package metrics

import (
	"testing"

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

// Verifies that all exported PVE metrics follow the Prometheus naming conventions
// (base units, '_total' suffix on counters, '_info' suffix on info metrics, ...)
// so that tools such as promtool or Grafana do not report naming problems.
func TestPveMetricNamesFollowPrometheusConventions(t *testing.T) {
	registry := prometheus.NewRegistry()

	// Collectors register their metrics on the default registerer, so it is
	// temporarily replaced by a dedicated registry.
	defaultRegisterer := prometheus.DefaultRegisterer
	prometheus.DefaultRegisterer = registry
	defer func() { prometheus.DefaultRegisterer = defaultRegisterer }()

	// Collector constructors only create metrics, the API client is used during
	// collection only, so a nil client is enough here.
	ttlRegistry := NewTTLRegistry()
	NewPveClusterStateCollector(nil, ttlRegistry)
	NewPveNodeStatusCollector(nil, ttlRegistry)
	NewPveSubscriptionCollector(nil, ttlRegistry)
	NewPveNodeDiskCollector(nil, ttlRegistry)
	NewPveNodeZfsCollector(nil, ttlRegistry)
	NewPveSdnCollector(nil, ttlRegistry)
	NewPveStorageCollector(nil, ttlRegistry)
	NewPveContainerCollector(nil, ttlRegistry)
	NewPveVirtualMachineCollector(nil, ttlRegistry)

	// Metric vectors are exported only once they hold a label set.
	for _, metric := range ttlRegistry.metrics {
		switch m := metric.(type) {
		case *TTLGaugeVec:
			m.With(emptyLabels(m.labelNames)).Set(0)
		case *TTLCounterVec:
			m.With(emptyLabels(m.labelNames)).Set(0)
		default:
			t.Fatalf("Unknown TTL metric type %T.", metric)
		}
	}

	families, err := registry.Gather()
	if err != nil {
		t.Fatalf("Unable to gather metrics. Error: %s.", err)
	}
	if len(families) != len(ttlRegistry.metrics) {
		t.Fatalf("Gathered %d metric families but %d metrics are registered.", len(families), len(ttlRegistry.metrics))
	}

	problems, err := promlint.NewWithMetricFamilies(families).Lint()
	if err != nil {
		t.Fatalf("Unable to lint metrics. Error: %s.", err)
	}

	for _, problem := range problems {
		t.Errorf("Metric '%s' violates the Prometheus naming conventions: %s.", problem.Metric, problem.Text)
	}
}

// emptyLabels builds a label set with all given label names set to an empty value.
func emptyLabels(labelNames []string) prometheus.Labels {
	labels := prometheus.Labels{}
	for _, name := range labelNames {
		labels[name] = ""
	}
	return labels
}