| 1 | package plugin |
| 2 | |
| 3 | import ( |
| 4 | "bufio" |
| 5 | "bytes" |
| 6 | "context" |
| 7 | "encoding/json" |
| 8 | "errors" |
| 9 | "fmt" |
| 10 | "io" |
| 11 | "net/http" |
| 12 | "net/url" |
| 13 | "strings" |
| 14 | "sync" |
| 15 | "time" |
| 16 | |
| 17 | "reasonix/internal/tool" |
| 18 | ) |
| 19 | |
| 20 | // sseTransport implements MCP's legacy HTTP+SSE transport. The client keeps a |
| 21 | // long-lived GET stream open; the server announces a POST endpoint through an |
| 22 | // `event: endpoint` frame, and all JSON-RPC messages travel to that endpoint |
| 23 | // while responses and server messages return on the GET stream. |
| 24 | type sseTransport struct { |
| 25 | name string |
| 26 | getURL *url.URL |
| 27 | headers map[string]string |
| 28 | client *http.Client |
| 29 | roots []mcpRoot |
| 30 | progress progressRouter |
| 31 | replies chan inboundMessage |
| 32 | replyTimeout time.Duration |
| 33 | |
| 34 | ctx context.Context |
| 35 | cancel context.CancelFunc |
| 36 | |
| 37 | callMu sync.Mutex |
| 38 | mu sync.Mutex |
| 39 | nextID int |
| 40 | pending map[int]chan rpcResponse |
| 41 | readErr error |
| 42 | endpoint *url.URL |
| 43 | endpointErr error |
| 44 | endpointReady chan struct{} |
| 45 | endpointOnce sync.Once |
| 46 | closeOnce sync.Once |
| 47 | } |
| 48 | |
| 49 | // sseReplyQueueBound keeps a server-request flood from creating an unbounded |
| 50 | // number of blocked HTTP POST goroutines. Overflow is intentionally dropped so |
| 51 | // the GET reader can continue routing client responses and notifications. |
| 52 | const sseReplyQueueBound = 16 |
| 53 | |
| 54 | func newSSETransport(ctx context.Context, s Spec) (*sseTransport, error) { |
| 55 | if strings.TrimSpace(s.URL) == "" { |
| 56 | return nil, fmt.Errorf("sse plugin %q: url is required", s.Name) |
| 57 | } |
| 58 | getURL, err := url.Parse(s.URL) |
| 59 | if err != nil || getURL.Scheme == "" || getURL.Host == "" { |
| 60 | return nil, fmt.Errorf("sse plugin %q: invalid url %q", s.Name, s.URL) |
| 61 | } |
| 62 | headers := make(map[string]string, len(s.Headers)) |
| 63 | for key, value := range s.Headers { |
| 64 | headers[key] = value |
| 65 | } |
| 66 | lifeCtx, cancel := context.WithCancel(ctx) |
| 67 | t := &sseTransport{ |
| 68 | name: s.Name, |
| 69 | getURL: getURL, |
| 70 | headers: headers, |
| 71 | roots: mcpRoots(s.WorkspaceRoot), |
| 72 | replies: make(chan inboundMessage, sseReplyQueueBound), |
| 73 | replyTimeout: s.CallTimeout, |
| 74 | ctx: lifeCtx, |
| 75 | cancel: cancel, |
| 76 | pending: map[int]chan rpcResponse{}, |
| 77 | endpointReady: make(chan struct{}), |
| 78 | } |
| 79 | if t.replyTimeout <= 0 { |
| 80 | t.replyTimeout = s.DefaultCallTimeout |
| 81 | } |
| 82 | if t.replyTimeout <= 0 { |
| 83 | t.replyTimeout = defaultCallTimeout |
| 84 | } |
| 85 | t.client = &http.Client{CheckRedirect: func(req *http.Request, via []*http.Request) error { |
| 86 | if len(via) == 0 || sameHTTPOrigin(via[0].URL, req.URL) { |
| 87 | return nil |
| 88 | } |
| 89 | return http.ErrUseLastResponse |
| 90 | }} |
| 91 | go t.replyLoop() |
| 92 | go t.readLoop() |
| 93 | return t, nil |
| 94 | } |
| 95 | |
| 96 | func (t *sseTransport) registerProgress(token string, sink tool.ProgressFunc) func() { |
| 97 | return t.progress.registerProgress(token, sink) |
| 98 | } |
| 99 | |
| 100 | func (t *sseTransport) readLoop() { |
| 101 | defer close(t.replies) |
| 102 | req, err := http.NewRequestWithContext(t.ctx, http.MethodGet, t.getURL.String(), nil) |
| 103 | if err != nil { |
| 104 | t.fail(err) |
| 105 | return |
| 106 | } |
| 107 | req.Header.Set("Accept", "text/event-stream") |
| 108 | for key, value := range t.headers { |
| 109 | req.Header.Set(key, value) |
| 110 | } |
| 111 | resp, err := t.client.Do(req) |
| 112 | if err != nil { |
| 113 | t.fail(err) |
| 114 | return |
| 115 | } |
| 116 | defer resp.Body.Close() |
| 117 | if resp.StatusCode/100 != 2 { |
| 118 | body, _ := io.ReadAll(io.LimitReader(resp.Body, 4096)) |
| 119 | t.fail(fmt.Errorf("GET %s: http %d: %s", t.getURL, resp.StatusCode, strings.TrimSpace(string(body)))) |
| 120 | return |
| 121 | } |
| 122 | if !strings.HasPrefix(strings.ToLower(resp.Header.Get("Content-Type")), "text/event-stream") { |
| 123 | t.fail(fmt.Errorf("GET %s: expected text/event-stream, got %q", t.getURL, resp.Header.Get("Content-Type"))) |
| 124 | return |
| 125 | } |
| 126 | |
| 127 | baseURL := resp.Request.URL |
| 128 | scanner := bufio.NewScanner(resp.Body) |
| 129 | scanner.Buffer(make([]byte, 0, 64*1024), maxHTTPBody) |
| 130 | eventName := "message" |
| 131 | var data strings.Builder |
| 132 | dispatch := func() { |
| 133 | if data.Len() == 0 { |
| 134 | eventName = "message" |
| 135 | return |
| 136 | } |
| 137 | payload := data.String() |
| 138 | data.Reset() |
| 139 | t.handleEvent(eventName, payload, baseURL) |
| 140 | eventName = "message" |
| 141 | } |
| 142 | for scanner.Scan() { |
| 143 | line := scanner.Text() |
| 144 | if line == "" { |
| 145 | dispatch() |
| 146 | continue |
| 147 | } |
| 148 | if strings.HasPrefix(line, ":") { |
| 149 | continue |
| 150 | } |
| 151 | if value, ok := strings.CutPrefix(line, "event:"); ok { |
| 152 | eventName = strings.TrimSpace(value) |
| 153 | continue |
| 154 | } |
| 155 | if value, ok := strings.CutPrefix(line, "data:"); ok { |
| 156 | if data.Len() > 0 { |
| 157 | data.WriteByte('\n') |
| 158 | } |
| 159 | data.WriteString(strings.TrimPrefix(value, " ")) |
| 160 | } |
| 161 | } |
| 162 | dispatch() |
| 163 | if err := scanner.Err(); err != nil { |
| 164 | t.fail(fmt.Errorf("read SSE: %w", err)) |
| 165 | return |
| 166 | } |
| 167 | t.fail(io.EOF) |
| 168 | } |
| 169 | |
| 170 | func (t *sseTransport) handleEvent(eventName, payload string, baseURL *url.URL) { |
| 171 | switch eventName { |
| 172 | case "endpoint": |
| 173 | endpoint, err := url.Parse(strings.TrimSpace(payload)) |
| 174 | if err == nil { |
| 175 | endpoint = baseURL.ResolveReference(endpoint) |
| 176 | if !sameHTTPOrigin(baseURL, endpoint) { |
| 177 | err = fmt.Errorf("server announced cross-origin endpoint %s", endpoint) |
| 178 | } |
| 179 | } |
| 180 | t.setEndpoint(endpoint, err) |
| 181 | case "message", "": |
| 182 | t.handleMessage([]byte(payload)) |
| 183 | } |
| 184 | } |
| 185 | |
| 186 | func (t *sseTransport) setEndpoint(endpoint *url.URL, err error) { |
| 187 | set := false |
| 188 | t.endpointOnce.Do(func() { |
| 189 | t.mu.Lock() |
| 190 | t.endpoint = endpoint |
| 191 | t.endpointErr = err |
| 192 | t.mu.Unlock() |
| 193 | close(t.endpointReady) |
| 194 | set = true |
| 195 | }) |
| 196 | if set && err != nil { |
| 197 | t.failPending(err) |
| 198 | } |
| 199 | } |
| 200 | |
| 201 | func (t *sseTransport) handleMessage(payload []byte) { |
| 202 | message, ok := decodeInboundMessage(payload) |
| 203 | if !ok { |
| 204 | return |
| 205 | } |
| 206 | if message.Method != "" { |
| 207 | if isNotificationID(message.ID) { |
| 208 | if message.Method == "notifications/progress" { |
| 209 | t.progress.dispatchProgress(message.Params) |
| 210 | } |
| 211 | return |
| 212 | } |
| 213 | select { |
| 214 | case t.replies <- message: |
| 215 | default: |
| 216 | // Let the remote server time out excess requests. Blocking here could |
| 217 | // prevent an unrelated client response from ever reaching its caller. |
| 218 | } |
| 219 | return |
| 220 | } |
| 221 | var response rpcResponse |
| 222 | if err := json.Unmarshal(payload, &response); err != nil { |
| 223 | return |
| 224 | } |
| 225 | t.mu.Lock() |
| 226 | ch := t.pending[response.ID] |
| 227 | delete(t.pending, response.ID) |
| 228 | t.mu.Unlock() |
| 229 | if ch != nil { |
| 230 | ch <- response |
| 231 | } |
| 232 | } |
| 233 | |
| 234 | // replyLoop serializes server-request responses through one bounded worker. |
| 235 | // Each POST has a finite deadline inherited from the server's call-timeout |
| 236 | // configuration; after a transport error the worker keeps draining so the SSE |
| 237 | // reader never waits on the queue. |
| 238 | func (t *sseTransport) replyLoop() { |
| 239 | dead := false |
| 240 | for message := range t.replies { |
| 241 | if dead { |
| 242 | continue |
| 243 | } |
| 244 | body, err := json.Marshal(serverRequestReply(message.ID, message.Method, t.roots)) |
| 245 | if err == nil { |
| 246 | ctx, cancel := context.WithTimeout(t.ctx, t.replyTimeout) |
| 247 | err = t.post(ctx, body) |
| 248 | cancel() |
| 249 | } |
| 250 | if err != nil && t.ctx.Err() == nil { |
| 251 | t.fail(fmt.Errorf("reply to %s: %w", message.Method, err)) |
| 252 | dead = true |
| 253 | } |
| 254 | } |
| 255 | } |
| 256 | |
| 257 | func (t *sseTransport) call(ctx context.Context, method string, params any) (json.RawMessage, error) { |
| 258 | t.callMu.Lock() |
| 259 | defer t.callMu.Unlock() |
| 260 | |
| 261 | if err := t.waitEndpoint(ctx); err != nil { |
| 262 | return nil, fmt.Errorf("plugin %q: %s: %w", t.name, method, err) |
| 263 | } |
| 264 | t.mu.Lock() |
| 265 | if t.readErr != nil { |
| 266 | err := t.readErr |
| 267 | t.mu.Unlock() |
| 268 | return nil, fmt.Errorf("plugin %q: %s: %w", t.name, method, err) |
| 269 | } |
| 270 | t.nextID++ |
| 271 | id := t.nextID |
| 272 | ch := make(chan rpcResponse, 1) |
| 273 | t.pending[id] = ch |
| 274 | t.mu.Unlock() |
| 275 | defer func() { |
| 276 | t.mu.Lock() |
| 277 | delete(t.pending, id) |
| 278 | t.mu.Unlock() |
| 279 | }() |
| 280 | |
| 281 | body, err := json.Marshal(rpcRequest{JSONRPC: "2.0", ID: id, Method: method, Params: params}) |
| 282 | if err != nil { |
| 283 | return nil, err |
| 284 | } |
| 285 | if err := t.post(ctx, body); err != nil { |
| 286 | return nil, fmt.Errorf("plugin %q: %s: %w", t.name, method, err) |
| 287 | } |
| 288 | select { |
| 289 | case <-ctx.Done(): |
| 290 | return nil, ctx.Err() |
| 291 | case response, ok := <-ch: |
| 292 | if !ok { |
| 293 | t.mu.Lock() |
| 294 | err := t.readErr |
| 295 | t.mu.Unlock() |
| 296 | return nil, fmt.Errorf("plugin %q: %s: %w", t.name, method, err) |
| 297 | } |
| 298 | if response.Error != nil { |
| 299 | return nil, fmt.Errorf("plugin %q: %w", t.name, response.Error) |
| 300 | } |
| 301 | return response.Result, nil |
| 302 | } |
| 303 | } |
| 304 | |
| 305 | func (t *sseTransport) notify(ctx context.Context, method string, params any) error { |
| 306 | if err := t.waitEndpoint(ctx); err != nil { |
| 307 | return fmt.Errorf("plugin %q: %s: %w", t.name, method, err) |
| 308 | } |
| 309 | body, err := json.Marshal(rpcRequest{JSONRPC: "2.0", Method: method, Params: params}) |
| 310 | if err != nil { |
| 311 | return err |
| 312 | } |
| 313 | if err := t.post(ctx, body); err != nil { |
| 314 | return fmt.Errorf("plugin %q: %s: %w", t.name, method, err) |
| 315 | } |
| 316 | return nil |
| 317 | } |
| 318 | |
| 319 | func (t *sseTransport) waitEndpoint(ctx context.Context) error { |
| 320 | select { |
| 321 | case <-ctx.Done(): |
| 322 | return ctx.Err() |
| 323 | case <-t.endpointReady: |
| 324 | t.mu.Lock() |
| 325 | defer t.mu.Unlock() |
| 326 | if t.endpointErr != nil { |
| 327 | return t.endpointErr |
| 328 | } |
| 329 | if t.endpoint == nil { |
| 330 | return errSSEEndpointMissing |
| 331 | } |
| 332 | return nil |
| 333 | } |
| 334 | } |
| 335 | |
| 336 | var errSSEEndpointMissing = errors.New("SSE stream ended before announcing an endpoint") |
| 337 | |
| 338 | func (t *sseTransport) post(ctx context.Context, body []byte) error { |
| 339 | t.mu.Lock() |
| 340 | endpoint := t.endpoint |
| 341 | t.mu.Unlock() |
| 342 | if endpoint == nil { |
| 343 | return errSSEEndpointMissing |
| 344 | } |
| 345 | req, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint.String(), bytes.NewReader(body)) |
| 346 | if err != nil { |
| 347 | return err |
| 348 | } |
| 349 | req.Header.Set("Content-Type", "application/json") |
| 350 | req.Header.Set("Accept", "application/json, text/event-stream") |
| 351 | for key, value := range t.headers { |
| 352 | req.Header.Set(key, value) |
| 353 | } |
| 354 | resp, err := t.client.Do(req) |
| 355 | if err != nil { |
| 356 | return err |
| 357 | } |
| 358 | defer resp.Body.Close() |
| 359 | responseBody, _ := io.ReadAll(io.LimitReader(resp.Body, 4096)) |
| 360 | if resp.StatusCode/100 != 2 { |
| 361 | return fmt.Errorf("http %d: %s", resp.StatusCode, strings.TrimSpace(string(responseBody))) |
| 362 | } |
| 363 | return nil |
| 364 | } |
| 365 | |
| 366 | func (t *sseTransport) fail(err error) { |
| 367 | t.endpointOnce.Do(func() { |
| 368 | t.mu.Lock() |
| 369 | t.endpointErr = err |
| 370 | t.mu.Unlock() |
| 371 | close(t.endpointReady) |
| 372 | }) |
| 373 | t.failPending(err) |
| 374 | } |
| 375 | |
| 376 | func (t *sseTransport) failPending(err error) { |
| 377 | t.mu.Lock() |
| 378 | if t.readErr == nil { |
| 379 | t.readErr = err |
| 380 | } |
| 381 | for id, ch := range t.pending { |
| 382 | close(ch) |
| 383 | delete(t.pending, id) |
| 384 | } |
| 385 | t.mu.Unlock() |
| 386 | } |
| 387 | |
| 388 | func (t *sseTransport) close() { |
| 389 | t.closeOnce.Do(func() { |
| 390 | t.cancel() |
| 391 | t.client.CloseIdleConnections() |
| 392 | }) |
| 393 | } |
| 394 |