// ABOUTME: Prometheus metrics collection module for production monitoring.
// ABOUTME: Exposes counters, gauges, and histograms for Garmin sync, email, and decision engine.

import * as promClient from "prom-client";

// Create a new registry for our application metrics
export const metricsRegistry = new promClient.Registry();

// Collect default Node.js metrics (heap, event loop, etc.)
promClient.collectDefaultMetrics({ register: metricsRegistry });

// Custom metric: Garmin sync operations counter
export const garminSyncTotal = new promClient.Counter({
  name: "phaseflow_garmin_sync_total",
  help: "Total number of Garmin sync operations",
  labelNames: ["status"] as const,
  registers: [metricsRegistry],
});

// Custom metric: Garmin sync duration histogram
export const garminSyncDuration = new promClient.Histogram({
  name: "phaseflow_garmin_sync_duration_seconds",
  help: "Duration of Garmin sync operations in seconds",
  buckets: [0.1, 0.5, 1, 2, 5, 10],
  registers: [metricsRegistry],
});

// Custom metric: Email sent counter
export const emailSentTotal = new promClient.Counter({
  name: "phaseflow_email_sent_total",
  help: "Total number of emails sent",
  labelNames: ["type"] as const,
  registers: [metricsRegistry],
});

// Custom metric: Decision engine calls counter
export const decisionEngineCallsTotal = new promClient.Counter({
  name: "phaseflow_decision_engine_calls_total",
  help: "Total number of decision engine calls",
  labelNames: ["decision"] as const,
  registers: [metricsRegistry],
});

// Custom metric: Active users gauge
export const activeUsersGauge = new promClient.Gauge({
  name: "phaseflow_active_users",
  help: "Number of users with activity in the last 24 hours",
  registers: [metricsRegistry],
});

// Build info metric: exposes version and git commit for deployment verification
const buildInfo = new promClient.Gauge({
  name: "phaseflow_build_info",
  help: "Build information with version and git commit",
  labelNames: ["version", "commit"] as const,
  registers: [metricsRegistry],
});

// Set build info at module load (value is always 1, labels contain the info)
buildInfo
  .labels({
    version: process.env.npm_package_version || "unknown",
    commit: process.env.GIT_COMMIT || "unknown",
  })
  .set(1);