package breaker

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

	"github.com/bilibili/kratos/pkg/stat/metric"
	xtime "github.com/bilibili/kratos/pkg/time"

	"github.com/stretchr/testify/assert"
)

func getSRE() Breaker {
	return NewGroup(&Config{
		Window:  xtime.Duration(1 * time.Second),
		Bucket:  10,
		Request: 100,
		K:       2,
	}).Get("")
}

func getSREBreaker() *sreBreaker {
	counterOpts := metric.RollingCounterOpts{
		Size:           10,
		BucketDuration: time.Millisecond * 100,
	}
	stat := metric.NewRollingCounter(counterOpts)
	return &sreBreaker{
		stat: stat,

		request: 100,
		k:       2,
		state:   StateClosed,
	}
}

func markSuccessWithDuration(b Breaker, count int, sleep time.Duration) {
	for i := 0; i < count; i++ {
		b.MarkSuccess()
		time.Sleep(sleep)
	}
}

func markFailedWithDuration(b Breaker, count int, sleep time.Duration) {
	for i := 0; i < count; i++ {
		b.MarkFailed()
		time.Sleep(sleep)
	}
}

func testSREClose(t *testing.T, b Breaker) {
	markSuccess(b, 80)
	assert.Equal(t, b.Allow(), nil)
	markSuccess(b, 120)
	assert.Equal(t, b.Allow(), nil)
}

func testSREOpen(t *testing.T, b Breaker) {
	markSuccess(b, 100)
	assert.Equal(t, b.Allow(), nil)
	markFailed(b, 10000000)
	assert.NotEqual(t, b.Allow(), nil)
}

func testSREHalfOpen(t *testing.T, b Breaker) {
	// failback
	assert.Equal(t, b.Allow(), nil)
	t.Run("allow single failed", func(t *testing.T) {
		markFailed(b, 10000000)
		assert.NotEqual(t, b.Allow(), nil)
	})
	time.Sleep(2 * time.Second)
	t.Run("allow single succeed", func(t *testing.T) {
		assert.Equal(t, b.Allow(), nil)
		markSuccess(b, 10000000)
		assert.Equal(t, b.Allow(), nil)
	})
}

func TestSRE(t *testing.T) {
	b := getSRE()
	testSREClose(t, b)

	b = getSRE()
	testSREOpen(t, b)

	b = getSRE()
	testSREHalfOpen(t, b)
}

func TestSRESelfProtection(t *testing.T) {
	t.Run("total request < 100", func(t *testing.T) {
		b := getSRE()
		markFailed(b, 99)
		assert.Equal(t, b.Allow(), nil)
	})
	t.Run("total request > 100, total < 2 * success", func(t *testing.T) {
		b := getSRE()
		size := rand.Intn(10000000)
		succ := int(math.Ceil(float64(size))) + 1
		markSuccess(b, succ)
		markFailed(b, size-succ)
		assert.Equal(t, b.Allow(), nil)
	})
}

func TestSRESummary(t *testing.T) {
	var (
		b           *sreBreaker
		succ, total int64
	)

	sleep := 50 * time.Millisecond
	t.Run("succ == total", func(t *testing.T) {
		b = getSREBreaker()
		markSuccessWithDuration(b, 10, sleep)
		succ, total = b.summary()
		assert.Equal(t, succ, int64(10))
		assert.Equal(t, total, int64(10))
	})

	t.Run("fail == total", func(t *testing.T) {
		b = getSREBreaker()
		markFailedWithDuration(b, 10, sleep)
		succ, total = b.summary()
		assert.Equal(t, succ, int64(0))
		assert.Equal(t, total, int64(10))
	})

	t.Run("succ = 1/2 * total, fail = 1/2 * total", func(t *testing.T) {
		b = getSREBreaker()
		markFailedWithDuration(b, 5, sleep)
		markSuccessWithDuration(b, 5, sleep)
		succ, total = b.summary()
		assert.Equal(t, succ, int64(5))
		assert.Equal(t, total, int64(10))
	})

	t.Run("auto reset rolling counter", func(t *testing.T) {
		time.Sleep(time.Second)
		succ, total = b.summary()
		assert.Equal(t, succ, int64(0))
		assert.Equal(t, total, int64(0))
	})
}

func TestTrueOnProba(t *testing.T) {
	const proba = math.Pi / 10
	const total = 100000
	const epsilon = 0.05
	var count int
	for i := 0; i < total; i++ {
		if trueOnProba(proba) {
			count++
		}
	}

	ratio := float64(count) / float64(total)
	assert.InEpsilon(t, proba, ratio, epsilon)
}

func BenchmarkSreBreakerAllow(b *testing.B) {
	breaker := getSRE()
	b.ResetTimer()
	for i := 0; i <= b.N; i++ {
		breaker.Allow()
		if i%2 == 0 {
			breaker.MarkSuccess()
		} else {
			breaker.MarkFailed()
		}
	}
}