| 1 | package plugin |
| 2 | |
| 3 | import ( |
| 4 | "bufio" |
| 5 | "bytes" |
| 6 | "context" |
| 7 | "encoding/json" |
| 8 | "fmt" |
| 9 | "io" |
| 10 | "net/http" |
| 11 | "net/url" |
| 12 | "strings" |
| 13 | "sync" |
| 14 | |
| 15 | "reasonix/internal/tool" |
| 16 | ) |
| 17 | |
| 18 | // maxHTTPBody caps how much of a JSON / SSE response body we read, so a |
| 19 | // misbehaving server can't make us buffer without bound. |
| 20 | const maxHTTPBody = 16 << 20 // 16 MiB |
| 21 | |
| 22 | // httpTransport speaks MCP's Streamable HTTP transport: every JSON-RPC message |
| 23 | // is an HTTP POST to the server URL. The server replies with either |
| 24 | // application/json (one response) or text/event-stream (an SSE stream carrying |
| 25 | // the response plus any server notifications). The Mcp-Session-Id header, once |
| 26 | // the server assigns one, is echoed on every subsequent request. |
| 27 | // |
| 28 | // The mutex serialises a request and its response. That means concurrent tool |
| 29 | // calls to the *same* server run one at a time; calls to different servers use |
| 30 | // different transports and stay concurrent. Correctness over latency for P1 — |
| 31 | // it also keeps nextID and the session id race-free. |
| 32 | type httpTransport struct { |
| 33 | name string |
| 34 | url string |
| 35 | headers map[string]string |
| 36 | client *http.Client |
| 37 | roots []mcpRoot |
| 38 | progress progressRouter |
| 39 | |
| 40 | mu sync.Mutex |
| 41 | nextID int |
| 42 | session string // Mcp-Session-Id, captured from responses |
| 43 | } |
| 44 | |
| 45 | func newHTTPTransport(s Spec) (*httpTransport, error) { |
| 46 | if s.URL == "" { |
| 47 | return nil, fmt.Errorf("http plugin %q: url is required", s.Name) |
| 48 | } |
| 49 | headers := make(map[string]string, len(s.Headers)) |
| 50 | for key, value := range s.Headers { |
| 51 | headers[key] = value |
| 52 | } |
| 53 | return &httpTransport{ |
| 54 | name: s.Name, |
| 55 | url: s.URL, |
| 56 | headers: headers, |
| 57 | roots: mcpRoots(s.WorkspaceRoot), |
| 58 | client: &http.Client{CheckRedirect: func(req *http.Request, via []*http.Request) error { |
| 59 | if len(via) == 0 || sameHTTPOrigin(via[0].URL, req.URL) { |
| 60 | return nil |
| 61 | } |
| 62 | // Do not send configured credentials to another origin. Returning |
| 63 | // ErrUseLastResponse exposes the 3xx to the normal status handling |
| 64 | // without issuing the redirected request. |
| 65 | return http.ErrUseLastResponse |
| 66 | }}, |
| 67 | }, nil |
| 68 | } |
| 69 | |
| 70 | func sameHTTPOrigin(a, b *url.URL) bool { |
| 71 | if a == nil || b == nil || !strings.EqualFold(a.Scheme, b.Scheme) || !strings.EqualFold(a.Hostname(), b.Hostname()) { |
| 72 | return false |
| 73 | } |
| 74 | effectivePort := func(u *url.URL) string { |
| 75 | if port := u.Port(); port != "" { |
| 76 | return port |
| 77 | } |
| 78 | switch strings.ToLower(u.Scheme) { |
| 79 | case "http": |
| 80 | return "80" |
| 81 | case "https": |
| 82 | return "443" |
| 83 | default: |
| 84 | return "" |
| 85 | } |
| 86 | } |
| 87 | return effectivePort(a) == effectivePort(b) |
| 88 | } |
| 89 | |
| 90 | func (t *httpTransport) call(ctx context.Context, method string, params any) (json.RawMessage, error) { |
| 91 | t.mu.Lock() |
| 92 | defer t.mu.Unlock() |
| 93 | |
| 94 | t.nextID++ |
| 95 | id := t.nextID |
| 96 | body, err := json.Marshal(rpcRequest{JSONRPC: "2.0", ID: id, Method: method, Params: params}) |
| 97 | if err != nil { |
| 98 | return nil, err |
| 99 | } |
| 100 | |
| 101 | resp, err := t.do(ctx, body) |
| 102 | if err != nil { |
| 103 | return nil, fmt.Errorf("plugin %q: %s: %w", t.name, method, err) |
| 104 | } |
| 105 | defer resp.Body.Close() |
| 106 | t.captureSession(resp) |
| 107 | |
| 108 | if resp.StatusCode/100 != 2 { |
| 109 | b, _ := io.ReadAll(io.LimitReader(resp.Body, 4096)) |
| 110 | msg := strings.TrimSpace(string(b)) |
| 111 | if isHTTPSessionExpiredResponse(resp.StatusCode, b) { |
| 112 | t.session = "" |
| 113 | return nil, fmt.Errorf("plugin %q: %s: %w", t.name, method, &httpSessionExpiredError{ |
| 114 | status: resp.StatusCode, |
| 115 | body: msg, |
| 116 | }) |
| 117 | } |
| 118 | return nil, fmt.Errorf("plugin %q: %s: http %d: %s", t.name, method, resp.StatusCode, msg) |
| 119 | } |
| 120 | |
| 121 | if strings.HasPrefix(resp.Header.Get("Content-Type"), "text/event-stream") { |
| 122 | return t.readSSEResponse(ctx, resp.Body, id) |
| 123 | } |
| 124 | return decodeRPCResult(resp.Body, t.name) |
| 125 | } |
| 126 | |
| 127 | func (t *httpTransport) notify(ctx context.Context, method string, params any) error { |
| 128 | t.mu.Lock() |
| 129 | defer t.mu.Unlock() |
| 130 | |
| 131 | body, err := json.Marshal(rpcRequest{JSONRPC: "2.0", Method: method, Params: params}) |
| 132 | if err != nil { |
| 133 | return err |
| 134 | } |
| 135 | resp, err := t.do(ctx, body) |
| 136 | if err != nil { |
| 137 | return fmt.Errorf("plugin %q: %s: %w", t.name, method, err) |
| 138 | } |
| 139 | defer resp.Body.Close() |
| 140 | t.captureSession(resp) |
| 141 | _, _ = io.Copy(io.Discard, io.LimitReader(resp.Body, maxHTTPBody)) |
| 142 | if resp.StatusCode/100 != 2 { |
| 143 | return fmt.Errorf("plugin %q: %s: http %d", t.name, method, resp.StatusCode) |
| 144 | } |
| 145 | return nil |
| 146 | } |
| 147 | |
| 148 | func (t *httpTransport) close() { |
| 149 | t.client.CloseIdleConnections() |
| 150 | } |
| 151 | |
| 152 | func (t *httpTransport) registerProgress(token string, sink tool.ProgressFunc) func() { |
| 153 | return t.progress.registerProgress(token, sink) |
| 154 | } |
| 155 | |
| 156 | // do POSTs one JSON-RPC body with the standard MCP headers, the configured |
| 157 | // static headers, and the session id (once known). Caller holds t.mu. |
| 158 | func (t *httpTransport) do(ctx context.Context, body []byte) (*http.Response, error) { |
| 159 | req, err := http.NewRequestWithContext(ctx, http.MethodPost, t.url, bytes.NewReader(body)) |
| 160 | if err != nil { |
| 161 | return nil, err |
| 162 | } |
| 163 | req.Header.Set("Content-Type", "application/json") |
| 164 | req.Header.Set("Accept", "application/json, text/event-stream") |
| 165 | for k, v := range t.headers { |
| 166 | req.Header.Set(k, v) |
| 167 | } |
| 168 | if t.session != "" { |
| 169 | req.Header.Set("Mcp-Session-Id", t.session) |
| 170 | } |
| 171 | return t.client.Do(req) |
| 172 | } |
| 173 | |
| 174 | func (t *httpTransport) captureSession(resp *http.Response) { |
| 175 | if sid := resp.Header.Get("Mcp-Session-Id"); sid != "" { |
| 176 | t.session = sid |
| 177 | } |
| 178 | } |
| 179 | |
| 180 | type httpSessionExpiredError struct { |
| 181 | status int |
| 182 | body string |
| 183 | } |
| 184 | |
| 185 | func (e *httpSessionExpiredError) Error() string { |
| 186 | if e.body == "" { |
| 187 | return fmt.Sprintf("http %d: MCP session expired", e.status) |
| 188 | } |
| 189 | return fmt.Sprintf("http %d: %s", e.status, e.body) |
| 190 | } |
| 191 | |
| 192 | func isHTTPSessionExpiredResponse(status int, body []byte) bool { |
| 193 | if status != http.StatusNotFound { |
| 194 | return false |
| 195 | } |
| 196 | var resp rpcResponse |
| 197 | if err := json.Unmarshal(bytes.TrimSpace(body), &resp); err != nil || resp.Error == nil { |
| 198 | return false |
| 199 | } |
| 200 | return resp.Error.Code == -32001 && strings.Contains(strings.ToLower(resp.Error.Message), "session not found") |
| 201 | } |
| 202 | |
| 203 | // readSSEResponse scans an SSE stream for the JSON-RPC response matching id, |
| 204 | // skipping server notifications and any other-id messages. Per the SSE spec, |
| 205 | // consecutive data: lines within one event are joined with "\n" and an event is |
| 206 | // dispatched on the blank line that terminates it. |
| 207 | func (t *httpTransport) readSSEResponse(ctx context.Context, body io.Reader, id int) (json.RawMessage, error) { |
| 208 | sc := bufio.NewScanner(io.LimitReader(body, maxHTTPBody)) |
| 209 | sc.Buffer(make([]byte, 0, 64*1024), maxHTTPBody) |
| 210 | |
| 211 | var data strings.Builder |
| 212 | // match reports whether the accumulated event data is our response; it |
| 213 | // returns (result, matched, error). |
| 214 | match := func() (json.RawMessage, bool, error) { |
| 215 | if data.Len() == 0 { |
| 216 | return nil, false, nil |
| 217 | } |
| 218 | payload := data.String() |
| 219 | data.Reset() |
| 220 | message, ok := decodeInboundMessage([]byte(payload)) |
| 221 | if !ok { |
| 222 | return nil, false, nil // not a JSON-RPC message we care about |
| 223 | } |
| 224 | if message.Method != "" { |
| 225 | if isNotificationID(message.ID) { |
| 226 | if message.Method == "notifications/progress" { |
| 227 | t.progress.dispatchProgress(message.Params) |
| 228 | } |
| 229 | return nil, false, nil |
| 230 | } |
| 231 | if err := t.replyServerRequest(ctx, message); err != nil { |
| 232 | return nil, false, err |
| 233 | } |
| 234 | return nil, false, nil |
| 235 | } |
| 236 | var resp rpcResponse |
| 237 | if err := json.Unmarshal([]byte(payload), &resp); err != nil { |
| 238 | return nil, false, nil |
| 239 | } |
| 240 | if resp.ID != id { |
| 241 | return nil, false, nil // a notification or another call's response |
| 242 | } |
| 243 | if resp.Error != nil { |
| 244 | return nil, false, fmt.Errorf("plugin %q: %w", t.name, resp.Error) |
| 245 | } |
| 246 | return resp.Result, true, nil |
| 247 | } |
| 248 | |
| 249 | for sc.Scan() { |
| 250 | line := sc.Text() |
| 251 | if line == "" { // event boundary |
| 252 | if res, ok, err := match(); err != nil || ok { |
| 253 | return res, err |
| 254 | } |
| 255 | continue |
| 256 | } |
| 257 | if v, found := strings.CutPrefix(line, "data:"); found { |
| 258 | if data.Len() > 0 { |
| 259 | data.WriteByte('\n') |
| 260 | } |
| 261 | data.WriteString(strings.TrimPrefix(v, " ")) |
| 262 | } |
| 263 | // event:, id:, retry: and comments (":") are ignored |
| 264 | } |
| 265 | if err := sc.Err(); err != nil { |
| 266 | return nil, fmt.Errorf("plugin %q: read SSE: %w", t.name, err) |
| 267 | } |
| 268 | if res, ok, err := match(); err != nil || ok { // stream ended on a final unterminated event |
| 269 | return res, err |
| 270 | } |
| 271 | return nil, fmt.Errorf("plugin %q: SSE stream ended without a response to id %d", t.name, id) |
| 272 | } |
| 273 | |
| 274 | // replyServerRequest sends a JSON-RPC response on a separate Streamable HTTP |
| 275 | // POST while the original response stream remains open. call holds t.mu here, |
| 276 | // so do can safely read the current session id without taking another lock. |
| 277 | func (t *httpTransport) replyServerRequest(ctx context.Context, message inboundMessage) error { |
| 278 | body, err := json.Marshal(serverRequestReply(message.ID, message.Method, t.roots)) |
| 279 | if err != nil { |
| 280 | return err |
| 281 | } |
| 282 | resp, err := t.do(ctx, body) |
| 283 | if err != nil { |
| 284 | return fmt.Errorf("plugin %q: reply to %s: %w", t.name, message.Method, err) |
| 285 | } |
| 286 | defer resp.Body.Close() |
| 287 | t.captureSession(resp) |
| 288 | _, _ = io.Copy(io.Discard, io.LimitReader(resp.Body, maxHTTPBody)) |
| 289 | if resp.StatusCode/100 != 2 { |
| 290 | return fmt.Errorf("plugin %q: reply to %s: http %d", t.name, message.Method, resp.StatusCode) |
| 291 | } |
| 292 | return nil |
| 293 | } |
| 294 | |
| 295 | // decodeRPCResult parses a single application/json JSON-RPC response body. |
| 296 | func decodeRPCResult(body io.Reader, name string) (json.RawMessage, error) { |
| 297 | b, err := io.ReadAll(io.LimitReader(body, maxHTTPBody)) |
| 298 | if err != nil { |
| 299 | return nil, fmt.Errorf("plugin %q: read response: %w", name, err) |
| 300 | } |
| 301 | var resp rpcResponse |
| 302 | if err := json.Unmarshal(bytes.TrimSpace(b), &resp); err != nil { |
| 303 | return nil, fmt.Errorf("plugin %q: decode response: %w", name, err) |
| 304 | } |
| 305 | if resp.Error != nil { |
| 306 | return nil, fmt.Errorf("plugin %q: %w", name, resp.Error) |
| 307 | } |
| 308 | return resp.Result, nil |
| 309 | } |
| 310 |