rust-sdk/examples/servers/src/common/counter.rs

#![allow(dead_code)]
use std::sync::Arc;

use rmcp::{
    ErrorData as McpError, RoleServer, ServerHandler,
    handler::server::{
        router::{prompt::PromptRouter, tool::ToolRouter},
        wrapper::Parameters,
    },
    model::*,
    prompt, prompt_handler, prompt_router, schemars,
    service::RequestContext,
    tool, tool_handler, tool_router,
};
use serde_json::json;
use tokio::sync::Mutex;

#[derive(Debug, serde::Deserialize, schemars::JsonSchema)]
pub struct StructRequest {
    pub a: i32,
    pub b: i32,
}

#[derive(Debug, serde::Serialize, serde::Deserialize, schemars::JsonSchema)]
pub struct ExamplePromptArgs {
    /// A message to put in the prompt
    pub message: String,
}

/// MCP spec types prompt arguments as `Record<string, string>`, so
/// spec-compliant clients stringify all values. Accept both wire forms.
fn deserialize_i32_from_string_or_int<'de, D>(deserializer: D) -> Result<i32, D::Error>
where
    D: serde::Deserializer<'de>,
{
    use serde::Deserialize;
    #[derive(Deserialize)]
    #[serde(untagged)]
    enum StringOrInt {
        Int(i32),
        Str(String),
    }
    match StringOrInt::deserialize(deserializer)? {
        StringOrInt::Int(n) => Ok(n),
        StringOrInt::Str(s) => s.parse::<i32>().map_err(serde::de::Error::custom),
    }
}

#[derive(Debug, serde::Serialize, serde::Deserialize, schemars::JsonSchema)]
pub struct CounterAnalysisArgs {
    /// The target value you're trying to reach
    #[serde(deserialize_with = "deserialize_i32_from_string_or_int")]
    pub goal: i32,
    /// Preferred strategy: 'fast' or 'careful'
    #[serde(skip_serializing_if = "Option::is_none")]
    pub strategy: Option<String>,
}

#[derive(Clone)]
pub struct Counter {
    counter: Arc<Mutex<i32>>,
    tool_router: ToolRouter<Counter>,
    prompt_router: PromptRouter<Counter>,
}

#[tool_router]
impl Counter {
    #[allow(dead_code)]
    pub fn new() -> Self {
        Self {
            counter: Arc::new(Mutex::new(0)),
            tool_router: Self::tool_router(),
            prompt_router: Self::prompt_router(),
        }
    }

    fn _create_resource_text(&self, uri: &str, name: &str) -> Resource {
        Resource::new(uri, name.to_string())
    }

    #[tool(description = "Increment the counter by 1")]
    async fn increment(&self) -> Result<CallToolResult, McpError> {
        let mut counter = self.counter.lock().await;
        *counter += 1;
        Ok(CallToolResult::success(vec![ContentBlock::text(
            counter.to_string(),
        )]))
    }

    #[tool(description = "Decrement the counter by 1")]
    async fn decrement(&self) -> Result<CallToolResult, McpError> {
        let mut counter = self.counter.lock().await;
        *counter -= 1;
        Ok(CallToolResult::success(vec![ContentBlock::text(
            counter.to_string(),
        )]))
    }

    #[tool(description = "Get the current counter value")]
    async fn get_value(&self) -> Result<CallToolResult, McpError> {
        let counter = self.counter.lock().await;
        Ok(CallToolResult::success(vec![ContentBlock::text(
            counter.to_string(),
        )]))
    }

    #[tool(description = "Long running task example")]
    async fn long_task(&self) -> Result<CallToolResult, McpError> {
        tokio::time::sleep(std::time::Duration::from_secs(10)).await;
        Ok(CallToolResult::success(vec![ContentBlock::text(
            "Long task completed",
        )]))
    }

    #[tool(description = "Say hello to the client")]
    fn say_hello(&self) -> Result<CallToolResult, McpError> {
        Ok(CallToolResult::success(vec![ContentBlock::text("hello")]))
    }

    #[tool(description = "Repeat what you say")]
    fn echo(&self, Parameters(object): Parameters<JsonObject>) -> Result<CallToolResult, McpError> {
        Ok(CallToolResult::success(vec![ContentBlock::text(
            serde_json::Value::Object(object).to_string(),
        )]))
    }

    #[tool(description = "Calculate the sum of two numbers")]
    fn sum(
        &self,
        Parameters(StructRequest { a, b }): Parameters<StructRequest>,
    ) -> Result<CallToolResult, McpError> {
        Ok(CallToolResult::success(vec![ContentBlock::text(
            (a + b).to_string(),
        )]))
    }

    /// Returns the `Mcp-Session-Id` of the current session (streamable HTTP only).
    #[tool(description = "Get the session ID for this connection")]
    fn get_session_id(&self, ctx: RequestContext<RoleServer>) -> Result<CallToolResult, McpError> {
        let session_id = ctx
            .extensions
            .get::<axum::http::request::Parts>()
            .and_then(|parts| parts.headers.get("mcp-session-id"))
            .map(|v| v.to_str().unwrap_or("(non-ascii)").to_owned());

        match session_id {
            Some(id) => Ok(CallToolResult::success(vec![ContentBlock::text(id)])),
            None => Ok(CallToolResult::success(vec![ContentBlock::text(
                "no session (not running over streamable HTTP?)",
            )])),
        }
    }
}

#[prompt_router]
impl Counter {
    /// This is an example prompt that takes one required argument, message
    #[prompt(
        name = "example_prompt",
        meta = MetaObject(rmcp::object!({"meta_key": "meta_value"}))
    )]
    async fn example_prompt(
        &self,
        Parameters(args): Parameters<ExamplePromptArgs>,
        _ctx: RequestContext<RoleServer>,
    ) -> Result<Vec<PromptMessage>, McpError> {
        let prompt = format!(
            "This is an example prompt with your message here: '{}'",
            args.message
        );
        Ok(vec![PromptMessage::new_text(Role::User, prompt)])
    }

    /// Analyze the current counter value and suggest next steps
    #[prompt(name = "counter_analysis")]
    async fn counter_analysis(
        &self,
        Parameters(args): Parameters<CounterAnalysisArgs>,
        _ctx: RequestContext<RoleServer>,
    ) -> Result<GetPromptResult, McpError> {
        let strategy = args.strategy.unwrap_or_else(|| "careful".to_string());
        let current_value = *self.counter.lock().await;
        let difference = args.goal - current_value;

        let messages = vec![
            PromptMessage::new_text(
                Role::Assistant,
                "I'll analyze the counter situation and suggest the best approach.",
            ),
            PromptMessage::new_text(
                Role::User,
                format!(
                    "Current counter value: {}\nGoal value: {}\nDifference: {}\nStrategy preference: {}\n\nPlease analyze the situation and suggest the best approach to reach the goal.",
                    current_value, args.goal, difference, strategy
                ),
            ),
        ];

        Ok(GetPromptResult::new(messages).with_description(format!(
            "Counter analysis for reaching {} from {}",
            args.goal, current_value
        )))
    }
}

#[tool_handler(meta = MetaObject(rmcp::object!({"tool_meta_key": "tool_meta_value"})))]
#[prompt_handler(meta = MetaObject(rmcp::object!({"router_meta_key": "router_meta_value"})))]
impl ServerHandler for Counter {
    fn get_info(&self) -> ServerInfo {
        ServerInfo::new(
            ServerCapabilities::builder()
                .enable_prompts()
                .enable_resources()
                .enable_tools()
                .build(),
        )
        .with_server_info(Implementation::from_build_env())
        .with_protocol_version(ProtocolVersion::V_2024_11_05)
        .with_instructions("This server provides counter tools and prompts. Tools: increment, decrement, get_value, say_hello, echo, sum. Prompts: example_prompt (takes a message), counter_analysis (analyzes counter state with a goal).".to_string())
    }

    async fn list_resources(
        &self,
        _request: Option<PaginatedRequestParams>,
        _: RequestContext<RoleServer>,
    ) -> Result<ListResourcesResult, McpError> {
        Ok(ListResourcesResult {
            resources: vec![
                self._create_resource_text("str:////Users/to/some/path/", "cwd"),
                self._create_resource_text("memo://insights", "memo-name"),
            ],
            ..Default::default()
        })
    }

    async fn read_resource(
        &self,
        request: ReadResourceRequestParams,
        _: RequestContext<RoleServer>,
    ) -> Result<ReadResourceResponse, McpError> {
        let uri = &request.uri;
        match uri.as_str() {
            "str:////Users/to/some/path/" => {
                let cwd = "/Users/to/some/path/";
                Ok(ReadResourceResult::new(vec![ResourceContents::text(cwd, uri.clone())]).into())
            }
            "memo://insights" => {
                let memo = "Business Intelligence Memo\n\nAnalysis has revealed 5 key insights ...";
                Ok(ReadResourceResult::new(vec![ResourceContents::text(memo, uri.clone())]).into())
            }
            _ => Err(McpError::resource_not_found(
                "resource_not_found",
                Some(json!({
                    "uri": uri
                })),
            )),
        }
    }

    async fn list_resource_templates(
        &self,
        _request: Option<PaginatedRequestParams>,
        _: RequestContext<RoleServer>,
    ) -> Result<ListResourceTemplatesResult, McpError> {
        Ok(ListResourceTemplatesResult {
            resource_templates: Vec::new(),
            ..Default::default()
        })
    }

    async fn initialize(
        &self,
        _request: InitializeRequestParams,
        context: RequestContext<RoleServer>,
    ) -> Result<InitializeResult, McpError> {
        if let Some(http_request_part) = context.extensions.get::<axum::http::request::Parts>() {
            let initialize_headers = &http_request_part.headers;
            let initialize_uri = &http_request_part.uri;
            tracing::info!(?initialize_headers, %initialize_uri, "initialize from http server");
        }
        Ok(self.get_info())
    }
}

#[cfg(test)]
mod tests {
    use rmcp::{ClientHandler, ServiceExt};
    use tokio::time::Duration;

    use super::*;

    #[derive(Default, Clone)]
    struct TestClient;

    impl ClientHandler for TestClient {}

    #[tokio::test]
    async fn test_prompt_attributes_generated() {
        // Verify that the prompt macros generate the expected attributes
        let example_attr = Counter::example_prompt_prompt_attr();
        assert_eq!(example_attr.name, "example_prompt");
        assert!(example_attr.description.is_some());
        assert!(example_attr.arguments.is_some());

        let args = example_attr.arguments.unwrap();
        assert_eq!(args.len(), 1);
        assert_eq!(args[0].name, "message");
        assert_eq!(args[0].required, Some(true));

        let analysis_attr = Counter::counter_analysis_prompt_attr();
        assert_eq!(analysis_attr.name, "counter_analysis");
        assert!(analysis_attr.description.is_some());
        assert!(analysis_attr.arguments.is_some());

        let args = analysis_attr.arguments.unwrap();
        assert_eq!(args.len(), 2);
        assert_eq!(args[0].name, "goal");
        assert_eq!(args[0].required, Some(true));
        assert_eq!(args[1].name, "strategy");
        assert_eq!(args[1].required, Some(false));
    }

    #[test]
    fn test_counter_analysis_args_accepts_integer_goal() {
        let json = serde_json::json!({ "goal": 20 });
        let args: CounterAnalysisArgs = serde_json::from_value(json).unwrap();
        assert_eq!(args.goal, 20);
    }

    #[test]
    fn test_counter_analysis_args_accepts_string_goal() {
        let json = serde_json::json!({ "goal": "20" });
        let args: CounterAnalysisArgs = serde_json::from_value(json).unwrap();
        assert_eq!(args.goal, 20);
    }

    #[test]
    fn test_counter_analysis_args_accepts_negative_string_goal() {
        let json = serde_json::json!({ "goal": "-7" });
        let args: CounterAnalysisArgs = serde_json::from_value(json).unwrap();
        assert_eq!(args.goal, -7);
    }

    #[test]
    fn test_counter_analysis_args_rejects_non_numeric_string_goal() {
        let json = serde_json::json!({ "goal": "not a number" });
        let result: Result<CounterAnalysisArgs, _> = serde_json::from_value(json);
        assert!(result.is_err());
    }

    #[tokio::test]
    async fn test_prompt_router_has_routes() {
        let router = Counter::prompt_router();
        assert!(router.has_route("example_prompt"));
        assert!(router.has_route("counter_analysis"));

        let prompts = router.list_all();
        assert_eq!(prompts.len(), 2);
    }
}