using System.Collections;
using System.Collections.Generic;
using System.IO;
using Cysharp.Threading.Tasks;
using NUnit.Framework;
using UnityEngine;
using UnityEngine.TestTools;
using AssetBundleHub;
using AssetBundleHub.Tasks;
using System;
using System.Threading;

namespace AssetBundleHubTests
{
    public class QueueRequestDecoratorTest
    {
        public class Counter
        {
            public int startCount = 0;
            public int endCount = 0;
            int delayFrameCount;

            public Counter(int delayFrameCount = 10)
            {
                this.delayFrameCount = delayFrameCount;
            }

            public async UniTask<IDownloadResponseContext> Run(IDownloadRequestContext context, CancellationToken cancellationToken)
            {
                cancellationToken.ThrowIfCancellationRequested();
                startCount++;
                await UniTask.DelayFrame(delayFrameCount, cancellationToken: cancellationToken);
                endCount++;
                return null;
            }
        }

        [UnityTest]
        public IEnumerator 正常系_キャパ1() => UniTask.ToCoroutine(async () =>
        {
            int runCapacity = 1;
            var counter = new Counter();
            var context = DownloadRequestContextFixture.Load();
            var describedClass = new QueueRequestDecorator(runCapacity);
            using var cts = new CancellationTokenSource();

            var task1 = describedClass.DownloadAsync(context, cts.Token, counter.Run);
            Assert.That(counter.startCount, Is.EqualTo(1));  // キャパ以内なので待たない
            Assert.That(describedClass.RunningCount, Is.EqualTo(1));
            var task2 = describedClass.DownloadAsync(context, cts.Token, counter.Run);
            Assert.That(counter.startCount, Is.EqualTo(1));  // キャパ以上なので待つ
            Assert.That(describedClass.RunningCount, Is.EqualTo(1));
            var task3 = describedClass.DownloadAsync(context, cts.Token, counter.Run);
            Assert.That(counter.startCount, Is.EqualTo(1));  // キャパ以上なので待つ
            Assert.That(describedClass.RunningCount, Is.EqualTo(1));
            await task1;
            await UniTask.Yield(); // 次のタスク開始は1フレーム後に実行されるので1フレーム待つ
            Assert.That(counter.startCount, Is.EqualTo(2));  // 1つ目が終わって2つ目が開始される
            Assert.That(counter.endCount, Is.EqualTo(1));
            await task2;
            await UniTask.Yield(); // 次のタスク開始よりresultが早く来るので1フレーム待つ
            Assert.That(counter.startCount, Is.EqualTo(3));  // 2つ目が終わって3つ目が開始される
            Assert.That(counter.endCount, Is.EqualTo(2));
            await task3;
            Assert.That(counter.startCount, Is.EqualTo(3));  // 3つ目が終わって終了
            Assert.That(counter.endCount, Is.EqualTo(3));
            await UniTask.Yield();  // RunningCount--よりresultが早く来るので1フレーム待つ
            Assert.That(describedClass.RunningCount, Is.EqualTo(0));
        });

        [UnityTest]
        public IEnumerator 正常系_キャパ4() => UniTask.ToCoroutine(async () =>
        {
            int runCapacity = 4;
            var counter = new Counter();
            var context = DownloadRequestContextFixture.Load();
            var describedClass = new QueueRequestDecorator(runCapacity);
            var cts = new CancellationTokenSource();

            var tasks = new List<UniTask<IDownloadResponseContext>>();
            for (int i = 0; i < runCapacity; i++)
            {
                tasks.Add(describedClass.DownloadAsync(context, cts.Token, counter.Run));
                await UniTask.DelayFrame(2); // 徐々にRunnningCountが減るのをテストしたいので少し待つ
                Assert.That(counter.startCount, Is.EqualTo(i + 1));  // キャパ以内なので待たない
                Assert.That(describedClass.RunningCount, Is.EqualTo(i + 1));
            }
            tasks.Add(describedClass.DownloadAsync(context, cts.Token, counter.Run));
            Assert.That(counter.startCount, Is.EqualTo(runCapacity));  // キャパ以上なので待つ
            Assert.That(describedClass.RunningCount, Is.EqualTo(runCapacity));
            await tasks[0];
            await UniTask.Yield();
            Assert.That(counter.startCount, Is.EqualTo(runCapacity + 1));  // 待ち状態のタスクが実行される
            Assert.That(counter.endCount, Is.EqualTo(1));
            Assert.That(describedClass.RunningCount, Is.EqualTo(runCapacity));
            for (int i = 1; i < tasks.Count; i++)
            {
                await tasks[i];
                await UniTask.Yield();
                Assert.That(counter.endCount, Is.EqualTo(i + 1));
                Assert.That(describedClass.RunningCount, Is.EqualTo(runCapacity - i));
            }
        });

        [UnityTest]
        public IEnumerator 正常系_キャンセル() => UniTask.ToCoroutine(async () =>
        {
            int runCapacity = 4;
            int runCount = 8;
            var counter = new Counter(20);
            var context = DownloadRequestContextFixture.Load();
            var describedClass = new QueueRequestDecorator(runCapacity);
            var ctsList = new List<CancellationTokenSource>();
            var tasks = new List<UniTask<IDownloadResponseContext>>();
            for (int i = 0; i < runCount; i++)
            {
                var cts = new CancellationTokenSource();
                var task = describedClass.DownloadAsync(context, cts.Token, counter.Run);
                if (i != runCount - 1)
                {
                    task.Forget();
                }
                tasks.Add(task);
                ctsList.Add(cts);
            }
            Assert.That(counter.startCount, Is.EqualTo(runCapacity));
            Assert.That(counter.endCount, Is.EqualTo(0));
            Assert.That(describedClass.RunningCount, Is.EqualTo(runCapacity));
            ctsList[0].Cancel(); //先頭キャンセル
            await UniTask.DelayFrame(2); // 1フレーム後にfinallyが呼ばれるので2フレ待つ
            Assert.That(counter.startCount, Is.EqualTo(runCapacity + 1));
            Assert.That(counter.endCount, Is.EqualTo(0));
            Assert.That(describedClass.RunningCount, Is.EqualTo(runCapacity));
            ctsList[runCapacity].Cancel(); // Runで実行されたタスクをキャンセル
            await UniTask.Yield(); // 次フレームにcatchされてすぐ次のrunが実行される。
            Assert.That(counter.startCount, Is.EqualTo(runCapacity + 2));
            Assert.That(counter.endCount, Is.EqualTo(0));
            Assert.That(describedClass.RunningCount, Is.EqualTo(runCapacity));
            ctsList[ctsList.Count - 2].Cancel(); //末尾から一つ手前のまだ実行されてないタスクをキャンセル
            await tasks[tasks.Count - 1]; // 全部終わるまで待つ。
            await UniTask.Yield();
            Assert.That(counter.startCount, Is.EqualTo(runCount - 1)); // 1つ実行前キャンセルしているため
            Assert.That(counter.endCount, Is.EqualTo(runCount - 3)); // 3つキャンセルしているため
            Assert.That(describedClass.RunningCount, Is.EqualTo(0));
        });
    }
}