// Copyright 2019, OpenTelemetry Authors
//
// 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 gauge

import (
	"context"
	"math/rand"
	"testing"

	"github.com/stretchr/testify/require"

	"go.opentelemetry.io/otel/api/core"
	export "go.opentelemetry.io/otel/sdk/export/metric"
	"go.opentelemetry.io/otel/sdk/export/metric/aggregator"
	"go.opentelemetry.io/otel/sdk/metric/aggregator/test"
)

const count = 100

var _ export.Aggregator = &Aggregator{}

func TestGaugeNonMonotonic(t *testing.T) {
	ctx := context.Background()

	test.RunProfiles(t, func(t *testing.T, profile test.Profile) {
		agg := New()

		record := test.NewAggregatorTest(export.GaugeKind, profile.NumberKind, false)

		var last core.Number
		for i := 0; i < count; i++ {
			x := profile.Random(rand.Intn(1)*2 - 1)
			last = x
			test.CheckedUpdate(t, agg, x, record)
		}

		agg.Checkpoint(ctx, record)

		lv, _, err := agg.LastValue()
		require.Equal(t, last, lv, "Same last value - non-monotonic")
		require.Nil(t, err)
	})
}

func TestGaugeMonotonic(t *testing.T) {
	ctx := context.Background()

	test.RunProfiles(t, func(t *testing.T, profile test.Profile) {
		agg := New()

		record := test.NewAggregatorTest(export.GaugeKind, profile.NumberKind, true)

		small := profile.Random(+1)
		last := small
		for i := 0; i < count; i++ {
			x := profile.Random(+1)
			last.AddNumber(profile.NumberKind, x)
			test.CheckedUpdate(t, agg, last, record)
		}

		agg.Checkpoint(ctx, record)

		lv, _, err := agg.LastValue()
		require.Equal(t, last, lv, "Same last value - monotonic")
		require.Nil(t, err)
	})
}

func TestGaugeMonotonicDescending(t *testing.T) {
	ctx := context.Background()

	test.RunProfiles(t, func(t *testing.T, profile test.Profile) {
		agg := New()

		record := test.NewAggregatorTest(export.GaugeKind, profile.NumberKind, true)

		first := profile.Random(+1)
		test.CheckedUpdate(t, agg, first, record)

		for i := 0; i < count; i++ {
			x := profile.Random(-1)

			err := agg.Update(ctx, x, record)
			if err != aggregator.ErrNonMonotoneInput {
				t.Error("Expected ErrNonMonotoneInput", err)
			}
		}

		agg.Checkpoint(ctx, record)

		lv, _, err := agg.LastValue()
		require.Equal(t, first, lv, "Same last value - monotonic")
		require.Nil(t, err)
	})
}

func TestGaugeNormalMerge(t *testing.T) {
	ctx := context.Background()

	test.RunProfiles(t, func(t *testing.T, profile test.Profile) {
		agg1 := New()
		agg2 := New()

		descriptor := test.NewAggregatorTest(export.GaugeKind, profile.NumberKind, false)

		first1 := profile.Random(+1)
		first2 := profile.Random(+1)
		first1.AddNumber(profile.NumberKind, first2)

		test.CheckedUpdate(t, agg1, first1, descriptor)
		test.CheckedUpdate(t, agg2, first2, descriptor)

		agg1.Checkpoint(ctx, descriptor)
		agg2.Checkpoint(ctx, descriptor)

		_, t1, err := agg1.LastValue()
		require.Nil(t, err)
		_, t2, err := agg2.LastValue()
		require.Nil(t, err)
		require.True(t, t1.Before(t2))

		test.CheckedMerge(t, agg1, agg2, descriptor)

		lv, ts, err := agg1.LastValue()
		require.Nil(t, err)
		require.Equal(t, t2, ts, "Merged timestamp - non-monotonic")
		require.Equal(t, first2, lv, "Merged value - non-monotonic")
	})
}

func TestGaugeMonotonicMerge(t *testing.T) {
	ctx := context.Background()

	test.RunProfiles(t, func(t *testing.T, profile test.Profile) {
		agg1 := New()
		agg2 := New()

		descriptor := test.NewAggregatorTest(export.GaugeKind, profile.NumberKind, true)

		first1 := profile.Random(+1)
		test.CheckedUpdate(t, agg1, first1, descriptor)

		first2 := profile.Random(+1)
		first2.AddNumber(profile.NumberKind, first1)
		test.CheckedUpdate(t, agg2, first2, descriptor)

		agg1.Checkpoint(ctx, descriptor)
		agg2.Checkpoint(ctx, descriptor)

		test.CheckedMerge(t, agg1, agg2, descriptor)

		_, ts2, err := agg1.LastValue()
		require.Nil(t, err)

		lv, ts1, err := agg1.LastValue()
		require.Nil(t, err)
		require.Equal(t, first2, lv, "Merged value - monotonic")
		require.Equal(t, ts2, ts1, "Merged timestamp - monotonic")
	})
}

func TestGaugeNotSet(t *testing.T) {
	descriptor := test.NewAggregatorTest(export.GaugeKind, core.Int64NumberKind, true)

	g := New()
	g.Checkpoint(context.Background(), descriptor)

	value, timestamp, err := g.LastValue()
	require.Equal(t, aggregator.ErrNoLastValue, err)
	require.True(t, timestamp.IsZero())
	require.Equal(t, core.Number(0), value)
}