import { Registry, Counter, Histogram, Gauge } from 'prom-client';

/**
 * Prometheus Metrics Registry
 * Sammelt Metriken für Monitoring und Alerting
 */
export const register = new Registry();

// Default Metrics (CPU, Memory, etc.)
register.setDefaultLabels({
  app: 'graphql-middlelayer',
});

// Query Metrics
export const queryCounter = new Counter({
  name: 'graphql_queries_total',
  help: 'Total number of GraphQL queries',
  labelNames: ['operation', 'status'],
  registers: [register],
});

export const queryDuration = new Histogram({
  name: 'graphql_query_duration_seconds',
  help: 'Duration of GraphQL queries in seconds',
  labelNames: ['operation'],
  buckets: [0.01, 0.05, 0.1, 0.5, 1, 2, 5],
  registers: [register],
});

// Cache Metrics
export const cacheHits = new Counter({
  name: 'cache_hits_total',
  help: 'Total number of cache hits',
  labelNames: ['cache_type'],
  registers: [register],
});

export const cacheMisses = new Counter({
  name: 'cache_misses_total',
  help: 'Total number of cache misses',
  labelNames: ['cache_type'],
  registers: [register],
});

// DataService Metrics
export const dataServiceCalls = new Counter({
  name: 'dataservice_calls_total',
  help: 'Total number of DataService calls',
  labelNames: ['method', 'status'],
  registers: [register],
});

export const dataServiceDuration = new Histogram({
  name: 'dataservice_duration_seconds',
  help: 'Duration of DataService calls in seconds',
  labelNames: ['method'],
  buckets: [0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1],
  registers: [register],
});

// Error Metrics
export const errorCounter = new Counter({
  name: 'errors_total',
  help: 'Total number of errors',
  labelNames: ['type', 'operation'],
  registers: [register],
});

// Active Connections
export const activeConnections = new Gauge({
  name: 'active_connections',
  help: 'Number of active connections',
  registers: [register],
});

// Query Complexity
export const queryComplexityGauge = new Gauge({
  name: 'graphql_query_complexity',
  help: 'Complexity of GraphQL queries',
  labelNames: ['operation'],
  registers: [register],
});

/**
 * Exportiert Metriken im Prometheus-Format
 */
export async function getMetrics(): Promise<string> {
  return register.metrics();
}