package metrics

import (
	"context"
	"io"
	"net"
	"net/http"
	"strings"
	"testing"
	"time"
)

func TestMetricsServerCanBindLoopback(t *testing.T) {
	registry := NewRegistry(RegistryOptions{})
	server := NewServer("127.0.0.1:0", registry.Gatherer)
	ln, err := net.Listen("tcp", server.Addr)
	if err != nil {
		t.Fatalf("listen: %v", err)
	}

	errCh := make(chan error, 1)
	go func() {
		errCh <- server.Serve(ln)
	}()
	t.Cleanup(func() {
		ctx, cancel := context.WithTimeout(context.Background(), time.Second)
		defer cancel()
		_ = server.Shutdown(ctx)
		if err := <-errCh; err != nil && err != http.ErrServerClosed {
			t.Fatalf("serve: %v", err)
		}
	})

	resp, err := http.Get("http://" + ln.Addr().String() + "/metrics")
	if err != nil {
		t.Fatalf("get /metrics: %v", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		t.Fatalf("/metrics status = %d, want %d", resp.StatusCode, http.StatusOK)
	}
	body, _ := io.ReadAll(resp.Body)
	if !strings.Contains(string(body), "multica_build_info") {
		t.Fatalf("/metrics body missing build info: %s", body)
	}
}