package dataext

import (
	"context"
	"sync"
	"sync/atomic"
	"testing"
	"time"
)

func TestCASMutex_LockUnlock(t *testing.T) {
	m := NewCASMutex()
	m.Lock()
	m.Unlock()
}

func TestCASMutex_TryLock(t *testing.T) {
	m := NewCASMutex()
	if !m.TryLock() {
		t.Fatal("TryLock should succeed on fresh mutex")
	}
	if m.TryLock() {
		t.Fatal("TryLock should fail when already locked")
	}
	m.Unlock()
	if !m.TryLock() {
		t.Fatal("TryLock should succeed after Unlock")
	}
	m.Unlock()
}

func TestCASMutex_TryLockWithTimeout(t *testing.T) {
	m := NewCASMutex()
	m.Lock()
	start := time.Now()
	if m.TryLockWithTimeout(20 * time.Millisecond) {
		t.Fatal("TryLockWithTimeout should fail when locked")
	}
	if time.Since(start) < 15*time.Millisecond {
		t.Fatal("TryLockWithTimeout returned too quickly")
	}
	m.Unlock()

	if !m.TryLockWithTimeout(50 * time.Millisecond) {
		t.Fatal("TryLockWithTimeout should succeed when unlocked")
	}
	m.Unlock()
}

func TestCASMutex_TryLockWithContext_Cancel(t *testing.T) {
	m := NewCASMutex()
	m.Lock()
	defer m.Unlock()

	ctx, cancel := context.WithCancel(context.Background())
	go func() {
		time.Sleep(10 * time.Millisecond)
		cancel()
	}()
	if m.TryLockWithContext(ctx) {
		t.Fatal("expected lock to fail after cancel")
	}
}

func TestCASMutex_RLockMultiple(t *testing.T) {
	m := NewCASMutex()
	if !m.RTryLock() {
		t.Fatal("RTryLock should succeed")
	}
	if !m.RTryLock() {
		t.Fatal("Second RTryLock should succeed")
	}
	if m.TryLock() {
		t.Fatal("Write TryLock should fail with read locks held")
	}
	m.RUnlock()
	m.RUnlock()
	if !m.TryLock() {
		t.Fatal("Write TryLock should succeed after read unlocks")
	}
	m.Unlock()
}

func TestCASMutex_RLocker(t *testing.T) {
	m := NewCASMutex()
	rl := m.RLocker()
	rl.Lock()
	rl.Unlock()
}

func TestCASMutex_Concurrent(t *testing.T) {
	m := NewCASMutex()
	var counter int64
	const n = 50
	var wg sync.WaitGroup
	wg.Add(n)
	for i := 0; i < n; i++ {
		go func() {
			defer wg.Done()
			m.Lock()
			atomic.AddInt64(&counter, 1)
			m.Unlock()
		}()
	}
	wg.Wait()
	if atomic.LoadInt64(&counter) != n {
		t.Fatalf("counter=%d want %d", counter, n)
	}
}

func TestCASMutex_RTryLockWithTimeout(t *testing.T) {
	m := NewCASMutex()
	m.Lock()
	if m.RTryLockWithTimeout(20 * time.Millisecond) {
		t.Fatal("RTryLockWithTimeout should fail when write-locked")
	}
	m.Unlock()
	if !m.RTryLockWithTimeout(20 * time.Millisecond) {
		t.Fatal("RTryLockWithTimeout should succeed when free")
	}
	m.RUnlock()
}