const client = require('prom-client');

// Create a Registry to register the metrics
const register = new client.Registry();

// Add default metrics (CPU, memory, etc.)
client.collectDefaultMetrics({ 
  register,
  prefix: 'influence_app_'
});

// Custom metrics for the Influence application

// Email metrics
const emailsSentTotal = new client.Counter({
  name: 'influence_emails_sent_total',
  help: 'Total number of emails sent successfully',
  labelNames: ['campaign_id', 'representative_level'],
  registers: [register]
});

const emailsFailedTotal = new client.Counter({
  name: 'influence_emails_failed_total',
  help: 'Total number of emails that failed to send',
  labelNames: ['campaign_id', 'error_type'],
  registers: [register]
});

const emailQueueSize = new client.Gauge({
  name: 'influence_email_queue_size',
  help: 'Current number of emails in the queue',
  registers: [register]
});

const emailSendDuration = new client.Histogram({
  name: 'influence_email_send_duration_seconds',
  help: 'Time taken to send an email',
  labelNames: ['campaign_id'],
  buckets: [0.1, 0.5, 1, 2, 5, 10],
  registers: [register]
});

// API metrics
const httpRequestDuration = new client.Histogram({
  name: 'influence_http_request_duration_seconds',
  help: 'Duration of HTTP requests in seconds',
  labelNames: ['method', 'route', 'status_code'],
  buckets: [0.01, 0.05, 0.1, 0.5, 1, 2, 5],
  registers: [register]
});

const httpRequestsTotal = new client.Counter({
  name: 'influence_http_requests_total',
  help: 'Total number of HTTP requests',
  labelNames: ['method', 'route', 'status_code'],
  registers: [register]
});

// User metrics
const activeUsersGauge = new client.Gauge({
  name: 'influence_active_users_total',
  help: 'Number of currently active users',
  registers: [register]
});

const userRegistrationsTotal = new client.Counter({
  name: 'influence_user_registrations_total',
  help: 'Total number of user registrations',
  registers: [register]
});

const loginAttemptsTotal = new client.Counter({
  name: 'influence_login_attempts_total',
  help: 'Total number of login attempts',
  labelNames: ['status'],
  registers: [register]
});

// Campaign metrics
const campaignCreationsTotal = new client.Counter({
  name: 'influence_campaign_creations_total',
  help: 'Total number of campaigns created',
  registers: [register]
});

const campaignParticipationTotal = new client.Counter({
  name: 'influence_campaign_participation_total',
  help: 'Total number of campaign participations',
  labelNames: ['campaign_id'],
  registers: [register]
});

const activeCampaignsGauge = new client.Gauge({
  name: 'influence_active_campaigns_total',
  help: 'Number of currently active campaigns',
  registers: [register]
});

const campaignConversionRate = new client.Gauge({
  name: 'influence_campaign_conversion_rate',
  help: 'Campaign conversion rate (participants / visitors)',
  labelNames: ['campaign_id'],
  registers: [register]
});

// Representative metrics
const representativeLookupTotal = new client.Counter({
  name: 'influence_representative_lookup_total',
  help: 'Total number of representative lookups',
  labelNames: ['lookup_type'],
  registers: [register]
});

const representativeResponsesTotal = new client.Counter({
  name: 'influence_representative_responses_total',
  help: 'Total number of representative responses received',
  labelNames: ['representative_level'],
  registers: [register]
});

const representativeResponseRate = new client.Gauge({
  name: 'influence_representative_response_rate',
  help: 'Representative response rate (responses / emails sent)',
  labelNames: ['representative_level'],
  registers: [register]
});

// Rate limiting metrics
const rateLimitHitsTotal = new client.Counter({
  name: 'influence_rate_limit_hits_total',
  help: 'Total number of rate limit hits',
  labelNames: ['endpoint', 'limit_type'],
  registers: [register]
});

// External service metrics
const externalServiceRequestsTotal = new client.Counter({
  name: 'influence_external_service_requests_total',
  help: 'Total number of requests to external services',
  labelNames: ['service', 'status'],
  registers: [register]
});

const externalServiceLatency = new client.Histogram({
  name: 'influence_external_service_latency_seconds',
  help: 'Latency of external service requests',
  labelNames: ['service'],
  buckets: [0.1, 0.5, 1, 2, 5, 10],
  registers: [register]
});

// Geographic metrics
const participationByPostalCode = new client.Counter({
  name: 'influence_participation_by_postal_code_total',
  help: 'Participation count by postal code prefix',
  labelNames: ['postal_prefix'],
  registers: [register]
});

// Middleware to track HTTP requests
const metricsMiddleware = (req, res, next) => {
  const start = Date.now();
  
  res.on('finish', () => {
    const duration = (Date.now() - start) / 1000;
    const route = req.route ? req.route.path : req.path;
    const labels = {
      method: req.method,
      route: route,
      status_code: res.statusCode
    };
    
    httpRequestDuration.observe(labels, duration);
    httpRequestsTotal.inc(labels);
  });
  
  next();
};

// Helper functions for common metric operations
const metrics = {
  // Email metrics
  recordEmailSent: (campaignId, representativeLevel) => {
    emailsSentTotal.inc({ campaign_id: campaignId, representative_level: representativeLevel });
  },
  
  recordEmailFailed: (campaignId, errorType) => {
    emailsFailedTotal.inc({ campaign_id: campaignId, error_type: errorType });
  },
  
  setEmailQueueSize: (size) => {
    emailQueueSize.set(size);
  },
  
  observeEmailSendDuration: (campaignId, durationSeconds) => {
    emailSendDuration.observe({ campaign_id: campaignId }, durationSeconds);
  },
  
  // User metrics
  setActiveUsers: (count) => {
    activeUsersGauge.set(count);
  },
  
  recordUserRegistration: () => {
    userRegistrationsTotal.inc();
  },
  
  recordLoginAttempt: (success) => {
    loginAttemptsTotal.inc({ status: success ? 'success' : 'failed' });
  },
  
  // Campaign metrics
  recordCampaignCreation: () => {
    campaignCreationsTotal.inc();
  },
  
  recordCampaignParticipation: (campaignId) => {
    campaignParticipationTotal.inc({ campaign_id: campaignId });
  },
  
  setActiveCampaigns: (count) => {
    activeCampaignsGauge.set(count);
  },
  
  setCampaignConversionRate: (campaignId, rate) => {
    campaignConversionRate.set({ campaign_id: campaignId }, rate);
  },
  
  // Representative metrics
  recordRepresentativeLookup: (lookupType) => {
    representativeLookupTotal.inc({ lookup_type: lookupType });
  },
  
  recordRepresentativeResponse: (representativeLevel) => {
    representativeResponsesTotal.inc({ representative_level: representativeLevel });
  },
  
  setRepresentativeResponseRate: (representativeLevel, rate) => {
    representativeResponseRate.set({ representative_level: representativeLevel }, rate);
  },
  
  // Rate limiting metrics
  recordRateLimitHit: (endpoint, limitType) => {
    rateLimitHitsTotal.inc({ endpoint, limit_type: limitType });
  },
  
  // External service metrics
  recordExternalServiceRequest: (service, success) => {
    externalServiceRequestsTotal.inc({ service, status: success ? 'success' : 'failed' });
  },
  
  observeExternalServiceLatency: (service, durationSeconds) => {
    externalServiceLatency.observe({ service }, durationSeconds);
  },
  
  // Geographic metrics
  recordParticipationByPostalCode: (postalCode) => {
    const prefix = postalCode.substring(0, 3).toUpperCase();
    participationByPostalCode.inc({ postal_prefix: prefix });
  },
  
  // Get metrics endpoint handler
  getMetrics: async () => {
    return await register.metrics();
  },
  
  // Get content type for metrics
  getContentType: () => {
    return register.contentType;
  },
  
  // Middleware
  middleware: metricsMiddleware
};

module.exports = metrics;