/*
Copyright 2014 The Kubernetes Authors All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package wait

import (
	"errors"
	"fmt"
	"sync/atomic"
	"testing"
	"time"

	"k8s.io/kubernetes/pkg/util"
)

func TestExponentialBackoff(t *testing.T) {
	opts := Backoff{Factor: 1.0, Steps: 3}

	// waits up to steps
	i := 0
	err := ExponentialBackoff(opts, func() (bool, error) {
		i++
		return false, nil
	})
	if err != ErrWaitTimeout || i != opts.Steps {
		t.Errorf("unexpected error: %v", err)
	}

	// returns immediately
	i = 0
	err = ExponentialBackoff(opts, func() (bool, error) {
		i++
		return true, nil
	})
	if err != nil || i != 1 {
		t.Errorf("unexpected error: %v", err)
	}

	// returns immediately on error
	testErr := fmt.Errorf("some other error")
	err = ExponentialBackoff(opts, func() (bool, error) {
		return false, testErr
	})
	if err != testErr {
		t.Errorf("unexpected error: %v", err)
	}

	// invoked multiple times
	i = 1
	err = ExponentialBackoff(opts, func() (bool, error) {
		if i < opts.Steps {
			i++
			return false, nil
		}
		return true, nil
	})
	if err != nil || i != opts.Steps {
		t.Errorf("unexpected error: %v", err)
	}
}

func TestPoller(t *testing.T) {
	done := make(chan struct{})
	defer close(done)
	w := poller(time.Millisecond, 2*time.Millisecond)
	ch := w(done)
	count := 0
DRAIN:
	for {
		select {
		case _, open := <-ch:
			if !open {
				break DRAIN
			}
			count++
		case <-time.After(util.ForeverTestTimeout):
			t.Errorf("unexpected timeout after poll")
		}
	}
	if count > 3 {
		t.Errorf("expected up to three values, got %d", count)
	}
}

func fakeTicker(max int, used *int32) WaitFunc {
	return func(done <-chan struct{}) <-chan struct{} {
		ch := make(chan struct{})
		go func() {
			defer close(ch)
			for i := 0; i < max; i++ {
				select {
				case ch <- struct{}{}:
				case <-done:
					return
				}
				if used != nil {
					atomic.AddInt32(used, 1)
				}
			}
		}()
		return ch
	}
}

type fakePoller struct {
	max  int
	used int32 // accessed with atomics
}

func (fp *fakePoller) GetWaitFunc(interval, timeout time.Duration) WaitFunc {
	return fakeTicker(fp.max, &fp.used)
}

func TestPoll(t *testing.T) {
	invocations := 0
	f := ConditionFunc(func() (bool, error) {
		invocations++
		return true, nil
	})
	fp := fakePoller{max: 1}
	if err := pollInternal(fp.GetWaitFunc(time.Microsecond, time.Microsecond), f); err != nil {
		t.Fatalf("unexpected error %v", err)
	}
	if invocations != 1 {
		t.Errorf("Expected exactly one invocation, got %d", invocations)
	}
	used := atomic.LoadInt32(&fp.used)
	if used != 1 {
		t.Errorf("Expected exactly one tick, got %d", used)
	}

	expectedError := errors.New("Expected error")
	f = ConditionFunc(func() (bool, error) {
		return false, expectedError
	})
	fp = fakePoller{max: 1}
	if err := pollInternal(fp.GetWaitFunc(time.Microsecond, time.Microsecond), f); err == nil || err != expectedError {
		t.Fatalf("Expected error %v, got none %v", expectedError, err)
	}
	if invocations != 1 {
		t.Errorf("Expected exactly one invocation, got %d", invocations)
	}
	used = atomic.LoadInt32(&fp.used)
	if used != 1 {
		t.Errorf("Expected exactly one tick, got %d", used)
	}
}

func TestPollImmediate(t *testing.T) {
	invocations := 0
	f := ConditionFunc(func() (bool, error) {
		invocations++
		return true, nil
	})
	fp := fakePoller{max: 0}
	if err := pollImmediateInternal(fp.GetWaitFunc(time.Microsecond, time.Microsecond), f); err != nil {
		t.Fatalf("unexpected error %v", err)
	}
	if invocations != 1 {
		t.Errorf("Expected exactly one invocation, got %d", invocations)
	}
	used := atomic.LoadInt32(&fp.used)
	if used != 0 {
		t.Errorf("Expected exactly zero ticks, got %d", used)
	}

	expectedError := errors.New("Expected error")
	f = ConditionFunc(func() (bool, error) {
		return false, expectedError
	})
	fp = fakePoller{max: 0}
	if err := pollImmediateInternal(fp.GetWaitFunc(time.Microsecond, time.Microsecond), f); err == nil || err != expectedError {
		t.Fatalf("Expected error %v, got none %v", expectedError, err)
	}
	if invocations != 1 {
		t.Errorf("Expected exactly one invocation, got %d", invocations)
	}
	used = atomic.LoadInt32(&fp.used)
	if used != 0 {
		t.Errorf("Expected exactly zero ticks, got %d", used)
	}
}

func TestPollForever(t *testing.T) {
	ch := make(chan struct{})
	done := make(chan struct{}, 1)
	complete := make(chan struct{})
	go func() {
		f := ConditionFunc(func() (bool, error) {
			ch <- struct{}{}
			select {
			case <-done:
				return true, nil
			default:
			}
			return false, nil
		})

		if err := PollInfinite(time.Microsecond, f); err != nil {
			t.Fatalf("unexpected error %v", err)
		}

		close(ch)
		complete <- struct{}{}
	}()

	// ensure the condition is opened
	<-ch

	// ensure channel sends events
	for i := 0; i < 10; i++ {
		select {
		case _, open := <-ch:
			if !open {
				t.Fatalf("did not expect channel to be closed")
			}
		case <-time.After(util.ForeverTestTimeout):
			t.Fatalf("channel did not return at least once within the poll interval")
		}
	}

	// at most two poll notifications should be sent once we return from the condition
	done <- struct{}{}
	go func() {
		for i := 0; i < 2; i++ {
			_, open := <-ch
			if open {
				<-complete
				return
			}
		}
		t.Fatalf("expected closed channel after two iterations")
	}()
	<-complete
}

func TestWaitFor(t *testing.T) {
	var invocations int
	testCases := map[string]struct {
		F       ConditionFunc
		Ticks   int
		Invoked int
		Err     bool
	}{
		"invoked once": {
			ConditionFunc(func() (bool, error) {
				invocations++
				return true, nil
			}),
			2,
			1,
			false,
		},
		"invoked and returns a timeout": {
			ConditionFunc(func() (bool, error) {
				invocations++
				return false, nil
			}),
			2,
			3, // the contract of WaitFor() says the func is called once more at the end of the wait
			true,
		},
		"returns immediately on error": {
			ConditionFunc(func() (bool, error) {
				invocations++
				return false, errors.New("test")
			}),
			2,
			1,
			true,
		},
	}
	for k, c := range testCases {
		invocations = 0
		ticker := fakeTicker(c.Ticks, nil)
		err := func() error {
			done := make(chan struct{})
			defer close(done)
			return WaitFor(ticker, c.F, done)
		}()
		switch {
		case c.Err && err == nil:
			t.Errorf("%s: Expected error, got nil", k)
			continue
		case !c.Err && err != nil:
			t.Errorf("%s: Expected no error, got: %#v", k, err)
			continue
		}
		if invocations != c.Invoked {
			t.Errorf("%s: Expected %d invocations, got %d", k, c.Invoked, invocations)
		}
	}
}
