// Copyright The 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 metric // import "go.opentelemetry.io/otel/sdk/metric/reader"

import (
	"context"
	"sync"
	"testing"
	"time"

	"github.com/go-logr/logr/testr"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/suite"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/sdk/instrumentation"
	"go.opentelemetry.io/otel/sdk/metric/metricdata"
	"go.opentelemetry.io/otel/sdk/resource"
)

type readerTestSuite struct {
	suite.Suite

	Factory func() Reader
	Reader  Reader
}

func (ts *readerTestSuite) SetupSuite() {
	otel.SetLogger(testr.New(ts.T()))
}

func (ts *readerTestSuite) SetupTest() {
	ts.Reader = ts.Factory()
}

func (ts *readerTestSuite) TearDownTest() {
	// Ensure Reader is allowed attempt to clean up.
	_ = ts.Reader.Shutdown(context.Background())
}

func (ts *readerTestSuite) TestErrorForNotRegistered() {
	err := ts.Reader.Collect(context.Background(), &metricdata.ResourceMetrics{})
	ts.ErrorIs(err, ErrReaderNotRegistered)
}

func (ts *readerTestSuite) TestSDKProducer() {
	ts.Reader.register(testSDKProducer{})
	m := metricdata.ResourceMetrics{}
	err := ts.Reader.Collect(context.Background(), &m)
	ts.NoError(err)
	ts.Equal(testResourceMetricsA, m)
}

func (ts *readerTestSuite) TestExternalProducer() {
	ts.Reader.register(testSDKProducer{})
	ts.Reader.RegisterProducer(testExternalProducer{})
	m := metricdata.ResourceMetrics{}
	err := ts.Reader.Collect(context.Background(), &m)
	ts.NoError(err)
	ts.Equal(testResourceMetricsAB, m)
}

func (ts *readerTestSuite) TestCollectAfterShutdown() {
	ctx := context.Background()
	ts.Reader.register(testSDKProducer{})
	ts.Reader.RegisterProducer(testExternalProducer{})
	ts.Require().NoError(ts.Reader.Shutdown(ctx))

	m := metricdata.ResourceMetrics{}
	err := ts.Reader.Collect(ctx, &m)
	ts.ErrorIs(err, ErrReaderShutdown)
	ts.Equal(metricdata.ResourceMetrics{}, m)
}

func (ts *readerTestSuite) TestShutdownTwice() {
	ctx := context.Background()
	ts.Reader.register(testSDKProducer{})
	ts.Reader.RegisterProducer(testExternalProducer{})
	ts.Require().NoError(ts.Reader.Shutdown(ctx))
	ts.ErrorIs(ts.Reader.Shutdown(ctx), ErrReaderShutdown)
}

func (ts *readerTestSuite) TestMultipleForceFlush() {
	ctx := context.Background()
	ts.Reader.register(testSDKProducer{})
	ts.Reader.RegisterProducer(testExternalProducer{})
	ts.Require().NoError(ts.Reader.ForceFlush(ctx))
	ts.NoError(ts.Reader.ForceFlush(ctx))
}

func (ts *readerTestSuite) TestMultipleRegister() {
	p0 := testSDKProducer{
		produceFunc: func(ctx context.Context) (metricdata.ResourceMetrics, error) {
			// Differentiate this producer from the second by returning an
			// error.
			return testResourceMetricsA, assert.AnError
		},
	}
	p1 := testSDKProducer{}

	ts.Reader.register(p0)
	// This should be ignored.
	ts.Reader.register(p1)

	err := ts.Reader.Collect(context.Background(), &metricdata.ResourceMetrics{})
	ts.Equal(assert.AnError, err)
}

func (ts *readerTestSuite) TestExternalProducerPartialSuccess() {
	ts.Reader.register(testSDKProducer{})
	ts.Reader.RegisterProducer(
		testExternalProducer{
			produceFunc: func(ctx context.Context) ([]metricdata.ScopeMetrics, error) {
				return []metricdata.ScopeMetrics{}, assert.AnError
			},
		},
	)
	ts.Reader.RegisterProducer(
		testExternalProducer{
			produceFunc: func(ctx context.Context) ([]metricdata.ScopeMetrics, error) {
				return []metricdata.ScopeMetrics{testScopeMetricsB}, nil
			},
		},
	)

	m := metricdata.ResourceMetrics{}
	err := ts.Reader.Collect(context.Background(), &m)
	ts.Equal(assert.AnError, err)
	ts.Equal(testResourceMetricsAB, m)
}

func (ts *readerTestSuite) TestSDKFailureBlocksExternalProducer() {
	ts.Reader.register(testSDKProducer{
		produceFunc: func(ctx context.Context) (metricdata.ResourceMetrics, error) {
			return metricdata.ResourceMetrics{}, assert.AnError
		}})
	ts.Reader.RegisterProducer(testExternalProducer{})

	m := metricdata.ResourceMetrics{}
	err := ts.Reader.Collect(context.Background(), &m)
	ts.Equal(assert.AnError, err)
	ts.Equal(metricdata.ResourceMetrics{}, m)
}

func (ts *readerTestSuite) TestMethodConcurrency() {
	// Requires the race-detector (a default test option for the project).

	// All reader methods should be concurrent-safe.
	ts.Reader.register(testSDKProducer{})
	ts.Reader.RegisterProducer(testExternalProducer{})
	ctx := context.Background()

	var wg sync.WaitGroup
	const threads = 2
	for i := 0; i < threads; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()
			_ = ts.Reader.Collect(ctx, nil)
		}()

		wg.Add(1)
		go func() {
			defer wg.Done()
			_ = ts.Reader.ForceFlush(ctx)
		}()

		wg.Add(1)
		go func() {
			defer wg.Done()
			_ = ts.Reader.Shutdown(ctx)
		}()
	}
	wg.Wait()
}

func (ts *readerTestSuite) TestShutdownBeforeRegister() {
	ctx := context.Background()
	ts.Require().NoError(ts.Reader.Shutdown(ctx))
	// Registering after shutdown should not revert the shutdown.
	ts.Reader.register(testSDKProducer{})
	ts.Reader.RegisterProducer(testExternalProducer{})

	m := metricdata.ResourceMetrics{}
	err := ts.Reader.Collect(ctx, &m)
	ts.ErrorIs(err, ErrReaderShutdown)
	ts.Equal(metricdata.ResourceMetrics{}, m)
}

func (ts *readerTestSuite) TestCollectNilResourceMetricError() {
	ctx := context.Background()
	ts.Assert().Error(ts.Reader.Collect(ctx, nil))
}

var testScopeMetricsA = metricdata.ScopeMetrics{
	Scope: instrumentation.Scope{Name: "sdk/metric/test/reader"},
	Metrics: []metricdata.Metrics{{
		Name:        "fake data",
		Description: "Data used to test a reader",
		Unit:        "1",
		Data: metricdata.Sum[int64]{
			Temporality: metricdata.CumulativeTemporality,
			IsMonotonic: true,
			DataPoints: []metricdata.DataPoint[int64]{{
				Attributes: attribute.NewSet(attribute.String("user", "alice")),
				StartTime:  time.Now(),
				Time:       time.Now().Add(time.Second),
				Value:      -1,
			}},
		},
	}},
}

var testScopeMetricsB = metricdata.ScopeMetrics{
	Scope: instrumentation.Scope{Name: "sdk/metric/test/reader/external"},
	Metrics: []metricdata.Metrics{{
		Name:        "fake scope data",
		Description: "Data used to test a Producer reader",
		Unit:        "ms",
		Data: metricdata.Gauge[int64]{
			DataPoints: []metricdata.DataPoint[int64]{{
				Attributes: attribute.NewSet(attribute.String("user", "ben")),
				StartTime:  time.Now(),
				Time:       time.Now().Add(time.Second),
				Value:      10,
			}},
		},
	}},
}

var testResourceMetricsA = metricdata.ResourceMetrics{
	Resource:     resource.NewSchemaless(attribute.String("test", "Reader")),
	ScopeMetrics: []metricdata.ScopeMetrics{testScopeMetricsA},
}

var testResourceMetricsAB = metricdata.ResourceMetrics{
	Resource:     resource.NewSchemaless(attribute.String("test", "Reader")),
	ScopeMetrics: []metricdata.ScopeMetrics{testScopeMetricsA, testScopeMetricsB},
}

type testSDKProducer struct {
	produceFunc func(context.Context) (metricdata.ResourceMetrics, error)
}

func (p testSDKProducer) produce(ctx context.Context) (metricdata.ResourceMetrics, error) {
	if p.produceFunc != nil {
		return p.produceFunc(ctx)
	}
	return testResourceMetricsA, nil
}

type testExternalProducer struct {
	produceFunc func(context.Context) ([]metricdata.ScopeMetrics, error)
}

func (p testExternalProducer) Produce(ctx context.Context) ([]metricdata.ScopeMetrics, error) {
	if p.produceFunc != nil {
		return p.produceFunc(ctx)
	}
	return []metricdata.ScopeMetrics{testScopeMetricsB}, nil
}

func benchReaderCollectFunc(r Reader) func(*testing.B) {
	ctx := context.Background()
	r.register(testSDKProducer{})

	// Store bechmark results in a closure to prevent the compiler from
	// inlining and skipping the function.
	var (
		collectedMetrics metricdata.ResourceMetrics
		err              error
	)

	return func(b *testing.B) {
		b.ReportAllocs()
		b.ResetTimer()

		for n := 0; n < b.N; n++ {
			err = r.Collect(ctx, &collectedMetrics)
			assert.Equalf(b, testResourceMetricsA, collectedMetrics, "unexpected Collect response: (%#v, %v)", collectedMetrics, err)
		}
	}
}

func TestDefaultAggregationSelector(t *testing.T) {
	var undefinedInstrument InstrumentKind
	assert.Panics(t, func() { DefaultAggregationSelector(undefinedInstrument) })

	iKinds := []InstrumentKind{
		InstrumentKindCounter,
		InstrumentKindUpDownCounter,
		InstrumentKindHistogram,
		InstrumentKindObservableCounter,
		InstrumentKindObservableUpDownCounter,
		InstrumentKindObservableGauge,
	}

	for _, ik := range iKinds {
		assert.NoError(t, DefaultAggregationSelector(ik).Err(), ik)
	}
}

func TestDefaultTemporalitySelector(t *testing.T) {
	var undefinedInstrument InstrumentKind
	for _, ik := range []InstrumentKind{
		undefinedInstrument,
		InstrumentKindCounter,
		InstrumentKindUpDownCounter,
		InstrumentKindHistogram,
		InstrumentKindObservableCounter,
		InstrumentKindObservableUpDownCounter,
		InstrumentKindObservableGauge,
	} {
		assert.Equal(t, metricdata.CumulativeTemporality, DefaultTemporalitySelector(ik))
	}
}

type notComparable [0]func() // nolint:unused  // non-comparable type itself is used.

type noCompareReader struct {
	notComparable // nolint:unused  // non-comparable type itself is used.
	Reader
}

func TestReadersNotRequiredToBeComparable(t *testing.T) {
	r := noCompareReader{Reader: NewManualReader()}
	assert.NotPanics(t, func() { _ = NewMeterProvider(WithReader(r)) })
}