package imgcache

import (
	"errors"
	"testing"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/testutil"
)

// TestNewCache_RegistersItsCountersOnItsRegistry checks that NewCache
// registers the cache's counters on the registry it is given, under the
// names README.md gives them.
func TestNewCache_RegistersItsCountersOnItsRegistry(t *testing.T) {
	t.Parallel()

	registry := prometheus.NewRegistry()

	_, err := NewCache(evictionTestDB(t),
		Config{StateDir: t.TempDir(), MaxBytes: 1 << 30}, registry)
	if err != nil {
		t.Fatalf("NewCache() error = %v", err)
	}

	names := []string{
		"pixa_cache_hits_total",
		"pixa_cache_misses_total",
	}

	count, err := testutil.GatherAndCount(registry, names...)
	if err != nil {
		t.Fatalf("testutil.GatherAndCount() error = %v", err)
	}

	if count != len(names) {
		t.Errorf("%d of the counters %v are on the registry, want %d",
			count, names, len(names))
	}
}

// TestNewCache_FailsWhenItsCountersCannotBeRegistered makes a second cache
// on the registry of a first. Its counters have the same names, so the
// registry refuses them, and NewCache must return that error.
func TestNewCache_FailsWhenItsCountersCannotBeRegistered(t *testing.T) {
	t.Parallel()

	registry := prometheus.NewRegistry()

	_, err := NewCache(evictionTestDB(t),
		Config{StateDir: t.TempDir(), MaxBytes: 1 << 30}, registry)
	if err != nil {
		t.Fatalf("NewCache() of the first cache error = %v", err)
	}

	_, err = NewCache(evictionTestDB(t),
		Config{StateDir: t.TempDir(), MaxBytes: 1 << 30}, registry)
	t.Logf("NewCache() of the second cache error = %v", err)

	var alreadyRegistered prometheus.AlreadyRegisteredError
	if !errors.As(err, &alreadyRegistered) {
		t.Errorf("NewCache() of the second cache error = %v, want %T",
			err, alreadyRegistered)
	}
}