// Copyright The Prometheus 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 notifier

import (
	"bytes"
	"context"
	"io"
	"log/slog"
	"net/http"
	"strconv"
	"testing"

	"github.com/prometheus/client_golang/prometheus"
	prom_testutil "github.com/prometheus/client_golang/prometheus/testutil"
	"github.com/stretchr/testify/require"

	"github.com/prometheus/prometheus/config"
	"github.com/prometheus/prometheus/model/labels"
)

func TestCustomDo(t *testing.T) {
	const testURL = "http://testurl.com/"
	const testBody = "testbody"

	var received bool
	h := sendLoop{
		opts: &Options{
			Do: func(_ context.Context, _ *http.Client, req *http.Request) (*http.Response, error) {
				received = true
				body, err := io.ReadAll(req.Body)

				require.NoError(t, err)

				require.Equal(t, testBody, string(body))

				require.Equal(t, testURL, req.URL.String())

				return &http.Response{
					Body: io.NopCloser(bytes.NewBuffer(nil)),
				}, nil
			},
		},
	}

	h.sendOne(context.Background(), nil, testURL, []byte(testBody))

	require.True(t, received)
}

func TestHandlerNextBatch(t *testing.T) {
	sendLoop := newSendLoop("http://mock", nil, &config.DefaultAlertmanagerConfig, &Options{MaxBatchSize: DefaultMaxBatchSize}, slog.New(slog.DiscardHandler), newAlertMetrics(prometheus.NewRegistry(), nil))

	for i := range make([]struct{}, 2*DefaultMaxBatchSize+1) {
		sendLoop.queue = append(sendLoop.queue, &Alert{
			Labels: labels.FromStrings("alertname", strconv.Itoa(i)),
		})
	}
	expected := append([]*Alert{}, sendLoop.queue...)

	require.NoError(t, alertsEqual(expected[0:DefaultMaxBatchSize], sendLoop.nextBatch()))
	require.NoError(t, alertsEqual(expected[DefaultMaxBatchSize:2*DefaultMaxBatchSize], sendLoop.nextBatch()))
	require.NoError(t, alertsEqual(expected[2*DefaultMaxBatchSize:], sendLoop.nextBatch()))
	require.Empty(t, sendLoop.queue)
}

func TestAddAlertsToQueue(t *testing.T) {
	alert1 := &Alert{Labels: labels.FromStrings("alertname", "existing1")}
	alert2 := &Alert{Labels: labels.FromStrings("alertname", "existing2")}

	s := newSendLoop("http://foo.bar/", nil, nil, &Options{QueueCapacity: 5}, slog.New(slog.DiscardHandler), newAlertMetrics(prometheus.NewRegistry(), nil))
	s.add(alert1, alert2)
	require.Equal(t, []*Alert{alert1, alert2}, s.queue)
	require.Len(t, s.queue, 2)

	alert3 := &Alert{Labels: labels.FromStrings("alertname", "new1")}
	alert4 := &Alert{Labels: labels.FromStrings("alertname", "new2")}

	// Add new alerts to the queue, expect 0 dropped
	s.add(alert3, alert4)
	require.Zero(t, prom_testutil.ToFloat64(s.metrics.dropped.WithLabelValues(s.alertmanagerURL)))

	// Verify all new alerts were added to the queue
	require.Equal(t, []*Alert{alert1, alert2, alert3, alert4}, s.queue)
	require.Len(t, s.queue, 4)
}

func TestAddAlertsToQueueExceedingCapacity(t *testing.T) {
	alert1 := &Alert{Labels: labels.FromStrings("alertname", "alert1")}
	alert2 := &Alert{Labels: labels.FromStrings("alertname", "alert2")}

	s := newSendLoop("http://foo.bar/", nil, nil, &Options{QueueCapacity: 3}, slog.New(slog.DiscardHandler), newAlertMetrics(prometheus.NewRegistry(), nil))
	s.add(alert1, alert2)

	alert3 := &Alert{Labels: labels.FromStrings("alertname", "alert3")}
	alert4 := &Alert{Labels: labels.FromStrings("alertname", "alert4")}

	// Add new alerts to queue, expect 1 dropped
	s.add(alert3, alert4)
	require.Equal(t, 1.0, prom_testutil.ToFloat64(s.metrics.dropped.WithLabelValues(s.alertmanagerURL)))

	// Verify all new alerts were added to the queue
	require.Equal(t, []*Alert{alert2, alert3, alert4}, s.queue)
}

func TestAddAlertsToQueueExceedingTotalCapacity(t *testing.T) {
	alert1 := &Alert{Labels: labels.FromStrings("alertname", "alert1")}
	alert2 := &Alert{Labels: labels.FromStrings("alertname", "alert2")}

	s := newSendLoop("http://foo.bar/", nil, nil, &Options{QueueCapacity: 3}, slog.New(slog.DiscardHandler), newAlertMetrics(prometheus.NewRegistry(), nil))
	s.add(alert1, alert2)

	alert3 := &Alert{Labels: labels.FromStrings("alertname", "alert3")}
	alert4 := &Alert{Labels: labels.FromStrings("alertname", "alert4")}
	alert5 := &Alert{Labels: labels.FromStrings("alertname", "alert5")}
	alert6 := &Alert{Labels: labels.FromStrings("alertname", "alert6")}

	// Add new alerts to queue, expect 3 dropped: 1 from new batch + 2 from existing queued items
	s.add(alert3, alert4, alert5, alert6)
	require.Equal(t, 3.0, prom_testutil.ToFloat64(s.metrics.dropped.WithLabelValues(s.alertmanagerURL)))

	// Verify all new alerts were added to the queue
	require.Equal(t, []*Alert{alert4, alert5, alert6}, s.queue)
}

func TestNextBatchAlertsFromQueue(t *testing.T) {
	s := newSendLoop("http://foo.bar/", nil, nil, &Options{QueueCapacity: 5, MaxBatchSize: 3}, slog.New(slog.DiscardHandler), newAlertMetrics(prometheus.NewRegistry(), nil))

	alert1 := &Alert{Labels: labels.FromStrings("alertname", "alert1")}
	alert2 := &Alert{Labels: labels.FromStrings("alertname", "alert2")}
	alert3 := &Alert{Labels: labels.FromStrings("alertname", "alert3")}
	s.add(alert1, alert2, alert3)

	// Test batch-size alerts in the queue
	require.Equal(t, []*Alert{alert1, alert2, alert3}, s.nextBatch())
	require.Empty(t, s.nextBatch())

	// Test full queue
	alert4 := &Alert{Labels: labels.FromStrings("alertname", "alert4")}
	alert5 := &Alert{Labels: labels.FromStrings("alertname", "alert5")}
	s.add(alert1, alert2, alert3, alert4, alert5)
	require.Equal(t, []*Alert{alert1, alert2, alert3}, s.nextBatch())
	require.Equal(t, []*Alert{alert4, alert5}, s.nextBatch())
	require.Empty(t, s.nextBatch())
}

func TestMetrics(t *testing.T) {
	const alertmanagerURL = "http://alertmanager:9093"

	// Use a single registry throughout the test - this is critical to catch registry conflicts
	reg := prometheus.NewRegistry()
	alertmanagersDiscoveredFunc := func() float64 { return 0 }
	metrics := newAlertMetrics(reg, alertmanagersDiscoveredFunc)

	logger := slog.New(slog.DiscardHandler)
	opts := &Options{QueueCapacity: 10, MaxBatchSize: DefaultMaxBatchSize}

	// Create first sendLoop - this initializes metrics with the alertmanager URL label
	sendLoop1 := newSendLoop(alertmanagerURL, nil, &config.DefaultAlertmanagerConfig, opts, logger, metrics)

	// Verify metrics are initialized
	require.Equal(t, 0.0, prom_testutil.ToFloat64(metrics.dropped.WithLabelValues(alertmanagerURL)))
	require.Equal(t, 0.0, prom_testutil.ToFloat64(metrics.sent.WithLabelValues(alertmanagerURL)))

	// Stop the sendLoop - this should clean up all metrics
	sendLoop1.stop()

	// Create second sendLoop with the same URL - this should NOT panic or conflict
	// because metrics were properly cleaned up
	sendLoop2 := newSendLoop(alertmanagerURL, nil, &config.DefaultAlertmanagerConfig, opts, logger, metrics)
	defer sendLoop2.stop()

	// Verify metrics are re-initialized correctly
	require.Equal(t, 0.0, prom_testutil.ToFloat64(metrics.dropped.WithLabelValues(alertmanagerURL)))
	require.Equal(t, 0.0, prom_testutil.ToFloat64(metrics.sent.WithLabelValues(alertmanagerURL)))
}