turul_mcp_aws_lambda/

server.rs

//! Lambda MCP Server Implementation
//!
//! This module provides the main Lambda MCP server implementation that mirrors
//! the architecture of turul-mcp-server but adapted for AWS Lambda deployment.

use std::collections::HashMap;
use std::sync::Arc;

use tracing::{debug, info};

use turul_http_mcp_server::{ServerConfig, StreamConfig, StreamManager};
use turul_mcp_protocol::{Implementation, ServerCapabilities};
use turul_mcp_server::{
    McpCompletion, McpNotification, McpPrompt, McpResource, McpTool, handlers::McpHandler,
    session::SessionManager,
};
#[cfg(feature = "protocol-2025-11-25")]
use turul_mcp_server::{McpElicitation, McpLogger, McpSampling};
use turul_mcp_session_storage::BoxedSessionStorage;

use crate::error::Result;
use crate::handler::LambdaMcpHandler;

#[cfg(feature = "cors")]
use crate::cors::CorsConfig;

/// Main Lambda MCP server
///
/// This server stores all configuration and can create Lambda handlers when needed.
/// It mirrors the architecture of McpServer but is designed for Lambda deployment.
#[allow(dead_code)]
pub struct LambdaMcpServer {
    /// Server implementation information
    pub implementation: Implementation,
    /// Server capabilities
    pub capabilities: ServerCapabilities,
    /// Registered tools
    tools: HashMap<String, Arc<dyn McpTool>>,
    /// Registered resources
    resources: HashMap<String, Arc<dyn McpResource>>,
    /// Registered prompts
    prompts: HashMap<String, Arc<dyn McpPrompt>>,
    /// Registered elicitations
    #[cfg(feature = "protocol-2025-11-25")]
    elicitations: HashMap<String, Arc<dyn McpElicitation>>,
    /// Registered sampling providers
    #[cfg(feature = "protocol-2025-11-25")]
    sampling: HashMap<String, Arc<dyn McpSampling>>,
    /// Registered completion providers
    completions: Vec<Arc<dyn McpCompletion>>,
    /// Registered loggers
    #[cfg(feature = "protocol-2025-11-25")]
    loggers: HashMap<String, Arc<dyn McpLogger>>,
    /// Registered root providers
    /// Registered notification providers
    notifications: HashMap<String, Arc<dyn McpNotification>>,
    /// Registered handlers
    handlers: HashMap<String, Arc<dyn McpHandler>>,
    /// Configured roots
    // `Root` is deprecated-but-present in 2026-07-28 (SEP-2577); roots remain a valid feature.
    #[allow(deprecated)]
    roots: Vec<turul_mcp_protocol::roots::Root>,
    /// Optional client instructions
    instructions: Option<String>,
    /// Session manager for state persistence
    session_manager: Arc<SessionManager>,
    /// Session storage backend (shared between SessionManager and handler)
    session_storage: Arc<BoxedSessionStorage>,
    /// Strict MCP lifecycle enforcement
    strict_lifecycle: bool,
    /// Server configuration
    server_config: ServerConfig,
    /// Enable SSE streaming
    enable_sse: bool,
    /// Stream configuration
    stream_config: StreamConfig,
    /// CORS configuration (if enabled)
    #[cfg(feature = "cors")]
    cors_config: Option<CorsConfig>,
    /// Middleware stack for request/response interception
    middleware_stack: turul_http_mcp_server::middleware::MiddlewareStack,
    /// Custom route registry (e.g., .well-known endpoints)
    route_registry: Arc<turul_http_mcp_server::RouteRegistry>,
    /// Optional task runtime for MCP task support
    #[cfg(feature = "protocol-2025-11-25")]
    task_runtime: Option<Arc<turul_mcp_server::TaskRuntime>>,
    /// Stable fingerprint of the registered tool set for session versioning
    tool_fingerprint: String,
    /// Dynamic tool registry (only in Dynamic mode)
    #[cfg(feature = "dynamic-tools")]
    tool_registry: Option<Arc<turul_mcp_server::ToolRegistry>>,
    /// Whether cross-instance coordination is enabled (explicit storage was provided)
    #[cfg(feature = "dynamic-tools")]
    coordination_enabled: bool,
}

impl LambdaMcpServer {
    /// Create a new Lambda MCP server (use builder instead)
    #[allow(clippy::too_many_arguments)]
    // `Root` is deprecated-but-present in 2026-07-28 (SEP-2577); roots remain a valid feature.
    #[allow(deprecated)]
    pub(crate) fn new(
        implementation: Implementation,
        capabilities: ServerCapabilities,
        tools: HashMap<String, Arc<dyn McpTool>>,
        resources: HashMap<String, Arc<dyn McpResource>>,
        prompts: HashMap<String, Arc<dyn McpPrompt>>,
        #[cfg(feature = "protocol-2025-11-25")] elicitations: HashMap<
            String,
            Arc<dyn McpElicitation>,
        >,
        #[cfg(feature = "protocol-2025-11-25")] sampling: HashMap<String, Arc<dyn McpSampling>>,
        completions: Vec<Arc<dyn McpCompletion>>,
        #[cfg(feature = "protocol-2025-11-25")] loggers: HashMap<String, Arc<dyn McpLogger>>,
        notifications: HashMap<String, Arc<dyn McpNotification>>,
        handlers: HashMap<String, Arc<dyn McpHandler>>,
        roots: Vec<turul_mcp_protocol::roots::Root>,
        instructions: Option<String>,
        session_storage: Arc<BoxedSessionStorage>,
        strict_lifecycle: bool,
        server_config: ServerConfig,
        enable_sse: bool,
        stream_config: StreamConfig,
        #[cfg(feature = "cors")] cors_config: Option<CorsConfig>,
        middleware_stack: turul_http_mcp_server::middleware::MiddlewareStack,
        route_registry: Arc<turul_http_mcp_server::RouteRegistry>,
        #[cfg(feature = "protocol-2025-11-25")] task_runtime: Option<
            Arc<turul_mcp_server::TaskRuntime>,
        >,
        tool_fingerprint: String,
        #[cfg(feature = "dynamic-tools")] dynamic_tools: bool,
        #[cfg(feature = "dynamic-tools")] server_state_storage: Option<
            Arc<dyn turul_mcp_server_state_storage::ServerStateStorage>,
        >,
    ) -> Self {
        // Create session manager with server capabilities
        let session_manager = Arc::new(SessionManager::with_storage_and_timeouts(
            Arc::clone(&session_storage),
            capabilities.clone(),
            std::time::Duration::from_secs(30 * 60), // 30 minutes default
            std::time::Duration::from_secs(60),      // 1 minute cleanup interval
        ));

        // Coordination enabled only for shared backends that can be accessed by multiple instances.
        // InMemory and SQLite are local-only. Only PostgreSQL and DynamoDB are shared.
        #[cfg(feature = "dynamic-tools")]
        let coordination_enabled = server_state_storage
            .as_ref()
            .map(|s| matches!(s.backend_name(), "PostgreSQL" | "DynamoDB"))
            .unwrap_or(false);

        // Create ToolRegistry when dynamic mode is enabled
        #[cfg(feature = "dynamic-tools")]
        let tool_registry = if dynamic_tools {
            let storage = server_state_storage.unwrap_or_else(|| {
                Arc::new(turul_mcp_server_state_storage::InMemoryServerStateStorage::new())
            });
            Some(Arc::new(turul_mcp_server::ToolRegistry::new(
                tools.clone(),
                session_manager.clone(),
                storage,
            )))
        } else {
            None
        };

        Self {
            implementation,
            capabilities,
            tools,
            resources,
            prompts,
            #[cfg(feature = "protocol-2025-11-25")]
            elicitations,
            #[cfg(feature = "protocol-2025-11-25")]
            sampling,
            completions,
            #[cfg(feature = "protocol-2025-11-25")]
            loggers,
            notifications,
            handlers,
            roots,
            instructions,
            session_manager,
            session_storage,
            strict_lifecycle,
            server_config,
            enable_sse,
            stream_config,
            #[cfg(feature = "cors")]
            cors_config,
            middleware_stack,
            route_registry,
            #[cfg(feature = "protocol-2025-11-25")]
            task_runtime,
            tool_fingerprint,
            #[cfg(feature = "dynamic-tools")]
            tool_registry,
            #[cfg(feature = "dynamic-tools")]
            coordination_enabled,
        }
    }

    /// Get a reference to the server capabilities.
    pub fn capabilities(&self) -> &ServerCapabilities {
        &self.capabilities
    }

    /// Whether a task runtime is configured (always false when tasks are not part of the spec).
    fn has_task_runtime(&self) -> bool {
        #[cfg(feature = "protocol-2025-11-25")]
        {
            self.task_runtime.is_some()
        }
        #[cfg(not(feature = "protocol-2025-11-25"))]
        {
            false
        }
    }

    /// Create a Lambda handler ready for use with Lambda runtime
    ///
    /// This is equivalent to McpServer::run_http() but creates a handler instead of running a server.
    pub async fn handler(&self) -> Result<LambdaMcpHandler> {
        info!(
            "Creating Lambda MCP handler: {} v{}",
            self.implementation.name, self.implementation.version
        );
        info!("Session management: enabled with automatic cleanup");

        if self.enable_sse {
            info!("SSE notifications: enabled for Lambda responses");

            // ⚠️ GUARDRAIL: SSE enabled without streaming feature
            #[cfg(not(feature = "streaming"))]
            {
                use tracing::warn;
                warn!("⚠️  SSE is enabled but 'streaming' feature is not available!");
                warn!(
                    "   For real SSE streaming, use handle_streaming() with run_with_streaming_response"
                );
                warn!(
                    "   Current handle() method will return SSE snapshots, not real-time streams"
                );
                warn!("   To enable streaming: add 'streaming' feature to turul-mcp-aws-lambda");
            }
        }

        // Start session cleanup task (same as MCP server)
        let _cleanup_task = self.session_manager.clone().start_cleanup_task();

        // Sync tool registry with shared storage on startup (coordination mode only)
        #[cfg(feature = "dynamic-tools")]
        if self.coordination_enabled
            && let Some(ref registry) = self.tool_registry
        {
            use tracing::warn;
            match registry.sync_from_storage().await {
                Ok(_) => {
                    info!("Dynamic: synced tool registry with shared storage");
                }
                Err(e) => {
                    warn!(error = %e, "Dynamic: failed to sync with shared storage on cold start");
                }
            }
        }

        // Cold-start recovery: handler() is called once per Lambda cold start from main().
        // The returned LambdaMcpHandler is Clone'd for each request — recovery runs exactly once.
        #[cfg(feature = "protocol-2025-11-25")]
        if let Some(ref runtime) = self.task_runtime {
            match runtime.recover_stuck_tasks().await {
                Ok(recovered) if !recovered.is_empty() => {
                    info!(
                        count = recovered.len(),
                        "Recovered stuck tasks from previous invocations"
                    );
                }
                Err(e) => {
                    use tracing::warn;
                    warn!(error = %e, "Failed to recover stuck tasks on startup");
                }
                _ => {}
            }
        }

        // Create stream manager for SSE
        let stream_manager = Arc::new(StreamManager::with_config(
            self.session_storage.clone(),
            self.stream_config.clone(),
        ));

        // Install awaited event dispatcher for guaranteed persistence.
        // Custom events are persisted via StreamManager on the request path,
        // not via the detached bridge task.
        {
            use turul_mcp_server::SessionEventDispatcher;

            struct LambdaEventDispatcher {
                stream_manager: Arc<StreamManager>,
            }

            #[async_trait::async_trait]
            impl SessionEventDispatcher for LambdaEventDispatcher {
                async fn dispatch_to_session(
                    &self,
                    session_id: &str,
                    event_type: String,
                    data: serde_json::Value,
                ) -> std::result::Result<(), String> {
                    self.stream_manager
                        .broadcast_to_session(session_id, event_type, data)
                        .await
                        .map(|_| ())
                        .map_err(|e| e.to_string())
                }
            }

            let dispatcher = Arc::new(LambdaEventDispatcher {
                stream_manager: Arc::clone(&stream_manager),
            });
            self.session_manager.set_event_dispatcher(dispatcher).await;
            debug!("Lambda event dispatcher installed (guaranteed persistence for Custom events)");
        }

        // SSE event bridge — observer-only for Custom events.
        // The dispatcher above handles persistence on the request path.
        {
            let mut global_events = self.session_manager.subscribe_all_session_events();

            tokio::spawn(async move {
                debug!("Lambda SSE Event Bridge: started (observer-only for Custom events)");

                while let Ok((session_id, event)) = global_events.recv().await {
                    match event {
                        turul_mcp_server::session::SessionEvent::Custom {
                            ref event_type, ..
                        } => {
                            debug!(
                                "Lambda SSE Bridge: observed custom event '{}' for session {} (dispatcher handles persistence)",
                                event_type, session_id
                            );
                        }
                        _ => {
                            debug!(
                                "Lambda SSE Bridge: non-custom event for session {}",
                                session_id
                            );
                        }
                    }
                }

                debug!("Lambda SSE Event Bridge: stopped");
            });
        }

        // Create JSON-RPC dispatcher
        use turul_rpc::JsonRpcDispatcher;
        let mut dispatcher = JsonRpcDispatcher::new();

        // Create session-aware initialize handler (2025-11-25 stateful handshake;
        // the 2026-07-28 stateless core has no `initialize` method).
        #[cfg(feature = "protocol-2025-11-25")]
        {
            use turul_mcp_server::SessionAwareInitializeHandler;
            #[cfg_attr(not(feature = "dynamic-tools"), allow(unused_mut))]
            let mut init_handler = SessionAwareInitializeHandler::new(
                self.implementation.clone(),
                self.capabilities.clone(),
                self.instructions.clone(),
                self.session_manager.clone(),
                self.strict_lifecycle,
                self.tool_fingerprint.clone(),
            );
            #[cfg(feature = "dynamic-tools")]
            if let Some(ref registry) = self.tool_registry {
                init_handler = init_handler.with_tool_registry(Arc::clone(registry));
            }
            dispatcher.register_method("initialize".to_string(), init_handler);
        }

        // Create session-aware tools/list handler (reuse MCP server handler)
        use turul_mcp_server::ListToolsHandler;
        #[allow(unused_mut)]
        let mut list_handler = ListToolsHandler::new_with_session_manager(
            self.tools.clone(),
            self.session_manager.clone(),
            self.strict_lifecycle,
            self.has_task_runtime(),
        );
        #[cfg(feature = "dynamic-tools")]
        if let Some(ref registry) = self.tool_registry {
            list_handler = list_handler.with_tool_registry(Arc::clone(registry));
        }
        dispatcher.register_method("tools/list".to_string(), list_handler);

        // Create session-aware tool handler for tools/call (reuse MCP server handler)
        use turul_mcp_server::SessionAwareToolHandler;
        #[cfg_attr(
            not(any(feature = "protocol-2025-11-25", feature = "dynamic-tools")),
            allow(unused_mut)
        )]
        let mut tool_handler = SessionAwareToolHandler::new(
            self.tools.clone(),
            self.session_manager.clone(),
            self.strict_lifecycle,
        );
        #[cfg(feature = "protocol-2025-11-25")]
        if let Some(ref runtime) = self.task_runtime {
            tool_handler = tool_handler.with_task_runtime(Arc::clone(runtime));
        }
        #[cfg(feature = "dynamic-tools")]
        if let Some(ref registry) = self.tool_registry {
            tool_handler = tool_handler.with_tool_registry(Arc::clone(registry));
        }
        dispatcher.register_method("tools/call".to_string(), tool_handler);

        #[cfg(feature = "protocol-2026-07-28")]
        {
            use turul_mcp_protocol::SERVER_DISCOVER_METHOD;
            use turul_mcp_server::DiscoverHandler;
            dispatcher.register_method(
                SERVER_DISCOVER_METHOD.to_string(),
                DiscoverHandler::new(self.capabilities.clone(), self.instructions.clone()),
            );
        }

        // Register all MCP handlers with session awareness (reuse MCP server bridge)
        use turul_mcp_server::SessionAwareMcpHandlerBridge;
        for (method, handler) in &self.handlers {
            let bridge_handler = SessionAwareMcpHandlerBridge::new(
                handler.clone(),
                self.session_manager.clone(),
                self.strict_lifecycle,
            );
            dispatcher.register_method(method.clone(), bridge_handler);
        }

        // notifications/initialized exists only in the 2025-11-25 lifecycle; the
        // 2026-07-28 stateless core has no initialize/initialized handshake.
        #[cfg(feature = "protocol-2025-11-25")]
        {
            use turul_mcp_server::handlers::InitializedNotificationHandler;
            let initialized_handler =
                InitializedNotificationHandler::new(self.session_manager.clone());
            let initialized_bridge = SessionAwareMcpHandlerBridge::new(
                Arc::new(initialized_handler),
                self.session_manager.clone(),
                self.strict_lifecycle,
            );
            dispatcher.register_method("notifications/initialized".to_string(), initialized_bridge);
        }

        // Create the Lambda handler with all components and middleware
        let middleware_stack = Arc::new(self.middleware_stack.clone());

        let handler = LambdaMcpHandler::with_middleware_and_fingerprint(
            self.server_config.clone(),
            Arc::new(dispatcher),
            self.session_storage.clone(),
            stream_manager,
            self.stream_config.clone(),
            self.capabilities.clone(),
            middleware_stack,
            self.enable_sse,
            Arc::clone(&self.route_registry),
            Some(self.tool_fingerprint.clone()),
        )
        .with_server_info(self.implementation.clone());

        // Wire tool change notifier for restart/redeploy fingerprint mismatch.
        // Uses SessionManager → dispatch_custom_event() → dispatcher → guaranteed persistence.
        // dispatch_custom_event is storage-backed and does NOT depend on the in-memory session cache.
        let handler = {
            struct LambdaToolNotifier {
                session_manager: Arc<turul_mcp_server::SessionManager>,
            }
            #[async_trait::async_trait]
            impl turul_http_mcp_server::ToolChangeNotifier for LambdaToolNotifier {
                async fn notify_tools_changed(
                    &self,
                    session_id: &str,
                ) -> std::result::Result<(), String> {
                    let notification = turul_rpc::JsonRpcNotification::new_no_params(
                        "notifications/tools/list_changed".to_string(),
                    );
                    let data = serde_json::to_value(&notification).map_err(|e| e.to_string())?;
                    self.session_manager
                        .dispatch_custom_event(
                            session_id,
                            "notifications/tools/list_changed".to_string(),
                            data,
                        )
                        .await
                }
            }
            handler.with_tool_notifier(Arc::new(LambdaToolNotifier {
                session_manager: Arc::clone(&self.session_manager),
            }))
        };

        #[cfg(feature = "dynamic-tools")]
        let handler = if let Some(ref registry) = self.tool_registry {
            handler.with_tool_registry(Arc::clone(registry))
        } else {
            handler
        };

        // Propagate builder-configured CORS to the constructed handler.
        // Must be applied after notifier/registry wiring so the final handler
        // returned to the caller carries the CORS config — every
        // `if let Some(cors_config)` branch inside `LambdaMcpHandler` reads
        // from `self.cors_config`, which `with_middleware_and_fingerprint`
        // initializes to `None`.
        #[cfg(feature = "cors")]
        let handler = match self.cors_config.clone() {
            Some(cors) => handler.with_cors(cors),
            None => handler,
        };

        Ok(handler)
    }

    /// Get information about the session storage backend
    pub fn session_storage_info(&self) -> &str {
        "Session storage configured"
    }
}