package metrics

import (
	"math/rand"
	"runtime"
	"testing"
	"time"
)

func TestExpDecaySample10(t *testing.T) {
	s := NewExpDecaySample(100, 0.99)
	for i := 0; i < 10; i++ {
		s.Update(int64(i))
	}
	if size := s.Size(); 10 != size {
		t.Errorf("s.Size(): 10 != %v\n", size)
	}
	if l := len(s.Values()); 10 != l {
		t.Errorf("len(s.Values()): 10 != %v\n", l)
	}
	for _, v := range s.Values() {
		if v > 10 || v < 0 {
			t.Errorf("out of range [0, 10): %v\n", v)
		}
	}
}

func TestExpDecaySample100(t *testing.T) {
	s := NewExpDecaySample(1000, 0.01)
	for i := 0; i < 100; i++ {
		s.Update(int64(i))
	}
	if size := s.Size(); 100 != size {
		t.Errorf("s.Size(): 100 != %v\n", size)
	}
	if l := len(s.Values()); 100 != l {
		t.Errorf("len(s.Values()): 100 != %v\n", l)
	}
	for _, v := range s.Values() {
		if v > 100 || v < 0 {
			t.Errorf("out of range [0, 100): %v\n", v)
		}
	}
}

func TestExpDecaySample1000(t *testing.T) {
	s := NewExpDecaySample(100, 0.99)
	for i := 0; i < 1000; i++ {
		s.Update(int64(i))
	}
	if size := s.Size(); 100 != size {
		t.Errorf("s.Size(): 100 != %v\n", size)
	}
	if l := len(s.Values()); 100 != l {
		t.Errorf("len(s.Values()): 100 != %v\n", l)
	}
	for _, v := range s.Values() {
		if v > 1000 || v < 0 {
			t.Errorf("out of range [0, 100): %v\n", v)
		}
	}
}

// This test makes sure that the sample's priority is not amplified by using
// nanosecond duration since start rather than second duration since start.
// The priority becomes +Inf quickly after starting if this is done,
// effectively freezing the set of samples until a rescale step happens.
func TestExpDecaySampleNanosecondRegression(t *testing.T) {
	s := NewExpDecaySample(100, 0.99)

	for i := 0; i < 100; i++ {
		s.Update(10)
	}

	time.Sleep(1 * time.Millisecond)

	for i := 0; i < 100; i++ {
		s.Update(20)
	}

	v := s.Values()
	avg := float64(0)

	for i := 0; i < len(v); i++ {
		avg += float64(v[i])
	}

	avg /= float64(len(v))
	if avg > 16 || avg < 14 {
		t.Errorf("out of range [14, 16]: %v\n", avg)
	}
}

func TestUniformSample(t *testing.T) {
	s := NewUniformSample(100)
	for i := 0; i < 1000; i++ {
		s.Update(int64(i))
	}
	if size := s.Size(); 100 != size {
		t.Errorf("s.Size(): 100 != %v\n", size)
	}
	if l := len(s.Values()); 100 != l {
		t.Errorf("len(s.Values()): 100 != %v\n", l)
	}
	for _, v := range s.Values() {
		if v > 1000 || v < 0 {
			t.Errorf("out of range [0, 100): %v\n", v)
		}
	}
}

func TestUniformSampleIncludesTail(t *testing.T) {
	s := NewUniformSample(100)
	max := 100

	for i := 0; i < max; i++ {
		s.Update(int64(i))
	}

	v := s.Values()
	sum := 0
	exp := (max - 1) * max / 2

	for i := 0; i < len(v); i++ {
		sum += int(v[i])
	}

	if exp != sum {
		t.Errorf("sum: %v != %v\n", exp, sum)
	}
}

func benchmarkSample(b *testing.B, s Sample) {
	var m runtime.MemStats
	var p [2]uint64

	runtime.ReadMemStats(&m)
	p[0] = m.PauseTotalNs

	for i := 0; i < b.N; i++ {
		s.Update(rand.Int63())
	}

	runtime.GC()

	runtime.ReadMemStats(&m)
	p[1] = m.PauseTotalNs

	b.Logf("GC cost: %d ns/op", int(p[1]-p[0])/b.N)
}

func BenchmarkExpDecaySample257(b *testing.B) {
	benchmarkSample(b, NewExpDecaySample(257, 0.015))
}

func BenchmarkExpDecaySample514(b *testing.B) {
	benchmarkSample(b, NewExpDecaySample(514, 0.015))
}

func BenchmarkExpDecaySample1028(b *testing.B) {
	benchmarkSample(b, NewExpDecaySample(1028, 0.015))
}

func BenchmarkUniformSample257(b *testing.B) {
	benchmarkSample(b, NewUniformSample(257))
}

func BenchmarkUniformSample514(b *testing.B) {
	benchmarkSample(b, NewUniformSample(514))
}

func BenchmarkUniformSample1028(b *testing.B) {
	benchmarkSample(b, NewUniformSample(1028))
}