rust-sdk/crates/rmcp/src/handler/client.rs

pub mod progress;
use crate::{
    error::ErrorData as McpError,
    model::*,
    service::{NotificationContext, RequestContext, RoleClient, Service, ServiceRole},
};

impl<H: ClientHandler> Service<RoleClient> for H {
    async fn handle_request(
        &self,
        request: <RoleClient as ServiceRole>::PeerReq,
        context: RequestContext<RoleClient>,
    ) -> Result<<RoleClient as ServiceRole>::Resp, McpError> {
        match request {
            ServerRequest::PingRequest(_) => self.ping(context).await.map(ClientResult::empty),
            ServerRequest::CreateMessageRequest(request) => self
                .create_message(request.params, context)
                .await
                .map(Box::new)
                .map(ClientResult::CreateMessageResult),
            ServerRequest::ListRootsRequest(_) => self
                .list_roots(context)
                .await
                .map(ClientResult::ListRootsResult),
            ServerRequest::CreateElicitationRequest(request) => self
                .create_elicitation(request.params, context)
                .await
                .map(ClientResult::CreateElicitationResult),
        }
    }

    async fn handle_notification(
        &self,
        notification: <RoleClient as ServiceRole>::PeerNot,
        context: NotificationContext<RoleClient>,
    ) -> Result<(), McpError> {
        match notification {
            ServerNotification::CancelledNotification(notification) => {
                self.on_cancelled(notification.params, context).await
            }
            ServerNotification::ProgressNotification(notification) => {
                self.on_progress(notification.params, context).await
            }
            ServerNotification::LoggingMessageNotification(notification) => {
                self.on_logging_message(notification.params, context).await
            }
            ServerNotification::ResourceUpdatedNotification(notification) => {
                self.on_resource_updated(notification.params, context).await
            }
            ServerNotification::ResourceListChangedNotification(_notification_no_param) => {
                self.on_resource_list_changed(context).await
            }
            ServerNotification::ToolListChangedNotification(_notification_no_param) => {
                self.on_tool_list_changed(context).await
            }
            ServerNotification::PromptListChangedNotification(_notification_no_param) => {
                self.on_prompt_list_changed(context).await
            }
        };
        Ok(())
    }

    fn get_info(&self) -> <RoleClient as ServiceRole>::Info {
        self.get_info()
    }
}

#[allow(unused_variables)]
pub trait ClientHandler: Sized + Send + Sync + 'static {
    fn ping(
        &self,
        context: RequestContext<RoleClient>,
    ) -> impl Future<Output = Result<(), McpError>> + Send + '_ {
        std::future::ready(Ok(()))
    }

    fn create_message(
        &self,
        params: CreateMessageRequestParam,
        context: RequestContext<RoleClient>,
    ) -> impl Future<Output = Result<CreateMessageResult, McpError>> + Send + '_ {
        std::future::ready(Err(
            McpError::method_not_found::<CreateMessageRequestMethod>(),
        ))
    }

    fn list_roots(
        &self,
        context: RequestContext<RoleClient>,
    ) -> impl Future<Output = Result<ListRootsResult, McpError>> + Send + '_ {
        std::future::ready(Ok(ListRootsResult::default()))
    }

    /// Handle an elicitation request from a server asking for user input.
    ///
    /// This method is called when a server needs interactive input from the user
    /// during tool execution. Implementations should present the message to the user,
    /// collect their input according to the requested schema, and return the result.
    ///
    /// # Arguments
    /// * `request` - The elicitation request with message and schema
    /// * `context` - The request context
    ///
    /// # Returns
    /// The user's response including action (accept/decline/cancel) and optional data
    ///
    /// # Default Behavior
    /// The default implementation automatically declines all elicitation requests.
    /// Real clients should override this to provide user interaction.
    fn create_elicitation(
        &self,
        request: CreateElicitationRequestParam,
        context: RequestContext<RoleClient>,
    ) -> impl Future<Output = Result<CreateElicitationResult, McpError>> + Send + '_ {
        // Default implementation declines all requests - real clients should override this
        let _ = (request, context);
        std::future::ready(Ok(CreateElicitationResult {
            action: ElicitationAction::Decline,
            content: None,
        }))
    }

    fn on_cancelled(
        &self,
        params: CancelledNotificationParam,
        context: NotificationContext<RoleClient>,
    ) -> impl Future<Output = ()> + Send + '_ {
        std::future::ready(())
    }
    fn on_progress(
        &self,
        params: ProgressNotificationParam,
        context: NotificationContext<RoleClient>,
    ) -> impl Future<Output = ()> + Send + '_ {
        std::future::ready(())
    }
    fn on_logging_message(
        &self,
        params: LoggingMessageNotificationParam,
        context: NotificationContext<RoleClient>,
    ) -> impl Future<Output = ()> + Send + '_ {
        std::future::ready(())
    }
    fn on_resource_updated(
        &self,
        params: ResourceUpdatedNotificationParam,
        context: NotificationContext<RoleClient>,
    ) -> impl Future<Output = ()> + Send + '_ {
        std::future::ready(())
    }
    fn on_resource_list_changed(
        &self,
        context: NotificationContext<RoleClient>,
    ) -> impl Future<Output = ()> + Send + '_ {
        std::future::ready(())
    }
    fn on_tool_list_changed(
        &self,
        context: NotificationContext<RoleClient>,
    ) -> impl Future<Output = ()> + Send + '_ {
        std::future::ready(())
    }
    fn on_prompt_list_changed(
        &self,
        context: NotificationContext<RoleClient>,
    ) -> impl Future<Output = ()> + Send + '_ {
        std::future::ready(())
    }

    fn get_info(&self) -> ClientInfo {
        ClientInfo::default()
    }
}

/// Do nothing, with default client info.
impl ClientHandler for () {}

/// Do nothing, with a specific client info.
impl ClientHandler for ClientInfo {
    fn get_info(&self) -> ClientInfo {
        self.clone()
    }
}