import { randomUUID } from "node:crypto";
import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
import { isInitializeRequest } from "@modelcontextprotocol/sdk/types.js";
import { createDocmostMcpServer } from "./index.js";
/**
 * Build a stateful Streamable-HTTP handler for the Docmost MCP server. The
 * embedding host (the gitmost NestJS server) bridges its raw Node req/res into
 * `handleRequest`. One McpServer + transport is created per MCP session and
 * kept alive between requests, keyed by the `mcp-session-id` header.
 */
export function createMcpHttpHandler(config) {
    // One transport (and one McpServer) per MCP session, keyed by session id.
    const transports = {};
    // Last activity timestamp per session id, used for idle eviction.
    const lastSeen = {};
    // Idle session TTL (ms): a session with no activity for this long is evicted.
    // Defaults to 30 min; overridable via MCP_SESSION_IDLE_MS.
    const idleTtlMs = (() => {
        const parsed = parseInt(process.env.MCP_SESSION_IDLE_MS ?? "", 10);
        return Number.isFinite(parsed) && parsed > 0 ? parsed : 30 * 60 * 1000;
    })();
    // Periodically close transports idle longer than the TTL. transport.close()
    // triggers its onclose, which removes it from `transports`; we also drop the
    // lastSeen entry. unref() so this timer never keeps the process alive.
    const sweepIntervalMs = 5 * 60 * 1000;
    const sweepTimer = setInterval(() => {
        const now = Date.now();
        for (const sid of Object.keys(transports)) {
            if (now - (lastSeen[sid] ?? 0) > idleTtlMs) {
                void transports[sid].close();
                delete lastSeen[sid];
            }
        }
    }, sweepIntervalMs);
    sweepTimer.unref();
    async function handleRequest(req, res, parsedBody) {
        const sessionId = req.headers["mcp-session-id"];
        const method = (req.method || "GET").toUpperCase();
        let transport = sessionId ? transports[sessionId] : undefined;
        if (method === "POST" && !transport) {
            // A new session may only be created by an initialize request without a
            // session id.
            if (sessionId || !isInitializeRequest(parsedBody)) {
                res.statusCode = 400;
                res.setHeader("Content-Type", "application/json");
                res.end(JSON.stringify({
                    jsonrpc: "2.0",
                    error: {
                        code: -32000,
                        message: "Bad Request: no valid session ID provided",
                    },
                    id: null,
                }));
                return;
            }
            transport = new StreamableHTTPServerTransport({
                sessionIdGenerator: () => randomUUID(),
                onsessioninitialized: (sid) => {
                    transports[sid] = transport;
                    lastSeen[sid] = Date.now();
                },
            });
            transport.onclose = () => {
                const sid = transport.sessionId;
                if (sid && transports[sid])
                    delete transports[sid];
            };
            const server = createDocmostMcpServer(config);
            await server.connect(transport);
            await transport.handleRequest(req, res, parsedBody);
            return;
        }
        if (!transport) {
            res.statusCode = 400;
            res.setHeader("Content-Type", "application/json");
            res.end(JSON.stringify({
                jsonrpc: "2.0",
                error: {
                    code: -32000,
                    message: "Bad Request: no valid session ID provided",
                },
                id: null,
            }));
            return;
        }
        // Routing to an existing transport: refresh its idle timestamp.
        if (sessionId)
            lastSeen[sessionId] = Date.now();
        await transport.handleRequest(req, res, parsedBody);
    }
    return { handleRequest };
}