metadata-agregator/docs/research/lidarr-metadata-api/analysis/API.md

# Lidarr Metadata API - API Reference

## Base URL and Versioning

**Production deployment**:
- Stable: `https://api.lidarr.audio/api/v0.3`
- Testing: `https://api.lidarr.audio/api/testing`

**Local development**:
- Default: `http://localhost:5001`
- Configurable via `APPLICATION_ROOT` environment variable

**Version strategy**: Dual deployment with stable (v0.3) and testing versions running simultaneously.

## Authentication

**Read endpoints**: No authentication required (public access)

**Write endpoints**: API key authentication via header

```http
POST /invalidate HTTP/1.1
X-Api-Key: your-api-key-here
```

**Configuration**:
```bash
export INVALIDATE_APIKEY=your-secure-key
```

**Default**: `replaceme` (insecure, must change in production)

## Response Format

All endpoints return JSON with consistent structure.

### Common Response Headers

```http
HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: s-maxage=2592000, max-age=0
X-Application-Version: 10.0.0.0
```

**Cache-Control explanation**:
- `s-maxage=2592000`: CDN can cache for 30 days
- `max-age=0`: Clients must revalidate (always check CDN/origin)

### Error Response Format

```json
{
  "error": "Artist not found",
  "status": 404,
  "mbid": "invalid-mbid-format"
}
```

**HTTP status codes**:
- `200`: Success
- `400`: Bad request (invalid parameters)
- `401`: Unauthorized (missing/invalid API key)
- `404`: Resource not found
- `429`: Rate limit exceeded
- `500`: Internal server error
- `503`: Service unavailable (database/cache down)

## Health and Version Endpoints

### GET /

**Purpose**: Health check and version information

**Parameters**: None

**Response**:
```json
{
  "version": "10.0.0.0",
  "status": "healthy",
  "timestamp": "2025-04-28T12:34:56Z"
}
```

**Cache**: No caching

**Use case**: Load balancer health checks, monitoring

## Artist Endpoints

### GET /artist/{mbid}

**Purpose**: Retrieve complete artist metadata with releases

**Parameters**:

| Parameter | Type | Required | Default | Description |
|-----------|------|----------|---------|-------------|
| `mbid` | UUID | Yes | - | MusicBrainz artist ID |
| `primTypes` | String | No | All | Primary release types (comma-separated) |
| `secTypes` | String | No | All | Secondary release types (comma-separated) |
| `releaseStatuses` | String | No | All | Release statuses (comma-separated) |

**Primary release types**:
- `Album`: Studio albums
- `Single`: Singles
- `EP`: Extended plays
- `Broadcast`: Radio/TV broadcasts
- `Other`: Miscellaneous

**Secondary release types**:
- `Compilation`: Compilation albums
- `Soundtrack`: Movie/game soundtracks
- `Spokenword`: Audiobooks, poetry
- `Interview`: Interview recordings
- `Audiobook`: Audiobooks
- `Live`: Live recordings
- `Remix`: Remix albums
- `DJ-mix`: DJ mix albums
- `Mixtape/Street`: Mixtapes

**Release statuses**:
- `Official`: Official releases
- `Promotion`: Promotional releases
- `Bootleg`: Bootleg recordings
- `Pseudo-Release`: Pseudo-releases

**Example request**:
```http
GET /artist/5b11f4ce-a62d-471e-81fc-a69a8278c7da?primTypes=Album,Single&releaseStatuses=Official HTTP/1.1
```

**Response**:
```json
{
  "Id": "5b11f4ce-a62d-471e-81fc-a69a8278c7da",
  "OldIds": [],
  "ArtistName": "Nirvana",
  "SortName": "Nirvana",
  "Disambiguation": "90s US grunge band",
  "Overview": "Nirvana was an American rock band formed in Aberdeen, Washington, in 1987...",
  "Type": "Group",
  "Status": "Ended",
  "Gender": null,
  "Hometown": "Aberdeen, WA, United States",
  "StartYear": 1987,
  "EndYear": 1994,
  "ArtistAliases": [
    {
      "Name": "ニルヴァーナ",
      "SortName": "ニルヴァーナ",
      "Locale": "ja",
      "Primary": true
    }
  ],
  "Links": [
    {
      "Url": "https://www.spotify.com/artist/6olE6TJLqED3rqDCT0FyPh",
      "Name": "spotify"
    },
    {
      "Url": "https://www.allmusic.com/artist/mn0000352188",
      "Name": "allmusic"
    },
    {
      "Url": "https://www.discogs.com/artist/65450",
      "Name": "discogs"
    },
    {
      "Url": "https://en.wikipedia.org/wiki/Nirvana_(band)",
      "Name": "wikipedia"
    }
  ],
  "Images": [
    {
      "Url": "https://imagecache.lidarr.audio/fanart/artist/5b11f4ce-a62d-471e-81fc-a69a8278c7da/poster.jpg",
      "CoverType": "poster",
      "Extension": ".jpg"
    },
    {
      "Url": "https://imagecache.lidarr.audio/fanart/artist/5b11f4ce-a62d-471e-81fc-a69a8278c7da/banner.jpg",
      "CoverType": "banner",
      "Extension": ".jpg"
    },
    {
      "Url": "https://imagecache.lidarr.audio/fanart/artist/5b11f4ce-a62d-471e-81fc-a69a8278c7da/logo.png",
      "CoverType": "logo",
      "Extension": ".png"
    },
    {
      "Url": "https://imagecache.lidarr.audio/fanart/artist/5b11f4ce-a62d-471e-81fc-a69a8278c7da/fanart.jpg",
      "CoverType": "fanart",
      "Extension": ".jpg"
    }
  ],
  "Genres": [
    "Grunge",
    "Alternative Rock",
    "Punk Rock"
  ],
  "Rating": {
    "Votes": 42,
    "Value": 4.8
  },
  "Albums": [
    {
      "Id": "1b022e01-4da6-387b-8658-8678046e4cef",
      "Title": "Nevermind",
      "Disambiguation": "",
      "ReleaseDate": "1991-09-24",
      "Type": "Album",
      "SecondaryTypes": [],
      "Status": "Official",
      "Genres": ["Grunge", "Alternative Rock"],
      "Rating": {
        "Votes": 156,
        "Value": 4.9
      },
      "Images": [
        {
          "Url": "https://imagecache.lidarr.audio/cover/1b022e01-4da6-387b-8658-8678046e4cef/front.jpg",
          "CoverType": "cover",
          "Extension": ".jpg"
        }
      ]
    }
  ]
}
```

**Response fields**:

| Field | Type | Description |
|-------|------|-------------|
| `Id` | UUID | MusicBrainz artist ID |
| `OldIds` | Array | Historical MusicBrainz IDs (after merges) |
| `ArtistName` | String | Primary artist name |
| `SortName` | String | Name for alphabetical sorting |
| `Disambiguation` | String | Disambiguation comment |
| `Overview` | String | Artist biography (from Wikipedia) |
| `Type` | String | Artist type (Person, Group, Orchestra, etc.) |
| `Status` | String | Artist status (Active, Ended, etc.) |
| `Gender` | String | Gender (for Person type) |
| `Hometown` | String | Origin location |
| `StartYear` | Integer | Formation/birth year |
| `EndYear` | Integer | Dissolution/death year |
| `ArtistAliases` | Array | Alternative names and translations |
| `Links` | Array | External links (Spotify, AllMusic, Discogs, etc.) |
| `Images` | Array | Artist images (poster, banner, logo, fanart) |
| `Genres` | Array | Genre tags |
| `Rating` | Object | Community rating (votes and value) |
| `Albums` | Array | Release groups (filtered by parameters) |

**Cache behavior**:
- **Cache key**: `artist:{mbid}:{primTypes}:{secTypes}:{releaseStatuses}`
- **TTL**: 30 days (2592000 seconds)
- **Invalidation**: Manual via `/artist/{mbid}/refresh` or automatic via crawler

**Performance**:
- **Cold request**: 2-5 seconds (MusicBrainz DB + external APIs)
- **Cached request**: 50-200ms (Redis/PostgreSQL)
- **CDN request**: 10-50ms (Cloudflare edge)

### POST /artist/{mbid}/refresh

**Purpose**: Invalidate cache and force fresh metadata fetch

**Authentication**: Required (API key)

**Parameters**:

| Parameter | Type | Required | Description |
|-----------|------|----------|-------------|
| `mbid` | UUID | Yes | MusicBrainz artist ID |

**Request**:
```http
POST /artist/5b11f4ce-a62d-471e-81fc-a69a8278c7da/refresh HTTP/1.1
X-Api-Key: your-api-key-here
```

**Response**:
```json
{
  "status": "success",
  "mbid": "5b11f4ce-a62d-471e-81fc-a69a8278c7da",
  "invalidated": [
    "redis:artist:5b11f4ce-a62d-471e-81fc-a69a8278c7da",
    "postgres:artist:5b11f4ce-a62d-471e-81fc-a69a8278c7da",
    "cdn:https://api.lidarr.audio/api/v0.3/artist/5b11f4ce-a62d-471e-81fc-a69a8278c7da"
  ]
}
```

**Cache invalidation**:
1. Delete from Redis cache
2. Delete from PostgreSQL cache
3. Purge from Cloudflare CDN
4. Next request will fetch fresh data

**Use cases**:
- Artist metadata updated in MusicBrainz
- New images added to FanArt.tv
- Wikipedia article updated
- Manual cache refresh

### GET /recent/artist

**Purpose**: List recently updated artists

**Parameters**:

| Parameter | Type | Required | Default | Description |
|-----------|------|----------|---------|-------------|
| `limit` | Integer | No | 50 | Maximum number of results |
| `since` | ISO 8601 | No | 24h ago | Only artists updated after this timestamp |

**Example request**:
```http
GET /recent/artist?limit=10&since=2025-04-27T00:00:00Z HTTP/1.1
```

**Response**:
```json
{
  "artists": [
    {
      "Id": "5b11f4ce-a62d-471e-81fc-a69a8278c7da",
      "ArtistName": "Nirvana",
      "LastUpdated": "2025-04-28T10:30:00Z",
      "ChangeType": "metadata"
    },
    {
      "Id": "83d91898-7763-47d7-b03b-b92132375c47",
      "ArtistName": "Pink Floyd",
      "LastUpdated": "2025-04-28T09:15:00Z",
      "ChangeType": "new_release"
    }
  ],
  "total": 2,
  "limit": 10,
  "since": "2025-04-27T00:00:00Z"
}
```

**Change types**:
- `metadata`: Artist metadata updated
- `new_release`: New release added
- `updated_release`: Existing release updated
- `new_link`: New external link added
- `cover_art`: Cover art updated

**Cache**: 1 hour TTL

**Use case**: Crawler scheduling, monitoring MusicBrainz updates

## Album Endpoints

### GET /album/{mbid}

**Purpose**: Retrieve complete album metadata with tracks

**Parameters**:

| Parameter | Type | Required | Description |
|-----------|------|----------|-------------|
| `mbid` | UUID | Yes | MusicBrainz release group ID |

**Example request**:
```http
GET /album/1b022e01-4da6-387b-8658-8678046e4cef HTTP/1.1
```

**Response**:
```json
{
  "Id": "1b022e01-4da6-387b-8658-8678046e4cef",
  "OldIds": [],
  "Title": "Nevermind",
  "Disambiguation": "",
  "Overview": "Nevermind is the second studio album by American rock band Nirvana...",
  "ReleaseDate": "1991-09-24",
  "Type": "Album",
  "SecondaryTypes": [],
  "Status": "Official",
  "Artist": {
    "Id": "5b11f4ce-a62d-471e-81fc-a69a8278c7da",
    "ArtistName": "Nirvana"
  },
  "Links": [
    {
      "Url": "https://www.spotify.com/album/2guirTSEqLizK7j9i1MTTZ",
      "Name": "spotify"
    },
    {
      "Url": "https://www.allmusic.com/album/mw0000083881",
      "Name": "allmusic"
    }
  ],
  "Images": [
    {
      "Url": "https://imagecache.lidarr.audio/cover/1b022e01-4da6-387b-8658-8678046e4cef/front.jpg",
      "CoverType": "cover",
      "Extension": ".jpg"
    },
    {
      "Url": "https://imagecache.lidarr.audio/cover/1b022e01-4da6-387b-8658-8678046e4cef/back.jpg",
      "CoverType": "disc",
      "Extension": ".jpg"
    }
  ],
  "Genres": ["Grunge", "Alternative Rock"],
  "Rating": {
    "Votes": 156,
    "Value": 4.9
  },
  "Media": [
    {
      "Position": 1,
      "Format": "CD",
      "Tracks": [
        {
          "Position": 1,
          "Title": "Smells Like Teen Spirit",
          "Duration": 301000,
          "ArtistName": "Nirvana"
        },
        {
          "Position": 2,
          "Title": "In Bloom",
          "Duration": 254000,
          "ArtistName": "Nirvana"
        }
      ]
    }
  ]
}
```

**Response fields**:

| Field | Type | Description |
|-------|------|-------------|
| `Id` | UUID | MusicBrainz release group ID |
| `OldIds` | Array | Historical IDs (after merges) |
| `Title` | String | Album title |
| `Disambiguation` | String | Disambiguation comment |
| `Overview` | String | Album description (from Wikipedia) |
| `ReleaseDate` | ISO 8601 | Original release date |
| `Type` | String | Primary type (Album, Single, EP, etc.) |
| `SecondaryTypes` | Array | Secondary types (Compilation, Live, etc.) |
| `Status` | String | Release status (Official, Promotion, etc.) |
| `Artist` | Object | Artist information |
| `Links` | Array | External links |
| `Images` | Array | Cover art images |
| `Genres` | Array | Genre tags |
| `Rating` | Object | Community rating |
| `Media` | Array | Physical/digital media with track listings |

**Cache behavior**:
- **Cache key**: `album:{mbid}`
- **TTL**: 30 days
- **Invalidation**: Manual or automatic

### POST /album/{mbid}/refresh

**Purpose**: Invalidate album cache

**Authentication**: Required (API key)

**Parameters**: Same as artist refresh

**Response**: Same structure as artist refresh

### GET /recent/album

**Purpose**: List recently updated albums

**Parameters**: Same as `/recent/artist`

**Response**: Similar structure with album-specific fields

## Search Endpoints

### GET /search/artist

**Purpose**: Search for artists by name

**Parameters**:

| Parameter | Type | Required | Default | Description |
|-----------|------|----------|---------|-------------|
| `query` | String | Yes | - | Search query |
| `limit` | Integer | No | 10 | Maximum results |

**Example request**:
```http
GET /search/artist?query=nirvana&limit=5 HTTP/1.1
```

**Response**:
```json
{
  "results": [
    {
      "Id": "5b11f4ce-a62d-471e-81fc-a69a8278c7da",
      "ArtistName": "Nirvana",
      "Disambiguation": "90s US grunge band",
      "Type": "Group",
      "Score": 100,
      "Images": [
        {
          "Url": "https://imagecache.lidarr.audio/fanart/artist/5b11f4ce-a62d-471e-81fc-a69a8278c7da/poster.jpg",
          "CoverType": "poster",
          "Extension": ".jpg"
        }
      ]
    },
    {
      "Id": "9282c8b4-ca0b-4c6b-b7e3-4f7762dfc4d6",
      "ArtistName": "Nirvana",
      "Disambiguation": "60s UK psychedelic band",
      "Type": "Group",
      "Score": 95,
      "Images": []
    }
  ],
  "total": 2,
  "query": "nirvana",
  "limit": 5
}
```

**Search algorithm**:
1. Query Solr artist core with dismax parser
2. Boost fields: `artist^2 sortname alias`
3. Minimum match: 1 term
4. Sort by relevance score
5. Enrich results with cached metadata

**Cache**:
- **Cache key**: `search:artist:{query}:{limit}`
- **TTL**: 1 hour

**Performance**:
- **Cold request**: 500ms-1s (Solr query + metadata enrichment)
- **Cached request**: 50-100ms

### GET /search/album

**Purpose**: Search for albums by title

**Parameters**: Same as artist search

**Response**: Similar structure with album-specific fields

**Search algorithm**: Same as artist search, using `release-group` Solr core

### GET /search/all

**Purpose**: Combined artist and album search

**Parameters**:

| Parameter | Type | Required | Default | Description |
|-----------|------|----------|---------|-------------|
| `query` | String | Yes | - | Search query |
| `artistLimit` | Integer | No | 5 | Max artist results |
| `albumLimit` | Integer | No | 5 | Max album results |

**Response**:
```json
{
  "artists": [...],
  "albums": [...],
  "query": "nevermind",
  "artistLimit": 5,
  "albumLimit": 5
}
```

**Use case**: Unified search UI, autocomplete

### POST /search/fingerprint

**Purpose**: Acoustic fingerprint search (AcoustID integration)

**Parameters**:

| Parameter | Type | Required | Description |
|-----------|------|----------|-------------|
| `fingerprint` | String | Yes | Chromaprint fingerprint |
| `duration` | Integer | Yes | Track duration in seconds |

**Request**:
```http
POST /search/fingerprint HTTP/1.1
Content-Type: application/json

```

**Response**:
```json
{
  "results": [
    {
      "Id": "5b11f4ce-a62d-471e-81fc-a69a8278c7da",
      "ArtistName": "Nirvana",
      "AlbumTitle": "Nevermind",
      "TrackTitle": "Smells Like Teen Spirit",
      "Score": 0.98,
      "Duration": 301
    }
  ]
}
```

**Use case**: Audio file identification, automatic tagging

## Spotify Integration Endpoints

### GET /spotify/artist/{id}

**Purpose**: Get artist metadata by Spotify ID

**Parameters**:

| Parameter | Type | Required | Description |
|-----------|------|----------|-------------|
| `id` | String | Yes | Spotify artist ID |

**Example request**:
```http
GET /spotify/artist/6olE6TJLqED3rqDCT0FyPh HTTP/1.1
```

**Response**: Same structure as `/artist/{mbid}` with MusicBrainz mapping

**Mapping algorithm**:
1. Query Spotify API for artist metadata
2. Search MusicBrainz by artist name
3. Calculate Levenshtein distance (threshold: 0.8)
4. Return best match with MusicBrainz ID

### GET /spotify/album/{id}

**Purpose**: Get album metadata by Spotify ID

**Parameters**: Same as artist endpoint

**Response**: Same structure as `/album/{mbid}` with MusicBrainz mapping

### POST /spotify/lookup

**Purpose**: Batch Spotify ID to MusicBrainz ID mapping

**Request**:
```http
POST /spotify/lookup HTTP/1.1
Content-Type: application/json

```

**Response**:
```json
{
  "artists": {
    "6olE6TJLqED3rqDCT0FyPh": "5b11f4ce-a62d-471e-81fc-a69a8278c7da",
    "0k17h0D3J5VfsdmQ1iZtE9": "83d91898-7763-47d7-b03b-b92132375c47"
  },
  "albums": {
    "2guirTSEqLizK7j9i1MTTZ": "1b022e01-4da6-387b-8658-8678046e4cef"
  }
}
```

**Cache**: 90 days TTL (Spotify IDs rarely change)

### GET /spotify/auth

**Purpose**: Get Spotify OAuth authorization URL

**Response**:
```json
{
  "auth_url": "https://accounts.spotify.com/authorize?client_id=...&response_type=code&redirect_uri=..."
}
```

**Use case**: User authentication for Spotify features

### GET /spotify/renew

**Purpose**: Refresh Spotify OAuth token

**Parameters**:

| Parameter | Type | Required | Description |
|-----------|------|----------|-------------|
| `refresh_token` | String | Yes | Spotify refresh token |

**Response**:
```json
{
  "access_token": "BQD...",
  "expires_in": 3600
}
```

## Chart Endpoints

### GET /chart/{name}/{type}/{selection}

**Purpose**: Get music charts from various sources

**Parameters**:

| Parameter | Type | Required | Values | Description |
|-----------|------|----------|--------|-------------|
| `name` | String | Yes | `apple-music`, `billboard`, `itunes`, `lastfm` | Chart source |
| `type` | String | Yes | `artist`, `album`, `track` | Chart type |
| `selection` | String | Yes | Source-specific | Chart category |

**Chart sources and selections**:

#### Apple Music

**Selections**:
- `top-albums`: Top 100 albums
- `new-releases`: New album releases
- `top-songs`: Top 100 songs

**Example**:
```http
GET /chart/apple-music/album/top-albums HTTP/1.1
```

#### Billboard

**Selections**:
- `hot-100`: Billboard Hot 100
- `billboard-200`: Billboard 200 albums
- `artist-100`: Top artists
- `streaming-songs`: Top streaming songs

**Example**:
```http
GET /chart/billboard/track/hot-100 HTTP/1.1
```

#### iTunes

**Selections**:
- `top-albums`: iTunes top albums
- `top-songs`: iTunes top songs

**Example**:
```http
GET /chart/itunes/album/top-albums HTTP/1.1
```

#### Last.fm

**Selections**:
- `top-artists`: Most scrobbled artists
- `top-albums`: Most scrobbled albums
- `top-tracks`: Most scrobbled tracks

**Example**:
```http
GET /chart/lastfm/artist/top-artists HTTP/1.1
```

**Response**:
```json
{
  "chart": "billboard",
  "type": "track",
  "selection": "hot-100",
  "date": "2025-04-28",
  "entries": [
    {
      "position": 1,
      "previousPosition": 2,
      "peakPosition": 1,
      "weeksOnChart": 12,
      "artist": {
        "Id": "5b11f4ce-a62d-471e-81fc-a69a8278c7da",
        "ArtistName": "Nirvana"
      },
      "album": {
        "Id": "1b022e01-4da6-387b-8658-8678046e4cef",
        "Title": "Nevermind"
      },
      "track": {
        "Title": "Smells Like Teen Spirit",
        "Duration": 301000
      }
    }
  ]
}
```

**Cache**: 6 hours TTL (charts update daily)

**MusicBrainz mapping**: Chart entries are automatically mapped to MusicBrainz IDs when possible

## Series Endpoints

### GET /series/{mbid}

**Purpose**: Get series metadata (box sets, compilations)

**Parameters**:

| Parameter | Type | Required | Description |
|-----------|------|----------|-------------|
| `mbid` | UUID | Yes | MusicBrainz series ID |

**Response**:
```json
{
  "Id": "series-mbid",
  "Name": "The Beatles Remastered Series",
  "Type": "Release group series",
  "Albums": [
    {
      "Id": "album-mbid-1",
      "Title": "Please Please Me",
      "Position": 1
    },
    {
      "Id": "album-mbid-2",
      "Title": "With the Beatles",
      "Position": 2
    }
  ]
}
```

**Use case**: Box set tracking, series completion

## Cache Management Endpoints

### POST /invalidate

**Purpose**: Batch cache invalidation

**Authentication**: Required (API key)

**Request**:
```http
POST /invalidate HTTP/1.1
X-Api-Key: your-api-key-here
Content-Type: application/json

```

**Response**:
```json
{
  "status": "success",
  "invalidated": {
    "artists": 2,
    "albums": 1,
    "total_keys": 6
  }
}
```

**Invalidation scope**:
- Redis cache
- PostgreSQL cache
- Cloudflare CDN cache

**Use case**: Bulk cache refresh after MusicBrainz updates

## Rate Limiting

**Default**: No rate limiting (NullRateLimiter)

**Optional**: Redis-based distributed rate limiting

**Configuration**:
```python
RATE_LIMITER = 'redis'
RATE_LIMIT_REQUESTS = 100
RATE_LIMIT_WINDOW = 60  # seconds
```

**Rate limit response**:
```http
HTTP/1.1 429 Too Many Requests
Retry-After: 30

{
  "error": "Rate limit exceeded",
  "limit": 100,
  "window": 60,
  "retry_after": 30
}
```

## CORS Support

**Default**: CORS enabled for all origins

**Headers**:
```http
Access-Control-Allow-Origin: *
Access-Control-Allow-Methods: GET, POST, OPTIONS
Access-Control-Allow-Headers: Content-Type, X-Api-Key
```

**Configuration**:
```python
CORS_ORIGINS = ['https://lidarr.audio', 'https://app.lidarr.audio']
```

## Pagination

**Not implemented**: All endpoints return complete result sets

**Workaround**: Use `limit` parameter on search and recent endpoints

**Future consideration**: Cursor-based pagination for large result sets

## Filtering and Sorting

**Artist endpoint**:
- Filter by release type: `primTypes`, `secTypes`
- Filter by release status: `releaseStatuses`
- Sort: Albums sorted by release date (descending)

**Search endpoints**:
- Sort: Relevance score (descending)
- Filter: Not implemented

**Chart endpoints**:
- Sort: Chart position (ascending)
- Filter: Not implemented

## Compression

**Response compression**: Supported via `Accept-Encoding: gzip`

**Request compression**: Not supported

**Example**:
```http
GET /artist/5b11f4ce-a62d-471e-81fc-a69a8278c7da HTTP/1.1
Accept-Encoding: gzip

HTTP/1.1 200 OK
Content-Encoding: gzip
Content-Length: 1234
```

**Compression ratio**: Typically 5:1 for JSON responses

## Conditional Requests

**ETag support**: Not implemented

**Last-Modified support**: Not implemented

**Future consideration**: ETag generation based on cache timestamp

## Webhooks

**Not implemented**: No webhook support for cache invalidation or updates

**Workaround**: Poll `/recent/artist` and `/recent/album` endpoints

**Future consideration**: WebSocket or Server-Sent Events for real-time updates

## API Versioning Strategy

**Current approach**: Path-based versioning (`/api/v0.3`)

**Version lifecycle**:
1. New features developed in `testing` version
2. Tested in production alongside stable version
3. Promoted to new stable version (e.g., v0.4)
4. Old stable version deprecated after 6 months

**Breaking changes**: Only in major version increments

**Backward compatibility**: Maintained within minor versions

## Performance Benchmarks

| Endpoint | Cold (ms) | Cached (ms) | CDN (ms) |
|----------|-----------|-------------|----------|
| GET /artist/{mbid} | 2000-5000 | 50-200 | 10-50 |
| GET /album/{mbid} | 1500-3000 | 50-150 | 10-50 |
| GET /search/artist | 500-1000 | 50-100 | N/A |
| GET /chart/billboard/hot-100 | 3000-5000 | 100-200 | 20-100 |
| POST /artist/{mbid}/refresh | 100-200 | N/A | N/A |

**Factors affecting cold request performance**:
- MusicBrainz database query complexity
- Number of external API calls (FanArt, Wikipedia, etc.)
- External API response times
- Network latency

**Cache hit rate**: 85%+ with crawler enabled

## Error Handling Examples

**Invalid MBID format**:
```http
GET /artist/invalid-mbid HTTP/1.1

HTTP/1.1 400 Bad Request
{
  "error": "Invalid MBID format",
  "mbid": "invalid-mbid"
}
```

**Artist not found**:
```http
GET /artist/00000000-0000-0000-0000-000000000000 HTTP/1.1

HTTP/1.1 404 Not Found
{
  "error": "Artist not found",
  "mbid": "00000000-0000-0000-0000-000000000000"
}
```

**Missing API key**:
```http
POST /invalidate HTTP/1.1

HTTP/1.1 401 Unauthorized
{
  "error": "Missing or invalid API key"
}
```

**Database connection error**:
```http
GET /artist/5b11f4ce-a62d-471e-81fc-a69a8278c7da HTTP/1.1

HTTP/1.1 503 Service Unavailable
{
  "error": "Database unavailable",
  "retry_after": 60
}
```

## Client Implementation Examples

### Python

```python
import requests

class LidarrMetadataClient:
    def __init__(self, base_url='https://api.lidarr.audio/api/v0.3'):
        self.base_url = base_url
        self.session = requests.Session()
    
    def get_artist(self, mbid, prim_types=None, sec_types=None, statuses=None):
        params = {}
        if prim_types:
            params['primTypes'] = ','.join(prim_types)
        if sec_types:
            params['secTypes'] = ','.join(sec_types)
        if statuses:
            params['releaseStatuses'] = ','.join(statuses)
        
        response = self.session.get(f'{self.base_url}/artist/{mbid}', params=params)
        response.raise_for_status()
        return response.json()
    
    def search_artist(self, query, limit=10):
        response = self.session.get(
            f'{self.base_url}/search/artist',
            params={'query': query, 'limit': limit}
        )
        response.raise_for_status()
        return response.json()

# Usage
client = LidarrMetadataClient()
artist = client.get_artist('5b11f4ce-a62d-471e-81fc-a69a8278c7da', prim_types=['Album'])
results = client.search_artist('nirvana')
```

### JavaScript

```javascript
class LidarrMetadataClient {
  constructor(baseUrl = 'https://api.lidarr.audio/api/v0.3') {
    this.baseUrl = baseUrl;
  }
  
  async getArtist(mbid, options = {}) {
    const params = new URLSearchParams();
    if (options.primTypes) params.set('primTypes', options.primTypes.join(','));
    if (options.secTypes) params.set('secTypes', options.secTypes.join(','));
    if (options.releaseStatuses) params.set('releaseStatuses', options.releaseStatuses.join(','));
    
    const response = await fetch(`${this.baseUrl}/artist/${mbid}?${params}`);
    if (!response.ok) throw new Error(`HTTP ${response.status}`);
    return response.json();
  }
  
  async searchArtist(query, limit = 10) {
    const params = new URLSearchParams({ query, limit });
    const response = await fetch(`${this.baseUrl}/search/artist?${params}`);
    if (!response.ok) throw new Error(`HTTP ${response.status}`);
    return response.json();
  }
}

// Usage
const client = new LidarrMetadataClient();
const artist = await client.getArtist('5b11f4ce-a62d-471e-81fc-a69a8278c7da', {
  primTypes: ['Album']
});
const results = await client.searchArtist('nirvana');
```

## Conclusion

The API provides comprehensive music metadata with:

- **15+ endpoints** covering artists, albums, search, charts, and Spotify integration
- **Multi-source aggregation** from MusicBrainz, FanArt.tv, Wikipedia, Spotify, Last.fm, Billboard
- **Intelligent caching** with 30-day TTL and CDN integration
- **Flexible filtering** for release types and statuses
- **Chart integration** from 4 major sources
- **Spotify mapping** for cross-platform compatibility

The API is production-ready with excellent performance characteristics when properly cached. The dual-version deployment strategy allows safe rollout of new features.

Key strengths: comprehensive metadata, excellent caching, multi-source enrichment.

Key weaknesses: no authentication on read endpoints, no pagination, no webhooks.