)

// local lock servers
var globalLockServer *localLocker

// RWLocker - locker interface to introduce GetRLock, RUnlock.
type RWLocker interface {
	GetLock(ctx context.Context, timeout *dynamicTimeout) (lkCtx LockContext, timedOutErr error)
	Unlock(lkCtx LockContext)
	GetRLock(ctx context.Context, timeout *dynamicTimeout) (lkCtx LockContext, timedOutErr error)
	RUnlock(lkCtx LockContext)
}

func (lm *LRWMutex) RLock() {
	const isWriteLock = false
	lm.lockLoop(context.Background(), lm.id, lm.source, 1<<63-1, isWriteLock)
}

// GetRLock tries to get a read lock on lm before the timeout occurs.
func (lm *LRWMutex) GetRLock(ctx context.Context, id string, source string, timeout time.Duration) (locked bool) {
	const isWriteLock = false
	return lm.lockLoop(ctx, id, source, timeout, isWriteLock)
}

func testSimpleWriteLock(t *testing.T, duration time.Duration) (locked bool) {
	ctx := context.Background()
	lrwm := NewLRWMutex()

	if !lrwm.GetRLock(ctx, "", "object1", time.Second) {
		panic("Failed to acquire read lock")
	}
	// fmt.Println("1st read lock acquired, waiting...")

	if !lrwm.GetRLock(ctx, "", "object1", time.Second) {
		panic("Failed to acquire read lock")
	}
	// fmt.Println("2nd read lock acquired, waiting...")

	ctx1, cancel1 := context.WithCancel(context.Background())
	if !drwm1.GetRLock(ctx1, cancel1, id, source, Options{Timeout: time.Second}) {
		panic("Failed to acquire read lock")
	}
	// fmt.Println("1st read lock acquired, waiting...")

	drwm2 := NewDRWMutex(ds, "simplelock")
	ctx2, cancel2 := context.WithCancel(context.Background())
	if !drwm2.GetRLock(ctx2, cancel2, id, source, Options{Timeout: time.Second}) {

	if opts.CheckPrecondFn != nil {
		// Lock the object before reading.
		lk := er.NewNSLock(bucket, object)
		lkctx, err := lk.GetRLock(ctx, globalOperationTimeout)
		if err != nil {
			return nil, err
		}
		rctx := lkctx.Context()
		obj, err := er.getObjectInfo(rctx, bucket, object, opts)
		lk.RUnlock(lkctx)

		Timeout: drwMutexInfinite,
	})
}

// GetRLock tries to get a read lock on dm before the timeout elapses.
//
// If one or more read locks are already in use, it will grant another lock.
// Otherwise the calling go routine blocks until either the mutex becomes
// available and return success or more time has passed than the timeout
// value and return false.

	nsUnlocker := func() {}
	defer func() {
		if unlockOnDefer {
			nsUnlocker()
		}
	}()

	// Acquire lock
	if !opts.NoLock {
		lock := er.NewNSLock(bucket, object)
		lkctx, err := lock.GetRLock(ctx, globalOperationTimeout)
		if err != nil {
			return nil, err
		}
		ctx = lkctx.Context()

		// Release lock when the metadata is verified, and reader
		// is ready to be read.
		//

	nsUnlocker := func() {}
	defer func() {
		if unlockOnDefer {
			nsUnlocker()
		}
	}()

	// Acquire lock
	if !opts.NoLock {
		lock := z.NewNSLock(bucket, object)
		lkctx, err := lock.GetRLock(ctx, globalOperationTimeout)
		if err != nil {
			return nil, err
		}
		ctx = lkctx.Context()
		nsUnlocker = func() { lock.RUnlock(lkctx) }
		unlockOnDefer = true
	}

		return
	}

	// Take read lock on object, here so subsequent lower-level
	// calls do not need to.
	lock := objectAPI.NewNSLock(bucket, object)
	lkctx, err := lock.GetRLock(ctx, globalOperationTimeout)
	if err != nil {
		writeErrorResponse(ctx, w, toAPIError(ctx, err), r.URL)
		return
	}
	ctx = lkctx.Context()
	defer lock.RUnlock(lkctx)