// Copyright (c) 2016 Daniel Grunwald
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Diagnostics;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Reflection.Metadata;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

using ICSharpCode.Decompiler.CSharp.OutputVisitor;
using ICSharpCode.Decompiler.CSharp.Syntax;
using ICSharpCode.Decompiler.CSharp.Transforms;
using ICSharpCode.Decompiler.DebugInfo;
using ICSharpCode.Decompiler.Instrumentation;
using ICSharpCode.Decompiler.Metadata;
using ICSharpCode.Decompiler.Semantics;
using ICSharpCode.Decompiler.Solution;
using ICSharpCode.Decompiler.TypeSystem;
using ICSharpCode.Decompiler.Util;

using static ICSharpCode.Decompiler.Metadata.MetadataExtensions;

#nullable enable

namespace ICSharpCode.Decompiler.CSharp.ProjectDecompiler
{
	/// <summary>
	/// Decompiles an assembly into a visual studio project file.
	/// </summary>
	public class WholeProjectDecompiler : IProjectInfoProvider
	{
		const int maxSegmentLength = 255;

		#region Settings
		/// <summary>
		/// Gets the setting this instance uses for decompiling.
		/// </summary>
		public DecompilerSettings Settings { get; }

		LanguageVersion? languageVersion;

		/// <summary>
		/// The C# language version written into the exported project file as LangVersion.
		/// This is an export parameter, not decompiler state: when not set explicitly, it defaults
		/// to <see cref="DecompilerSettings.GetMinimumRequiredVersion"/> of the current settings,
		/// and an explicit value below that minimum is rejected (here and again when the export
		/// starts) because the emitted code could not compile under it.
		/// </summary>
		public LanguageVersion LanguageVersion {
			get { return languageVersion ?? Settings.GetMinimumRequiredVersion(); }
			set {
				ValidateLanguageVersion(value);
				languageVersion = value;
			}
		}

		void ValidateLanguageVersion(LanguageVersion version)
		{
			var minVersion = Settings.GetMinimumRequiredVersion();
			if (version < minVersion)
			{
				throw new InvalidOperationException($"The chosen settings require at least {minVersion}." +
					" Please change the DecompilerSettings accordingly.");
			}
		}

		bool IProjectInfoProvider.CheckForOverflowUnderflow => Settings.CheckForOverflowUnderflow;

		public IAssemblyResolver AssemblyResolver { get; }

		public IAssemblyReferenceClassifier AssemblyReferenceClassifier { get; }

		public IDebugInfoProvider? DebugInfoProvider { get; }

		/// <summary>
		/// The MSBuild ProjectGuid to use for the new project.
		/// </summary>
		public Guid ProjectGuid { get; }

		/// <summary>
		/// The target directory that the decompiled files are written to.
		/// </summary>
		/// <remarks>
		/// This property is set by DecompileProject() and protected so that overridden protected members
		/// can access it.
		/// </remarks>
		public string TargetDirectory { get; protected set; } = string.Empty;

		/// <summary>
		/// Path to the snk file to use for signing.
		/// <c>null</c> to not sign.
		/// </summary>
		public string? StrongNameKeyFile { get; set; }

		public int MaxDegreeOfParallelism { get; set; } = Environment.ProcessorCount;

		public IProgress<DecompilationProgress>? ProgressIndicator { get; set; }
		#endregion

		public WholeProjectDecompiler(IAssemblyResolver assemblyResolver)
			: this(new DecompilerSettings(), assemblyResolver, projectWriter: null, assemblyReferenceClassifier: null, debugInfoProvider: null)
		{
		}

		public WholeProjectDecompiler(
			DecompilerSettings settings,
			IAssemblyResolver assemblyResolver,
			IProjectFileWriter? projectWriter,
			IAssemblyReferenceClassifier? assemblyReferenceClassifier,
			IDebugInfoProvider? debugInfoProvider)
			: this(settings, Guid.NewGuid(), assemblyResolver, projectWriter ?? IProjectFileWriter.FromSettings(settings), assemblyReferenceClassifier ?? new AssemblyReferenceClassifier(), debugInfoProvider)
		{
		}

		protected WholeProjectDecompiler(
			DecompilerSettings settings,
			Guid projectGuid,
			IAssemblyResolver assemblyResolver,
			IProjectFileWriter projectWriter,
			IAssemblyReferenceClassifier assemblyReferenceClassifier,
			IDebugInfoProvider? debugInfoProvider)
		{
			Settings = settings ?? throw new ArgumentNullException(nameof(settings));
			ProjectGuid = projectGuid;
			AssemblyResolver = assemblyResolver ?? throw new ArgumentNullException(nameof(assemblyResolver));
			AssemblyReferenceClassifier = assemblyReferenceClassifier ?? throw new ArgumentNullException(nameof(assemblyReferenceClassifier));
			DebugInfoProvider = debugInfoProvider;
			this.projectWriter = projectWriter ?? throw new ArgumentNullException(nameof(projectWriter));
		}

		// per-run members
		HashSet<string> directories = new HashSet<string>(Platform.FileNameComparer);
		readonly Dictionary<string, int> resourceFileNames = new Dictionary<string, int>(Platform.FileNameComparer);
		readonly List<DecompilerException> errors = new List<DecompilerException>();
		readonly IProjectFileWriter projectWriter;

		/// <summary>
		/// Everything that went wrong during the last <see cref="DecompileProject(MetadataFile, string, CancellationToken)"/>.
		/// An export never aborts on a member, file or resource it cannot handle; it writes the
		/// error text where the content would have gone and continues, so a single unsupported
		/// method still yields a complete project. Callers should show this list to the user -
		/// otherwise the failures ship silently and never get reported.
		/// </summary>
		public IReadOnlyList<DecompilerException> Errors => errors;

		void RecordError(DecompilerException error)
		{
			lock (errors)
			{
				errors.Add(error);
			}
		}

		/// <summary>
		/// Yields the items of <paramref name="items"/> until one of them throws; the failure is
		/// recorded instead of aborting the export.
		/// </summary>
		IEnumerable<T> RecordingErrors<T>(IEnumerable<T> items, MetadataFile file, string what)
		{
			using var enumerator = items.GetEnumerator();
			bool lastMoveFailed = false;
			while (true)
			{
				T item;
				try
				{
					if (!enumerator.MoveNext())
						yield break;
					item = enumerator.Current;
				}
				catch (Exception ex) when (!(ex is OperationCanceledException))
				{
					RecordError(ex as DecompilerException ?? new DecompilerException(file, $"Error writing {what}", ex));
					// Skip the item that failed and try the next one, but give up once two attempts
					// in a row fail: an enumerator that throws without advancing - which nothing
					// stops an override from being - would otherwise loop forever.
					if (lastMoveFailed)
						yield break;
					lastMoveFailed = true;
					continue;
				}
				lastMoveFailed = false;
				yield return item;
			}
		}

		/// <summary>
		/// Puts the error text where the file's contents would have gone. The writer itself may be
		/// what failed - a full disk, a stream already closed - so a second failure while reporting
		/// the first is dropped rather than allowed to take the export down.
		/// </summary>
		static void WriteErrorComment(TextWriter? writer, Exception error)
		{
			if (writer == null)
				return;
			try
			{
				// The failure may have interrupted the output visitor mid-line.
				writer.WriteLine();
				foreach (string line in CSharpDecompiler.GetErrorCommentLines(error))
				{
					writer.WriteLine("// " + line);
				}
			}
			catch (Exception ex) when (!(ex is OperationCanceledException))
			{
			}
		}

		public void DecompileProject(MetadataFile file, string targetDirectory, CancellationToken cancellationToken = default(CancellationToken))
		{
			string projectFileName = Path.Combine(targetDirectory, CleanUpFileName(file.Name, ".csproj"));
			using (var writer = CreateFile(projectFileName))
			{
				DecompileProject(file, targetDirectory, writer, cancellationToken);
			}
		}

		public ProjectId DecompileProject(MetadataFile file, string targetDirectory, TextWriter projectFileWriter, CancellationToken cancellationToken = default(CancellationToken))
		{
			if (string.IsNullOrEmpty(targetDirectory))
			{
				throw new InvalidOperationException("Must set TargetDirectory");
			}
			// The LanguageVersion setter already rejects a version below what the settings require,
			// but Settings is mutable and shared, so re-validate against the settings actually in
			// effect now - otherwise the exported project would carry a LangVersion under which the
			// emitted code cannot compile.
			if (languageVersion is { } explicitVersion)
			{
				ValidateLanguageVersion(explicitVersion);
			}
			DecompilerEventSource.Log.ProjectDecompilationStart(file.Name);
			int codeFileCount = 0, resourceFileCount = 0;
			try
			{
				TargetDirectory = targetDirectory;
				directories.Clear();
				resourceFileNames.Clear();
				errors.Clear();
				var resources = RecordingErrors(WriteResourceFilesInProject(file), file, "resource files").ToList();
				resourceFileCount = resources.Count;
				var files = WriteCodeFilesInProject(file, resources.SelectMany(r => r.PartialTypes ?? Enumerable.Empty<PartialTypeInfo>()).ToList(), cancellationToken).ToList();
				codeFileCount = files.Count;
				files.AddRange(resources);
				var module = file as PEFile;
				if (module != null)
				{
					files.AddRange(RecordingErrors(WriteMiscellaneousFilesInProject(module), file, "miscellaneous files"));
				}
				if (StrongNameKeyFile != null)
				{
					File.Copy(StrongNameKeyFile, Path.Combine(targetDirectory, Path.GetFileName(StrongNameKeyFile)), overwrite: true);
				}

				projectWriter.Write(projectFileWriter, this, files, file);

				string platformName = module != null ? TargetServices.GetPlatformName(module) : "AnyCPU";
				return new ProjectId(platformName, ProjectGuid, ProjectTypeGuids.CSharpWindows);
			}
			finally
			{
				DecompilerEventSource.Log.ProjectDecompilationStop(file.Name, codeFileCount, resourceFileCount);
			}
		}

		#region WriteCodeFilesInProject
		protected virtual bool IncludeTypeWhenDecompilingProject(MetadataFile module, TypeDefinitionHandle type)
		{
			var metadata = module.Metadata;
			var typeDef = metadata.GetTypeDefinition(type);
			string name = metadata.GetString(typeDef.Name);
			string ns = metadata.GetString(typeDef.Namespace);
			if (name == "<Module>" || CSharpDecompiler.MemberIsHidden(module, type, Settings))
				return false;
			if (ns == "XamlGeneratedNamespace" && name == "GeneratedInternalTypeHelper")
				return false;
			if (!typeDef.IsNested && RemoveEmbeddedAttributes.attributeNames.Contains(ns + "." + name))
				return false;
			return true;
		}

		protected virtual TextWriter CreateFile(string path)
		{
			return new StreamWriter(path);
		}

		protected virtual void CreateDirectory(string path)
		{
			try
			{
				Directory.CreateDirectory(path);
			}
			catch (IOException)
			{
				File.Delete(path);
				Directory.CreateDirectory(path);
			}
		}

		protected virtual CSharpDecompiler CreateDecompiler(DecompilerTypeSystem ts)
		{
			var decompiler = new CSharpDecompiler(ts, Settings);
			decompiler.DebugInfoProvider = DebugInfoProvider;
			decompiler.AstTransforms.Add(new EscapeInvalidIdentifiers());
			decompiler.AstTransforms.Add(new RemoveCLSCompliantAttribute());
			return decompiler;
		}

		IEnumerable<ProjectItemInfo> WriteAssemblyInfo(DecompilerTypeSystem ts, CancellationToken cancellationToken)
		{
			var decompiler = CreateDecompiler(ts);
			decompiler.CancellationToken = cancellationToken;
			decompiler.AstTransforms.Add(new RemoveCompilerGeneratedAssemblyAttributes());
			SyntaxTree syntaxTree = decompiler.DecompileModuleAndAssemblyAttributes();

			const string prop = "Properties";
			if (directories.Add(prop))
				CreateDirectory(Path.Combine(TargetDirectory, prop));
			string assemblyInfo = Path.Combine(prop, "AssemblyInfo.cs");
			using (var w = CreateFile(Path.Combine(TargetDirectory, assemblyInfo)))
			{
				syntaxTree.AcceptVisitor(new CSharpOutputVisitor(w, Settings.CSharpFormattingOptions));
			}
			return new[] { new ProjectItemInfo("Compile", assemblyInfo) };
		}

		IEnumerable<ProjectItemInfo> WriteCodeFilesInProject(MetadataFile module, IList<PartialTypeInfo> partialTypes, CancellationToken cancellationToken)
		{
			var metadata = module.Metadata;
			var files = module.Metadata.GetTopLevelTypeDefinitions().Where(td => IncludeTypeWhenDecompilingProject(module, td))
				.GroupBy(GetFileFileNameForHandle, StringComparer.OrdinalIgnoreCase).ToList();
			var progressReporter = ProgressIndicator;
			var progress = new DecompilationProgress { TotalUnits = files.Count, Title = "Exporting project..." };
			DecompilerTypeSystem ts = new DecompilerTypeSystem(module, AssemblyResolver, Settings);
			var missingFiles = new ConcurrentBag<string>();
			var workList = new HashSet<TypeDefinitionHandle>();
			var processedTypes = new HashSet<TypeDefinitionHandle>();
			ProcessFiles(files);
			while (workList.Count > 0)
			{
				var additionalFiles = workList
					.GroupBy(GetFileFileNameForHandle, StringComparer.OrdinalIgnoreCase).ToList();
				workList.Clear();
				ProcessFiles(additionalFiles);
				files.AddRange(additionalFiles);
				progress.TotalUnits = files.Count;
			}

			// The assembly-level attributes are a single file like any other: failing to decompile
			// them costs that file, not the export.
			IEnumerable<ProjectItemInfo> assemblyInfo;
			try
			{
				assemblyInfo = WriteAssemblyInfo(ts, cancellationToken);
			}
			catch (Exception ex) when (!(ex is OperationCanceledException))
			{
				RecordError(ex as DecompilerException ?? new DecompilerException(module, "Error decompiling the module and assembly attributes", ex));
				assemblyInfo = Enumerable.Empty<ProjectItemInfo>();
			}

			return files.Select(f => f.Key).Except(missingFiles, Platform.FileNameComparer)
				.Select(f => new ProjectItemInfo("Compile", f)).Concat(assemblyInfo);

			string GetFileFileNameForHandle(TypeDefinitionHandle h)
			{
				var type = metadata.GetTypeDefinition(h);
				string file = CleanUpFileName(metadata.GetString(type.Name), ".cs");
				string ns = metadata.GetString(type.Namespace);
				if (string.IsNullOrEmpty(ns))
				{
					return file;
				}
				else
				{
					string dir = Settings.UseNestedDirectoriesForNamespaces ? CleanUpPath(ns) : CleanUpDirectoryName(ns);
					if (directories.Add(dir))
					{
						var path = Path.Combine(TargetDirectory, dir);
						CreateDirectory(path);
					}
					return Path.Combine(dir, file);
				}
			}

			void ProcessFiles(List<IGrouping<string, TypeDefinitionHandle>> files)
			{
				processedTypes.AddRange(files.SelectMany(f => f));
				Parallel.ForEach(
					Partitioner.Create(files, loadBalance: true),
					new ParallelOptions {
						MaxDegreeOfParallelism = this.MaxDegreeOfParallelism,
						CancellationToken = cancellationToken
					},
					delegate (IGrouping<string, TypeDefinitionHandle> file) {
						var declaredTypes = file.ToArray();
						DecompilerEventSource.Log.ProjectFileStart(file.Key, declaredTypes.Length);
						// Everything that can fail for this one file - creating it included, which is
						// where a path too long for the file system surfaces - belongs inside the try.
						TextWriter? w = null;
						CSharpDecompiler? decompiler = null;
						try
						{
							w = CreateFile(Path.Combine(TargetDirectory, file.Key));
							decompiler = CreateDecompiler(ts);

							foreach (var partialType in partialTypes)
							{
								decompiler.AddPartialTypeDefinition(partialType);
							}

							decompiler.CancellationToken = cancellationToken;
							var syntaxTree = decompiler.DecompileTypes(declaredTypes);

							foreach (var node in syntaxTree.Descendants)
							{
								var td = (node.GetResolveResult() as TypeResolveResult)?.Type.GetDefinition();
								if (td?.ParentModule != ts.MainModule)
									continue;
								while (td?.DeclaringTypeDefinition != null)
								{
									td = td.DeclaringTypeDefinition;
								}
								if (td != null && td.MetadataToken is { IsNil: false } token && !processedTypes.Contains((TypeDefinitionHandle)token))
								{
									lock (workList)
									{
										workList.Add((TypeDefinitionHandle)token);
									}
								}
							}

							// A member the output visitor cannot write is replaced by the error text
							// rather than truncating the file where it failed.
							var outputVisitor = new ErrorTolerantOutputVisitor(w, Settings.CSharpFormattingOptions);
							syntaxTree.AcceptVisitor(outputVisitor);
							foreach (var outputError in outputVisitor.Errors)
							{
								RecordError(new DecompilerException(module, $"Error writing '{file.Key}'", outputError));
							}
						}
						catch (Exception innerException) when (!(innerException is OperationCanceledException))
						{
							// Whatever the decompiler could not cope with here, the remaining files
							// are unaffected and the user still gets a complete project; the error
							// takes the place of the file's contents.
							RecordError(innerException as DecompilerException ?? new DecompilerException(module, $"Error decompiling for '{file.Key}'", innerException));
							if (w == null)
							{
								// Nothing was written, so nothing can carry the error text - and the
								// project must not claim a file that is not there.
								missingFiles.Add(file.Key);
							}
							WriteErrorComment(w, innerException);
						}
						finally
						{
							foreach (var error in decompiler?.Errors ?? (IReadOnlyList<DecompilerException>)Array.Empty<DecompilerException>())
							{
								RecordError(error);
							}
							try
							{
								w?.Dispose();
							}
							catch (Exception ex) when (!(ex is OperationCanceledException))
							{
								// Dispose flushes: on a full disk this is where the write actually fails.
								RecordError(new DecompilerException(module, $"Error writing '{file.Key}'", ex));
							}
							DecompilerEventSource.Log.ProjectFileStop(file.Key);
						}
						progress.Status = file.Key;
						Interlocked.Increment(ref progress.UnitsCompleted);
						progressReporter?.Report(progress);
					});
			}
		}
		#endregion

		#region WriteResourceFilesInProject
		protected virtual IEnumerable<ProjectItemInfo> WriteResourceFilesInProject(MetadataFile module)
		{
			foreach (var r in module.Resources.Where(r => r.ResourceType == ResourceType.Embedded))
			{
				List<ProjectItemInfo> items;
				try
				{
					items = WriteResourceFileInProject(module, r).ToList();
				}
				catch (Exception ex) when (!(ex is OperationCanceledException))
				{
					// One resource nobody can decode - a mangled .resources blob, a BAML stream the
					// decompiler chokes on - costs that resource, not the ones behind it.
					RecordError(ex as DecompilerException ?? new DecompilerException(module, $"Error writing resource '{r.Name}'", ex));
					continue;
				}
				foreach (var item in items)
				{
					yield return item;
				}
			}
		}

		IEnumerable<ProjectItemInfo> WriteResourceFileInProject(MetadataFile module, Resource r)
		{
			Stream? stream = r.TryOpenStream();
			if (stream == null)
				yield break;

			stream.Position = 0;

			if (r.Name.EndsWith(".resources", StringComparison.OrdinalIgnoreCase))
			{
				bool decodedIntoIndividualFiles;
				var individualResources = new List<ProjectItemInfo>();
				try
				{
					var resourcesFile = new ResourcesFile(stream);
					if (resourcesFile.AllEntriesAreStreams())
					{
						bool entryNamesAreEscaped = IsWpfGeneratedResourceContainer(r.Name);
						foreach (var (name, value) in resourcesFile)
						{
							string fileName = ReserveResourceFileName(SanitizeFileName(entryNamesAreEscaped ? Uri.UnescapeDataString(name) : name));
							string? dirName = Path.GetDirectoryName(fileName);
							Stream entryStream = (Stream)value!;
							entryStream.Position = 0;
							try
							{
								// Inside the recovery, because an entry named after a directory another
								// entry needs makes this throw, and that must cost the one entry rather
								// than every entry left in the container.
								if (!string.IsNullOrEmpty(dirName) && !directories.Contains(dirName))
								{
									CreateDirectory(Path.Combine(TargetDirectory, dirName));
									directories.Add(dirName);
								}
								foreach (var item in WriteResourceToFile(fileName, name, entryStream))
								{
									individualResources.Add(entryNamesAreEscaped ? ToWpfProjectItem(item, name) : item);
								}
							}
							catch (Exception ex) when (!(ex is OperationCanceledException))
							{
								// One entry nobody can decode - a BAML stream carrying characters XML
								// cannot represent, say - costs that entry, not every other entry
								// sharing the container with it.
								RecordError(ex as DecompilerException ?? new DecompilerException(module, $"Error writing resource '{name}'", ex));
							}
						}
						decodedIntoIndividualFiles = true;
					}
					else
					{
						decodedIntoIndividualFiles = false;
					}
				}
				catch (BadImageFormatException)
				{
					decodedIntoIndividualFiles = false;
				}
				catch (EndOfStreamException)
				{
					decodedIntoIndividualFiles = false;
				}
				if (decodedIntoIndividualFiles)
				{
					foreach (var entry in individualResources)
					{
						yield return entry;
					}
				}
				else
				{
					stream.Position = 0;
					string fileName = ReserveResourceFileName(GetFileNameForResource(r.Name));
					foreach (var entry in WriteResourceToFile(fileName, r.Name, stream))
					{
						yield return entry;
					}
				}
			}
			else
			{
				string fileName = ReserveResourceFileName(GetFileNameForResource(r.Name));
				using (FileStream fs = new FileStream(Path.Combine(TargetDirectory, fileName), FileMode.Create, FileAccess.Write))
				{
					stream.Position = 0;
					stream.CopyTo(fs);
				}
				yield return new ProjectItemInfo("EmbeddedResource", fileName).With("LogicalName", r.Name);
			}
		}

		protected virtual IEnumerable<ProjectItemInfo> WriteResourceToFile(string fileName, string resourceName, Stream entryStream)
		{
			if (fileName.EndsWith(".resources", StringComparison.OrdinalIgnoreCase))
			{
				string resx = Path.ChangeExtension(fileName, ".resx");
				try
				{
					using (FileStream fs = new FileStream(Path.Combine(TargetDirectory, resx), FileMode.Create, FileAccess.Write))
					using (ResXResourceWriter writer = new ResXResourceWriter(fs))
					{
						foreach (var entry in new ResourcesFile(entryStream))
						{
							writer.AddResource(entry.Key, entry.Value);
						}
					}
					return new[] { new ProjectItemInfo("EmbeddedResource", resx).With("LogicalName", resourceName) };
				}
				catch (BadImageFormatException)
				{
					// if the .resources can't be decoded, just save them as-is
				}
				catch (EndOfStreamException)
				{
					// if the .resources can't be decoded, just save them as-is
				}
			}
			using (FileStream fs = new FileStream(Path.Combine(TargetDirectory, fileName), FileMode.Create, FileAccess.Write))
			{
				entryStream.CopyTo(fs);
			}
			return new[] { new ProjectItemInfo("EmbeddedResource", fileName).With("LogicalName", resourceName) };
		}

		/// <summary>
		/// Adjusts a project item produced from an entry of a WPF-generated ".g.resources" container
		/// so that rebuilding the exported project puts the entry back under its original resource
		/// ID. The file on disk cannot carry that ID - it is sanitized, and the ID is escaped - so
		/// the item pins it with a LogicalName holding the decoded name: the WPF build tasks
		/// lower-case and escape the LogicalName again, arriving back at the original ID. Entries
		/// that no handler turned into some other item type are WPF Resource items; leaving them as
		/// EmbeddedResource would rebuild them into a manifest resource of their own instead of
		/// putting them into ".g.resources".
		/// </summary>
		static ProjectItemInfo ToWpfProjectItem(ProjectItemInfo item, string escapedEntryName)
		{
			string logicalName = Uri.UnescapeDataString(escapedEntryName);
			if (item.FileName.EndsWith(".xaml", StringComparison.OrdinalIgnoreCase))
			{
				// A decompiled BAML page is written as .xaml, and the build derives the .baml
				// extension of the resource ID from the Page item type, not from the LogicalName.
				logicalName = Path.ChangeExtension(logicalName, ".xaml");
			}
			var result = item with {
				ItemType = item.ItemType == "EmbeddedResource" ? "Resource" : item.ItemType
			};
			result.AdditionalProperties ??= new Dictionary<string, string>();
			result.AdditionalProperties["LogicalName"] = logicalName;
			return result;
		}

		/// <summary>
		/// Claims <paramref name="fileName"/> for one resource, appending "_2", "_3", ... until the
		/// name is free. Sanitizing is not injective - "a+b/logo.png" and "a&amp;b/logo.png" both come out
		/// as "a-b/logo.png" - and the writers create files with FileMode.Create, so without this the
		/// entries after the first are lost silently, and an assembly can be built to make that happen
		/// to as many of them as it likes. The exported project keeps the true name in the item's
		/// LogicalName, so the file on disk only has to be unique, not faithful.
		/// </summary>
		string ReserveResourceFileName(string fileName)
		{
			if (!resourceFileNames.TryGetValue(fileName, out int lastSuffix))
			{
				resourceFileNames.Add(fileName, 1);
				return fileName;
			}
			// Resuming the count where the last collision on this name left off keeps the export
			// linear in the number of colliding entries; restarting at 2 each time would make it
			// quadratic, which is worth something when the count is the assembly's to choose.
			string candidate;
			do
			{
				candidate = AppendFileNameSuffix(fileName, ++lastSuffix);
			}
			while (resourceFileNames.ContainsKey(candidate));
			resourceFileNames[fileName] = lastSuffix;
			resourceFileNames.Add(candidate, 1);
			return candidate;
		}

		/// <summary>
		/// Inserts "_<paramref name="suffix"/>" before the extension, trimming the name if the segment
		/// would otherwise outgrow what the file system takes - a name already at the limit is an
		/// ordinary thing to find in an assembly, and the write would throw.
		/// </summary>
		static string AppendFileNameSuffix(string fileName, int suffix)
		{
			string directory = Path.GetDirectoryName(fileName) ?? string.Empty;
			string name = Path.GetFileNameWithoutExtension(fileName);
			string extension = Path.GetExtension(fileName);
			string marker = "_" + suffix.ToString(CultureInfo.InvariantCulture);
			// Trimming whole characters removes at least as many bytes as it has to, so measuring the
			// overflow the way CleanUpName measures a segment cannot leave the result over the limit.
			int overflow = SegmentLength(name) + SegmentLength(marker) + SegmentLength(extension) - maxSegmentLength;
			if (overflow > 0)
				name = name.Substring(0, Math.Max(0, name.Length - overflow));
			return Path.Combine(directory, name + marker + extension);
		}

		static int SegmentLength(string text)
		{
			return RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? text.Length : Encoding.UTF8.GetByteCount(text);
		}

		/// <summary>
		/// WPF's build tasks put every Page and Resource item into "&lt;AssemblyName&gt;.g.resources"
		/// (and into "&lt;AssemblyName&gt;.g.&lt;culture&gt;.resources" in satellite assemblies), keyed by
		/// the item's relative path, lower-cased and URI-escaped: a folder named "My Images" becomes
		/// "my%20images". Those escapes are not part of the name and have to be decoded before the
		/// name is turned into a file name, otherwise the percent sign is sanitized away and
		/// "my%20images/logo.png" lands in a directory called "my-20images".
		/// </summary>
		static bool IsWpfGeneratedResourceContainer(string resourceName)
		{
			const string extension = ".resources";
			if (!resourceName.EndsWith(extension, StringComparison.OrdinalIgnoreCase))
				return false;
			string name = resourceName.Substring(0, resourceName.Length - extension.Length);
			return name.EndsWith(".g", StringComparison.OrdinalIgnoreCase)
				|| name.Substring(0, Math.Max(0, name.LastIndexOf('.'))).EndsWith(".g", StringComparison.OrdinalIgnoreCase);
		}

		string GetFileNameForResource(string fullName)
		{
			// Clean up the name first and ensure the length does not exceed the maximum length
			// supported by the OS.
			fullName = SanitizeFileName(fullName);
			// The purpose of the below algorithm is to "maximize" the directory name and "minimize" the file name.
			// That is, a full name of the form "Namespace1.Namespace2{...}.NamespaceN.ResourceName" is split such that
			// the directory part Namespace1\Namespace2\... reuses as many existing directories as
			// possible, and only the remaining name parts are used as prefix for the filename.
			// This is not affected by the UseNestedDirectoriesForNamespaces setting.
			string[] splitName = fullName.Split('\\', '/');
			string fileName = string.Join(".", splitName);
			string separator = Path.DirectorySeparatorChar.ToString();
			for (int i = splitName.Length - 1; i > 0; i--)
			{
				string ns = string.Join(separator, splitName, 0, i);
				if (directories.Contains(ns))
				{
					string name = string.Join(".", splitName, i, splitName.Length - i);
					fileName = Path.Combine(ns, name);
					break;
				}
			}
			return fileName;
		}
		#endregion

		#region WriteMiscellaneousFilesInProject
		protected virtual IEnumerable<ProjectItemInfo> WriteMiscellaneousFilesInProject(PEFile module)
		{
			var resources = module.Reader.ReadWin32Resources();
			if (resources == null)
				yield break;

			// Each file is written on its own, so the one that fails is the only one lost.
			foreach (var item in TryWrite(module, "app.ico", () => {
				byte[]? appIcon = CreateApplicationIcon(resources);
				if (appIcon == null)
					return null;
				File.WriteAllBytes(Path.Combine(TargetDirectory, "app.ico"), appIcon);
				return new ProjectItemInfo("ApplicationIcon", "app.ico");
			}))
			{
				yield return item;
			}

			foreach (var item in TryWrite(module, "app.manifest", () => {
				byte[]? appManifest = CreateApplicationManifest(resources);
				if (appManifest == null || IsDefaultApplicationManifest(appManifest))
					return null;
				File.WriteAllBytes(Path.Combine(TargetDirectory, "app.manifest"), appManifest);
				return new ProjectItemInfo("ApplicationManifest", "app.manifest");
			}))
			{
				yield return item;
			}

			foreach (var item in TryWrite(module, "app.config", () => {
				var appConfig = module.FileName + ".config";
				if (!File.Exists(appConfig))
					return null;
				File.Copy(appConfig, Path.Combine(TargetDirectory, "app.config"), overwrite: true);
				return new ProjectItemInfo("ApplicationConfig", Path.GetFileName(appConfig));
			}))
			{
				yield return item;
			}
		}

		IEnumerable<ProjectItemInfo> TryWrite(MetadataFile module, string what, Func<ProjectItemInfo?> write)
		{
			ProjectItemInfo? item;
			try
			{
				item = write();
			}
			catch (Exception ex) when (!(ex is OperationCanceledException))
			{
				RecordError(ex as DecompilerException ?? new DecompilerException(module, $"Error writing '{what}'", ex));
				yield break;
			}
			if (item.HasValue)
			{
				yield return item.Value;
			}
		}

		const int RT_ICON = 3;
		const int RT_GROUP_ICON = 14;

		unsafe static byte[]? CreateApplicationIcon(Win32ResourceDirectory resources)
		{
			var iconGroup = resources.Find(new Win32ResourceName(RT_GROUP_ICON))?.FirstDirectory()?.FirstData()?.Data;
			if (iconGroup == null)
				return null;

			var iconDir = resources.Find(new Win32ResourceName(RT_ICON));
			if (iconDir == null)
				return null;

			using var outStream = new MemoryStream();
			using var writer = new BinaryWriter(outStream);
			fixed (byte* pIconGroupData = iconGroup)
			{
				var pIconGroup = (GRPICONDIR*)pIconGroupData;
				writer.Write(pIconGroup->idReserved);
				writer.Write(pIconGroup->idType);
				writer.Write(pIconGroup->idCount);

				int iconCount = pIconGroup->idCount;
				uint offset = (2 * 3) + ((uint)iconCount * 0x10);
				for (int i = 0; i < iconCount; i++)
				{
					var pIconEntry = pIconGroup->idEntries + i;
					writer.Write(pIconEntry->bWidth);
					writer.Write(pIconEntry->bHeight);
					writer.Write(pIconEntry->bColorCount);
					writer.Write(pIconEntry->bReserved);
					writer.Write(pIconEntry->wPlanes);
					writer.Write(pIconEntry->wBitCount);
					writer.Write(pIconEntry->dwBytesInRes);
					writer.Write(offset);
					offset += pIconEntry->dwBytesInRes;
				}

				for (int i = 0; i < iconCount; i++)
				{
					var icon = iconDir.FindDirectory(new Win32ResourceName(pIconGroup->idEntries[i].nID))?.FirstData()?.Data;
					if (icon == null)
						return null;
					writer.Write(icon);
				}
			}

			return outStream.ToArray();
		}

		[StructLayout(LayoutKind.Sequential, Pack = 2)]
		unsafe struct GRPICONDIR
		{
			public ushort idReserved;
			public ushort idType;
			public ushort idCount;
			private fixed byte _idEntries[1];
			[System.Diagnostics.CodeAnalysis.SuppressMessage("Style", "IDE1006:Naming Styles", Justification = "<Pending>")]
			public GRPICONDIRENTRY* idEntries {
				get {
					fixed (byte* p = _idEntries)
						return (GRPICONDIRENTRY*)p;
				}
			}
		};

		[StructLayout(LayoutKind.Sequential, Pack = 2)]
		struct GRPICONDIRENTRY
		{
			public byte bWidth;
			public byte bHeight;
			public byte bColorCount;
			public byte bReserved;
			public ushort wPlanes;
			public ushort wBitCount;
			public uint dwBytesInRes;
			public short nID;
		};

		const int RT_MANIFEST = 24;

		unsafe static byte[]? CreateApplicationManifest(Win32ResourceDirectory resources)
		{
			return resources.Find(new Win32ResourceName(RT_MANIFEST))?.FirstDirectory()?.FirstData()?.Data;
		}

		static bool IsDefaultApplicationManifest(byte[] appManifest)
		{
			const string DEFAULT_APPMANIFEST =
				"<?xmlversion=\"1.0\"encoding=\"UTF-8\"standalone=\"yes\"?><assemblyxmlns=\"urn:schemas-microsoft-com" +
				":asm.v1\"manifestVersion=\"1.0\"><assemblyIdentityversion=\"1.0.0.0\"name=\"MyApplication.app\"/><tr" +
				"ustInfoxmlns=\"urn:schemas-microsoft-com:asm.v2\"><security><requestedPrivilegesxmlns=\"urn:schemas-" +
				"microsoft-com:asm.v3\"><requestedExecutionLevellevel=\"asInvoker\"uiAccess=\"false\"/></requestedPri" +
				"vileges></security></trustInfo></assembly>";

			string s = CleanUpApplicationManifest(appManifest);
			return s == DEFAULT_APPMANIFEST;
		}

		static string CleanUpApplicationManifest(byte[] appManifest)
		{
			bool bom = appManifest.Length >= 3 && appManifest[0] == 0xEF && appManifest[1] == 0xBB && appManifest[2] == 0xBF;
			string s = Encoding.UTF8.GetString(appManifest, bom ? 3 : 0, appManifest.Length - (bom ? 3 : 0));
			var sb = new StringBuilder(s.Length);
			for (int i = 0; i < s.Length; i++)
			{
				char c = s[i];
				switch (c)
				{
					case '\t':
					case '\n':
					case '\r':
					case ' ':
						continue;
				}
				sb.Append(c);
			}
			return sb.ToString();
		}
		#endregion

		/// <summary>
		/// Cleans up a node name for use as a file name.
		/// </summary>
		public static string CleanUpFileName(string text, string? extension)
		{
			if (string.IsNullOrEmpty(extension) || extension.StartsWith("."))
				text = $"{text}{extension}";
			else
				text = $"{text}.{extension}";

			return CleanUpName(text, separateAtDots: false, treatAsFileName: !string.IsNullOrEmpty(extension), treatAsPath: false);
		}

		/// <summary>
		/// Removes invalid characters from file names and reduces their length,
		/// but keeps file extensions and path structure intact.
		/// </summary>
		public static string SanitizeFileName(string fileName)
		{
			return CleanUpName(fileName, separateAtDots: false, treatAsFileName: true, treatAsPath: true);
		}

		/// <summary>
		/// Cleans up a node name for use as a file system name. If <paramref name="separateAtDots"/> is active,
		/// dots are seen as segment separators. Each segment is limited to maxSegmentLength characters.
		/// If <paramref name="treatAsFileName"/> is active, we check for file a extension and try to preserve it,
		/// if it's valid.
		/// </summary>
		static string CleanUpName(string text, bool separateAtDots, bool treatAsFileName, bool treatAsPath)
		{
			string? extension = null;
			int currentSegmentLength = 0;
			// Extract extension from the end of the name, if valid
			if (treatAsFileName)
			{
				// Check if input is a file name, i.e., has a valid extension
				// If yes, preserve extension and append it at the end.
				// But only, if the extension length does not exceed maxSegmentLength,
				// if that's the case we just give up and treat the extension no different
				// from the file name.
				int lastDot = text.LastIndexOf('.');
				if (lastDot >= 0 && text.Length - lastDot < maxSegmentLength)
				{
					string originalText = text;
					extension = text.Substring(lastDot);
					text = text.Remove(lastDot);
					foreach (var c in extension)
					{
						if (!(char.IsLetterOrDigit(c) || c == '-' || c == '_' || c == '.'))
						{
							// extension contains an invalid character, therefore cannot be a valid extension.
							extension = null;
							text = originalText;
							break;
						}
					}
				}
			}
			// Remove anything that could be confused with a rooted path.
			int pos = text.IndexOf(':');
			if (pos > 0)
				text = text.Substring(0, pos);
			text = text.Trim();
			// Remove generics
			pos = text.IndexOf('`');
			if (pos > 0)
			{
				text = text.Substring(0, pos).Trim();
			}
			// Whitelist allowed characters, replace everything else:
			StringBuilder b = new StringBuilder(text.Length + (extension?.Length ?? 0));
			bool countBytes = !RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
			int segmentStart = 0;
			int baseNameEnd = -1;
			foreach (var c in text)
			{
				if (char.IsLetterOrDigit(c) || c == '-' || c == '_')
				{
					unsafe
					{
						currentSegmentLength += countBytes ? Encoding.UTF8.GetByteCount(&c, 1) : 1;
					}
					// if the current segment exceeds maxSegmentLength characters,
					// skip until the end of the segment.
					if (currentSegmentLength <= maxSegmentLength)
						b.Append(c);
				}
				else if (c == '.' && b.Length > 0 && b[^1] != '.')
				{
					currentSegmentLength++;
					if (separateAtDots)
					{
						// The dot ends the current segment.
						EscapeReservedFileSystemName(b, segmentStart, baseNameEnd);
						b.Append('.');
						segmentStart = b.Length;
						baseNameEnd = -1;
						// Reset length at end of segment.
						currentSegmentLength = 0;
					}
					else if (currentSegmentLength <= maxSegmentLength)
					{
						// The first dot ends the segment's base name, the part Windows
						// device-name parsing looks at.
						if (baseNameEnd < 0)
							baseNameEnd = b.Length;
						b.Append('.'); // allow dot, but never two in a row
					}
				}
				else if (treatAsPath && (c is '/' or '\\') && currentSegmentLength > 0)
				{
					// if we treat this as a file name, we've started a new segment
					EscapeReservedFileSystemName(b, segmentStart, baseNameEnd);
					b.Append(Path.DirectorySeparatorChar);
					segmentStart = b.Length;
					baseNameEnd = -1;
					currentSegmentLength = 0;
				}
				else
				{
					if (char.IsHighSurrogate(c))
					{
						// only add one replacement character for surrogate pairs
						continue;
					}

					currentSegmentLength++;
					// if the current segment exceeds maxSegmentLength characters,
					// skip until the end of the segment.
					if (currentSegmentLength <= maxSegmentLength)
						b.Append('-');
				}
			}
			if (b.Length == 0)
				b.Append('-');
			EscapeReservedFileSystemName(b, segmentStart, baseNameEnd);
			string name = b.ToString();
			if (extension != null)
			{
				// make sure that adding the extension to the filename
				// does not exceed maxSegmentLength.
				// trim the name, if necessary.
				if (name.Length + extension.Length > maxSegmentLength)
					name = name.Remove(name.Length - extension.Length);
				name += extension;
			}

			if (name == ".")
				return "_";
			else
				return name;
		}

		/// <summary>
		/// Cleans up a node name for use as a directory name.
		/// </summary>
		public static string CleanUpDirectoryName(string text)
		{
			return CleanUpName(text, separateAtDots: false, treatAsFileName: false, treatAsPath: false);
		}

		public static string CleanUpPath(string text)
		{
			return CleanUpName(text, separateAtDots: true, treatAsFileName: false, treatAsPath: true)
				.Replace('.', Path.DirectorySeparatorChar);
		}

		/// <summary>
		/// Appends an underscore to the segment [<paramref name="segmentStart"/>..) of
		/// <paramref name="b"/> if its base name (the part before <paramref name="baseNameEnd"/>,
		/// or the whole segment when there was no dot) is a reserved Windows device name
		/// (CON, PRN, AUX, NUL, COM1-9, LPT1-9): "con" becomes "con_" and "con.txt" becomes
		/// "con_.txt". Windows device-name parsing ignores everything after the first dot, so the
		/// underscore must be inserted before it, not appended at the end.
		/// </summary>
		static void EscapeReservedFileSystemName(StringBuilder b, int segmentStart, int baseNameEnd)
		{
			if (baseNameEnd < 0)
				baseNameEnd = b.Length;
			int baseNameLength = baseNameEnd - segmentStart;
			// All reserved names are 3 or 4 characters long; checking the length first avoids
			// allocating a substring for segments that cannot be reserved anyway.
			if (baseNameLength is 3 or 4 && IsReservedFileSystemName(b.ToString(segmentStart, baseNameLength)))
				b.Insert(baseNameEnd, '_');
		}

		static bool IsReservedFileSystemName(string name)
		{
			switch (name.ToUpperInvariant())
			{
				case "AUX":
				case "COM1":
				case "COM2":
				case "COM3":
				case "COM4":
				case "COM5":
				case "COM6":
				case "COM7":
				case "COM8":
				case "COM9":
				case "CON":
				case "LPT1":
				case "LPT2":
				case "LPT3":
				case "LPT4":
				case "LPT5":
				case "LPT6":
				case "LPT7":
				case "LPT8":
				case "LPT9":
				case "NUL":
				case "PRN":
					return true;
				default:
					return false;
			}
		}

		public static bool CanUseSdkStyleProjectFormat(MetadataFile module)
		{
			return TargetServices.DetectTargetFramework(module).Moniker != null;
		}

		/// <summary>
		/// Determines whether the XAML file whose root object is <paramref name="rootType"/> belongs
		/// into an MSBuild &lt;ApplicationDefinition&gt; item instead of a &lt;Page&gt; item.
		/// The WPF markup compiler generates the program entry point from the application definition,
		/// so a module that has no entry point of its own - a library that happens to contain an
		/// <c>Application</c> subclass - must not get one.
		/// </summary>
		public static bool IsApplicationDefinition(ITypeDefinition? rootType, MetadataFile? module)
		{
			if (rootType == null)
				return false;
			if (module is not PEFile { Reader.PEHeaders.CorHeader.EntryPointTokenOrRelativeVirtualAddress: not 0 })
				return false;
			foreach (var baseType in rootType.GetNonInterfaceBaseTypes())
			{
				if (baseType.FullName == "System.Windows.Application")
					return true;
			}
			return false;
		}
	}

	public record struct ProjectItemInfo(string ItemType, string FileName)
	{
		public List<PartialTypeInfo>? PartialTypes { get; set; } = null;

		public Dictionary<string, string>? AdditionalProperties { get; set; } = null;

		public ProjectItemInfo With(string name, string value)
		{
			AdditionalProperties ??= new Dictionary<string, string>();
			AdditionalProperties.Add(name, value);
			return this;
		}

		public ProjectItemInfo With(IEnumerable<KeyValuePair<string, string>> pairs)
		{
			AdditionalProperties ??= new Dictionary<string, string>();
			AdditionalProperties.AddRange(pairs);
			return this;
		}
	}
}