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

namespace ShrinkDataSaver.Tests
{
    [TestFixture]
    public class LocalStorageProviderStrategyTests
    {
        private string _rootPath;

        [SetUp]
        public void SetUp()
        {
            _rootPath = Path.Combine(Path.GetTempPath(), $"ShrinkDataSaverStrategyTests_{Guid.NewGuid():N}");
            Directory.CreateDirectory(_rootPath);
        }

        [TearDown]
        public void TearDown()
        {
            if (Directory.Exists(_rootPath))
            {
                Directory.Delete(_rootPath, true);
            }
        }

        [Test]
        public void DefaultConstructor_UsesFileReplace()
        {
            Assert.AreEqual(LocalStorageCommitStrategy.FileReplace,
                new LocalStorageProvider(_rootPath).CommitStrategy);
        }

        [UnityTest]
        public IEnumerator RenameOnly_RotatesTwoBackups() => UniTask.ToCoroutine(async () =>
        {
            var provider = new LocalStorageProvider(_rootPath, LocalStorageCommitStrategy.RenameOnly, TestMove);
            await WriteAsync(provider, "one");
            await WriteAsync(provider, "two");
            await WriteAsync(provider, "three");

            Assert.AreEqual("three", await ReadAsync(provider, "save.dat"));
            Assert.AreEqual("two", await ReadAsync(provider, "save.dat.bak1"));
            Assert.AreEqual("one", await ReadAsync(provider, "save.dat.bak2"));
        });

        [UnityTest]
        public IEnumerator RenameOnly_RecoversPrimaryFromBak1_WhenPrimaryMissing() => UniTask.ToCoroutine(async () =>
        {
            var provider = new LocalStorageProvider(_rootPath, LocalStorageCommitStrategy.RenameOnly, TestMove);
            await WriteAsync(provider, "one");
            await WriteAsync(provider, "two");

            var primary = Path.Combine(_rootPath, "save.dat");
            var primaryBackup = primary + ".bak1";
            File.Delete(primaryBackup);
            File.Move(primary, primaryBackup);

            Assert.IsTrue(await provider.ExistsAsync("save.dat"));
            Assert.AreEqual("two", await ReadAsync(provider, "save.dat"));
            Assert.IsTrue(File.Exists(primary));
            Assert.IsFalse(File.Exists(primaryBackup));
        });

        [UnityTest]
        public IEnumerator RenameOnly_RecoversPrimaryFromBak2_WhenBak1Missing() => UniTask.ToCoroutine(async () =>
        {
            var provider = new LocalStorageProvider(_rootPath, LocalStorageCommitStrategy.RenameOnly, TestMove);
            await WriteAsync(provider, "one");
            await WriteAsync(provider, "two");
            await WriteAsync(provider, "three");

            var primary = Path.Combine(_rootPath, "save.dat");
            File.Delete(primary);
            File.Delete(primary + ".bak1");

            Assert.AreEqual("one", await ReadAsync(provider, "save.dat"));
        });

        [UnityTest]
        public IEnumerator RenameOnly_DeletesStaleTempBeforeWrite() => UniTask.ToCoroutine(async () =>
        {
            var provider = new LocalStorageProvider(_rootPath, LocalStorageCommitStrategy.RenameOnly, TestMove);
            await WriteAsync(provider, "one");
            var primary = Path.Combine(_rootPath, "save.dat");
            File.WriteAllText(primary + ".tmp", "stale", Encoding.UTF8);

            await WriteAsync(provider, "two");

            Assert.IsFalse(File.Exists(primary + ".tmp"));
            Assert.AreEqual("two", await ReadAsync(provider, "save.dat"));
        });

        [UnityTest]
        public IEnumerator RenameOnly_PreservesSecondGeneration_WhenBak1Missing() => UniTask.ToCoroutine(async () =>
        {
            var provider = new LocalStorageProvider(_rootPath, LocalStorageCommitStrategy.RenameOnly, TestMove);
            await WriteAsync(provider, "one");
            await WriteAsync(provider, "two");
            await WriteAsync(provider, "three");

            var primary = Path.Combine(_rootPath, "save.dat");
            File.Delete(primary + ".bak1");

            await WriteAsync(provider, "four");

            Assert.AreEqual("four", await ReadAsync(provider, "save.dat"));
            Assert.AreEqual("three", await ReadAsync(provider, "save.dat.bak1"));
            Assert.AreEqual("one", await ReadAsync(provider, "save.dat.bak2"));
        });

        [UnityTest]
        public IEnumerator RenameOnly_DoesNotPromoteOrphanTemp() => UniTask.ToCoroutine(async () =>
        {
            var provider = new LocalStorageProvider(_rootPath, LocalStorageCommitStrategy.RenameOnly, TestMove);
            var primary = Path.Combine(_rootPath, "save.dat");
            File.WriteAllText(primary + ".tmp", "partial", new UTF8Encoding(false));

            Assert.IsFalse(await provider.ExistsAsync("save.dat"));
            Assert.IsFalse(File.Exists(primary));
            Assert.IsFalse(File.Exists(primary + ".tmp"));

            var readFailed = false;
            try
            {
                await ReadAsync(provider, "save.dat");
            }
            catch (FileNotFoundException)
            {
                readFailed = true;
            }

            Assert.IsTrue(readFailed);
        });

        [UnityTest]
        public IEnumerator RenameOnly_PrefersBackupOverPartialTemp() => UniTask.ToCoroutine(async () =>
        {
            var provider = new LocalStorageProvider(_rootPath, LocalStorageCommitStrategy.RenameOnly, TestMove);
            await WriteAsync(provider, "one");
            await WriteAsync(provider, "two");

            var primary = Path.Combine(_rootPath, "save.dat");
            File.Delete(primary);
            File.WriteAllText(primary + ".tmp", "partial", new UTF8Encoding(false));

            Assert.IsTrue(await provider.ExistsAsync("save.dat"));
            Assert.AreEqual("one", await ReadAsync(provider, "save.dat"));
            Assert.IsFalse(File.Exists(primary + ".tmp"));
        });

        [UnityTest]
        public IEnumerator FileReplace_DoesNotApplyRenameOnlyRecovery() => UniTask.ToCoroutine(async () =>
        {
            var provider = new LocalStorageProvider(_rootPath);
            await WriteAsync(provider, "one");
            await WriteAsync(provider, "two");

            var primary = Path.Combine(_rootPath, "save.dat");
            File.Delete(primary);
            File.WriteAllText(primary + ".tmp", "partial", new UTF8Encoding(false));

            Assert.IsFalse(await provider.ExistsAsync("save.dat"));
            Assert.IsTrue(File.Exists(primary + ".bak1"));
            Assert.IsTrue(File.Exists(primary + ".tmp"));

            var readFailed = false;
            try
            {
                await ReadAsync(provider, "save.dat");
            }
            catch (FileNotFoundException)
            {
                readFailed = true;
            }

            Assert.IsTrue(readFailed);
        });

        [UnityTest]
        public IEnumerator DeleteAsync_RemovesBackupsAndTemp() => UniTask.ToCoroutine(async () =>
        {
            var provider = new LocalStorageProvider(_rootPath, LocalStorageCommitStrategy.RenameOnly, TestMove);
            await WriteAsync(provider, "one");
            await WriteAsync(provider, "two");
            var primary = Path.Combine(_rootPath, "save.dat");
            File.WriteAllText(primary + ".tmp", "stale", Encoding.UTF8);

            await provider.DeleteAsync("save.dat");

            Assert.IsFalse(File.Exists(primary));
            Assert.IsFalse(File.Exists(primary + ".bak1"));
            Assert.IsFalse(File.Exists(primary + ".bak2"));
            Assert.IsFalse(File.Exists(primary + ".tmp"));
        });

        [UnityTest]
        public IEnumerator PlatformInitialize_UsesInjectedStorage() => UniTask.ToCoroutine(async () =>
        {
            var storage = new MockStorageProvider();
            ShrinkSettings.ResetForTesting();
            ShrinkDataSaverPlatform.Initialize(storage, "runtime-root");
            ShrinkSettings.Set("injected", 7);
            await ShrinkSettings.SaveAsync();

            Assert.IsTrue(await storage.ExistsAsync("runtime-root/settings.json"));
            var bytes = await storage.ReadAsync("runtime-root/settings.json");
            StringAssert.Contains("\"injected\"", Encoding.UTF8.GetString(bytes));
        });

        // Tests the shared rotation contract; Godot integration tests exercise actual overwrite rename.
        private static void TestMove(string source, string destination)
        {
            if (File.Exists(destination)) File.Delete(destination);
            File.Move(source, destination);
        }

        [Test]
        public void RenameOnly_RequiresOverwriteCapability() => Assert.Throws<ArgumentException>(() =>
            new LocalStorageProvider(_rootPath, LocalStorageCommitStrategy.RenameOnly));

        private static async UniTask WriteAsync(IStorageProvider provider, string value)
        {
            await provider.WriteAsync("save.dat", Encoding.UTF8.GetBytes(value));
        }

        private static async UniTask<string> ReadAsync(IStorageProvider provider, string path)
        {
            var bytes = await provider.ReadAsync(path);
            return Encoding.UTF8.GetString(bytes);
        }
    }
}