// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Pool is no-op under race detector, so all these tests do not work.
// +build !race

package sync_test

import (
	"runtime"
	"runtime/debug"
	. "sync"
	"sync/atomic"
	"testing"
	"time"
)

func TestPool(t *testing.T) {
	// disable GC so we can control when it happens.
	defer debug.SetGCPercent(debug.SetGCPercent(-1))
	var p Pool
	if p.Get() != nil {
		t.Fatal("expected empty")
	}

	// Make sure that the goroutine doesn't migrate to another P
	// between Put and Get calls.
	Runtime_procPin()
	p.Put("a")
	p.Put("b")
	if g := p.Get(); g != "a" {
		t.Fatalf("got %#v; want a", g)
	}
	if g := p.Get(); g != "b" {
		t.Fatalf("got %#v; want b", g)
	}
	if g := p.Get(); g != nil {
		t.Fatalf("got %#v; want nil", g)
	}
	Runtime_procUnpin()

	p.Put("c")
	debug.SetGCPercent(100) // to allow following GC to actually run
	runtime.GC()
	if g := p.Get(); g != nil {
		t.Fatalf("got %#v; want nil after GC", g)
	}
}

func TestPoolNew(t *testing.T) {
	// disable GC so we can control when it happens.
	defer debug.SetGCPercent(debug.SetGCPercent(-1))

	i := 0
	p := Pool{
		New: func() interface{} {
			i++
			return i
		},
	}
	if v := p.Get(); v != 1 {
		t.Fatalf("got %v; want 1", v)
	}
	if v := p.Get(); v != 2 {
		t.Fatalf("got %v; want 2", v)
	}

	// Make sure that the goroutine doesn't migrate to another P
	// between Put and Get calls.
	Runtime_procPin()
	p.Put(42)
	if v := p.Get(); v != 42 {
		t.Fatalf("got %v; want 42", v)
	}
	Runtime_procUnpin()

	if v := p.Get(); v != 3 {
		t.Fatalf("got %v; want 3", v)
	}
}

// Test that Pool does not hold pointers to previously cached resources.
func TestPoolGC(t *testing.T) {
	testPool(t, true)
}

// Test that Pool releases resources on GC.
func TestPoolRelease(t *testing.T) {
	testPool(t, false)
}

func testPool(t *testing.T, drain bool) {
	var p Pool
	const N = 100
loop:
	for try := 0; try < 3; try++ {
		var fin, fin1 uint32
		for i := 0; i < N; i++ {
			v := new(string)
			runtime.SetFinalizer(v, func(vv *string) {
				atomic.AddUint32(&fin, 1)
			})
			p.Put(v)
		}
		if drain {
			for i := 0; i < N; i++ {
				p.Get()
			}
		}
		for i := 0; i < 5; i++ {
			runtime.GC()
			time.Sleep(time.Duration(i*100+10) * time.Millisecond)
			// 1 pointer can remain on stack or elsewhere
			if fin1 = atomic.LoadUint32(&fin); fin1 >= N-1 {
				continue loop
			}
		}
		t.Fatalf("only %v out of %v resources are finalized on try %v", fin1, N, try)
	}
}

func TestPoolStress(t *testing.T) {
	const P = 10
	N := int(1e6)
	if testing.Short() {
		N /= 100
	}
	var p Pool
	done := make(chan bool)
	for i := 0; i < P; i++ {
		go func() {
			var v interface{} = 0
			for j := 0; j < N; j++ {
				if v == nil {
					v = 0
				}
				p.Put(v)
				v = p.Get()
				if v != nil && v.(int) != 0 {
					t.Errorf("expect 0, got %v", v)
					break
				}
			}
			done <- true
		}()
	}
	for i := 0; i < P; i++ {
		<-done
	}
}

func TestPoolDequeue(t *testing.T) {
	const P = 10
	// In long mode, do enough pushes to wrap around the 21-bit
	// indexes.
	N := 1<<21 + 1000
	if testing.Short() {
		N = 1e3
	}
	d := NewPoolDequeue(16)
	have := make([]int32, N)
	var stop int32
	var wg WaitGroup

	// Start P-1 consumers.
	for i := 1; i < P; i++ {
		wg.Add(1)
		go func() {
			fail := 0
			for atomic.LoadInt32(&stop) == 0 {
				val, ok := d.PopTail()
				if ok {
					fail = 0
					atomic.AddInt32(&have[val.(int)], 1)
					if val.(int) == N-1 {
						atomic.StoreInt32(&stop, 1)
					}
				} else {
					// Speed up the test by
					// allowing the pusher to run.
					if fail++; fail%100 == 0 {
						runtime.Gosched()
					}
				}
			}
			wg.Done()
		}()
	}

	// Start 1 producer.
	nPopHead := 0
	wg.Add(1)
	go func() {
		for j := 0; j < N; j++ {
			for !d.PushHead(j) {
				// Allow a popper to run.
				runtime.Gosched()
			}
			if j%10 == 0 {
				val, ok := d.PopHead()
				if ok {
					nPopHead++
					atomic.AddInt32(&have[val.(int)], 1)
				}
			}
		}
		wg.Done()
	}()
	wg.Wait()

	// Check results.
	for i, count := range have {
		if count != 1 {
			t.Errorf("expected have[%d] = 1, got %d", i, count)
		}
	}
	if nPopHead == 0 {
		// In theory it's possible in a valid schedule for
		// popHead to never succeed, but in practice it almost
		// always succeeds, so this is unlikely to flake.
		t.Errorf("popHead never succeeded")
	}
}

func BenchmarkPool(b *testing.B) {
	var p Pool
	b.RunParallel(func(pb *testing.PB) {
		for pb.Next() {
			p.Put(1)
			p.Get()
		}
	})
}

func BenchmarkPoolOverflow(b *testing.B) {
	var p Pool
	b.RunParallel(func(pb *testing.PB) {
		for pb.Next() {
			for b := 0; b < 100; b++ {
				p.Put(1)
			}
			for b := 0; b < 100; b++ {
				p.Get()
			}
		}
	})
}