koan_server/
mcp.rs

1//! MCP (Model Context Protocol) server for koan.
2//!
3//! Exposes the GraphQL schema as MCP tools for Claude Desktop / MCP clients.
4
5use std::path::PathBuf;
6use std::sync::Arc;
7
8use crossbeam_channel::Sender;
9use koan_core::player::commands::PlayerCommand;
10use koan_core::player::state::SharedPlayerState;
11use rmcp::handler::server::router::tool::ToolRouter;
12use rmcp::handler::server::wrapper::Json;
13use rmcp::model::{ServerCapabilities, ServerInfo};
14use rmcp::{ServerHandler, schemars, tool_router};
15use serde::{Deserialize, Serialize};
16
17// ---------------------------------------------------------------------------
18// Parameter types
19// ---------------------------------------------------------------------------
20
21#[derive(Debug, Deserialize, schemars::JsonSchema)]
22pub struct GraphqlParams {
23    #[schemars(
24        description = "GraphQL query or mutation string. Use the schema_sdl tool first to learn available types, queries, mutations, and filter parameters."
25    )]
26    pub query: String,
27    #[schemars(description = "Optional JSON object of query variables")]
28    pub variables: Option<serde_json::Value>,
29}
30
31// ---------------------------------------------------------------------------
32// Response types
33// ---------------------------------------------------------------------------
34
35/// GraphQL execution result wrapper — MCP spec requires outputSchema to be an object type.
36#[derive(Debug, Serialize, schemars::JsonSchema)]
37pub struct GraphqlResponse {
38    /// The GraphQL response JSON (contains data and/or errors fields).
39    pub result: serde_json::Value,
40}
41
42// ---------------------------------------------------------------------------
43// MCP Server
44// ---------------------------------------------------------------------------
45
46#[derive(Clone)]
47pub struct KoanMcpServer {
48    #[allow(dead_code)]
49    tool_router: ToolRouter<Self>,
50    graphql_schema: crate::graphql::KoanSchema,
51}
52
53impl KoanMcpServer {
54    pub fn new(
55        state: Arc<SharedPlayerState>,
56        cmd_tx: Sender<PlayerCommand>,
57        db_path: PathBuf,
58    ) -> Self {
59        let graphql_schema =
60            crate::graphql::build_schema(state.clone(), cmd_tx.clone(), db_path.clone(), None);
61        Self {
62            tool_router: Self::tool_router(),
63            graphql_schema,
64        }
65    }
66}
67
68use rmcp::handler::server::wrapper::Parameters;
69use rmcp::tool;
70
71/// Role the MCP `graphql` tool executes at.
72///
73/// The transport carries no credential, so anything reachable here is reachable
74/// by whoever can talk to the MCP process. `User` covers everything the tool
75/// advertises — browsing, playback, queue, favourites, snapshots, radio — and
76/// leaves out the admin mutations that move files on disk (`organize*`), rewrite
77/// config, or change the output device. `KOAN_MCP_ADMIN=1` opts back in.
78fn mcp_role() -> koan_core::auth::Role {
79    if std::env::var("KOAN_MCP_ADMIN").is_ok_and(|v| v == "1") {
80        koan_core::auth::Role::Admin
81    } else {
82        koan_core::auth::Role::User
83    }
84}
85
86#[tool_router]
87impl KoanMcpServer {
88    #[tool(
89        description = "Get the full GraphQL schema in SDL format. CALL THIS FIRST to learn all \
90        available queries, mutations, types, and filter parameters. The schema is the complete \
91        reference for everything koan can do — library discovery, playback control, queue \
92        management, favourites, snapshots, radio mode, device switching, and more."
93    )]
94    fn schema_sdl(&self) -> Json<GraphqlResponse> {
95        let sdl = self.graphql_schema.sdl();
96        Json(GraphqlResponse {
97            result: serde_json::Value::String(sdl),
98        })
99    }
100
101    #[tool(
102        description = "Execute a GraphQL query or mutation against the koan music player. \
103        This is the primary interface for ALL operations — library browsing, playback control, \
104        queue management, favourites, snapshots, radio, devices.\n\n\
105        Call schema_sdl first to learn the full schema.\n\n\
106        Quick examples:\n\
107        - Search: { tracks(search: \"aphex\") { edges { node { id title artist album } } } }\n\
108        - Filter: { albums(yearEnd: 1995, codec: \"FLAC\") { edges { node { title artistName date } } } }\n\
109        - Now playing: { nowPlaying { state positionMs track { title artist codec sampleRate } } }\n\
110        - Queue tracks: mutation { addToQueue(trackIds: [42, 43]) { ok addedCount } }\n\
111        - Play/pause: mutation { pause { ok } } / mutation { resume { ok } }\n\
112        - Snapshot: mutation { saveSnapshot(name: \"techno\") { ok } }\n\
113        - Radio: mutation { enableRadio { ok } }\n\n\
114        Track IDs are integers from the library. Queue item IDs are UUIDs from the queue.\n\
115        All string filters are case-insensitive substrings."
116    )]
117    fn graphql(
118        &self,
119        Parameters(params): Parameters<GraphqlParams>,
120    ) -> Result<Json<GraphqlResponse>, String> {
121        let schema = self.graphql_schema.clone();
122        let query = params.query;
123        let variables = params.variables;
124        let rt =
125            tokio::runtime::Handle::try_current().map_err(|_| "no tokio runtime".to_string())?;
126        let result = tokio::task::block_in_place(|| {
127            rt.block_on(crate::graphql::execute_in_process(
128                &schema,
129                &query,
130                variables,
131                mcp_role(),
132            ))
133        });
134        Ok(Json(GraphqlResponse { result }))
135    }
136}
137
138#[rmcp::tool_handler]
139impl ServerHandler for KoanMcpServer {
140    fn get_info(&self) -> ServerInfo {
141        ServerInfo::new(ServerCapabilities::builder().enable_tools().build()).with_instructions(
142            "koan is a bit-perfect macOS music player. You control it entirely via GraphQL.\n\n\
143             ## How to use\n\
144             1. Call `schema_sdl` to get the full GraphQL schema\n\
145             2. Use the `graphql` tool for ALL queries and mutations\n\n\
146             ## What you can do\n\
147             - **Discover music**: query `artists`, `albums`, `tracks` with rich filters \
148               (genre, year range, codec, sample rate, bit depth, duration, favourites)\n\
149             - **Control playback**: mutations `play`, `pause`, `resume`, `stop`, `next`, \
150               `previous`, `seek`\n\
151             - **Manage queue**: `addToQueue`, `replaceQueue`, `removeFromQueue`, `moveInQueue`, \
152               `clearQueue`, `undo`, `redo`\n\
153             - **Favourites**: `favourite`, `unfavourite`, `toggleFavourite` (auto-syncs to \
154               Subsonic/Navidrome). Filter any query with `favouritesOnly: true`\n\
155             - **Snapshots**: `saveSnapshot`, `restoreSnapshot`, `deleteSnapshot` — bank curated \
156               mixes and switch between them\n\
157             - **Radio**: `enableRadio`, `disableRadio` — auto-queues similar tracks\n\
158             - **Devices**: query `devices`; `setDevice`/`clearDevice` need `KOAN_MCP_ADMIN=1`\n\
159             - **History**: query `playHistory`, `similarArtists`\n\n\
160             ## Not available\n\
161             Admin mutations — `organize*` (moves files on disk), `updateConfig`, \
162             `triggerScan`, `createShare` — are refused unless `KOAN_MCP_ADMIN=1` is set.\n\n\
163             ## ID conventions\n\
164             - Track IDs: integers from the library database\n\
165             - Queue item IDs: UUIDs assigned when tracks enter the queue",
166        )
167    }
168}
169
170/// Entry point for `koan mcp` — starts a headless player with an MCP server on stdio.
171pub fn cmd_mcp() {
172    use koan_core::player::Player;
173    use rmcp::ServiceExt;
174
175    // Validate DB is accessible before starting the server.
176    let _db = koan_core::db::connection::Database::open_default().expect("failed to open database");
177    let db_path = koan_core::config::db_path();
178
179    // Spawn the player engine (headless — no TUI).
180    let (state, _timeline, _viz, cmd_tx) = Player::spawn();
181
182    let server = KoanMcpServer::new(state, cmd_tx, db_path);
183
184    // Run the MCP server on the tokio runtime (blocking the main thread).
185    let rt = tokio::runtime::Runtime::new().expect("failed to create tokio runtime");
186    rt.block_on(async {
187        let transport = rmcp::transport::io::stdio();
188        let service = server
189            .serve(transport)
190            .await
191            .expect("failed to start MCP server");
192        let _ = service.waiting().await;
193    });
194}
195
196// ---------------------------------------------------------------------------
197// Tests
198// ---------------------------------------------------------------------------
199
200#[cfg(test)]
201mod tests {
202    use super::*;
203    use koan_core::db::connection::Database;
204    use koan_core::db::queries;
205    use koan_core::player::commands::CommandChannel;
206    use tempfile::TempDir;
207
208    fn test_server() -> (KoanMcpServer, CommandChannel, TempDir) {
209        let tmp = TempDir::new().unwrap();
210        let db_path = tmp.path().join("test.db");
211        let db = Database::open(&db_path).unwrap();
212        koan_core::db::schema::create_tables(&db.conn).unwrap();
213
214        let state = SharedPlayerState::new();
215        let ch = CommandChannel::new();
216        let tx = ch.tx.clone();
217
218        let server = KoanMcpServer::new(state, tx, db_path);
219        (server, ch, tmp)
220    }
221
222    fn insert_test_track(db_path: &std::path::Path, title: &str, artist: &str, album: &str) -> i64 {
223        let db = Database::open(db_path).unwrap();
224        let meta = queries::TrackMeta {
225            title: title.to_string(),
226            artist: artist.to_string(),
227            album_artist: Some(artist.to_string()),
228            album: album.to_string(),
229            track_number: Some(1),
230            disc: Some(1),
231            date: Some("2024".into()),
232            genre: Some("Electronic".into()),
233            duration_ms: Some(240000),
234            path: Some(format!(
235                "/tmp/test/{}.flac",
236                title.to_lowercase().replace(' ', "_")
237            )),
238            codec: Some("FLAC".into()),
239            sample_rate: Some(44100),
240            bit_depth: Some(16),
241            channels: Some(2),
242            bitrate: Some(1411),
243            size_bytes: Some(42_000_000),
244            mtime: Some(1700000000),
245            source: "local".into(),
246            remote_id: None,
247            remote_url: None,
248            album_remote_id: None,
249            artist_remote_id: None,
250            album_added_at: None,
251            label: None,
252        };
253        queries::upsert_track(&db.conn, &meta).unwrap()
254    }
255
256    #[test]
257    fn schema_sdl_returns_schema() {
258        let (server, _ch, _tmp) = test_server();
259        let Json(resp) = server.schema_sdl();
260        let sdl = resp.result.as_str().unwrap();
261        assert!(sdl.contains("type QueryRoot"));
262        assert!(sdl.contains("type MutationRoot"));
263        assert!(sdl.contains("artists"));
264        assert!(sdl.contains("nowPlaying"));
265    }
266
267    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
268    async fn graphql_query_works() {
269        let (server, _ch, tmp) = test_server();
270        let db_path = tmp.path().join("test.db");
271        insert_test_track(&db_path, "Windowlicker", "Aphex Twin", "Windowlicker EP");
272
273        let result = server.graphql(Parameters(GraphqlParams {
274            query: r#"{ tracks(search: "aphex") { edges { node { title artist } } } }"#.into(),
275            variables: None,
276        }));
277        assert!(result.is_ok());
278        let Json(resp) = result.unwrap();
279        let data = &resp.result["data"]["tracks"]["edges"];
280        assert_eq!(data.as_array().unwrap().len(), 1);
281        assert_eq!(data[0]["node"]["title"], "Windowlicker");
282    }
283
284    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
285    async fn graphql_mutation_works() {
286        let (server, _ch, _tmp) = test_server();
287        let result = server.graphql(Parameters(GraphqlParams {
288            query: "mutation { pause { ok message } }".into(),
289            variables: None,
290        }));
291        assert!(result.is_ok());
292        let Json(resp) = result.unwrap();
293        assert_eq!(resp.result["data"]["pause"]["ok"], true);
294    }
295
296    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
297    async fn graphql_now_playing_stopped() {
298        let (server, _ch, _tmp) = test_server();
299        let result = server.graphql(Parameters(GraphqlParams {
300            query: "{ nowPlaying { state positionMs } }".into(),
301            variables: None,
302        }));
303        assert!(result.is_ok());
304        let Json(resp) = result.unwrap();
305        assert_eq!(resp.result["data"]["nowPlaying"]["state"], "STOPPED");
306    }
307
308    #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
309    async fn graphql_library_stats() {
310        let (server, _ch, tmp) = test_server();
311        let db_path = tmp.path().join("test.db");
312        insert_test_track(&db_path, "T1", "A1", "Album1");
313
314        let result = server.graphql(Parameters(GraphqlParams {
315            query: "{ libraryStats { totalTracks totalArtists totalAlbums } }".into(),
316            variables: None,
317        }));
318        assert!(result.is_ok());
319        let Json(resp) = result.unwrap();
320        assert_eq!(resp.result["data"]["libraryStats"]["totalTracks"], 1);
321    }
322}
koan_server/mcp.rs

koan_server/
mcp.rs
