using System;
using System.IO;
using System.IO.Abstractions;
using System.IO.Abstractions.TestingHelpers;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

using Microsoft.VisualStudio.TestTools.UnitTesting;

using Tgstation.Server.Host.System;

namespace Tgstation.Server.Host.IO.Tests
{
	[TestClass]
	public sealed class TestIOManager
	{
		readonly IFileSystem fileSystem;
		readonly IIOManager ioManager;

		public TestIOManager()
		{
			fileSystem = new MockFileSystem();
			ioManager = new DefaultIOManager(fileSystem);
		}

		[TestMethod]
		public async Task TestDeleteDirectory()
		{
			var tempPath = fileSystem.Path.Combine(fileSystem.Path.GetTempPath(), fileSystem.Path.GetRandomFileName());
			fileSystem.File.Delete(tempPath);
			fileSystem.Directory.CreateDirectory(tempPath);
			try
			{
				await fileSystem.File.WriteAllTextAsync(Path.Combine(tempPath, "file.txt"), "asdf");
				var subDir = fileSystem.Path.Combine(tempPath, "subdir");
				fileSystem.Directory.CreateDirectory(subDir);
				await fileSystem.File.WriteAllTextAsync(Path.Combine(subDir, "file2.txt"), "fdsa");
				await ioManager.DeleteDirectory(tempPath, default);

				Assert.IsFalse(fileSystem.Directory.Exists(tempPath));
			}
			catch
			{
				fileSystem.Directory.Delete(tempPath, true);
				throw;
			}
		}

		[TestMethod]
		public async Task TestDeleteDirectoryWithSymlinkInsideDoesntRecurse()
		{
			// need a real FS here
			var fileSystem = new FileSystem();
			var ioManager = new DefaultIOManager(fileSystem);

			var linkFactory = (IFilesystemLinkFactory)(new PlatformIdentifier().IsWindows
				? new WindowsFilesystemLinkFactory(fileSystem)
				: new PosixFilesystemLinkFactory(fileSystem));

			var tempPath = fileSystem.Path.Combine(fileSystem.Path.GetTempPath(), fileSystem.Path.GetRandomFileName());
			fileSystem.File.Delete(tempPath);
			fileSystem.Directory.CreateDirectory(tempPath);
			try
			{
				var targetDir = ioManager.ConcatPath(tempPath, "targetdir");
				await ioManager.CreateDirectory(targetDir, CancellationToken.None);
				var fileInTargetDir = ioManager.ConcatPath(targetDir, "test1.txt");

				var expectedBytes = Encoding.UTF8.GetBytes("I want to live");
				await ioManager.WriteAllBytes(fileInTargetDir, expectedBytes, CancellationToken.None);

				var testDir = ioManager.ConcatPath(tempPath, "testdir");
				await ioManager.CreateDirectory(testDir, CancellationToken.None);
				var symlinkedFile = ioManager.ConcatPath(testDir, "test1.txt");
				var symlinkedDir = ioManager.ConcatPath(testDir, "linkedDir");

				await linkFactory.CreateSymbolicLink(targetDir, symlinkedDir, CancellationToken.None);
				await linkFactory.CreateSymbolicLink(fileInTargetDir, symlinkedFile, CancellationToken.None);

				Assert.IsTrue(await ioManager.DirectoryExists(symlinkedDir, CancellationToken.None));
				Assert.IsTrue(await ioManager.FileExists(symlinkedFile, CancellationToken.None));
				Assert.IsTrue(await ioManager.FileExists(ioManager.ConcatPath(symlinkedDir, "test1.txt"), CancellationToken.None));
				Assert.IsTrue(await ioManager.FileExists(fileInTargetDir, CancellationToken.None));

				await ioManager.DeleteDirectory(testDir, CancellationToken.None);

				Assert.IsFalse(await ioManager.DirectoryExists(symlinkedDir, CancellationToken.None));
				Assert.IsFalse(await ioManager.FileExists(symlinkedFile, CancellationToken.None));
				Assert.IsFalse(await ioManager.FileExists(ioManager.ConcatPath(symlinkedDir, "test1.txt"), CancellationToken.None));
				Assert.IsTrue(await ioManager.FileExists(fileInTargetDir, CancellationToken.None));
				Assert.IsTrue(expectedBytes.SequenceEqual(await ioManager.ReadAllBytes(fileInTargetDir, CancellationToken.None)));
			}
			catch
			{
				fileSystem.Directory.Delete(tempPath, true);
				throw;
			}
		}

		[TestMethod]
		public async Task TestFileExists()
		{
			var tempPath = fileSystem.Path.Combine(fileSystem.Path.GetTempPath(), fileSystem.Path.GetRandomFileName());
			await fileSystem.File.WriteAllBytesAsync(tempPath, Array.Empty<byte>());
			try
			{
				Assert.IsTrue(await ioManager.FileExists(tempPath, default));
			}
			finally
			{
				fileSystem.File.Delete(tempPath);
			}

			Assert.IsFalse(await ioManager.FileExists(tempPath, default));
		}

		[TestMethod]
		public async Task TestDirectoryExists()
		{
			var tempPath = fileSystem.Path.Combine(fileSystem.Path.GetTempPath(), fileSystem.Path.GetRandomFileName());
			fileSystem.File.Delete(tempPath);

			Assert.IsFalse(await ioManager.DirectoryExists(tempPath, default));

			fileSystem.Directory.CreateDirectory(tempPath);

			try
			{
				Assert.IsTrue(await ioManager.DirectoryExists(tempPath, default));
			}
			catch
			{
				fileSystem.Directory.Delete(tempPath);
				throw;
			}
		}

		[TestMethod]
		public async Task TestCopyDirectoryThrows()
		{
			int? throttle = null;
			var tempPath1 = Guid.NewGuid().ToString();
			var tempPath2 = Guid.NewGuid().ToString();

			await Assert.ThrowsExactlyAsync<ArgumentNullException>(() => ioManager.CopyDirectory(
				null,
				null,
				null,
				tempPath2,
				throttle,
				default).AsTask());
			await Assert.ThrowsExactlyAsync<ArgumentNullException>(() => ioManager.CopyDirectory(
				null,
				null,
				tempPath1,
				null,
				throttle,
				default).AsTask());
			await Assert.ThrowsExactlyAsync<ArgumentNullException>(() => ioManager.CopyDirectory(
				null,
				null,
				null,
				null,
				throttle,
				default).AsTask());
			await Assert.ThrowsExactlyAsync<ArgumentOutOfRangeException>(() => ioManager.CopyDirectory(
				null,
				null,
				tempPath1,
				tempPath2,
				-1,
				default).AsTask());
		}

		[TestMethod]
		public async Task TestCopyDirectoryOneTask()
		{
			await TestCopyDirectory(1);
		}

		[TestMethod]
		public async Task TestCopyDirectoryMaxTasks()
		{
			await TestCopyDirectory(Int32.MaxValue);
		}

		[TestMethod]
		public async Task TestCopyDirectoryUnlimitedTasks()
		{
			await TestCopyDirectory(null);
		}

		async Task TestCopyDirectory(int? throttle)
		{
			var tempPath = fileSystem.Path.Combine(fileSystem.Path.GetTempPath(), fileSystem.Path.GetRandomFileName());
			fileSystem.File.Delete(tempPath);
			fileSystem.Directory.CreateDirectory(tempPath);
			try
			{
				var tempPath2 = fileSystem.Path.Combine(fileSystem.Path.GetTempPath(), fileSystem.Path.GetRandomFileName());
				fileSystem.File.Delete(tempPath2);

				await fileSystem.File.WriteAllTextAsync(fileSystem.Path.Combine(tempPath, "file.txt"), "asdf");
				var subDir = fileSystem.Path.Combine(tempPath, "subdir");
				fileSystem.Directory.CreateDirectory(subDir);
				await fileSystem.File.WriteAllTextAsync(fileSystem.Path.Combine(subDir, "file2.txt"), "fdsa");

				try
				{
					await ioManager.CopyDirectory(
						null,
						null,
						tempPath,
						tempPath2,
						throttle,
						default);

					Assert.IsTrue(fileSystem.Directory.Exists(tempPath2));
					var newFilePath = fileSystem.Path.Combine(tempPath2, "file.txt");
					Assert.IsTrue(fileSystem.File.Exists(newFilePath));
					var newFileText = await fileSystem.File.ReadAllTextAsync(newFilePath);
					Assert.AreEqual("asdf", newFileText);
					var newDirPath = fileSystem.Path.Combine(tempPath2, "subdir");
					Assert.IsTrue(fileSystem.Directory.Exists(newDirPath));
					var newFile2Path = fileSystem.Path.Combine(newDirPath, "file2.txt");
					Assert.IsTrue(fileSystem.File.Exists(newFile2Path));
					var newFile2Text = await fileSystem.File.ReadAllTextAsync(newFile2Path);
					Assert.AreEqual("fdsa", newFile2Text);
				}
				finally
				{
					fileSystem.Directory.Delete(tempPath2, true);
				}
			}
			finally
			{
				fileSystem.Directory.Delete(tempPath, true);
			}
		}
	}
}