import promClient from "prom-client";

const registry = new promClient.Registry();
registry.setDefaultLabels({ service: "iam" });

registry.registerMetric(
  new promClient.Counter({
    name: "iam_requests_total",
    help: "Total number of iam requests",
    labelNames: ["method", "endpoint", "status"],
  }),
);

registry.registerMetric(
  new promClient.Histogram({
    name: "iam_request_duration_seconds",
    help: "Iam request duration in seconds",
    labelNames: ["method", "endpoint"],
    buckets: [0.01, 0.05, 0.1, 0.3, 0.5, 1, 3, 5],
  }),
);

// 自动收集 Node.js 进程级指标（CPU/内存/事件循环/GC等）
// 这些指标无需业务代码埋点，prom-client 自动采集
promClient.collectDefaultMetrics({ register: registry });

// Redis 权限缓存指标（I3 裁决：DB 驱动 + Redis 缓存可观测性）
registry.registerMetric(
  new promClient.Counter({
    name: "iam_permission_cache_hits_total",
    help: "Total number of permission cache hits (Redis)",
  }),
);

registry.registerMetric(
  new promClient.Counter({
    name: "iam_permission_cache_misses_total",
    help: "Total number of permission cache misses (Redis)",
  }),
);

registry.registerMetric(
  new promClient.Counter({
    name: "iam_permission_cache_invalidations_total",
    help: "Total number of permission cache invalidations (Redis)",
    labelNames: ["reason"],
  }),
);

/**
 * 缓存指标访问器：供 PermissionCacheService 使用.
 * 避免在业务代码中直接操作 registry，统一通过此门面.
 */
export const cacheMetrics = {
  recordHit(): void {
    const metric = registry.getSingleMetric("iam_permission_cache_hits_total");
    if (metric && "inc" in metric) {
      (metric as promClient.Counter).inc();
    }
  },
  recordMiss(): void {
    const metric = registry.getSingleMetric(
      "iam_permission_cache_misses_total",
    );
    if (metric && "inc" in metric) {
      (metric as promClient.Counter).inc();
    }
  },
  recordInvalidation(reason: string): void {
    const metric = registry.getSingleMetric(
      "iam_permission_cache_invalidations_total",
    );
    if (metric && "inc" in metric) {
      (metric as promClient.Counter).inc({ reason });
    }
  },
};

export { registry as metricsRegistry };