// <copyright file="MultipleReadersTests.cs" company="OpenTelemetry Authors">
// 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.
// </copyright>

using System.Collections.Generic;
using System.Diagnostics.Metrics;
using Microsoft.Extensions.DependencyInjection;
using OpenTelemetry.Tests;
using Xunit;

namespace OpenTelemetry.Metrics.Tests
{
    public class MultipleReadersTests
    {
        [Theory]
        [InlineData(MetricReaderTemporalityPreference.Delta, false)]
        [InlineData(MetricReaderTemporalityPreference.Delta, true)]
        [InlineData(MetricReaderTemporalityPreference.Cumulative, false)]
        [InlineData(MetricReaderTemporalityPreference.Cumulative, true)]
        public void SdkSupportsMultipleReaders(MetricReaderTemporalityPreference aggregationTemporality, bool hasViews)
        {
            var exportedItems1 = new List<Metric>();
            var exportedItems2 = new List<Metric>();

            using var meter = new Meter($"{Utils.GetCurrentMethodName()}.{aggregationTemporality}.{hasViews}");

            var counter = meter.CreateCounter<long>("counter");

            int index = 0;
            var values = new long[] { 100, 200, 300, 400 };
            long GetValue() => values[index++];
            var gauge = meter.CreateObservableGauge("gauge", () => GetValue());

            int indexSum = 0;
            var valuesSum = new long[] { 1000, 1200, 1300, 1400 };
            long GetSum() => valuesSum[indexSum++];
            var observableCounter = meter.CreateObservableCounter("obs-counter", () => GetSum());

            bool defaultNamedOptionsConfigureCalled = false;
            bool namedOptionsConfigureCalled = false;

            var meterProviderBuilder = Sdk.CreateMeterProviderBuilder()
                .ConfigureServices(services =>
                {
                    services.Configure<MetricReaderOptions>(o =>
                    {
                        defaultNamedOptionsConfigureCalled = true;
                    });
                    services.Configure<MetricReaderOptions>("Exporter2", o =>
                    {
                        namedOptionsConfigureCalled = true;
                    });
                })
                .AddMeter(meter.Name)
                .AddInMemoryExporter(exportedItems1, metricReaderOptions =>
                {
                    metricReaderOptions.TemporalityPreference = MetricReaderTemporalityPreference.Delta;
                })
                .AddInMemoryExporter("Exporter2", exportedItems2, metricReaderOptions =>
                {
                    metricReaderOptions.TemporalityPreference = aggregationTemporality;
                });

            if (hasViews)
            {
                meterProviderBuilder.AddView("counter", "renamedCounter");
                meterProviderBuilder.AddView("gauge", "renamedGauge");
                meterProviderBuilder.AddView("obs-counter", "renamedObservableCounter");
            }

            using var meterProvider = meterProviderBuilder.Build();

            Assert.True(defaultNamedOptionsConfigureCalled);
            Assert.True(namedOptionsConfigureCalled);

            counter.Add(10, new KeyValuePair<string, object>("key", "value"));

            meterProvider.ForceFlush();

            Assert.Equal(3, exportedItems1.Count);
            Assert.Equal(3, exportedItems2.Count);

            if (hasViews)
            {
                Assert.Equal("renamedCounter", exportedItems1[0].Name);
                Assert.Equal("renamedCounter", exportedItems2[0].Name);

                Assert.Equal("renamedGauge", exportedItems1[1].Name);
                Assert.Equal("renamedGauge", exportedItems2[1].Name);

                Assert.Equal("renamedObservableCounter", exportedItems1[2].Name);
                Assert.Equal("renamedObservableCounter", exportedItems2[2].Name);
            }
            else
            {
                Assert.Equal("counter", exportedItems1[0].Name);
                Assert.Equal("counter", exportedItems2[0].Name);

                Assert.Equal("gauge", exportedItems1[1].Name);
                Assert.Equal("gauge", exportedItems2[1].Name);

                Assert.Equal("obs-counter", exportedItems1[2].Name);
                Assert.Equal("obs-counter", exportedItems2[2].Name);
            }

            // Check value exported for Counter
            AssertLongSumValueForMetric(exportedItems1[0], 10);
            AssertLongSumValueForMetric(exportedItems2[0], 10);

            // Check value exported for Gauge
            AssertLongSumValueForMetric(exportedItems1[1], 100);
            AssertLongSumValueForMetric(exportedItems2[1], 200);

            // Check value exported for ObservableCounter
            AssertLongSumValueForMetric(exportedItems1[2], 1000);
            if (aggregationTemporality == MetricReaderTemporalityPreference.Delta)
            {
                AssertLongSumValueForMetric(exportedItems2[2], 1200);
            }
            else
            {
                AssertLongSumValueForMetric(exportedItems2[2], 1200);
            }

            exportedItems1.Clear();
            exportedItems2.Clear();

            counter.Add(15, new KeyValuePair<string, object>("key", "value"));

            meterProvider.ForceFlush();

            Assert.Equal(3, exportedItems1.Count);
            Assert.Equal(3, exportedItems2.Count);

            // Check value exported for Counter
            AssertLongSumValueForMetric(exportedItems1[0], 15);
            if (aggregationTemporality == MetricReaderTemporalityPreference.Delta)
            {
                AssertLongSumValueForMetric(exportedItems2[0], 15);
            }
            else
            {
                AssertLongSumValueForMetric(exportedItems2[0], 25);
            }

            // Check value exported for Gauge
            AssertLongSumValueForMetric(exportedItems1[1], 300);
            AssertLongSumValueForMetric(exportedItems2[1], 400);

            // Check value exported for ObservableCounter
            AssertLongSumValueForMetric(exportedItems1[2], 300);
            if (aggregationTemporality == MetricReaderTemporalityPreference.Delta)
            {
                AssertLongSumValueForMetric(exportedItems2[2], 200);
            }
            else
            {
                AssertLongSumValueForMetric(exportedItems2[2], 1400);
            }
        }

        [Theory]
        [InlineData(false)]
        [InlineData(true)]
        public void ObservableInstrumentCallbacksInvokedForEachReaders(bool hasViews)
        {
            var exportedItems1 = new List<Metric>();
            var exportedItems2 = new List<Metric>();
            using var meter = new Meter($"{Utils.GetCurrentMethodName()}.{hasViews}");
            int callbackInvocationCount = 0;
            var gauge = meter.CreateObservableGauge("gauge", () =>
            {
                callbackInvocationCount++;
                return 10 * callbackInvocationCount;
            });

            var meterProviderBuilder = Sdk.CreateMeterProviderBuilder()
                .AddMeter(meter.Name)
                .AddInMemoryExporter(exportedItems1)
                .AddInMemoryExporter(exportedItems2);

            if (hasViews)
            {
                meterProviderBuilder.AddView("gauge", "renamedGauge");
            }

            using var meterProvider = meterProviderBuilder.Build();
            meterProvider.ForceFlush();

            // VALIDATE
            Assert.Equal(2, callbackInvocationCount);
            Assert.Single(exportedItems1);
            Assert.Single(exportedItems2);

            if (hasViews)
            {
                Assert.Equal("renamedGauge", exportedItems1[0].Name);
                Assert.Equal("renamedGauge", exportedItems2[0].Name);
            }
            else
            {
                Assert.Equal("gauge", exportedItems1[0].Name);
                Assert.Equal("gauge", exportedItems2[0].Name);
            }
        }

        private static void AssertLongSumValueForMetric(Metric metric, long value)
        {
            var metricPoints = metric.GetMetricPoints();
            var metricPointsEnumerator = metricPoints.GetEnumerator();
            Assert.True(metricPointsEnumerator.MoveNext()); // One MetricPoint is emitted for the Metric
            ref readonly var metricPointForFirstExport = ref metricPointsEnumerator.Current;
            if (metric.MetricType.IsSum())
            {
                Assert.Equal(value, metricPointForFirstExport.GetSumLong());
            }
            else
            {
                Assert.Equal(value, metricPointForFirstExport.GetGaugeLastValueLong());
            }
        }
    }
}
