rust_web_server/mcp/
mod.rs

1//! Model Context Protocol (MCP) server — HTTP Streamable HTTP transport.
2//!
3//! [`McpServer`] implements [`Application`] so it can be passed directly to
4//! [`Server::run`]. Unmatched requests fall through to the built-in [`App`]
5//! controller chain (static files, health probes, etc.).
6//!
7//! # Quick start
8//!
9//! ```rust,no_run
10//! use rust_web_server::server::Server;
11//! use rust_web_server::mcp::{McpServer, McpContent, PromptMessage};
12//! # #[cfg(not(feature = "http2"))]
13//! # fn main() {
14//! let mcp = McpServer::new("my-server", "1.0")
15//!     // A tool: callable by the AI, like a function
16//!     .tool(
17//!         "echo",
18//!         "Echo text back",
19//!         r#"{"type":"object","properties":{"text":{"type":"string"}},"required":["text"]}"#,
20//!         |args| {
21//!             let text = rust_web_server::mcp::extract_arg(args, "text")
22//!                 .unwrap_or_else(|| "(nothing)".to_string());
23//!             Ok(McpContent::text(text))
24//!         },
25//!     )
26//!     // A resource: data the AI can read by URI
27//!     .resource(
28//!         "docs://{topic}",
29//!         "Documentation",
30//!         "Return documentation for a topic",
31//!         |uri| Ok(McpContent::text(format!("Documentation for: {uri}"))),
32//!     )
33//!     // A prompt template: reusable message structures
34//!     .prompt(
35//!         "summarize",
36//!         "Summarize the given text",
37//!         |args| {
38//!             let text = rust_web_server::mcp::extract_arg(args, "text")
39//!                 .unwrap_or_else(|| "some text".to_string());
40//!             Ok(vec![PromptMessage::user(format!("Please summarize: {text}"))])
41//!         },
42//!     );
43//!
44//! // let (listener, pool) = Server::setup().unwrap();
45//! // Server::run(listener, pool, mcp);
46//! # }
47//! ```
48//!
49//! # MCP endpoint
50//!
51//! All JSON-RPC messages are sent as `POST /mcp` (override with [`.at()`](McpServer::at)).
52//! The server implements the [MCP 2024-11-05 specification](https://spec.modelcontextprotocol.io).
53//!
54//! # Environment variables
55//!
56//! None — configure the server programmatically via the builder.
57
58mod json_rpc;
59
60#[cfg(test)]
61mod tests;
62
63use std::sync::Arc;
64
65use crate::app::App;
66use crate::application::Application;
67use crate::core::New;
68use crate::header::Header;
69use crate::mime_type::MimeType;
70use crate::range::Range;
71use crate::request::Request;
72use crate::response::{Response, STATUS_CODE_REASON_PHRASE};
73use crate::server::ConnectionInfo;
74
75const PROTOCOL_VERSION: &str = "2024-11-05";
76
77// ── public content types ──────────────────────────────────────────────────────
78
79/// Content returned by tool and resource handlers.
80///
81/// Create with [`McpContent::text`] (plain text or JSON strings) or
82/// [`McpContent::json`] (marks MIME type as `application/json`).
83#[derive(Clone, Debug)]
84pub struct McpContent {
85    /// Always `"text"` in the current MCP spec.
86    pub kind: &'static str,
87    /// The content string.
88    pub text: String,
89    /// Optional MIME type override (default `"text/plain"`).
90    pub mime_type: Option<String>,
91}
92
93impl McpContent {
94    /// Plain-text content.
95    pub fn text(s: impl Into<String>) -> Self {
96        McpContent { kind: "text", text: s.into(), mime_type: None }
97    }
98
99    /// JSON content — sets `mimeType` to `application/json`.
100    pub fn json(s: impl Into<String>) -> Self {
101        McpContent { kind: "text", text: s.into(), mime_type: Some("application/json".to_string()) }
102    }
103
104    fn to_content_json(&self) -> String {
105        let escaped = json_escape(&self.text);
106        format!(r#"{{"type":"{}","text":"{}"}}"#, self.kind, escaped)
107    }
108
109    fn mime(&self) -> &str {
110        self.mime_type.as_deref().unwrap_or("text/plain")
111    }
112}
113
114/// A single message in a prompt response.
115#[derive(Clone, Debug)]
116pub struct PromptMessage {
117    /// `"user"` or `"assistant"`.
118    pub role: &'static str,
119    /// The message content.
120    pub content: McpContent,
121}
122
123impl PromptMessage {
124    /// Build a user-role message.
125    pub fn user(text: impl Into<String>) -> Self {
126        PromptMessage { role: "user", content: McpContent::text(text) }
127    }
128
129    /// Build an assistant-role message.
130    pub fn assistant(text: impl Into<String>) -> Self {
131        PromptMessage { role: "assistant", content: McpContent::text(text) }
132    }
133
134    fn to_json(&self) -> String {
135        format!(
136            r#"{{"role":"{}","content":{}}}"#,
137            self.role,
138            self.content.to_content_json(),
139        )
140    }
141}
142
143/// Argument definition for a prompt template.
144#[derive(Clone)]
145pub struct PromptArgDef {
146    pub name: String,
147    pub description: String,
148    pub required: bool,
149}
150
151impl PromptArgDef {
152    pub fn required(name: impl Into<String>, description: impl Into<String>) -> Self {
153        PromptArgDef { name: name.into(), description: description.into(), required: true }
154    }
155
156    pub fn optional(name: impl Into<String>, description: impl Into<String>) -> Self {
157        PromptArgDef { name: name.into(), description: description.into(), required: false }
158    }
159}
160
161// ── internal handler registrations ───────────────────────────────────────────
162
163type ToolFn     = Arc<dyn Fn(&str) -> Result<McpContent, String>    + Send + Sync>;
164type ResourceFn = Arc<dyn Fn(&str) -> Result<McpContent, String>    + Send + Sync>;
165type PromptFn   = Arc<dyn Fn(&str) -> Result<Vec<PromptMessage>, String> + Send + Sync>;
166
167#[derive(Clone)]
168struct ToolDef {
169    name: String,
170    description: String,
171    input_schema: String,
172    handler: ToolFn,
173}
174
175#[derive(Clone)]
176struct ResourceDef {
177    uri_template: String,
178    name: String,
179    description: String,
180    handler: ResourceFn,
181}
182
183#[derive(Clone)]
184struct PromptDef {
185    name: String,
186    description: String,
187    arguments: Vec<PromptArgDef>,
188    handler: PromptFn,
189}
190
191// ── McpServer ─────────────────────────────────────────────────────────────────
192
193/// An HTTP server that implements the MCP 2024-11-05 protocol.
194///
195/// Register tools, resources, and prompts with the builder methods, then pass
196/// the server to [`Server::run`] (or [`Server::run_tls`]) as an [`Application`].
197/// Requests that do not match the MCP endpoint fall through to the built-in
198/// [`App`] controller chain.
199#[derive(Clone)]
200pub struct McpServer {
201    server_name: String,
202    server_version: String,
203    path: String,
204    tools: Vec<ToolDef>,
205    resources: Vec<ResourceDef>,
206    prompts: Vec<PromptDef>,
207    fallback: Option<Arc<dyn Application + Send + Sync>>,
208    auth_token: Option<String>,
209}
210
211impl McpServer {
212    /// Create a new `McpServer`.  The default MCP endpoint is `POST /mcp`.
213    pub fn new(name: impl Into<String>, version: impl Into<String>) -> Self {
214        McpServer {
215            server_name: name.into(),
216            server_version: version.into(),
217            path: "/mcp".to_string(),
218            tools: vec![],
219            resources: vec![],
220            prompts: vec![],
221            fallback: None,
222            auth_token: None,
223        }
224    }
225
226    /// Require a bearer token on every request to the MCP endpoint.
227    ///
228    /// The client must send `Authorization: Bearer <token>`. Requests with a
229    /// missing or wrong token receive `401 Unauthorized` before any JSON-RPC
230    /// processing occurs.
231    ///
232    /// Store the token in an environment variable — never hard-code it:
233    ///
234    /// ```rust,no_run
235    /// use rust_web_server::app::App;
236    /// use rust_web_server::core::New;
237    ///
238    /// let app = App::new()
239    ///     .mcp("my-server", "1.0")
240    ///     .require_bearer(std::env::var("MCP_TOKEN").expect("MCP_TOKEN not set"));
241    /// ```
242    ///
243    /// Claude Desktop config:
244    /// ```json
245    /// { "mcpServers": { "my-server": {
246    ///     "url": "http://localhost:7878/mcp",
247    ///     "headers": { "Authorization": "Bearer <token>" }
248    /// }}}
249    /// ```
250    pub fn require_bearer(mut self, token: impl Into<String>) -> Self {
251        self.auth_token = Some(token.into());
252        self
253    }
254
255    /// Wrap an existing [`Application`] so that non-MCP requests are forwarded
256    /// to it instead of the built-in [`App`].
257    ///
258    /// Use this when your existing server has custom routes, state, or
259    /// middleware that you want to keep alongside the MCP endpoint:
260    ///
261    /// ```rust,no_run
262    /// use rust_web_server::app::App;
263    /// use rust_web_server::mcp::{McpServer, McpContent};
264    /// use rust_web_server::response::{Response, STATUS_CODE_REASON_PHRASE};
265    /// use rust_web_server::test_client::TestClient;
266    ///
267    /// let existing_app = App::with_state(42u32)
268    ///     .get("/api/hello", |_req, _params, _conn, _state| {
269    ///         let mut r = Response::new();
270    ///         r.status_code = *STATUS_CODE_REASON_PHRASE.n200_ok.status_code;
271    ///         r.reason_phrase = STATUS_CODE_REASON_PHRASE.n200_ok.reason_phrase.to_string();
272    ///         r
273    ///     });
274    ///
275    /// let server = McpServer::new("my-app", "1.0")
276    ///     .tool("ping", "Ping", "{}", |_| Ok(McpContent::text("pong")))
277    ///     .wrap(existing_app);
278    ///
279    /// // Both /mcp and /api/hello are now handled by the same server.
280    /// let client = TestClient::new(server);
281    /// ```
282    pub fn wrap(mut self, app: impl Application + Send + Sync + 'static) -> Self {
283        self.fallback = Some(Arc::new(app));
284        self
285    }
286
287    /// Override the HTTP path for the MCP endpoint (default `"/mcp"`).
288    pub fn at(mut self, path: impl Into<String>) -> Self {
289        self.path = path.into();
290        self
291    }
292
293    /// Register a callable tool.
294    ///
295    /// - `name` — tool identifier (snake_case recommended)
296    /// - `description` — human-readable description shown to the AI
297    /// - `input_schema` — JSON Schema object for the tool's arguments
298    /// - `handler` — closure receiving the raw `arguments` JSON string
299    ///
300    /// The handler returns [`McpContent`] on success or an error string.  An
301    /// error is returned to the client as `isError: true` (not a protocol error).
302    pub fn tool<F>(mut self, name: &str, description: &str, input_schema: &str, handler: F) -> Self
303    where
304        F: Fn(&str) -> Result<McpContent, String> + Send + Sync + 'static,
305    {
306        self.tools.push(ToolDef {
307            name: name.to_string(),
308            description: description.to_string(),
309            input_schema: input_schema.to_string(),
310            handler: Arc::new(handler),
311        });
312        self
313    }
314
315    /// Register a readable resource.
316    ///
317    /// `uri_template` uses `{param}` placeholders, e.g. `"user://{id}"`.
318    /// The handler receives the full concrete URI string.
319    pub fn resource<F>(mut self, uri_template: &str, name: &str, description: &str, handler: F) -> Self
320    where
321        F: Fn(&str) -> Result<McpContent, String> + Send + Sync + 'static,
322    {
323        self.resources.push(ResourceDef {
324            uri_template: uri_template.to_string(),
325            name: name.to_string(),
326            description: description.to_string(),
327            handler: Arc::new(handler),
328        });
329        self
330    }
331
332    /// Register a prompt template.
333    ///
334    /// The handler receives the raw `arguments` JSON string and returns a
335    /// list of [`PromptMessage`] values.
336    pub fn prompt<F>(mut self, name: &str, description: &str, handler: F) -> Self
337    where
338        F: Fn(&str) -> Result<Vec<PromptMessage>, String> + Send + Sync + 'static,
339    {
340        self.prompts.push(PromptDef {
341            name: name.to_string(),
342            description: description.to_string(),
343            arguments: vec![],
344            handler: Arc::new(handler),
345        });
346        self
347    }
348
349    /// Register a prompt template with explicit argument definitions.
350    pub fn prompt_with_args<F>(
351        mut self,
352        name: &str,
353        description: &str,
354        args: Vec<PromptArgDef>,
355        handler: F,
356    ) -> Self
357    where
358        F: Fn(&str) -> Result<Vec<PromptMessage>, String> + Send + Sync + 'static,
359    {
360        self.prompts.push(PromptDef {
361            name: name.to_string(),
362            description: description.to_string(),
363            arguments: args,
364            handler: Arc::new(handler),
365        });
366        self
367    }
368
369    // ── request dispatch ──────────────────────────────────────────────────────
370
371    /// Process a raw JSON-RPC body and return an HTTP response.
372    pub fn handle_request(&self, body: &str) -> Response {
373        let method = match json_rpc::extract_str(body, "method") {
374            Some(m) => m,
375            None => return rpc_error(None, json_rpc::INVALID_REQUEST, "Missing method"),
376        };
377
378        let id = json_rpc::extract_id(body);
379
380        // Notifications have no `id` — acknowledge with 202 and no body.
381        if method == "notifications/initialized" || (id.is_none() && method != "ping") {
382            return no_content();
383        }
384
385        let result: Result<String, (i32, String)> = match method.as_str() {
386            "initialize"     => self.do_initialize(),
387            "ping"           => Ok("{}".to_string()),
388            "tools/list"     => self.do_tools_list(),
389            "tools/call"     => self.do_tools_call(body),
390            "resources/list" => self.do_resources_list(),
391            "resources/read" => self.do_resources_read(body),
392            "prompts/list"   => self.do_prompts_list(),
393            "prompts/get"    => self.do_prompts_get(body),
394            _                => Err((json_rpc::METHOD_NOT_FOUND, format!("Unknown method: {method}"))),
395        };
396
397        let id_str = id.as_deref().unwrap_or("null");
398
399        match result {
400            Ok(result_json) => json_response(&format!(
401                r#"{{"jsonrpc":"2.0","result":{result_json},"id":{id_str}}}"#
402            )),
403            Err((code, msg)) => {
404                let escaped = json_escape(&msg);
405                json_response(&format!(
406                    r#"{{"jsonrpc":"2.0","error":{{"code":{code},"message":"{escaped}"}},"id":{id_str}}}"#
407                ))
408            }
409        }
410    }
411
412    // ── method handlers ───────────────────────────────────────────────────────
413
414    fn do_initialize(&self) -> Result<String, (i32, String)> {
415        let caps = format!(
416            r#"{{"tools":{{"listChanged":false}},"resources":{{"subscribe":false,"listChanged":false}},"prompts":{{"listChanged":false}}}}"#
417        );
418        Ok(format!(
419            r#"{{"protocolVersion":"{PROTOCOL_VERSION}","capabilities":{caps},"serverInfo":{{"name":"{}","version":"{}"}}}}"#,
420            json_escape(&self.server_name),
421            json_escape(&self.server_version),
422        ))
423    }
424
425    fn do_tools_list(&self) -> Result<String, (i32, String)> {
426        let items: Vec<String> = self.tools.iter().map(|t| {
427            format!(
428                r#"{{"name":"{}","description":"{}","inputSchema":{}}}"#,
429                json_escape(&t.name),
430                json_escape(&t.description),
431                t.input_schema,
432            )
433        }).collect();
434        Ok(format!(r#"{{"tools":[{}]}}"#, items.join(",")))
435    }
436
437    fn do_tools_call(&self, body: &str) -> Result<String, (i32, String)> {
438        let params = json_rpc::extract_raw(body, "params")
439            .ok_or((json_rpc::INVALID_PARAMS, "Missing params".to_string()))?;
440        let name = json_rpc::extract_str(&params, "name")
441            .ok_or((json_rpc::INVALID_PARAMS, "Missing tool name".to_string()))?;
442        let args = json_rpc::extract_raw(&params, "arguments")
443            .unwrap_or_else(|| "{}".to_string());
444
445        let tool = self.tools.iter().find(|t| t.name == name)
446            .ok_or_else(|| (json_rpc::INVALID_PARAMS, format!("Unknown tool: {name}")))?;
447
448        match (tool.handler)(&args) {
449            Ok(c) => Ok(format!(
450                r#"{{"content":[{}],"isError":false}}"#,
451                c.to_content_json(),
452            )),
453            Err(e) => {
454                let escaped = json_escape(&e);
455                Ok(format!(
456                    r#"{{"content":[{{"type":"text","text":"{escaped}"}}],"isError":true}}"#
457                ))
458            }
459        }
460    }
461
462    fn do_resources_list(&self) -> Result<String, (i32, String)> {
463        let items: Vec<String> = self.resources.iter().map(|r| {
464            format!(
465                r#"{{"uri":"{}","name":"{}","description":"{}","mimeType":"text/plain"}}"#,
466                json_escape(&r.uri_template),
467                json_escape(&r.name),
468                json_escape(&r.description),
469            )
470        }).collect();
471        Ok(format!(r#"{{"resources":[{}]}}"#, items.join(",")))
472    }
473
474    fn do_resources_read(&self, body: &str) -> Result<String, (i32, String)> {
475        let params = json_rpc::extract_raw(body, "params")
476            .ok_or((json_rpc::INVALID_PARAMS, "Missing params".to_string()))?;
477        let uri = json_rpc::extract_str(&params, "uri")
478            .ok_or((json_rpc::INVALID_PARAMS, "Missing uri".to_string()))?;
479
480        let resource = self.resources.iter().find(|r| uri_matches(&r.uri_template, &uri))
481            .ok_or_else(|| (json_rpc::INVALID_PARAMS, format!("Resource not found: {uri}")))?;
482
483        match (resource.handler)(&uri) {
484            Ok(c) => {
485                let text_esc = json_escape(&c.text);
486                let uri_esc  = json_escape(&uri);
487                Ok(format!(
488                    r#"{{"contents":[{{"uri":"{uri_esc}","mimeType":"{}","text":"{text_esc}"}}]}}"#,
489                    c.mime(),
490                ))
491            }
492            Err(e) => Err((json_rpc::INVALID_PARAMS, e)),
493        }
494    }
495
496    fn do_prompts_list(&self) -> Result<String, (i32, String)> {
497        let items: Vec<String> = self.prompts.iter().map(|p| {
498            let arg_defs: Vec<String> = p.arguments.iter().map(|a| {
499                format!(
500                    r#"{{"name":"{}","description":"{}","required":{}}}"#,
501                    json_escape(&a.name),
502                    json_escape(&a.description),
503                    a.required,
504                )
505            }).collect();
506            format!(
507                r#"{{"name":"{}","description":"{}","arguments":[{}]}}"#,
508                json_escape(&p.name),
509                json_escape(&p.description),
510                arg_defs.join(","),
511            )
512        }).collect();
513        Ok(format!(r#"{{"prompts":[{}]}}"#, items.join(",")))
514    }
515
516    fn do_prompts_get(&self, body: &str) -> Result<String, (i32, String)> {
517        let params = json_rpc::extract_raw(body, "params")
518            .ok_or((json_rpc::INVALID_PARAMS, "Missing params".to_string()))?;
519        let name = json_rpc::extract_str(&params, "name")
520            .ok_or((json_rpc::INVALID_PARAMS, "Missing prompt name".to_string()))?;
521        let args = json_rpc::extract_raw(&params, "arguments")
522            .unwrap_or_else(|| "{}".to_string());
523
524        let prompt = self.prompts.iter().find(|p| p.name == name)
525            .ok_or_else(|| (json_rpc::INVALID_PARAMS, format!("Unknown prompt: {name}")))?;
526
527        match (prompt.handler)(&args) {
528            Ok(msgs) => {
529                let msg_jsons: Vec<String> = msgs.iter().map(|m| m.to_json()).collect();
530                Ok(format!(
531                    r#"{{"description":"{}","messages":[{}]}}"#,
532                    json_escape(&prompt.description),
533                    msg_jsons.join(","),
534                ))
535            }
536            Err(e) => Err((json_rpc::INVALID_PARAMS, e)),
537        }
538    }
539}
540
541// ── Application ───────────────────────────────────────────────────────────────
542
543impl Application for McpServer {
544    fn execute(&self, request: &Request, connection: &ConnectionInfo) -> Result<Response, String> {
545        if request.request_uri == self.path {
546            // Check bearer token before processing any MCP request.
547            if let Some(expected) = &self.auth_token {
548                let provided = request.headers.iter()
549                    .find(|h| h.name.eq_ignore_ascii_case("authorization"))
550                    .map(|h| h.value.as_str())
551                    .unwrap_or("");
552                let bearer = provided.strip_prefix("Bearer ").unwrap_or("");
553                if bearer != expected.as_str() {
554                    return Ok(unauthorized());
555                }
556            }
557
558            return Ok(match request.method.as_str() {
559                "POST" => {
560                    let body = std::str::from_utf8(&request.body).unwrap_or("");
561                    self.handle_request(body)
562                }
563                "OPTIONS" => {
564                    // CORS preflight for browser-based MCP clients
565                    let mut r = Response::new();
566                    r.status_code = *STATUS_CODE_REASON_PHRASE.n200_ok.status_code;
567                    r.reason_phrase = STATUS_CODE_REASON_PHRASE.n200_ok.reason_phrase.to_string();
568                    r.headers.push(Header {
569                        name: "Allow".to_string(),
570                        value: "POST, OPTIONS".to_string(),
571                    });
572                    r
573                }
574                _ => {
575                    let mut r = Response::new();
576                    r.status_code = *STATUS_CODE_REASON_PHRASE.n405_method_not_allowed.status_code;
577                    r.reason_phrase = STATUS_CODE_REASON_PHRASE.n405_method_not_allowed.reason_phrase.to_string();
578                    r.headers.push(Header {
579                        name: "Allow".to_string(),
580                        value: "POST, OPTIONS".to_string(),
581                    });
582                    r.content_range_list = vec![Range::get_content_range(
583                        b"MCP endpoint only accepts POST".to_vec(),
584                        MimeType::TEXT_PLAIN.to_string(),
585                    )];
586                    r
587                }
588            });
589        }
590
591        // Not an MCP path — fall through to the wrapped app (or built-in App).
592        match &self.fallback {
593            Some(app) => app.execute(request, connection),
594            None      => App::new().execute(request, connection),
595        }
596    }
597}
598
599// ── public helper ─────────────────────────────────────────────────────────────
600
601/// Extract a string argument from a tool/prompt `arguments` JSON object.
602///
603/// ```rust
604/// use rust_web_server::mcp::extract_arg;
605/// assert_eq!(extract_arg(r#"{"text":"hello"}"#, "text").as_deref(), Some("hello"));
606/// assert_eq!(extract_arg(r#"{}"#, "missing"), None);
607/// ```
608pub fn extract_arg(arguments: &str, name: &str) -> Option<String> {
609    json_rpc::extract_str(arguments, name)
610}
611
612// ── internal helpers ──────────────────────────────────────────────────────────
613
614fn json_response(body: &str) -> Response {
615    let mut r = Response::new();
616    r.status_code = *STATUS_CODE_REASON_PHRASE.n200_ok.status_code;
617    r.reason_phrase = STATUS_CODE_REASON_PHRASE.n200_ok.reason_phrase.to_string();
618    r.content_range_list = vec![Range::get_content_range(
619        body.as_bytes().to_vec(),
620        MimeType::APPLICATION_JSON.to_string(),
621    )];
622    r
623}
624
625fn no_content() -> Response {
626    let mut r = Response::new();
627    r.status_code = *STATUS_CODE_REASON_PHRASE.n202_accepted.status_code;
628    r.reason_phrase = STATUS_CODE_REASON_PHRASE.n202_accepted.reason_phrase.to_string();
629    r
630}
631
632fn unauthorized() -> Response {
633    let mut r = Response::new();
634    r.status_code = *STATUS_CODE_REASON_PHRASE.n401_unauthorized.status_code;
635    r.reason_phrase = STATUS_CODE_REASON_PHRASE.n401_unauthorized.reason_phrase.to_string();
636    r.headers.push(Header {
637        name: "WWW-Authenticate".to_string(),
638        value: "Bearer".to_string(),
639    });
640    r.content_range_list = vec![Range::get_content_range(
641        b"Unauthorized".to_vec(),
642        MimeType::TEXT_PLAIN.to_string(),
643    )];
644    r
645}
646
647fn rpc_error(id: Option<&str>, code: i32, message: &str) -> Response {
648    let id_str  = id.unwrap_or("null");
649    let escaped = json_escape(message);
650    json_response(&format!(
651        r#"{{"jsonrpc":"2.0","error":{{"code":{code},"message":"{escaped}"}},"id":{id_str}}}"#
652    ))
653}
654
655pub(crate) fn json_escape(s: &str) -> String {
656    let mut out = String::with_capacity(s.len() + 4);
657    for ch in s.chars() {
658        match ch {
659            '"'  => out.push_str("\\\""),
660            '\\' => out.push_str("\\\\"),
661            '\n' => out.push_str("\\n"),
662            '\r' => out.push_str("\\r"),
663            '\t' => out.push_str("\\t"),
664            c if (c as u32) < 0x20 => { let _ = std::fmt::Write::write_fmt(&mut out, format_args!("\\u{:04x}", c as u32)); }
665            c    => out.push(c),
666        }
667    }
668    out
669}
670
671fn uri_matches(template: &str, uri: &str) -> bool {
672    // Template `"user://{id}"` matches any URI starting with `"user://"`.
673    match template.find('{') {
674        Some(pos) => uri.starts_with(&template[..pos]),
675        None      => template == uri,
676    }
677}
rust_web_server/mcp/mod.rs

rust_web_server/mcp/
mod.rs
