// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.IO;
using Microsoft.Build.Framework;
using Microsoft.Build.Shared;
using Microsoft.Build.Utilities;

#nullable disable

namespace Microsoft.Build.Tasks
{
    /// <summary>
    /// Create a new list of items that have &lt;TargetPath&gt; attributes if none was present in
    /// the input.
    /// </summary>
    [MSBuildMultiThreadableTask]
    public class AssignTargetPath : TaskExtension, IMultiThreadableTask
    {
        #region Properties

        /// <summary>
        /// Gets or sets the task execution environment for thread-safe path resolution.
        /// </summary>
        public TaskEnvironment TaskEnvironment { get; set; } = TaskEnvironment.Fallback;


        /// <summary>
        /// The folder to make the links relative to.
        /// </summary>
        [Required]
        public string RootFolder { get; set; }

        /// <summary>
        /// The incoming list of files.
        /// </summary>
        public ITaskItem[] Files { get; set; } = Array.Empty<ITaskItem>();

        /// <summary>
        /// The resulting list of files.
        /// </summary>
        /// <value></value>
        [Output]
        public ITaskItem[] AssignedFiles { get; private set; }

        #endregion

        /// <summary>
        /// Execute the task.
        /// </summary>
        /// <returns></returns>
        public override bool Execute()
        {
            AssignedFiles = new ITaskItem[Files.Length];

            if (Files.Length > 0)
            {
                AbsolutePath fullRootPath = default;
                string fullRootPathString = null;
                bool isRootFolderSameAsCurrentDirectory;

                if (ChangeWaves.AreFeaturesEnabled(ChangeWaves.Wave18_5))
                {
                    // Compose a file in the root folder.
                    // NOTE: at this point fullRootPath may or may not have a trailing slash
                    // Ensure trailing slash otherwise c:\bin appears to match part of c:\bin2\foo
                    // Also ensure that relative segments in the path are resolved.
                    fullRootPath =
                        TaskEnvironment.GetAbsolutePath(FileUtilities.EnsureTrailingSlash(RootFolder)).GetCanonicalForm();

                    // Ensure trailing slash for comparison. Current directory is already canonical, so we don't need to call GetCanonicalForm on it.
                    AbsolutePath currentDirectory = FileUtilities.EnsureTrailingSlash(TaskEnvironment.ProjectDirectory);

                    // Check if the root folder is the same as the current directory - AbsolutePath handles OS-aware case sensitivity.
                    isRootFolderSameAsCurrentDirectory = fullRootPath == currentDirectory;
                }
                else
                {
                    // Compose a file in the root folder.
                    // NOTE: at this point fullRootPath may or may not have a trailing slash
                    // Ensure trailing slash otherwise c:\bin appears to match part of c:\bin2\foo
                    // Also ensure that relative segments in the path are resolved and throw on illegal characters in Path.GetFullPath to preserve pre-existing behavior.
                    fullRootPathString = 
#pragma warning disable MSBuildTask0002 // Path is already absolute from TaskEnvironment.GetAbsolutePath; GetFullPath only canonicalizes. Guarded by ChangeWave.
                        Path.GetFullPath(TaskEnvironment.GetAbsolutePath(FileUtilities.EnsureTrailingSlash(RootFolder)));
#pragma warning restore MSBuildTask0002

                    // Ensure trailing slash for comparison. Current directory is already canonical, so we don't need to call GetCanonicalForm on it.
                    AbsolutePath currentDirectory = FileUtilities.EnsureTrailingSlash(TaskEnvironment.ProjectDirectory);

                    // Check if the root folder is the same as the current directory. 
                    // Perform a case-insensitive comparison to match Path.GetFullPath behavior on Windows, even on case-sensitive file systems, 
                    // since that's what we're using to determine whether to preserve relative paths or not.
                    isRootFolderSameAsCurrentDirectory = String.Compare(fullRootPathString, currentDirectory, StringComparison.OrdinalIgnoreCase) == 0;
                }

                for (int i = 0; i < Files.Length; ++i)
                {
                    AssignedFiles[i] = new TaskItem(Files[i]);

                    // If TargetPath is already set, it takes priority.
                    // https://github.com/dotnet/msbuild/issues/2795
                    string targetPath = Files[i].GetMetadata(ItemMetadataNames.targetPath);

                    // If TargetPath not already set, fall back to default behavior.
                    if (string.IsNullOrEmpty(targetPath))
                    {
                        targetPath = Files[i].GetMetadata(ItemMetadataNames.link);
                    }

                    if (string.IsNullOrEmpty(targetPath))
                    {
                        if (// if the file path is relative
                            !Path.IsPathRooted(Files[i].ItemSpec) &&
                            // if the file path doesn't contain any relative specifiers
                            !Files[i].ItemSpec.Contains("." + Path.DirectorySeparatorChar) &&
                            // if the file path is already relative to the root folder
                            isRootFolderSameAsCurrentDirectory)
                        {
                            // then just use the file path as-is
                            // PERF NOTE: we do this to avoid calling Path.GetFullPath() below (which is called by GetCanonicalForm method),
                            // because that method consumes a lot of memory, esp. when we have a lot of items coming through this task
                            targetPath = Files[i].ItemSpec;
                        }
                        else
                        {
                            if (ChangeWaves.AreFeaturesEnabled(ChangeWaves.Wave18_5)) 
                            {
                                AbsolutePath itemSpecFullFileNamePath = 
                                    TaskEnvironment.GetAbsolutePath(Files[i].ItemSpec).GetCanonicalForm();


                                if (itemSpecFullFileNamePath.Value.StartsWith(fullRootPath.Value, FileUtilities.PathComparison))
                                {
                                    // The item spec file is in the "cone" of the RootFolder. Return the relative path from the cone root.
                                    targetPath = itemSpecFullFileNamePath.Value.Substring(fullRootPath.Value.Length);
                                }
                                else
                                {
                                    // The item spec file is not in the "cone" of the RootFolder. Return the filename only.
                                    targetPath = Path.GetFileName(Files[i].ItemSpec);
                                }
                            }
                            else 
                            {
                                string itemSpecFullFileNamePath = 
#pragma warning disable MSBuildTask0002 // Path is already absolute from TaskEnvironment.GetAbsolutePath; GetFullPath only canonicalizes. Guarded by ChangeWave.
                                    Path.GetFullPath(TaskEnvironment.GetAbsolutePath(Files[i].ItemSpec));
#pragma warning restore MSBuildTask0002

                                if (String.Compare(fullRootPathString, 0, itemSpecFullFileNamePath, 0, fullRootPathString.Length, StringComparison.CurrentCultureIgnoreCase) == 0)
                                {
                                    // The item spec file is in the "cone" of the RootFolder. Return the relative path from the cone root.
                                    targetPath = itemSpecFullFileNamePath.Substring(fullRootPathString.Length);
                                }
                                else
                                {
                                    // The item spec file is not in the "cone" of the RootFolder. Return the filename only.
                                    targetPath = Path.GetFileName(Files[i].ItemSpec);
                                }
                            }
                        }
                    }

                    AssignedFiles[i].SetMetadata(ItemMetadataNames.targetPath, EscapingUtilities.Escape(targetPath));
                }
            }

            return true;
        }
    }
}