or an error:
```json
{ "error": "text" }
```

---

### PUT /api/presets
**Purpose**: Save/update download presets.  

**Body**: An array of preset objects:
```json
[
  {
    "name": "My Preset", // required, unique name for the preset
    "id": "<uuid>",  // optional, will be generated if not provided
    "description": "...", // optional, description of the preset
    "folder": "my_channel/foo", // optional, relative to download_path
    "template": "%(title)s.%(ext)s", // optional, filename template
    "cookies": "...", // optional, Netscape HTTP Cookie format
    "cli": "--write-subs --embed-subs", // optional, additional command options for yt-dlp
  },
  ...
]
```

**Response**:
```json
[
  {
    "id": "<uuid>",
    "name": "My Preset",
    "description": "...",
  },
  ...
]
```

---

### GET /api/conditions
**Purpose**: Retrieve all configured download conditions.  

**Response**:
```json
[
  {
    "id": "<uuid>",
    "name": "condition_name",
    "filter": "...",
    "cli": "...",
    "extras": {},
    "enabled": true,
    "priority": 0,
    "description": "What this condition does"
  },
  ...
]
```

**Notes**:
- Conditions are evaluated in priority order (higher priority first).
- Priority defaults to 0 when not specified.

---

### PUT /api/conditions
**Purpose**: Save/update download conditions.  

**Body**: An array of condition objects:
```json
[
  {
    "id": "<uuid>",  // optional, will be generated if not provided
    "name": "Use proxy for region locked content",
    "filter": "availability = 'needs_auth' & channel_id = 'channel_id'",
    "cli": "--proxy http://myproxy.com:8080",
    "extras": {},
    "enabled": true,
    "priority": 10,
    "description": "Apply proxy for region-locked videos"
  },
  ...
]
```

**Response**:
```json
[
  {
    "id": "<uuid>",
    "name": "Use proxy for region locked content",
    "filter": "availability = 'needs_auth' & channel_id = 'channel_id'",
    "cli": "--proxy http://myproxy.com:8080",
    "extras": {},
    "enabled": true,
    "priority": 10,
    "description": "Apply proxy for region-locked videos"
  },
  ...
]
```

**Notes**:
- Disabled conditions (`enabled: false`) will be stored but ignored during matching.
- All conditions are enabled by default when the `enabled` field is not provided.
- Priority determines check order. Higher priority conditions are checked first.

---

### POST /api/conditions/test
**Purpose**: Evaluate a condition expression against info extracted from a URL.

**Body**:
```json
{ "url": "https://...", "condition": "yt:duration > 600", "preset": "<optional-preset>" }
```

**Response**:
```json
{
  "status": true,
  "condition": "...",
  "data": { ... }  // sanitized, possibly large
}
```

- `400 Bad Request` for invalid body, missing fields, or extractor failures.

---

### GET /api/logs
**Purpose**: Retrieve recent application logs (if file logging is enabled).  

**Query Parameters**:
- `offset=<number>` (optional, default: 0) - Number of log entries to skip.
- `limit=<number>` (optional, default: 100, max: 150) - Number of log entries to return.

**Response**:
```json
{
  "logs": [
    {
      "timestamp": "2023-01-01T12:00:00Z",
      "level": "INFO",
      "message": "...",
      ...
    },
    ...
  ],
  "offset": 0,
  "limit": 100,
  "next_offset": 100,
  "end_is_reached": false
}
```
- Returns `404 Not Found` if file logging is not enabled.

---

### GET /api/notifications
**Purpose**: Retrieve the configured notification targets and which event types are allowed.  

**Response** (example):
```json
{
  "notifications": [
    {
      "id": "uuid",
      "name":"...",
      "on": ["completed", "error",...], // empty array means all events.
      "request":{
        "type":"json|form",
        "method":"POST|PUT",
        "url":"https://...",
        "headers":[
          {"key":"...", "value":"..."},
          ...
        ]
        }
      }
    }
  ],
  "allowedTypes": ["added", "completed", "error", "cancelled", "cleared", "log_info", "log_success", "log_warning", "log_error", "test"]
}
```

---

### PUT /api/notifications
**Purpose**: Overwrites the entire list of notification targets.  

**Body**: An array of notification target configurations. Example:
```json
[
  {
    "id": "uuid",
    "name": "My Webhook",
    "on": ["completed", "error"],
    "request": {
      "type": "json",
      "method": "POST",
      "url": "https://...",
      "headers": [
        { "key": "Authorization", "value": "Bearer ..." }
      ]
    }
  },
  {
    "name": "Another Webhook",
    "on": ["completed"],
    "request": {
      "type": "form",
      "method": "PUT",
      "url": "https://...",
      "headers": []
    }
  }
  ...
]
```
- If `id` is not provided or is not a valid UUIDv4, it will be auto-generated.
- If the payload list is empty, all existing notifications are removed.

**Response**:
```json
{
  "notifications": [
    {
      "id": "uuid",
      "name": "...",
      "on": ["completed", "error", ...],
      "request": { ... }
    },
    ...
  ],
  "allowedTypes": ["added", "completed", "error", "cancelled", "cleared", "log_info", "log_success", ...]
}
```
---

### POST /api/yt-dlp/archive_id/
**Purpose**: Get the archive ID for a given URLs.
**Body**: Array of URLs.
```json
[
    "https://youtube.com/...",
    "https://..."
}
```

**Response**:
```json
[
  {
    "index": "index_of_the_url_in_request_array",
    "url": "the_url",
    "id": "the_video_id_or_null_if_not_found",
    "ie_key": "the_extractor_key_or_null_if_not_found",
    "archive_id": "the_archive_id_or_null_if_not_found",
    "error": "error_message_if_any_or_null"
  },
  ...
]
```

or an error:
```json
{
  "error": "text"
}
```

- If the body is not a valid JSON array, returns `400 Bad Request`.

---

### POST /api/notifications/test
**Purpose**: Triggers a test notification event to all configured targets.  

**Response**:
```json
{
  "type": "test",
  "message": "This is a test notification."
}
```

---

### GET /api/yt-dlp/options
**Purpose**: Get the current yt-dlp CLI options as a JSON object.

**Response**:
```json
[
  {
    "description": "Description of the option",
    "flags":[ "--option", "-o" ],
    "group": "Option Group",
    "ignored": false, // true if this option is ignored by ytptube.
  },
  ...
]
```

---

### POST /api/system/pause
**Purpose**: Pause all non-active downloads in the queue.

**Response**:
```json
{ "message": "Non-active downloads have been paused." }
```

- `200 OK` if downloads were successfully paused.
- `406 Not Acceptable` if downloads are already paused.

---

### POST /api/system/resume
**Purpose**: Resume all paused downloads in the queue.

**Response**:
```json
{ "message": "Resumed all downloads." }
```

- `200 OK` if downloads were successfully resumed.
- `406 Not Acceptable` if downloads are not paused.

---

### POST /api/system/shutdown
**Purpose**: Gracefully shut down the application (native mode only).

**Response**:
```json
{ "message": "The application shutting down." }
```

- `400 Bad Request` if not running in native mode.

---

### POST /api/system/check-updates
**Purpose**: Manually trigger a check for application updates from GitHub releases.

**Response**:
```json
{
  "status": "update_available",
  "current_version": "v1.0.14",
  "new_version": "v1.0.15"
}
```

**Status values**:
- `disabled`: Update checking is disabled in configuration
- `up_to_date`: No updates available
- `update_available`: New version is available
- `error`: Error occurred during check (HTTP error, network issue, etc.)

- `400 Bad Request` if update checking is disabled in configuration (`check_for_updates: false`).
- `new_version` will be `null` when status is `up_to_date`, `disabled`, or `error`.
- The check runs synchronously and returns the result immediately.
- Results are also stored in config and pushed to frontend via WebSocket.

---

### GET /api/dev/loop
**Purpose**: Development-only. Show event loop details and running tasks.

**Response**:
```json
{ "total_tasks": 1, "loop": "...", "tasks": [ { "task": "...", "stack": ["..."] } ] }
```

- `403 Forbidden` if not in development mode.

---

### GET /api/dev/pip
**Purpose**: Development-only. Return installed versions for configured pip packages.

**Response**:
```json
{ "package": "version-or-null", "...": null }
```

---

### GET /api/docs/{file}
**Purpose**: Serve documentation files from the GitHub repository.

**Path Parameter**:
- `file`: Documentation filename (e.g., `README.md`, `FAQ.md`, `API.md`, `sc_short.jpg`, `sc_simple.jpg`)

**Response**:
- File content with appropriate `Content-Type` header (text/markdown for .md, image/jpeg for .jpg, etc.)
- Cached for 1 hour

or an error:
```json
{ "error": "Doc file not found." }
```

- `404 Not Found` if the file is not in the allowed list.
- `500 Internal Server Error` if fetching from GitHub fails.

> **Note**: This endpoint also responds to direct file paths like `/README.md`, `/FAQ.md`, etc. without the `/api/docs/` prefix.

---

## WebSocket API

The WebSocket API provides real-time bidirectional communication between the client and server using Socket.IO protocol. It enables live updates for downloads, queue status, notifications, and terminal access.

> ![IMPORTANT]
> The WebSocket API is unstable and many events will be moved to REST endpoints in future releases. 
> Please do not rely on the WebSocket API for the time being.

### Connection

**URL**: `ws://localhost:8081/socket.io/` (development) or `https://yourdomain.com/socket.io/` (production)

The client automatically connects to the WebSocket server and receives a `connected` event with initial state. The connection uses automatic reconnection with exponential backoff (default: up to 30 attempts, 5s delay).

**Connection Options**:
```javascript
{
  transports: ['websocket', 'polling'],  // Fallback to long-polling if WebSocket unavailable
  withCredentials: true,                  // Include cookies for authentication
  reconnection: true,                     // Enable automatic reconnection
  reconnectionAttempts: 30,              // Max reconnection attempts
  reconnectionDelay: 5000                // Initial reconnection delay in ms
}
```

### Authentication

If Basic Authentication is configured, include credentials when establishing the WebSocket connection:

1. **Via HTTP Headers** (automatic in browsers):
   ```
   Authorization: Basic base64("<username>:<password>")
   ```

2. **Via Query Parameter**:
   ```
   ws://localhost:8081/socket.io/?apikey=<base64_urlsafe("<username>:<password>")>
   ```

### Message Format

All WebSocket messages are JSON-encoded and follow a consistent structure:

**Server-to-Client (Event)** - Emitted by server, received by client:
```json
{
  "id": "unique-event-id",
  "created_at": "2024-01-15T10:30:00.000000+00:00",
  "event": "item_added",
  "title": "Item Queued",
  "message": "Video added to download queue",
  "data": {...}
}
```

### Core Events

#### Connection Events

##### `connect` (Built-in)
Fired when WebSocket connection is established. No data payload.

```typescript
socket.on('connect', () => console.log('WebSocket connected'));
```

##### `disconnect` (Built-in)
Fired when WebSocket connection is closed. No data payload.

```typescript
socket.on('disconnect', (reason: string) => console.log('WebSocket disconnected:', reason));
```

##### `configuration` (Server → Client)
Sends the current application configuration.

**Data Fields**:
- `config`: Global configuration object
- `presets`: Available download presets
- `dl_fields`: Available download fields
- `paused`: Queue pause status (boolean)

##### `connected` (Server → Client)
When a client connects, this events sends the folder and current queue.

**Data Fields**:
- `queue`: Current download queue (array of items)
- `folders`: Directory structure for downloads

#### Logging Events

All logging events follow the same structure with JSON-encoded message:

##### `log_info` (Server → Client)
General informational message.

##### `log_success` (Server → Client)
Success notification message.

##### `log_warning` (Server → Client)
Warning notification message.

##### `log_error` (Server → Client)
Error notification message.

##### `log_lines` (Server → Client)
Continuous application log lines (requires subscription event).

**Data Fields**:
- `line`: Log line content
- `timestamp`: Log timestamp

### Download Queue Events

#### `item_added` (Server → Client)
Emitted when a new item is successfully added to the queue. The response payload is the complete item object.

```typescript
socket.on('item_added', (stream: string) => {
  const json = JSON.parse(stream);
  const item = json.data;
  console.log(`Added: ${item.title} [${item.url}]`);
});
```

#### `item_updated` (Server → Client)
Emitted when an item's status or progress changes **(high-frequency event)**.

**Data Fields**: Same as `item_added`

```typescript
socket.on('item_updated', (stream: string) => {
  const json = JSON.parse(stream);
  const item = json.data;
  console.log(`Progress: ${item.title} - ${item.progress}%`);
});
```

#### `item_completed` (Server → Client)
Emitted when a download completes. Item moves from queue to history.

**Data Fields**: Complete item object with final status

```typescript
socket.on('item_completed', (stream: string) => {
  const json = JSON.parse(stream);
  const item = json.data;
  console.log(`✓ Completed: ${item.title}`);
  console.log(`Saved to: ${item.output_path}`);
});
```

#### `item_cancelled` (Server → Client)
Emitted when a download is cancelled by user.

**Data Fields**: Item object with status `cancelled`

```typescript
socket.on('item_cancelled', (stream: string) => {
  const json = JSON.parse(stream);
  const item = json.data;
  console.log(`✗ Cancelled: ${item.title}`);
});
```

#### `item_deleted` (Server → Client)
Emitted when an item is deleted from history.

**Data Fields**: Item object

```typescript
socket.on('item_deleted', (stream: string) => {
  const json = JSON.parse(stream);
  console.log(`Deleted from history: ${json.data._id}`);
});
```

#### `item_moved` (Server → Client)
Emitted when an item moves between queue and history.

**Data Fields**:
- `to`: Destination location (`queue` or `history`)
- `item`: Complete item object

```typescript
socket.on('item_moved', (stream: string) => {
  const json = JSON.parse(stream);
  console.log(`Item moved to: ${json.data.to}`);
});
```

### Terminal/CLI Events

The terminal feature requires `YTP_CONSOLE_ENABLED=true`.

#### `cli_post` (Client → Server)
Execute a command via yt-dlp CLI.

**Data**: Command arguments as string (without `yt-dlp` prefix)

#### `cli_output` (Server → Client)
Output line from the CLI command execution.

**Data Fields**:
- `type`: Output type (`stdout` or `stderr`)
- `line`: Output line content

#### `cli_close` (Server → Client)
Emitted when CLI command execution completes.

**Data Fields**:
- `exitcode`: Command exit code (0 = success, non-zero = error)

---

## Error Responses

Most endpoints return standard error codes (`400`, `403`, `404`, `500`, etc.) and a JSON body on failure. For example:
```json
{
  "error": "url param is required."
}
```
with `400 Bad Request`, or:
```json
{
  "error": "Item not found."
}
```
with `404 Not Found`.

---
