package fxtime_test

import (
	"testing"
	"time"

	"fuchsia.googlesource.com/infra/infra/fxtime"
)

func TestFixedClock(t *testing.T) {
	t.Run("Now should return a fixed time", func(t *testing.T) {
		now := time.Date(1, 2, 3, 4, 5, 6, 7, time.UTC)
		clock := fxtime.NewFixedClock(now)
		expectTime(t, now, clock.Now())
		expectTime(t, now, clock.Now())
	})
}

func TestStopwatch(t *testing.T) {
	now := time.Date(0, 0, 0, 0, 0, 0, 0, time.UTC)

	t.Run("Restart should return the current time", func(t *testing.T) {
		clock := &TestClock{
			nowTimes: []time.Time{now, now.Add(time.Hour)},
		}
		stopwatch := fxtime.NewStopwatch(clock)
		expectTime(t, clock.nowTimes[1], stopwatch.Restart())
	})

	t.Run("Elapsed should return the duration since Restart() was last called",
		func(t *testing.T) {
			clock := &TestClock{
				nowTimes: []time.Time{
					now,
					now.Add(time.Hour),
					now.Add(24 * time.Hour),
					now.Add(72 * time.Hour),
				},
			}
			stopwatch := fxtime.NewStopwatch(clock)
			expectTime(t, clock.nowTimes[1], stopwatch.Restart())
			duration := clock.nowTimes[2].Sub(clock.nowTimes[1])
			expectDuration(t, duration, stopwatch.Elapsed())
			duration = clock.nowTimes[3].Sub(clock.nowTimes[1])
			expectDuration(t, duration, stopwatch.Elapsed())
		})
}

func expectTime(t *testing.T, expected, actual time.Time) {
	if expected != actual {
		t.Fatalf("expected time %v but got %v", expected, actual)
	}
}

func expectDuration(t *testing.T, expected, actual time.Duration) {
	if expected != actual {
		t.Fatalf("expected duration %v but got %v", expected, actual)
	}
}

// TestClock is used to test Stopwatch.
type TestClock struct {
	// List of Times to return when Now is called.
	nowTimes []time.Time
	// Current index in nowTimes
	i uint
}

// Returns the current time. This will panic if called more than len(nowTimes) times.
func (c *TestClock) Now() time.Time {
	t := c.nowTimes[c.i]
	c.i += 1
	return t
}