/**
 * Unit: the Prometheus text renderer (TASK-0135).
 *
 * `renderPrometheus()` renders the process-global MeterProvider to Prometheus
 * text (version 0.0.4) for the apps' /metrics routes. Asserts: (a) it renders
 * the metric names + HELP/TYPE lines, (b) it returns "" when there is no
 * reader (disabled) — the no-op contract.
 */
import { afterEach, describe, expect, it } from "vitest";
import { metrics as otelMetrics } from "@opentelemetry/api";
import {
  AggregationTemporality,
  InMemoryMetricExporter,
  MeterProvider,
  PeriodicExportingMetricReader
} from "@opentelemetry/sdk-metrics";
import { PrometheusExporter } from "@opentelemetry/exporter-prometheus";
import { renderPrometheus, hasPrometheusReader, setPrometheusReader } from "../prometheus.js";
import { m } from "../metrics.js";

describe("renderPrometheus (app /metrics renderer)", () => {
  afterEach(async () => {
    // detach the reader + drop the global so the disabled-case test is clean
    setPrometheusReader(undefined);
    otelMetrics.disable();
  });

  it("returns '' when no reader is attached (OTel disabled — the no-op contract)", async () => {
    setPrometheusReader(undefined);
    expect(hasPrometheusReader()).toBe(false);
    expect(await renderPrometheus()).toBe("");
  });

  it("renders the registered spec metrics as Prometheus text 0.0.4", async () => {
    otelMetrics.disable();
    const exporter = new InMemoryMetricExporter(AggregationTemporality.CUMULATIVE);
    const reader = new PeriodicExportingMetricReader({ exporter, exportIntervalMillis: 60_000 });
    // 0.57.0 ExporterConfig has no withoutScopeInfo/withoutTargetInfo (2.x-only).
    const prom = new PrometheusExporter({ preventServerStart: true });
    const mp = new MeterProvider({ readers: [reader, prom] });
    otelMetrics.setGlobalMeterProvider(mp);
    setPrometheusReader(prom);

    // exercise a counter + a histogram + a gauge (the three Prometheus types)
    m.error.record({ service: "factory-api", code: "NOT_FOUND" });
    m.http.record({ route: "/api/v1/pages/:id", method: "GET", status: "200" }, 0.012);
    m.queue.setDepth("webhooks", 7);

    const text = await renderPrometheus();
    expect(text).toContain("# HELP error_total");
    expect(text).toContain("# TYPE error_total counter");
    // label order is insertion order (toAttrs spreads in the order given)
    expect(text).toContain('error_total{service="factory-api",code="NOT_FOUND"} 1');
    expect(text).toContain("# TYPE http_request_duration_seconds histogram");
    expect(text).toContain("http_request_duration_seconds_bucket");
    expect(text).toContain('http_request_duration_seconds_sum{route="/api/v1/pages/:id",method="GET",status="200"} 0.012');
    // the explicit buckets (in SECONDS — the unit-consistency contract that
    // makes histogram_quantile correct)
    expect(text).toContain('http_request_duration_seconds_bucket{route="/api/v1/pages/:id",method="GET",status="200",le="0.005"} 0');
    expect(text).toContain('le="+Inf"');
    expect(text).toContain("# TYPE queue_depth gauge");
    expect(text).toContain('queue_depth{queue="webhooks"} 7');
    await mp.shutdown();
  });
});