#!/usr/bin/env node
/**
 * Memento MCP Server - Streamable HTTP Transport (Enhanced)
 *
 * Features:
 * - Prisma connection pooling
 * - Compact JSON output
 * - Bounded session cache
 * - Proper keep-alive & timeouts
 * - O(1) API key validation
 * - Structured error handling
 * - Observability metrics
 * - Rate limiting
 * - Input validation
 * - Audit logging
 *
 * Environment:
 *   PORT              Server port (default: 3001)
 *   DATABASE_URL      Prisma database URL
 *   USER_ID           Optional user ID filter
 *   APP_BASE_URL      Next.js app URL (default: http://localhost:3000)
 *   MCP_REQUIRE_AUTH  Set 'true' to require authentication
 *   MCP_API_KEY       Static fallback API key
 *   MCP_LOG_LEVEL     debug, info, warn, error (default: info)
 *   MCP_REQUEST_TIMEOUT  Timeout in ms (default: 30000)
 */

import { Server } from '@modelcontextprotocol/sdk/server/index.js';
import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
import { PrismaClient } from '@prisma/client';
import { randomBytes } from 'crypto';
import express from 'express';
import cors from 'cors';
import { registerTools } from './tools.js';
import { validateApiKey, resolveUser } from './auth.js';
import { requestContext } from './request-context.js';
import config, { validateConfig, printConfig } from './config.js';
import {
  mcpError,
  mcpErrorContent,
  McpErrors,
  getErrorCategory,
  withErrorHandling,
  logError,
} from './errors.js';
import {
  recordRequest,
  recordError,
  recordAuth,
  recordDbQuery,
  recordSession,
  getPrometheusMetrics,
  getMetricsSummary,
  updateCacheSize,
} from './metrics.js';
import { combinedRateLimitMiddleware, getRateLimitStats } from './rate-limit.js';
import { validateAndSanitize, checkXSS } from './validation.js';

// ═══════════════════════════════════════════════════════════════
// Configuration Validation
// ═══════════════════════════════════════════════════════════════

const configErrors = validateConfig();
if (configErrors.some((e) => e.critical)) {
  console.error('❌ CRITICAL CONFIGURATION ERRORS:');
  configErrors.forEach((e) => console.error(`   ${e.key}: ${e.message}`));
  process.exit(1);
}

if (configErrors.length > 0) {
  console.warn('⚠️  Configuration warnings:');
  configErrors.forEach((e) => console.warn(`   ${e.key}: ${e.message}`));
}

// ═══════════════════════════════════════════════════════════════
// Logging
// ═══════════════════════════════════════════════════════════════

const logLevels = { debug: 0, info: 1, warn: 2, error: 3, silent: 4 };
const currentLogLevel = logLevels[config.logLevel] ?? 1;

function log(level, ...args) {
  if (logLevels[level] >= currentLogLevel) {
    const timestamp = new Date().toISOString();
    console.error(`[${timestamp}] [${level.toUpperCase()}]`, ...args);
  }
}

// ═══════════════════════════════════════════════════════════════
// Database Setup
// ═══════════════════════════════════════════════════════════════

const databaseUrl = config.databaseUrl;
if (!databaseUrl) {
  console.error('ERROR: DATABASE_URL is required');
  process.exit(1);
}

const isPostgres = databaseUrl.startsWith('postgresql://') || databaseUrl.startsWith('postgres://');

const prisma = new PrismaClient({
  datasources: { db: { url: databaseUrl } },
  ...(isPostgres
    ? {
        datasources: {
          db: {
            url: `${databaseUrl}${databaseUrl.includes('?') ? '&' : '?'}connection_limit=${config.connectionLimit}&pool_timeout=${config.poolTimeout}`,
          },
        },
      }
    : {}),
  log: config.logLevel === 'debug' ? ['query', 'info', 'warn', 'error'] : ['warn', 'error'],
});

// Wrap Prisma for metrics
const originalQuery = prisma.$queryRaw.bind(prisma);
prisma.$queryRaw = async (...args) => {
  const start = Date.now();
  try {
    const result = await originalQuery(...args);
    recordDbQuery(true, Date.now() - start);
    return result;
  } catch (error) {
    recordDbQuery(false, Date.now() - start);
    throw error;
  }
};

const appBaseUrl = config.appBaseUrl;

// ═══════════════════════════════════════════════════════════════
// Bounded Session Cache
// ═══════════════════════════════════════════════════════════════

const sessions = new Map();

function cleanupSessions() {
  const now = Date.now();
  let cleaned = 0;
  for (const [key, s] of sessions) {
    if (now - s._lastSeen > config.sessionTtl) {
      sessions.delete(key);
      cleaned++;
    }
  }
  if (cleaned > 0) {
    log('debug', `Cleaned ${cleaned} expired sessions`);
    recordSession('expire', cleaned);
  }
  updateCacheSize(sessions.size);
}

function pruneIfFull() {
  if (sessions.size < config.maxSessions) return;
  const entries = [...sessions.entries()].sort((a, b) => a[1]._lastSeen - b[1]._lastSeen);
  for (let i = 0; i < Math.floor(config.maxSessions / 4); i++) {
    sessions.delete(entries[i][0]);
  }
}

setInterval(cleanupSessions, config.sessionCleanupInterval);

// ═══════════════════════════════════════════════════════════════
// Express App Setup
// ═══════════════════════════════════════════════════════════════

const app = express();

// CORS configuration
if (config.allowedOrigins.length > 0 && !config.allowedOrigins.includes('*')) {
  app.use(
    cors({
      origin: config.allowedOrigins,
      credentials: true,
    })
  );
} else {
  app.use(cors());
}

app.use(express.json({ limit: config.maxRequestSize }));

// ═══════════════════════════════════════════════════════════════
// Request Logging Middleware
// ═══════════════════════════════════════════════════════════════

app.use((req, res, next) => {
  const start = Date.now();
  res.on('finish', () => {
    const ms = Date.now() - start;
    const sid = req.userSession?.id?.substring(0, 8) || 'anon';
    log('debug', `[${sid}] ${req.method} ${req.path} ${res.statusCode} ${ms}ms`);
    recordRequest('http', res.statusCode, req.method, ms);
  });
  next();
});

// ═══════════════════════════════════════════════════════════════
// Timeout Middleware
// ═══════════════════════════════════════════════════════════════

app.use((req, res, next) => {
  req.setTimeout(config.requestTimeout);
  res.setTimeout(config.requestTimeout, () => {
    if (!res.headersSent) {
      recordError(getErrorCategory(McpErrors.TIMEOUT.code), McpErrors.TIMEOUT.code);
      res.status(408).json(mcpError(McpErrors.TIMEOUT.code));
    }
  });
  next();
});

// ═══════════════════════════════════════════════════════════════
// Security Middleware (XSS Check)
// ═══════════════════════════════════════════════════════════════

app.use((req, res, next) => {
  if (req.body && checkXSS(req.body)) {
    recordError('xss', 'xss_detected', { path: req.path });
    return res.status(400).json(mcpError(McpErrors.INVALID_PARAMS.code, {
      detail: 'Request contains potentially malicious content',
    }));
  }
  next();
});

// ═══════════════════════════════════════════════════════════════
// Rate Limiting Middleware
// ═══════════════════════════════════════════════════════════════

app.use(combinedRateLimitMiddleware);

// ═══════════════════════════════════════════════════════════════
// Health Endpoint (before auth - for Docker healthcheck)
// ═══════════════════════════════════════════════════════════════

app.get(config.healthPath, async (req, res) => {
  try {
    // Check database connection
    await prisma.$queryRaw`SELECT 1`;

    res.json({
      ok: true,
      uptime: process.uptime(),
      timestamp: new Date().toISOString(),
      metrics: getMetricsSummary(),
      rateLimit: getRateLimitStats(),
      sessions: {
        active: sessions.size,
        max: config.maxSessions,
      },
    });
  } catch (error) {
    res.status(503).json({
      ok: false,
      error: 'Database connection failed',
      uptime: process.uptime(),
      timestamp: new Date().toISOString(),
    });
  }
});

// ═══════════════════════════════════════════════════════════════
// Metrics Endpoint
// ═══════════════════════════════════════════════════════════════

if (config.enableMetrics) {
  app.get(config.metricsPath, (req, res) => {
    res.set('Content-Type', 'text/plain');
    res.send(getPrometheusMetrics());
  });
}

// ═══════════════════════════════════════════════════════════════
// Auth Middleware
// ═══════════════════════════════════════════════════════════════

app.use(
  withErrorHandling(async (req, res, next) => {
    if (!config.requireAuth) {
      req.userSession = { id: 'dev-user', name: 'Development User', isAuth: false };
      recordAuth(true, 'dev-mode');
      return next();
    }

    const apiKey = req.headers['x-api-key'];
    const headerUserId = req.headers['x-user-id'];

    if (!apiKey && !headerUserId) {
      recordAuth(false, 'missing-credentials');
      return res
        .status(401)
        .json(
          mcpError(McpErrors.AUTH_FAILED.code, {
            detail: 'Provide x-api-key or x-user-id header',
          })
        );
    }

    if (apiKey) {
      const keyUser = await validateApiKey(prisma, apiKey);
      if (keyUser) {
        req.userSession = getOrCreateSession(
          `key:${keyUser.apiKeyId}`,
          {
            name: `${keyUser.userName} (${keyUser.apiKeyName})`,
            userId: keyUser.userId,
            userName: keyUser.userName,
            apiKeyId: keyUser.apiKeyId,
            authMethod: 'api-key',
          }
        );
        recordAuth(true, 'api-key');
        return next();
      }

      if (config.staticApiKey && apiKey === config.staticApiKey) {
        req.userSession = getOrCreateSession(`static:${apiKey.substring(0, 8)}`, {
          name: 'Static API Key User',
          userId: config.userId || null,
          authMethod: 'static-key',
        });
        recordAuth(true, 'static-key');
        return next();
      }

      recordAuth(false, 'invalid-api-key');
      return res.status(401).json(mcpError(McpErrors.AUTH_FAILED.code, { detail: 'Invalid API key' }));
    }

    if (headerUserId) {
      const user = await resolveUser(prisma, headerUserId);
      if (!user) {
        recordAuth(false, 'user-not-found');
        return res.status(401).json(mcpError(McpErrors.AUTH_FAILED.code, { detail: 'User not found' }));
      }
      req.userSession = getOrCreateSession(`user:${user.id}`, {
        name: user.name,
        userId: user.id,
        userName: user.name,
        userEmail: user.email,
        userRole: user.role,
        authMethod: 'user-id',
      });
      recordAuth(true, 'user-id');
      return next();
    }

    recordAuth(false, 'auth-failed');
    return res.status(401).json(mcpError(McpErrors.AUTH_FAILED.code, { detail: 'Authentication failed' }));
  })
);

function getOrCreateSession(key, base) {
  const existing = sessions.get(key);
  if (existing) {
    existing._lastSeen = Date.now();
    existing.requestCount = (existing.requestCount || 0) + 1;
    return existing;
  }
  pruneIfFull();
  const s = {
    id: randomBytes(16).toString('hex'),
    ...base,
    connectedAt: new Date().toISOString(),
    requestCount: 1,
    isAuth: true,
    _lastSeen: Date.now(),
  };
  sessions.set(key, s);
  recordSession('create');
  return s;
}

// ═══════════════════════════════════════════════════════════════
// MCP Server Setup
// ═══════════════════════════════════════════════════════════════

const server = new Server(
  { name: 'memento-mcp-server', version: '3.2.0' },
  { capabilities: { tools: {} } },
);

registerTools(server, prisma);

// ═══════════════════════════════════════════════════════════════
// Routes
// ═══════════════════════════════════════════════════════════════

app.get('/', (req, res) => {
  res.json({
    name: 'Memento MCP Server',
    version: '3.2.0',
    status: 'running',
    endpoints: {
      mcp: '/mcp',
      health: config.healthPath,
      metrics: config.enableMetrics ? config.metricsPath : undefined,
      sessions: '/sessions',
    },
    auth: { enabled: config.requireAuth },
    tools: 22,
    uptime: process.uptime(),
  });
});

app.get('/sessions', (req, res) => {
  const list = [...sessions.values()].map((s) => ({
    id: s.id,
    name: s.name,
    connectedAt: s.connectedAt,
    requestCount: s.requestCount || 0,
    authMethod: s.authMethod,
  }));
  res.json({ activeUsers: list.length, sessions: list, uptime: process.uptime() });
});

// ═══════════════════════════════════════════════════════════════
// MCP Endpoint with Input Validation
// ═══════════════════════════════════════════════════════════════

const transports = {};

app.all(
  '/mcp',
  withErrorHandling(async (req, res) => {
    const sessionId = req.headers['mcp-session-id'];
    let transport;

    if (sessionId && transports[sessionId]) {
      transport = transports[sessionId];
    } else {
      transport = new StreamableHTTPServerTransport({
        sessionIdGenerator: () => randomBytes(16).toString('hex'),
        onsessioninitialized: (id) => {
          log('debug', `Session init: ${id}`);
          transports[id] = transport;
        },
      });

      transport.onclose = () => {
        const sid = transport.sessionId;
        if (sid) {
          log('debug', `Session close: ${sid}`);
          delete transports[sid];
        }
      };

      await server.connect(transport);
    }

    // Validate tool input if present
    if (req.body?.method) {
      const toolName = req.body.method;
      if (req.body?.params) {
        const validation = validateAndSanitize(toolName, req.body.params);
        if (!validation.success) {
          log('warn', `Validation failed for ${toolName}:`, validation.errors);
          return res
            .status(400)
            .json(
              mcpError(McpErrors.INVALID_PARAMS.code, {
                detail: 'Input validation failed',
                field: validation.errors[0]?.field,
                context: { toolName, errors: validation.errors },
              })
            );
        }
        // Update request with sanitized data
        req.body.params = validation.data;
      }
    }

    const ctx = { userId: req.userSession?.userId || null };
    await requestContext.run(ctx, async () => {
      await transport.handleRequest(req, res, req.body);
    });
  })
);

// Legacy /sse → /mcp redirect
app.all('/sse', (req, res) => {
  res.redirect(307, '/mcp');
});

// ═══════════════════════════════════════════════════════════════
// Debug Routes (only in development)
// ═══════════════════════════════════════════════════════════════

if (config.nodeEnv === 'development') {
  app.get('/debug/config', (req, res) => {
    const { getPublicConfig } = require('./config.js');
    res.json({ config: getPublicConfig() });
  });

  app.get('/debug/sessions', (req, res) => {
    const sessionList = [...sessions.entries()].map(([key, s]) => ({
      key,
      id: s.id,
      name: s.name,
      requestCount: s.requestCount || 0,
      _lastSeen: s._lastSeen,
    }));
    res.json({ sessions: sessionList, total: sessions.size });
  });

  app.delete('/debug/sessions/:key', (req, res) => {
    sessions.delete(req.params.key);
    res.json({ ok: true });
  });

  app.post('/debug/sessions/clear', (req, res) => {
    sessions.clear();
    res.json({ ok: true });
  });
}

// ═══════════════════════════════════════════════════════════════
// Start Server
// ═══════════════════════════════════════════════════════════════

async function main() {
  try {
    await prisma.$queryRaw`SELECT 1`;
  } catch (error) {
    console.error('FATAL: Database connection failed:', error.message);
    process.exit(1);
  }

  // Print configuration
  printConfig();

  app.listen(config.port, '0.0.0.0', () => {
    console.log(`
╔═══════════════════════════════════════════════════════╗
║  Memento MCP Server v3.2.0 (Enhanced)                  ║
║  Streamable HTTP Transport                             ║
╚═══════════════════════════════════════════════════════╝

  Server:   http://localhost:${config.port}
  MCP:      http://localhost:${config.port}/mcp
  Health:   http://localhost:${config.port}${config.healthPath}
  Metrics:  http://localhost:${config.port}${config.metricsPath}
  Auth:     ${config.requireAuth ? 'ENABLED' : 'DISABLED (dev)'}
  Timeout:  ${config.requestTimeout}ms
  Database: ${isPostgres ? 'PostgreSQL' : 'SQLite'}
  Tools:    22
  Features: ${config.enableMetrics ? 'Metrics' : ''}${config.enableAuditLog ? ', Audit Log' : ''}
`);
  });
}

main().catch((error) => {
  console.error('Server error:', error);
  process.exit(1);
});

// ═══════════════════════════════════════════════════════════════
// Shutdown Handler
// ═══════════════════════════════════════════════════════════════

async function shutdown() {
  log('info', 'Shutting down...');
  await prisma.$disconnect();

  // Close all transports
  for (const [id, transport] of Object.entries(transports)) {
    try {
      transport.close();
    } catch (e) {
      // Ignore errors during shutdown
    }
  }

  process.exit(0);
}

process.on('SIGINT', shutdown);
process.on('SIGTERM', shutdown);
process.on('uncaughtException', (err) => {
  logError(log, err);
  process.exit(1);
});
process.on('unhandledRejection', (reason) => {
  log('error', 'Unhandled rejection:', reason);
  recordError(getErrorCategory(McpErrors.INTERNAL_ERROR.code), 'unhandled_rejection');
});