/*
Copyright 2022 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package aggregated_test

import (
	"fmt"
	"io"
	"strings"
	"testing"

	"k8s.io/component-base/metrics/legacyregistry"
	"k8s.io/component-base/metrics/testutil"

	apidiscoveryv2 "k8s.io/api/apidiscovery/v2"
	discoveryendpoint "k8s.io/apiserver/pkg/endpoints/discovery/aggregated"
	genericfeatures "k8s.io/apiserver/pkg/features"
	utilfeature "k8s.io/apiserver/pkg/util/feature"
	featuregatetesting "k8s.io/component-base/featuregate/testing"
)

func formatExpectedMetrics(aggregationCount int) io.Reader {
	expected := ``
	if aggregationCount > 0 {
		expected = expected + `# HELP aggregator_discovery_aggregation_count_total [ALPHA] Counter of number of times discovery was aggregated
# TYPE aggregator_discovery_aggregation_count_total counter
aggregator_discovery_aggregation_count_total %d
`
	}
	args := []any{}
	if aggregationCount > 0 {
		args = append(args, aggregationCount)
	}
	return strings.NewReader(fmt.Sprintf(expected, args...))
}

func TestBasicMetrics(t *testing.T) {
	legacyregistry.Reset()
	manager := discoveryendpoint.NewResourceManager("apis")

	apis := fuzzAPIGroups(1, 3, 10)
	manager.SetGroups(apis.Items)

	interests := []string{"aggregator_discovery_aggregation_count_total"}

	_, _, _ = fetchPath(manager, "application/json", discoveryPath, "")
	// A single fetch should aggregate and increment regeneration counter.
	if err := testutil.GatherAndCompare(legacyregistry.DefaultGatherer, formatExpectedMetrics(1), interests...); err != nil {
		t.Fatal(err)
	}
	_, _, _ = fetchPath(manager, "application/json", discoveryPath, "")
	// Subsequent fetches should not reaggregate discovery.
	if err := testutil.GatherAndCompare(legacyregistry.DefaultGatherer, formatExpectedMetrics(1), interests...); err != nil {
		t.Fatal(err)
	}
}

func TestMetricsModified(t *testing.T) {
	legacyregistry.Reset()
	manager := discoveryendpoint.NewResourceManager("apis")

	apis := fuzzAPIGroups(1, 3, 10)
	manager.SetGroups(apis.Items)

	interests := []string{"aggregator_discovery_aggregation_count_total"}

	_, _, _ = fetchPath(manager, "application/json", discoveryPath, "")
	// A single fetch should aggregate and increment regeneration counter.
	if err := testutil.GatherAndCompare(legacyregistry.DefaultGatherer, formatExpectedMetrics(1), interests...); err != nil {
		t.Fatal(err)
	}

	// Update discovery document.
	manager.SetGroups(fuzzAPIGroups(1, 3, 10).Items)
	_, _, _ = fetchPath(manager, "application/json", discoveryPath, "")
	// If the discovery content has changed, reaggregation should be performed.
	if err := testutil.GatherAndCompare(legacyregistry.DefaultGatherer, formatExpectedMetrics(2), interests...); err != nil {
		t.Fatal(err)
	}
}

func TestPeerAggregatedDiscoveryMetrics(t *testing.T) {
	legacyregistry.Reset()
	featuregatetesting.SetFeatureGateDuringTest(t, utilfeature.DefaultFeatureGate, genericfeatures.UnknownVersionInteroperabilityProxy, true)
	manager := discoveryendpoint.NewResourceManager("apis")
	localGroup := newAPIGroup("local.example.com", "v1", "local-resource")
	manager.AddGroupVersion(localGroup.Name, localGroup.Versions[0])
	peerProvider := &mockPeerDiscoveryProvider{
		resources: map[string][]apidiscoveryv2.APIGroupDiscovery{
			"peer-server-1": {
				newAPIGroup("peer.example.com", "v2", "peer-resource"),
			},
		},
	}
	peerAggregatedDiscoveryManager := discoveryendpoint.NewPeerAggregatedDiscoveryHandler("test-server", manager, peerProvider, "apis")
	wrapped := discoveryendpoint.WrapAggregatedDiscoveryToHandler(manager, manager, peerAggregatedDiscoveryManager)

	_ = legacyregistry.Register(discoveryendpoint.PeerAggregatedCacheHitsCounter)
	_ = legacyregistry.Register(discoveryendpoint.PeerAggregatedCacheMissesCounter)
	_ = legacyregistry.Register(discoveryendpoint.NoPeerDiscoveryRequestCounter)

	// Make 3 peer-aggregated requests.
	fetchPath(wrapped, "application/json", "/apis", "")
	fetchPath(wrapped, "application/json;profile=foo", "/apis", "")
	fetchPath(wrapped, "application/json;g=apidiscovery.k8s.io;v=v2;as=APIGroupDiscoveryList", "/apis", "")

	// Make 2 no-peer discovery requests.
	fetchPath(wrapped, "application/json;profile=nopeer", "/apis", "")
	peerAggregatedDiscoveryManager.InvalidateCache()
	fetchPath(wrapped, "application/json;profile=nopeer", "/apis", "")
	peerAggregatedDiscoveryManager.InvalidateCache()

	cacheHitsTotalMetric := `
# HELP aggregator_discovery_peer_aggregated_cache_hits_total [ALPHA] Counter of number of times discovery was served from peer-aggregated cache
# TYPE aggregator_discovery_peer_aggregated_cache_hits_total counter
aggregator_discovery_peer_aggregated_cache_hits_total 2
`

	cacheMissesTotalMetric := `
# HELP aggregator_discovery_peer_aggregated_cache_misses_total [ALPHA] Counter of number of times discovery was aggregated across all API servers
# TYPE aggregator_discovery_peer_aggregated_cache_misses_total counter
aggregator_discovery_peer_aggregated_cache_misses_total 1
`

	noPeerDiscoveryTotalMetric := `
# HELP aggregator_discovery_nopeer_requests_total [ALPHA] Counter of number of times no-peer (non peer-aggregated) discovery was requested
# TYPE aggregator_discovery_nopeer_requests_total counter
aggregator_discovery_nopeer_requests_total 2
`

	if err := testutil.GatherAndCompare(legacyregistry.DefaultGatherer, strings.NewReader(cacheHitsTotalMetric), "aggregator_discovery_peer_aggregated_cache_hits_total"); err != nil {
		t.Errorf("unexpected metrics output: %v", err)
	}

	if err := testutil.GatherAndCompare(legacyregistry.DefaultGatherer, strings.NewReader(cacheMissesTotalMetric), "aggregator_discovery_peer_aggregated_cache_misses_total"); err != nil {
		t.Errorf("unexpected metrics output: %v", err)
	}

	if err := testutil.GatherAndCompare(legacyregistry.DefaultGatherer, strings.NewReader(noPeerDiscoveryTotalMetric), "aggregator_discovery_nopeer_requests_total"); err != nil {
		t.Errorf("unexpected metrics output: %v", err)
	}
}
