const express = require('express');
const fs = require('fs');
const path = require('path');
const { execSync } = require('child_process');
const { TIMEOUTS } = require('../constants');
const { exists } = require('../fs-helpers');
const { paginate, parsePaginationParams } = require('../pagination');
const platformPaths = require('../platform-paths');
const { resolveServiceUrl } = require('../url-resolver');
const { success, error: errorResponse } = require('../response-helpers');

/**
 * Health routes factory
 * @param {Object} deps - Explicit dependencies
 * @param {Function} deps.fetchT - Fetch wrapper with timeout
 * @param {string} deps.SERVICES_FILE - Path to services.json
 * @param {Object} deps.servicesStateManager - State manager for services.json
 * @param {Object} deps.siteConfig - Site configuration
 * @param {Function} deps.buildServiceUrl - URL builder function
 * @param {Function} deps.asyncHandler - Async route handler wrapper
 * @param {Function} deps.logError - Error logging function
 * @param {Object} deps.healthChecker - Health check manager instance
 * @returns {express.Router}
 */
module.exports = function({
  fetchT,
  SERVICES_FILE,
  servicesStateManager,
  siteConfig,
  buildServiceUrl,
  asyncHandler,
  logError,
  healthChecker
}) {
  const router = express.Router();

  // In-memory cache for health results (local to this router)
  let serviceHealthCache = {};
  let lastHealthCheck = null;

  /**
   * Check a URL directly via fetch. Returns health object or null on failure.
   */
  async function checkDirect(url) {
    // Try HEAD first
    try {
      const controller = new AbortController();
      const timeout = setTimeout(() => controller.abort(), 5000);
      const response = await fetchT(url, { method: 'HEAD', signal: controller.signal, redirect: 'follow' });
      clearTimeout(timeout);
      return {
        status: response.ok || response.status < 500 ? 'healthy' : 'unhealthy',
        statusCode: response.status,
        url,
        checkedAt: new Date().toISOString()
      };
    } catch (_) {}

    // Fallback to GET
    try {
      const controller = new AbortController();
      const timeout = setTimeout(() => controller.abort(), 5000);
      const response = await fetchT(url, { method: 'GET', signal: controller.signal, redirect: 'follow' });
      clearTimeout(timeout);
      return {
        status: response.ok || response.status < 500 ? 'healthy' : 'unhealthy',
        statusCode: response.status,
        url,
        checkedAt: new Date().toISOString()
      };
    } catch (e) {
      return null; // Direct check completely failed
    }
  }

  /**
   * Check a URL through a Pylon relay. Returns health object or null on failure.
   */
  async function checkViaPylon(pylonConfig, url) {
    if (!pylonConfig?.url) return null;
    try {
      const probeUrl = `${pylonConfig.url}/probe?url=${encodeURIComponent(url)}`;
      const headers = {};
      if (pylonConfig.key) headers['x-pylon-key'] = pylonConfig.key;
      const controller = new AbortController();
      const timeout = setTimeout(() => controller.abort(), 12000);
      const response = await fetchT(probeUrl, { method: 'GET', signal: controller.signal, headers });
      clearTimeout(timeout);
      if (!response.ok) return null;
      const data = await response.json();
      return {
        status: data.status || 'unhealthy',
        statusCode: data.statusCode,
        responseTime: data.responseTime,
        reason: data.reason,
        url,
        via: 'pylon',
        checkedAt: data.checkedAt || new Date().toISOString()
      };
    } catch (_) {
      return null;
    }
  }

  // ===== HEALTH / SERVICES =====

  // Check health of all services (performs live checks)
  router.get('/health/services', asyncHandler(async (req, res) => {
    if (!await exists(SERVICES_FILE)) {
      return success(res, { health: {} });
    }

    const servicesData = await servicesStateManager.read();
    const services = Array.isArray(servicesData) ? servicesData : servicesData.services || [];
    const health = {};
    const pylonConfig = siteConfig?.pylon;

    // Check each service
    await Promise.all(services.map(async (service) => {
      const serviceId = service.id || service.name?.toLowerCase();
      if (!serviceId) return;

      try {
        const url = resolveServiceUrl(serviceId, service, siteConfig, buildServiceUrl);
        if (!url) {
          health[serviceId] = { status: 'unknown', reason: 'No URL configured' };
          return;
        }

        // 1. Try direct check
        let result = await checkDirect(url);
        if (result) {
          health[serviceId] = result;
          return;
        }

        // 2. Direct failed — try through pylon relay
        if (pylonConfig) {
          result = await checkViaPylon(pylonConfig, url);
          if (result) {
            health[serviceId] = result;
            return;
          }
        }

        // 3. Both failed
        health[serviceId] = {
          status: 'unhealthy',
          reason: pylonConfig ? 'Unreachable (direct + pylon)' : 'fetch failed',
          url,
          checkedAt: new Date().toISOString()
        };
      } catch (e) {
        health[serviceId] = {
          status: 'error',
          reason: e.message,
          checkedAt: new Date().toISOString()
        };
      }
    }));

    // Cache results
    serviceHealthCache = health;
    lastHealthCheck = new Date().toISOString();

    const paginationParams = parsePaginationParams(req.query);
    const healthEntries = Object.entries(health);
    const result = paginate(healthEntries, paginationParams);
    const paginatedHealth = Object.fromEntries(result.data);
    success(res, {
      health: paginatedHealth,
      checkedAt: lastHealthCheck,
      ...(result.pagination && { pagination: result.pagination })
    });
  }, 'health-services'));

  // Get cached health status (fast, no re-check)
  router.get('/health/cached', asyncHandler(async (req, res) => {
    success(res, {
      health: serviceHealthCache,
      lastCheck: lastHealthCheck,
      cacheAge: lastHealthCheck ? Date.now() - new Date(lastHealthCheck).getTime() : null
    });
  }, 'health-cached'));

  // Check health of single service
  router.get('/health/service/:id', asyncHandler(async (req, res) => {
    const serviceId = req.params.id;

    // Load service config
    if (!await exists(SERVICES_FILE)) {
      const { NotFoundError } = require('../errors');
      throw new NotFoundError('Services file');
    }

    const servicesData = await servicesStateManager.read();
    const services = Array.isArray(servicesData) ? servicesData : servicesData.services || [];
    const service = services.find(s => (s.id || s.name?.toLowerCase()) === serviceId);

    if (!service) {
      const { NotFoundError } = require('../errors');
      throw new NotFoundError('Service');
    }

    // Determine URL
    const url = resolveServiceUrl(serviceId, service, siteConfig, buildServiceUrl);
    const pylonConfig = siteConfig?.pylon;

    // Try direct, then pylon relay
    let result = await checkDirect(url);
    if (!result && pylonConfig) {
      result = await checkViaPylon(pylonConfig, url);
    }
    if (!result) {
      result = {
        status: 'unhealthy',
        reason: pylonConfig ? 'Unreachable (direct + pylon)' : 'fetch failed',
        url,
        checkedAt: new Date().toISOString()
      };
    }

    success(res, { serviceId, health: result });
  }, 'health-service'));

  // ===== HEALTH / PROBE (Pylon-compatible) =====

  // Probe endpoint — lets this DashCaddy act as a pylon for other instances
  router.get('/health/probe', asyncHandler(async (req, res) => {
    const targetUrl = req.query.url;
    if (!targetUrl) {
      throw new ValidationError('Missing ?url= parameter');
    }
    const result = await checkDirect(targetUrl);
    res.json(result || {
      status: 'unhealthy',
      reason: 'fetch failed',
      url: targetUrl,
      checkedAt: new Date().toISOString()
    });
  }, 'health-probe'));

  // Pylon status — check if the configured pylon is reachable
  router.get('/health/pylon', asyncHandler(async (req, res) => {
    const pylonConfig = siteConfig?.pylon;
    if (!pylonConfig?.url) {
      return success(res, { configured: false });
    }
    try {
      const headers = {};
      if (pylonConfig.key) headers['x-pylon-key'] = pylonConfig.key;
      const response = await fetchT(`${pylonConfig.url}/health`, {
        method: 'GET',
        headers
      }, 5000);
      const data = await response.json();
      success(res, { configured: true, reachable: true, pylon: data });
    } catch (e) {
      success(res, { configured: true, reachable: false, error: e.message });
    }
  }, 'health-pylon'));

  // ===== HEALTH / CA =====

  // Get CA certificate health status
  router.get('/health/ca', asyncHandler(async (req, res) => {
    // Try deployed location first, then Caddy PKI location
    const deployedCertPath = path.join(platformPaths.caCertDir, 'root.crt');
    const pkiCertPath = platformPaths.pkiRootCert;
    const rootCertPath = await exists(deployedCertPath) ? deployedCertPath : pkiCertPath;

    try {
      // Check if certificate exists
      if (!await exists(rootCertPath)) {
        return res.json({
          status: 'error',
          message: 'Root CA certificate not found',
          daysUntilExpiration: null
        });
      }

      const dates = execSync(`openssl x509 -in "${rootCertPath}" -noout -dates`).toString();
      const notAfter = dates.match(/notAfter=(.*)/)[1].trim();
      const expirationDate = new Date(notAfter);
      const daysUntilExpiration = Math.floor((expirationDate - new Date()) / (1000 * 60 * 60 * 24));

      // Alert thresholds
      let status = 'healthy';
      let message = `CA certificate valid for ${daysUntilExpiration} days`;

      if (daysUntilExpiration < 0) {
        status = 'critical';
        message = `CA certificate EXPIRED ${Math.abs(daysUntilExpiration)} days ago!`;
      } else if (daysUntilExpiration < 7) {
        status = 'critical';
        message = `CA certificate expires in ${daysUntilExpiration} days!`;
      } else if (daysUntilExpiration < 30) {
        status = 'critical';
        message = `CA certificate expires in ${daysUntilExpiration} days!`;
      } else if (daysUntilExpiration < 90) {
        status = 'warning';
        message = `CA certificate expires in ${daysUntilExpiration} days`;
      }

      res.json({
        status: status,
        message: message,
        daysUntilExpiration: daysUntilExpiration,
        expiresAt: notAfter
      });
    } catch (error) {
      await logError('GET /api/health/ca', error);
      res.json({
        status: 'error',
        message: error.message,
        daysUntilExpiration: null
      });
    }
  }, 'health-ca'));

  // ===== HEALTH CHECK (health-checker module) =====

  // Get current status for all services
  router.get('/health-checks/status', asyncHandler(async (req, res) => {
    const status = healthChecker.getCurrentStatus();
    success(res, { status });
  }, 'health-check-status'));

  // Get service statistics
  router.get('/health-checks/:serviceId/stats', asyncHandler(async (req, res) => {
    const hours = parseInt(req.query.hours) || 24;
    const stats = healthChecker.getServiceStats(req.params.serviceId, hours);
    if (!stats) {
      const { NotFoundError } = require('../errors');
      throw new NotFoundError('Service');
    }
    success(res, { stats });
  }, 'health-check-stats'));

  // Configure health check
  router.post('/health-checks/:serviceId/configure', asyncHandler(async (req, res) => {
    healthChecker.configureService(req.params.serviceId, req.body);
    success(res, { message: 'Health check configured' });
  }, 'health-check-configure'));

  // Remove health check configuration
  router.delete('/health-checks/:serviceId/configure', asyncHandler(async (req, res) => {
    healthChecker.removeService(req.params.serviceId);
    success(res, { message: 'Health check removed' });
  }, 'health-check-remove'));

  // Get open incidents
  router.get('/health-checks/incidents', asyncHandler(async (req, res) => {
    const incidents = healthChecker.getOpenIncidents();
    const paginationParams = parsePaginationParams(req.query);
    const result = paginate(incidents, paginationParams);
    success(res, { incidents: result.data, ...(result.pagination && { pagination: result.pagination }) });
  }, 'health-check-incidents'));

  // Get incident history
  router.get('/health-checks/incidents/history', asyncHandler(async (req, res) => {
    const paginationParams = parsePaginationParams(req.query);
    // When paginating, fetch all history so pagination can slice correctly
    const fetchLimit = paginationParams ? Number.MAX_SAFE_INTEGER : (parseInt(req.query.limit) || 50);
    const history = healthChecker.getIncidentHistory(fetchLimit);
    const result = paginate(history, paginationParams);
    success(res, { history: result.data, ...(result.pagination && { pagination: result.pagination }) });
  }, 'health-check-incidents-history'));

  return router;
};