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using System;
using System.IO;
using System.Threading;
using System.Threading.Tasks;
using Moq;
using NUnit.Framework;
using Opc.Ua.Server.FileSystem;
using Opc.Ua.Server.Tests.NodeManager;
using Opc.Ua.Tests;

namespace Opc.Ua.Server.Tests.FileSystem
{
    /// <summary>
    /// Verifies mount-root protection and canonical path validation before file-system provider mutations.
    /// </summary>
    [TestFixture]
    [Category("FileSystem")]
    public sealed class FileSystemMountRegressionTests
    {
        /// <summary>
        /// Verifies that alternative root identifiers cannot delete, move, or copy the mounted root.
        /// </summary>
        [Test]
        public async Task AlternateRootIdsCannotDeleteMoveOrCopyMountAsync(
            [Values("delete", "move", "copy")] string operation,
            [ValueSource(nameof(s_rootIds))] string identifier)
        {
            Mock<IFileSystemProvider> provider = CreateProvider();
            using FileSystemNodeManager manager = CreateManager(provider.Object);
            DirectoryObjectState root = CreateRoot(manager);
            var source = new NodeId(identifier, manager.NamespaceIndex);

            ServiceResult result = await MutateAsync(root, manager.SystemContext, source, operation)
                .ConfigureAwait(false);

            Assert.Multiple(() =>
            {
                Assert.That(result.StatusCode.Code, Is.EqualTo(operation == "delete"
                    ? StatusCodes.BadUserAccessDenied
                    : StatusCodes.BadInvalidArgument));
                VerifyNoMutation(provider);
            });
        }

        /// <summary>
        /// Verifies that noncanonical source paths are rejected before reaching any provider mutation.
        /// </summary>
        [Test]
        public async Task NonCanonicalObjectPathsCannotDeleteMoveOrCopyAsync(
            [Values("delete", "move", "copy")] string operation,
            [ValueSource(nameof(s_nonCanonicalProviderPaths))] string providerPath,
            [Values] bool isDirectory)
        {
            Mock<IFileSystemProvider> provider = CreateProvider();
            using FileSystemNodeManager manager = CreateManager(provider.Object);
            DirectoryObjectState root = CreateRoot(manager);
            NodeId source = isDirectory
                ? FileSystemNodeId.BuildDirectory(providerPath, manager.NamespaceIndex)
                : FileSystemNodeId.BuildFile(providerPath, manager.NamespaceIndex);

            ServiceResult result = await MutateAsync(root, manager.SystemContext, source, operation)
                .ConfigureAwait(false);

            StatusCode expectedStatus = operation != "delete"
                ? StatusCodes.BadInvalidArgument
                : providerPath is "/" or "\\" or "//" or "\\\\" or "/\\/"
                    ? StatusCodes.BadUserAccessDenied
                    : StatusCodes.BadNotFound;
            Assert.Multiple(() =>
            {
                Assert.That(result.StatusCode, Is.EqualTo(expectedStatus));
                VerifyNoMutation(provider);
            });
        }

        /// <summary>
        /// Verifies that noncanonical destination paths reject moves and copies without returning a new node.
        /// </summary>
        [Test]
        public async Task NonCanonicalMoveOrCopyTargetsDoNotInvokeProviderAsync(
            [Values] bool createCopy,
            [ValueSource(nameof(s_invalidNonRootPaths))] string providerPath)
        {
            Mock<IFileSystemProvider> provider = CreateProvider();
            using FileSystemNodeManager manager = CreateManager(provider.Object);
            DirectoryObjectState root = CreateRoot(manager);
            NodeId source = FileSystemNodeId.BuildFile("keep.txt", manager.NamespaceIndex);
            NodeId target = FileSystemNodeId.BuildDirectory(providerPath, manager.NamespaceIndex);

            MoveOrCopyMethodStateResult result = await root.MoveOrCopy!.OnCallAsync!(
                manager.SystemContext, root.MoveOrCopy, root.NodeId, source, target,
                createCopy, "renamed.txt", CancellationToken.None).ConfigureAwait(false);

            Assert.Multiple(() =>
            {
                Assert.That(result.ServiceResult.StatusCode, Is.EqualTo(StatusCodes.BadInvalidArgument));
                Assert.That(result.NewNodeId.IsNull, Is.True);
                VerifyNoMutation(provider);
            });
        }

        /// <summary>
        /// Verifies that valid nested paths, including unusual legal names, reach the provider unchanged.
        /// </summary>
        [Test]
        public async Task OrdinaryNestedProviderPathsRemainUnchangedAsync(
            [Values("delete", "move", "copy")] string operation,
            [Values("sub/keep.txt", "sub/.hidden", "sub/name..txt", "sub/.../file",
                "data dir/nested file.txt", "sub/a&b?c.txt")] string providerPath,
            [Values] bool isDirectory)
        {
            Mock<IFileSystemProvider> provider = CreateProvider();
            using FileSystemNodeManager manager = CreateManager(provider.Object);
            // Delete and MoveOrCopy are called on the directory that organizes the source.
            string parentPath = providerPath[..providerPath.LastIndexOf('/')];
            var parent = new DirectoryObjectState(manager.SystemContext,
                FileSystemNodeId.BuildDirectory(parentPath, manager.NamespaceIndex), parentPath, parentPath,
                isRoot: false);
            NodeId source = isDirectory
                ? FileSystemNodeId.BuildDirectory(providerPath, manager.NamespaceIndex)
                : FileSystemNodeId.BuildFile(providerPath, manager.NamespaceIndex);
            const string TargetPath = "destination/nested/renamed.txt";

            if (operation == "delete")
            {
                ServiceResult result = await MutateAsync(parent, manager.SystemContext, source, operation)
                    .ConfigureAwait(false);
                Assert.That(result.StatusCode, Is.EqualTo(StatusCodes.Good));
            }
            else
            {
                NodeId target = FileSystemNodeId.BuildDirectory("destination/nested", manager.NamespaceIndex);
                MoveOrCopyMethodStateResult result = await parent.MoveOrCopy!.OnCallAsync!(
                    manager.SystemContext, parent.MoveOrCopy, parent.NodeId, source, target,
                    operation == "copy", "renamed.txt", CancellationToken.None).ConfigureAwait(false);
                NodeId expectedId = isDirectory
                    ? FileSystemNodeId.BuildDirectory(TargetPath, manager.NamespaceIndex)
                    : FileSystemNodeId.BuildFile(TargetPath, manager.NamespaceIndex);
                Assert.That(result.ServiceResult.StatusCode, Is.EqualTo(StatusCodes.Good));
                Assert.That(result.NewNodeId, Is.EqualTo(expectedId));
            }
            VerifySingleMutation(provider, operation, providerPath, TargetPath);
        }

        /// <summary>
        /// Verifies that empty or separator-only destinations resolve to the mount root without a path prefix.
        /// </summary>
        [Test]
        public async Task SeparatorOnlyTargetsResolveToCanonicalMountRootAsync(
            [Values] bool createCopy,
            [ValueSource(nameof(s_rootPaths))] string providerPath,
            [Values(FileSystemNodeId.Root, FileSystemNodeId.Directory)] int rootType)
        {
            Mock<IFileSystemProvider> provider = CreateProvider();
            using FileSystemNodeManager manager = CreateManager(provider.Object);
            DirectoryObjectState root = CreateRoot(manager);
            NodeId source = FileSystemNodeId.BuildFile("keep.txt", manager.NamespaceIndex);
            var target = new FileSystemNodeId(rootType, providerPath, manager.NamespaceIndex).ToNodeId();

            MoveOrCopyMethodStateResult result = await root.MoveOrCopy!.OnCallAsync!(
                manager.SystemContext, root.MoveOrCopy, root.NodeId, source, target,
                createCopy, "renamed.txt", CancellationToken.None).ConfigureAwait(false);

            Assert.That(result.ServiceResult.StatusCode, Is.EqualTo(StatusCodes.Good));
            Assert.That(result.NewNodeId,
                Is.EqualTo(FileSystemNodeId.BuildFile("renamed.txt", manager.NamespaceIndex)));
            VerifySingleMutation(provider, createCopy ? "copy" : "move", "keep.txt", "renamed.txt");
        }

        /// <summary>
        /// Verifies that invalid type prefixes, method identifiers, and foreign namespaces cannot mutate provider
        /// entries.
        /// </summary>
        [Test]
        public async Task InvalidObjectIdsCannotDeleteMoveOrCopyAsync(
            [Values("delete", "move", "copy")] string operation,
            [Values("3:keep.txt", "4294967298:keep.txt", "2147483648:keep.txt",
                "0:keep.txt", "2:keep.txt?Open", "2:keep.txt?")] string identifier,
            [Values] bool foreignNamespace)
        {
            Mock<IFileSystemProvider> provider = CreateProvider();
            using FileSystemNodeManager manager = CreateManager(provider.Object);
            DirectoryObjectState root = CreateRoot(manager);
            var source = new NodeId(identifier,
                foreignNamespace ? (ushort)(manager.NamespaceIndex + 1) : manager.NamespaceIndex);

            ServiceResult result = await MutateAsync(root, manager.SystemContext, source, operation)
                .ConfigureAwait(false);

            Assert.Multiple(() =>
            {
                Assert.That(result.StatusCode.Code, Is.EqualTo(operation == "delete"
                    ? StatusCodes.BadNotFound
                    : StatusCodes.BadInvalidArgument));
                VerifyNoMutation(provider);
            });
        }

        /// <summary>
        /// Verifies that a valid-looking path in another namespace cannot alias a mounted file.
        /// </summary>
        [Test]
        public async Task ForeignNamespaceCannotAliasAValidFileAsync(
            [Values("delete", "move", "copy")] string operation)
        {
            Mock<IFileSystemProvider> provider = CreateProvider();
            using FileSystemNodeManager manager = CreateManager(provider.Object);
            DirectoryObjectState root = CreateRoot(manager);
            NodeId source = FileSystemNodeId.BuildFile("keep.txt", (ushort)(manager.NamespaceIndex + 1));

            ServiceResult result = await MutateAsync(root, manager.SystemContext, source, operation)
                .ConfigureAwait(false);

            Assert.Multiple(() =>
            {
                Assert.That(ServiceResult.IsBad(result), Is.True);
                VerifyNoMutation(provider);
            });
        }

        /// <summary>
        /// Verifies that invalid destination node kinds or namespaces reject moves and copies before provider access.
        /// </summary>
        [Test]
        public async Task InvalidMoveOrCopyTargetDoesNotInvokeProviderAsync(
            [Values] bool createCopy,
            [Values("3:target", "2:target", "1:target?CreateFile", "0:target")] string identifier,
            [Values] bool foreignNamespace)
        {
            Mock<IFileSystemProvider> provider = CreateProvider();
            using FileSystemNodeManager manager = CreateManager(provider.Object);
            DirectoryObjectState root = CreateRoot(manager);
            NodeId source = FileSystemNodeId.BuildFile("keep.txt", manager.NamespaceIndex);
            var target = new NodeId(identifier,
                foreignNamespace ? (ushort)(manager.NamespaceIndex + 1) : manager.NamespaceIndex);

            MoveOrCopyMethodStateResult result = await root.MoveOrCopy!.OnCallAsync!(
                manager.SystemContext, root.MoveOrCopy, root.NodeId, source, target,
                createCopy, "renamed.txt", CancellationToken.None).ConfigureAwait(false);

            Assert.Multiple(() =>
            {
                Assert.That(result.ServiceResult.StatusCode.Code, Is.EqualTo(StatusCodes.BadInvalidArgument));
                VerifyNoMutation(provider);
            });
        }

        /// <summary>
        /// Verifies that parsing rejects unsupported node kinds and numeric prefixes that overflow the type range.
        /// </summary>
        [TestCase("3:")]
        [TestCase("2147483648:")]
        [TestCase("4294967296:")]
        [TestCase("4294967297:")]
        [TestCase("4294967298:")]
        [TestCase("999999999999999999999999999999999999:")]
        public void ParserRejectsUnsupportedAndOverflowingTypes(string identifier)
        {
            Assert.That(FileSystemNodeId.TryParse(new NodeId(identifier, 2), out _), Is.False);
        }

        /// <summary>
        /// Verifies that physical-provider root aliases are rejected while existing files and directories remain
        /// intact.
        /// </summary>
        [Test]
        public async Task PhysicalProviderRejectsRootMutationsBeforeTouchingContentsAsync(
            [Values("delete", "move", "copy")] string operation,
            [Values("", "/", ".", "child/..")] string source)
        {
            string root = Path.Combine(Path.GetTempPath(), "fs-root-regression-" + Guid.NewGuid().ToString("N"));
            Directory.CreateDirectory(Path.Combine(root, "child"));
            string sentinel = Path.Combine(root, "keep.txt");
            await WriteTextAsync(sentinel, "unchanged").ConfigureAwait(false);
            var provider = new PhysicalFileSystemProvider(root, "RootRegression");
            try
            {
                // An existing target also keeps the unfixed recursive copy bounded.
                Assert.ThrowsAsync<UnauthorizedAccessException>(async () =>
                {
                    switch (operation)
                    {
                        case "delete":
                            await provider.DeleteAsync(source, CancellationToken.None).ConfigureAwait(false);
                            break;
                        case "move":
                            await provider.MoveAsync(source, "keep.txt", CancellationToken.None).ConfigureAwait(false);
                            break;
                        default:
                            await provider.CopyAsync(source, "keep.txt", CancellationToken.None).ConfigureAwait(false);
                            break;
                    }
                });
                Assert.That(await ReadTextAsync(sentinel).ConfigureAwait(false), Is.EqualTo("unchanged"));
                Assert.That(Directory.Exists(Path.Combine(root, "child")), Is.True);
            }
            finally
            {
                if (Directory.Exists(root))
                {
                    Directory.Delete(root, recursive: true);
                }
            }
        }

        /// <summary>
        /// Verifies that protecting the mount root still permits deleting, moving, and copying ordinary child files.
        /// </summary>
        [Test]
        public async Task OrdinaryChildMutationsRemainSupportedAsync(
            [Values("delete", "move", "copy")] string operation)
        {
            string rootPath = Path.Combine(Path.GetTempPath(), "fs-child-regression-" + Guid.NewGuid().ToString("N"));
            var provider = new PhysicalFileSystemProvider(rootPath, "ChildRegression");
            try
            {
                await WriteTextAsync(Path.Combine(rootPath, "keep.txt"), "payload").ConfigureAwait(false);
                using FileSystemNodeManager manager = CreateManager(provider);
                DirectoryObjectState root = CreateRoot(manager);
                NodeId source = FileSystemNodeId.BuildFile("keep.txt", manager.NamespaceIndex);

                ServiceResult result = await MutateAsync(root, manager.SystemContext, source, operation)
                    .ConfigureAwait(false);

                Assert.That(ServiceResult.IsGood(result), Is.True);
                Assert.That(File.Exists(Path.Combine(rootPath, "keep.txt")), Is.EqualTo(operation == "copy"));
                if (operation != "delete")
                {
                    Assert.That(await ReadTextAsync(Path.Combine(rootPath, "renamed.txt"))
                        .ConfigureAwait(false), Is.EqualTo("payload"));
                }
            }
            finally
            {
                Directory.Delete(rootPath, recursive: true);
            }
        }

        /// <summary>
        /// Writes a sentinel payload used to detect unintended provider mutations.
        /// </summary>
        private static async Task WriteTextAsync(string path, string value)
        {
            using var writer = new StreamWriter(path);
            await writer.WriteAsync(value).ConfigureAwait(false);
        }

        /// <summary>
        /// Reads a sentinel or copied payload to verify preserved file contents.
        /// </summary>
        private static async Task<string> ReadTextAsync(string path)
        {
            using var reader = new StreamReader(path);
            return await reader.ReadToEndAsync().ConfigureAwait(false);
        }

        /// <summary>
        /// Creates a writable provider mock whose mutation calls can be checked for admission and exact paths.
        /// </summary>
        private static Mock<IFileSystemProvider> CreateProvider()
        {
            var provider = new Mock<IFileSystemProvider>();
            provider.SetupGet(p => p.MountName).Returns("MountRegression");
            provider.SetupGet(p => p.IsWritable).Returns(true);
            provider.Setup(p => p.DeleteAsync(It.IsAny<string>(), It.IsAny<CancellationToken>()))
                .Returns(default(ValueTask));
            provider.Setup(p => p.MoveAsync(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<CancellationToken>()))
                .Returns(default(ValueTask));
            provider.Setup(p => p.CopyAsync(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<CancellationToken>()))
                .Returns(default(ValueTask));
            return provider;
        }

        /// <summary>
        /// Creates a file-system manager over the supplied provider and deterministic server mock.
        /// </summary>
        private static FileSystemNodeManager CreateManager(IFileSystemProvider provider)
        {
            Mock<IServerInternal> server = DeterministicServerMock.Create(out _);
            server.SetupGet(s => s.Telemetry).Returns(NUnitTelemetryContext.Create());
            return new FileSystemNodeManager(server.Object, new ApplicationConfiguration(), provider);
        }

        /// <summary>
        /// Creates the mounted root node exposing file-system mutation methods.
        /// </summary>
        private static DirectoryObjectState CreateRoot(FileSystemNodeManager manager)
        {
            return new DirectoryObjectState(manager.SystemContext,
                FileSystemNodeId.BuildRoot(manager.NamespaceIndex), string.Empty, "Root", isRoot: true);
        }

        /// <summary>
        /// Invokes deletion or a move or copy into the root through the mounted directory methods.
        /// </summary>
        private static async ValueTask<ServiceResult> MutateAsync(
            DirectoryObjectState root,
            ISystemContext context,
            NodeId source,
            string operation)
        {
            if (operation == "delete")
            {
                DeleteFileMethodStateResult deleted = await root.DeleteFileSystemObject!.OnCallAsync!(
                    context, root.DeleteFileSystemObject, root.NodeId, source, CancellationToken.None)
                    .ConfigureAwait(false);
                return deleted.ServiceResult;
            }

            MoveOrCopyMethodStateResult moved = await root.MoveOrCopy!.OnCallAsync!(
                context, root.MoveOrCopy, root.NodeId, source, root.NodeId,
                operation == "copy", "renamed.txt", CancellationToken.None).ConfigureAwait(false);
            return moved.ServiceResult;
        }

        /// <summary>
        /// Verifies that no delete, move, or copy request reached the provider.
        /// </summary>
        private static void VerifyNoMutation(Mock<IFileSystemProvider> provider)
        {
            provider.Verify(p => p.DeleteAsync(It.IsAny<string>(), It.IsAny<CancellationToken>()), Times.Never);
            provider.Verify(p => p.MoveAsync(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<CancellationToken>()),
                Times.Never);
            provider.Verify(p => p.CopyAsync(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<CancellationToken>()),
                Times.Never);
        }

        /// <summary>
        /// Verifies that only the selected mutation occurred once with the expected source and destination paths.
        /// </summary>
        private static void VerifySingleMutation(
            Mock<IFileSystemProvider> provider,
            string operation,
            string source,
            string target)
        {
            provider.Verify(p => p.DeleteAsync(It.IsAny<string>(), It.IsAny<CancellationToken>()),
                Times.Exactly(operation == "delete" ? 1 : 0));
            provider.Verify(p => p.MoveAsync(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<CancellationToken>()),
                Times.Exactly(operation == "move" ? 1 : 0));
            provider.Verify(p => p.CopyAsync(It.IsAny<string>(), It.IsAny<string>(), It.IsAny<CancellationToken>()),
                Times.Exactly(operation == "copy" ? 1 : 0));
            provider.Verify(p => p.DeleteAsync(source, It.IsAny<CancellationToken>()),
                Times.Exactly(operation == "delete" ? 1 : 0));
            provider.Verify(p => p.MoveAsync(source, target, It.IsAny<CancellationToken>()),
                Times.Exactly(operation == "move" ? 1 : 0));
            provider.Verify(p => p.CopyAsync(source, target, It.IsAny<CancellationToken>()),
                Times.Exactly(operation == "copy" ? 1 : 0));
        }

        /// <summary>
        /// Supplies nonroot paths containing traversal, noncanonical separators, or invalid path components.
        /// </summary>
        private static readonly string[] s_invalidNonRootPaths =
        [
            ".", "..", "sub/..", "sub/../", "../sub", "sub/../leaf", "sub//leaf", "sub/./leaf", "/sub", "sub/",
            " ", "sub/ /leaf",
            .. Path.DirectorySeparatorChar == '\\'
                ? [ "sub\\..", "sub\\..\\", "sub\\..\\leaf", "sub\\\\leaf", "sub\\.\\leaf", "\\sub",
                    "sub\\leaf", "C:/sub", "C:\\sub", "sub/stream:name" ]
                : Array.Empty<string>()
        ];

        /// <summary>
        /// Combines root aliases and invalid nonroot paths for source-path admission tests.
        /// </summary>
        private static readonly string[] s_nonCanonicalProviderPaths =
        [
            "/", "//", .. s_invalidNonRootPaths,
            .. Path.DirectorySeparatorChar == '\\' ? ["\\", "\\\\", "/\\/"] : Array.Empty<string>()
        ];

        private static readonly string[] s_rootIds = Path.DirectorySeparatorChar == '\\'
            ? ["0:", "1:", "2:", "0:/", "0:\\", "0://"]
            : ["0:", "1:", "2:", "0:/", "0://"];

        private static readonly string[] s_rootPaths = Path.DirectorySeparatorChar == '\\'
            ? [string.Empty, "/", "\\", "//", "\\\\", "/\\/"]
            : [string.Empty, "/", "//"];
    }
}