// Copyright 2015 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 collector

import (
	"fmt"
	"net/http"
	"net/http/httptest"
	"os"
	"testing"

	"github.com/alecthomas/kingpin/v2"
	"github.com/go-kit/log"
	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
	"github.com/prometheus/common/promlog"
	"github.com/prometheus/common/promlog/flag"
)

type collectorAdapter struct {
	Collector
}

// Describe implements the prometheus.Collector interface.
func (a collectorAdapter) Describe(ch chan<- *prometheus.Desc) {
	// We have to send *some* metric in Describe, but we don't know which ones
	// we're going to get, so just send a dummy metric.
	ch <- prometheus.NewDesc("dummy_metric", "Dummy metric.", nil, nil)
}

// Collect implements the prometheus.Collector interface.
func (a collectorAdapter) Collect(ch chan<- prometheus.Metric) {
	if err := a.Update(ch); err != nil {
		panic(fmt.Sprintf("failed to update collector: %v", err))
	}
}

func TestTextfileCollector(t *testing.T) {
	tests := []struct {
		path string
		out  string
	}{
		{
			path: "fixtures/textfile/no_metric_files",
			out:  "fixtures/textfile/no_metric_files.out",
		},
		{
			path: "fixtures/textfile/two_metric_files",
			out:  "fixtures/textfile/two_metric_files.out",
		},
		{
			path: "fixtures/textfile/nonexistent_path",
			out:  "fixtures/textfile/nonexistent_path.out",
		},
		{
			path: "fixtures/textfile/client_side_timestamp",
			out:  "fixtures/textfile/client_side_timestamp.out",
		},
		{
			path: "fixtures/textfile/different_metric_types",
			out:  "fixtures/textfile/different_metric_types.out",
		},
		{
			path: "fixtures/textfile/inconsistent_metrics",
			out:  "fixtures/textfile/inconsistent_metrics.out",
		},
		{
			path: "fixtures/textfile/histogram",
			out:  "fixtures/textfile/histogram.out",
		},
		{
			path: "fixtures/textfile/histogram_extra_dimension",
			out:  "fixtures/textfile/histogram_extra_dimension.out",
		},
		{
			path: "fixtures/textfile/summary",
			out:  "fixtures/textfile/summary.out",
		},
		{
			path: "fixtures/textfile/summary_extra_dimension",
			out:  "fixtures/textfile/summary_extra_dimension.out",
		},
		{
			path: "fixtures/textfile/*_extra_dimension",
			out:  "fixtures/textfile/glob_extra_dimension.out",
		},
		{
			path: "fixtures/textfile/metrics_merge_empty_help",
			out:  "fixtures/textfile/metrics_merge_empty_help.out",
		},
		{
			path: "fixtures/textfile/metrics_merge_no_help",
			out:  "fixtures/textfile/metrics_merge_no_help.out",
		},
		{
			path: "fixtures/textfile/metrics_merge_same_help",
			out:  "fixtures/textfile/metrics_merge_same_help.out",
		},
		{
			path: "fixtures/textfile/metrics_merge_different_help",
			out:  "fixtures/textfile/metrics_merge_different_help.out",
		},
	}

	for i, test := range tests {
		mtime := 1.0
		c := &textFileCollector{
			path:   test.path,
			mtime:  &mtime,
			logger: log.NewNopLogger(),
		}

		// Suppress a log message about `nonexistent_path` not existing, this is
		// expected and clutters the test output.
		promlogConfig := &promlog.Config{}
		flag.AddFlags(kingpin.CommandLine, promlogConfig)
		if _, err := kingpin.CommandLine.Parse([]string{"--log.level", "debug"}); err != nil {
			t.Fatal(err)
		}

		registry := prometheus.NewRegistry()
		registry.MustRegister(collectorAdapter{c})

		rw := httptest.NewRecorder()
		promhttp.HandlerFor(registry, promhttp.HandlerOpts{ErrorHandling: promhttp.ContinueOnError}).ServeHTTP(rw, &http.Request{})
		got := string(rw.Body.String())

		want, err := os.ReadFile(test.out)
		if err != nil {
			t.Fatalf("%d. error reading fixture file %s: %s", i, test.out, err)
		}

		if string(want) != got {
			t.Fatalf("%d.%q want:\n\n%s\n\ngot:\n\n%s", i, test.path, string(want), got)
		}
	}
}