/**
 * Express application factory for SentryAgent.ai AgentIdP.
 * Creates and configures the Express app with all middleware and routes.
 * Exported as a factory function — does NOT call listen (testable).
 */

import express, { Application } from 'express';
import helmet from 'helmet';
import cors from 'cors';
import morgan from 'morgan';

import { getPool } from './db/pool.js';
import { getRedisClient } from './cache/redis.js';

import { AgentRepository } from './repositories/AgentRepository.js';
import { CredentialRepository } from './repositories/CredentialRepository.js';
import { TokenRepository } from './repositories/TokenRepository.js';
import { AuditRepository } from './repositories/AuditRepository.js';

import { AuditService } from './services/AuditService.js';
import { AgentService } from './services/AgentService.js';
import { CredentialService } from './services/CredentialService.js';
import { OAuth2Service } from './services/OAuth2Service.js';

import { AgentController } from './controllers/AgentController.js';
import { TokenController } from './controllers/TokenController.js';
import { CredentialController } from './controllers/CredentialController.js';
import { AuditController } from './controllers/AuditController.js';

import { createAgentsRouter } from './routes/agents.js';
import { createTokenRouter } from './routes/token.js';
import { createCredentialsRouter } from './routes/credentials.js';
import { createAuditRouter } from './routes/audit.js';
import { createHealthRouter } from './routes/health.js';
import { createMetricsRouter } from './routes/metrics.js';

import { errorHandler } from './middleware/errorHandler.js';
import { createOpaMiddleware } from './middleware/opa.js';
import { metricsMiddleware } from './middleware/metrics.js';
import { createVaultClientFromEnv } from './vault/VaultClient.js';
import { RedisClientType } from 'redis';
import path from 'path';

/**
 * Creates and returns a configured Express application.
 * All infrastructure dependencies (DB pool, Redis) are initialised here.
 *
 * @returns Promise resolving to the configured Express Application.
 * @throws Error if required environment variables are missing.
 */
export async function createApp(): Promise<Application> {
  const app = express();

  // ────────────────────────────────────────────────────────────────
  // Security headers
  // ────────────────────────────────────────────────────────────────
  app.use(helmet());

  // ────────────────────────────────────────────────────────────────
  // CORS
  // ────────────────────────────────────────────────────────────────
  const corsOrigin = process.env['CORS_ORIGIN'] ?? '*';
  app.use(cors({ origin: corsOrigin }));

  // ────────────────────────────────────────────────────────────────
  // Request logging
  // ────────────────────────────────────────────────────────────────
  if (process.env['NODE_ENV'] !== 'test') {
    app.use(morgan('combined'));
  }

  // ────────────────────────────────────────────────────────────────
  // Body parsers
  // JSON body parser for most routes
  // urlencoded parser for token endpoint (application/x-www-form-urlencoded)
  // ────────────────────────────────────────────────────────────────
  app.use(express.json());
  app.use(express.urlencoded({ extended: false }));

  // ────────────────────────────────────────────────────────────────
  // Prometheus HTTP metrics middleware — must be before all routes
  // ────────────────────────────────────────────────────────────────
  app.use(metricsMiddleware);

  // ────────────────────────────────────────────────────────────────
  // Infrastructure singletons
  // ────────────────────────────────────────────────────────────────
  const pool = getPool();
  const redis = await getRedisClient();

  // ────────────────────────────────────────────────────────────────
  // Repository layer
  // ────────────────────────────────────────────────────────────────
  const agentRepo = new AgentRepository(pool);
  const credentialRepo = new CredentialRepository(pool);
  // eslint-disable-next-line @typescript-eslint/no-unnecessary-type-assertion
  const tokenRepo = new TokenRepository(pool, redis as RedisClientType);
  const auditRepo = new AuditRepository(pool);

  // ────────────────────────────────────────────────────────────────
  // Optional integrations
  // ────────────────────────────────────────────────────────────────
  // Vault is optional. When VAULT_ADDR + VAULT_TOKEN are set, new credentials
  // are stored in Vault KV v2. When not set, bcrypt is used (Phase 1 behaviour).
  const vaultClient = createVaultClientFromEnv();
  if (vaultClient !== null) {
    console.log('[AgentIdP] Vault integration enabled — new credentials will use Vault KV v2');
  }

  // ────────────────────────────────────────────────────────────────
  // Service layer
  // ────────────────────────────────────────────────────────────────
  const auditService = new AuditService(auditRepo);
  const agentService = new AgentService(agentRepo, credentialRepo, auditService);
  const credentialService = new CredentialService(credentialRepo, agentRepo, auditService, vaultClient);

  const privateKey = process.env['JWT_PRIVATE_KEY'];
  const publicKey = process.env['JWT_PUBLIC_KEY'];
  if (!privateKey || !publicKey) {
    throw new Error('JWT_PRIVATE_KEY and JWT_PUBLIC_KEY environment variables are required');
  }

  const oauth2Service = new OAuth2Service(
    tokenRepo,
    credentialRepo,
    agentRepo,
    auditService,
    privateKey,
    publicKey,
    vaultClient,
  );

  // ────────────────────────────────────────────────────────────────
  // OPA authorization middleware (created once — shared across all routers)
  // ────────────────────────────────────────────────────────────────
  const opaMiddleware = await createOpaMiddleware();

  // ────────────────────────────────────────────────────────────────
  // Controller layer
  // ────────────────────────────────────────────────────────────────
  const agentController = new AgentController(agentService);
  const tokenController = new TokenController(oauth2Service);
  const credentialController = new CredentialController(credentialService);
  const auditController = new AuditController(auditService);

  // ────────────────────────────────────────────────────────────────
  // Routes
  // ────────────────────────────────────────────────────────────────
  const API_BASE = '/api/v1';

  // Health check — unauthenticated, no OPA
  app.use('/health', createHealthRouter(pool, redis as RedisClientType));

  // Prometheus metrics — unauthenticated, internal scraping only
  app.use('/metrics', createMetricsRouter());

  app.use(`${API_BASE}/agents`, createAgentsRouter(agentController, opaMiddleware));
  app.use(
    `${API_BASE}/agents/:agentId/credentials`,
    createCredentialsRouter(credentialController, opaMiddleware),
  );
  app.use(`${API_BASE}/token`, createTokenRouter(tokenController, opaMiddleware));
  app.use(`${API_BASE}/audit`, createAuditRouter(auditController, opaMiddleware));

  // ────────────────────────────────────────────────────────────────
  // Dashboard static assets (served from dashboard/dist/)
  // Placed after API routes so API routes take precedence.
  // __dirname is available because the project compiles to CommonJS.
  // ────────────────────────────────────────────────────────────────
  const dashboardDist = path.resolve(__dirname, '../../dashboard/dist');

  app.use('/dashboard', express.static(dashboardDist));

  // SPA fallback — serve index.html for all /dashboard/* routes not matching a static file
  app.get('/dashboard/*', (_req, res) => {
    res.sendFile(path.join(dashboardDist, 'index.html'));
  });

  // ────────────────────────────────────────────────────────────────
  // Global error handler (must be last)
  // ────────────────────────────────────────────────────────────────
  app.use(errorHandler);

  return app;
}