import type { Pool } from 'pg';
import { drizzle } from 'drizzle-orm/node-postgres';
import { roomMembers } from '../db/schema.js';
import { sql } from 'drizzle-orm';
import { roomsActiveGauge, dbQueryDurationHistogram } from '../lib/metrics.js';

/**
 * Collect active rooms metric from database
 */
async function collectRoomsActiveMetric(pool: Pool): Promise<void> {
  const db = drizzle(pool);
  const startTime = performance.now();

  try {
    // Count distinct rooms that have at least one member
    const result = await db
      .select({ count: sql<number>`count(distinct ${roomMembers.roomId})` })
      .from(roomMembers);

    const count = Number(result[0]?.count) || 0;
    roomsActiveGauge.set(count);

    const duration = (performance.now() - startTime) / 1000;
    dbQueryDurationHistogram.observe({ operation: 'count_active_rooms' }, duration);
  } catch (err) {
    console.error('Failed to collect rooms active metric:', err);
  }
}

/**
 * Start periodic metrics collection
 * Updates room metrics every 30 seconds
 */
export function startMetricsCollector(pool: Pool): void {
  // Collect immediately on startup
  collectRoomsActiveMetric(pool).catch(console.error);

  // Then collect every 30 seconds
  setInterval(() => {
    collectRoomsActiveMetric(pool).catch(console.error);
  }, 30_000);
}