using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using ICSharpCode.Decompiler.CSharp;
using ICSharpCode.Decompiler.CSharp.OutputVisitor;
using ICSharpCode.Decompiler.CSharp.Syntax;
using ICSharpCode.Decompiler.CSharp.Transforms;
using ICSharpCode.Decompiler.TypeSystem;
using McMaster.Extensions.CommandLineUtils;
using Mono.Cecil;

namespace ICSharpCode.Decompiler.Console
{
	class Program
    {
        static int Main(string[] args)
        {
            // https://github.com/natemcmaster/CommandLineUtils/
            // Older cmd line clients (for options reference): https://github.com/aerror2/ILSpy-For-MacOSX and https://github.com/andreif/ILSpyMono
            var app = new CommandLineApplication();

            app.HelpOption("-h|--help");
            var inputAssemblyFileName = app.Argument("Assembly filename name", "The assembly that is being decompiled. This argument is mandatory.");
            var projectOption = app.Option("-p|--project", "Decompile assembly as compilable project. This requires the output directory option.", CommandOptionType.NoValue);
            var outputOption = app.Option("-o|--outputdir <directory>", "The output directory, if omitted decompiler output is written to standard out.", CommandOptionType.SingleValue);
            var typeOption = app.Option("-t|--type <type-name>", "The FQN of the type to decompile.", CommandOptionType.SingleValue);
            var listOption = app.Option("-l|--list <entity-type(s)>", "Lists all entities of the specified type(s). Valid types: c(lass), i(interface), s(truct), d(elegate), e(num)", CommandOptionType.MultipleValue);
            app.ExtendedHelpText = Environment.NewLine + "-o is valid with every option and required when using -p.";

            app.ThrowOnUnexpectedArgument = false; // Ignore invalid arguments / options

            app.OnExecute(() => {
                // HACK : the CommandLineUtils package does not allow us to specify an argument as mandatory.
                // Therefore we're implementing it as simple as possible.
                if (inputAssemblyFileName.Value == null) {
                    app.ShowHint();
                    return -1;
                }
                if (!File.Exists(inputAssemblyFileName.Value)) {
                    app.Error.WriteLine($"ERROR: Input file not found.");
                    return -1;
                }
                if (!outputOption.HasValue() && projectOption.HasValue()) {
                    app.Error.WriteLine($"ERROR: Output directory not speciified.");
                    return -1;
                }
                if (outputOption.HasValue() && !Directory.Exists(outputOption.Value())) {
                    app.Error.WriteLine($"ERROR: Output directory '{outputOption.Value()}' does not exist.");
                    return -1;
                }
                if (projectOption.HasValue()) {
                    DecompileAsProject(inputAssemblyFileName.Value, outputOption.Value());
                } else if (listOption.HasValue()) {
                    var values = listOption.Values.SelectMany(v => v.Split(',', ';')).ToArray();
                    HashSet<TypeKind> kinds = ParseSelection(values);
                    TextWriter output = System.Console.Out;
                    if (outputOption.HasValue()) {
                        string directory = outputOption.Value();
                        string outputName = Path.GetFileNameWithoutExtension(inputAssemblyFileName.Value);
                        output = File.CreateText(Path.Combine(directory, outputName) + ".list.txt");
                    }
                    ListContent(inputAssemblyFileName.Value, output, kinds);
                } else {
                    TextWriter output = System.Console.Out;
                    if (outputOption.HasValue()) {
                        string directory = outputOption.Value();
                        string outputName = Path.GetFileNameWithoutExtension(inputAssemblyFileName.Value);
                        output = File.CreateText(Path.Combine(directory, (typeOption.Value() ?? outputName) + ".decompiled.cs"));
                    }
                    Decompile(inputAssemblyFileName.Value, output);
                }
                return 0;
            });

            return app.Execute(args);
        }

        static void ListContent(string assemblyFileName, TextWriter output, ISet<TypeKind> kinds)
        {
            DefaultAssemblyResolver resolver = new DefaultAssemblyResolver();
            resolver.AddSearchDirectory(Path.GetDirectoryName(assemblyFileName));
            resolver.RemoveSearchDirectory(".");

            var module = ModuleDefinition.ReadModule(assemblyFileName, new ReaderParameters {
                AssemblyResolver = resolver,
                InMemory = true
            });

            var typeSystem = new DecompilerTypeSystem(module);

            foreach (var type in typeSystem.MainAssembly.GetAllTypeDefinitions()) {
                if (!kinds.Contains(type.Kind))
                    continue;
                output.WriteLine($"{type.Kind} {type.FullName}");
            }
        }

        static void DecompileAsProject(string assemblyFileName, string outputDirectory)
        {
            ModuleDefinition module = LoadModule(assemblyFileName);
            WholeProjectDecompiler decompiler = new WholeProjectDecompiler();
            decompiler.DecompileProject(module, outputDirectory);
        }
        
        static void Decompile(string assemblyFileName, TextWriter output, string typeName = null)
        {
            ModuleDefinition module = LoadModule(assemblyFileName);
            var typeSystem = new DecompilerTypeSystem(module);
            CSharpDecompiler decompiler = new CSharpDecompiler(typeSystem, new DecompilerSettings());

            decompiler.AstTransforms.Add(new EscapeInvalidIdentifiers());
            SyntaxTree syntaxTree;
            if (typeName == null)
                syntaxTree = decompiler.DecompileWholeModuleAsSingleFile();
            else
                syntaxTree = decompiler.DecompileTypes(module.GetTypes().Where(td => string.Equals(td.FullName, typeName, StringComparison.OrdinalIgnoreCase)));

            var visitor = new CSharpOutputVisitor(output, FormattingOptionsFactory.CreateSharpDevelop());
            syntaxTree.AcceptVisitor(visitor);
        }

        static HashSet<TypeKind> ParseSelection(string[] values)
        {
            var possibleValues = new Dictionary<string, TypeKind>(StringComparer.OrdinalIgnoreCase) { ["class"] = TypeKind.Class, ["struct"] = TypeKind.Struct, ["interface"] = TypeKind.Interface, ["enum"] = TypeKind.Enum, ["delegate"] = TypeKind.Delegate };
            HashSet<TypeKind> kinds = new HashSet<TypeKind>();
            if (values.Length == 1 && !possibleValues.Keys.Any(v => values[0].StartsWith(v, StringComparison.OrdinalIgnoreCase))) {
                foreach (char ch in values[0]) {
                    switch (ch) {
                        case 'c':
                            kinds.Add(TypeKind.Class);
                            break;
                        case 'i':
                            kinds.Add(TypeKind.Interface);
                            break;
                        case 's':
                            kinds.Add(TypeKind.Struct);
                            break;
                        case 'd':
                            kinds.Add(TypeKind.Delegate);
                            break;
                        case 'e':
                            kinds.Add(TypeKind.Enum);
                            break;
                    }
                }
            } else {
                foreach (var value in values) {
                    string v = value;
                    while (v.Length > 0 && !possibleValues.ContainsKey(v))
                        v = v.Remove(v.Length - 1);
                    if (possibleValues.TryGetValue(v, out var kind))
                        kinds.Add(kind);
                }
            }
            return kinds;
        }

        static ModuleDefinition LoadModule(string assemblyFileName)
        {
            var resolver = new CustomAssemblyResolver(assemblyFileName);

            var module = ModuleDefinition.ReadModule(assemblyFileName, new ReaderParameters {
                AssemblyResolver = resolver,
                InMemory = true
            });

            resolver.TargetFramework = module.Assembly.DetectTargetFrameworkId();

            return module;
        }
    }
}