package prometheus

import (
	"runtime"
	"testing"
	"time"

	dto "github.com/prometheus/client_model/go"
)

func TestGoCollector(t *testing.T) {
	var (
		c      = NewGoCollector()
		ch     = make(chan Metric)
		waitc  = make(chan struct{})
		closec = make(chan struct{})
		old    = -1
	)
	defer close(closec)

	go func() {
		c.Collect(ch)
		go func(c <-chan struct{}) {
			<-c
		}(closec)
		<-waitc
		c.Collect(ch)
	}()

	for {
		select {
		case m := <-ch:
			// m can be Gauge or Counter,
			// currently just test the go_goroutines Gauge
			// and ignore others.
			if m.Desc().fqName != "go_goroutines" {
				continue
			}
			pb := &dto.Metric{}
			m.Write(pb)
			if pb.GetGauge() == nil {
				continue
			}

			if old == -1 {
				old = int(pb.GetGauge().GetValue())
				close(waitc)
				continue
			}

			if diff := int(pb.GetGauge().GetValue()) - old; diff != 1 {
				// TODO: This is flaky in highly concurrent situations.
				t.Errorf("want 1 new goroutine, got %d", diff)
			}

			// GoCollector performs three sends per call.
			// On line 27 we need to receive three more sends
			// to shut down cleanly.
			<-ch
			<-ch
			<-ch
			return
		case <-time.After(1 * time.Second):
			t.Fatalf("expected collect timed out")
		}
	}
}

func TestGCCollector(t *testing.T) {
	var (
		c        = NewGoCollector()
		ch       = make(chan Metric)
		waitc    = make(chan struct{})
		closec   = make(chan struct{})
		oldGC    uint64
		oldPause float64
	)
	defer close(closec)

	go func() {
		c.Collect(ch)
		// force GC
		runtime.GC()
		<-waitc
		c.Collect(ch)
	}()

	first := true
	for {
		select {
		case metric := <-ch:
			pb := &dto.Metric{}
			metric.Write(pb)
			if pb.GetSummary() == nil {
				continue
			}
			if len(pb.GetSummary().Quantile) != 5 {
				t.Errorf("expected 4 buckets, got %d", len(pb.GetSummary().Quantile))
			}
			for idx, want := range []float64{0.0, 0.25, 0.5, 0.75, 1.0} {
				if *pb.GetSummary().Quantile[idx].Quantile != want {
					t.Errorf("bucket #%d is off, got %f, want %f", idx, *pb.GetSummary().Quantile[idx].Quantile, want)
				}
			}
			if first {
				first = false
				oldGC = *pb.GetSummary().SampleCount
				oldPause = *pb.GetSummary().SampleSum
				close(waitc)
				continue
			}
			if diff := *pb.GetSummary().SampleCount - oldGC; diff != 1 {
				t.Errorf("want 1 new garbage collection run, got %d", diff)
			}
			if diff := *pb.GetSummary().SampleSum - oldPause; diff <= 0 {
				t.Errorf("want moar pause, got %f", diff)
			}
			return
		case <-time.After(1 * time.Second):
			t.Fatalf("expected collect timed out")
		}
	}
}