using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;

namespace CppSharp.Generators.CSharp
{
    public static class Helpers
    {
        // from https://github.com/mono/mono/blob/master/mcs/class/System/Microsoft.CSharp/CSharpCodeGenerator.cs
        private static readonly string[] Keywords = new string[]
            {
                "abstract", "event", "new", "struct", "as", "explicit", "null", "switch",
                "base", "extern", "this", "false", "operator", "throw", "break", "finally",
                "out", "true", "fixed", "override", "try", "case", "params", "typeof",
                "catch", "for", "private", "foreach", "protected", "checked", "goto",
                "public", "unchecked", "class", "if", "readonly", "unsafe", "const",
                "implicit", "ref", "continue", "in", "return", "using", "virtual", "default",
                "interface", "sealed", "volatile", "delegate", "internal", "do", "is",
                "sizeof", "while", "lock", "stackalloc", "else", "static", "enum",
                "namespace", "object", "bool", "byte", "float", "uint", "char", "ulong",
                "ushort", "decimal", "int", "sbyte", "short", "double", "long", "string",
                "void", "partial", "yield", "where"
            };

        public static string GeneratedIdentifier(string id)
        {
            return "__" + id;
        }

        public static string SafeIdentifier(string id)
        {
            id = new string(((IEnumerable<char>)id)
                .Select(c => char.IsLetterOrDigit(c) ? c : '_').ToArray());
            return Keywords.Contains(id) ? "@" + id : id;
        }

        public static string ToCSharpCallConv(CallingConvention convention)
        {
            switch (convention)
            {
                case CallingConvention.Default:
                    return "Winapi";
                case CallingConvention.C:
                    return "Cdecl";
                case CallingConvention.StdCall:
                    return "StdCall";
                case CallingConvention.ThisCall:
                    return "ThisCall";
                case CallingConvention.FastCall:
                    return "FastCall";
            }

            return "Winapi";
        }

        public static string InstanceIdentifier
        {
            get { return GeneratedIdentifier("Instance"); }
        }
    }

    public class CSharpTextTemplate : TextTemplate
    {
        public CSharpTypePrinter TypePrinter { get; private set; }

        public override string FileExtension
        {
            get { return "cs"; }
        }

        public CSharpTextTemplate(Driver driver, TranslationUnit unit,
            CSharpTypePrinter typePrinter)
            : base(driver, unit)
        {
            TypePrinter = typePrinter;
        }

        #region Identifiers

        public string QualifiedIdentifier(Declaration decl)
        {
            var names = new List<string> { decl.Name };

            var ctx = decl.Namespace;
            while (ctx != null)
            {
                if (!string.IsNullOrWhiteSpace(ctx.Name))
                    names.Add(ctx.Name);
                ctx = ctx.Namespace;
            }

            if (Options.GenerateLibraryNamespace)
                names.Add(Options.OutputNamespace);

            names.Reverse();
            return string.Join(".", names);
        }

        public static string GeneratedIdentifier(string id)
        {
            return Helpers.GeneratedIdentifier(id);
        }

        public static string SafeIdentifier(string id)
        {
            return Helpers.SafeIdentifier(id);
        }

        #endregion

        public override void Generate()
        {
            GenerateHeader();

            WriteLine("using System;");
            WriteLine("using System.Runtime.InteropServices;");
            WriteLine("using System.Security;");
            NewLine();

            if (Options.GenerateLibraryNamespace)
            {
                WriteLine("namespace {0}", SafeIdentifier(Driver.Options.OutputNamespace));
                WriteStartBraceIndent();
            }

            GenerateDeclContext(TranslationUnit);

            if (Options.GenerateLibraryNamespace)
                WriteCloseBraceIndent();
        }

        public void GenerateHeader()
        {
            if (Transform != null)
            {
                //Transform.GenerateStart(this);
                return;
            }

            WriteLine("//----------------------------------------------------------------------------");
            WriteLine("// This is autogenerated code by CppSharp.");
            WriteLine("// Do not edit this file or all your changes will be lost after re-generation.");
            WriteLine("//----------------------------------------------------------------------------");
        }

        private void GenerateDeclContext(DeclarationContext context)
        {
            var isNamespace = context is Namespace;
            var isTranslationUnit = context is TranslationUnit;

            var shouldGenerateNamespace = isNamespace && !isTranslationUnit;

            if (shouldGenerateNamespace)
            {
                WriteLine("namespace {0}", context.Name);
                WriteStartBraceIndent();
            }

            // Generate all the enum declarations.
            foreach (var @enum in context.Enums)
            {
                if (@enum.Ignore || @enum.IsIncomplete)
                    continue;

                NewLineIfNeeded();
                GenerateEnum(@enum);
                NeedNewLine();
            }

            // Generate all the typedef declarations.
            foreach (var typedef in context.Typedefs)
            {
                if (typedef.Ignore) continue;

                NewLineIfNeeded();

                if (!GenerateTypedef(typedef))
                    continue;

                NeedNewLine();
            }

            // Generate all the struct/class declarations.
            foreach (var @class in context.Classes)
            {
                if (@class.Ignore || @class.IsIncomplete)
                    continue;

                if (@class.IsDependent)
                    continue;

                NewLineIfNeeded();
                GenerateClass(@class);
                NeedNewLine();
            }

            if (context.HasFunctions)
            {
                NewLineIfNeeded();
                WriteLine("public partial class {0}{1}", SafeIdentifier(Options.LibraryName),
                    TranslationUnit.FileNameWithoutExtension);
                WriteStartBraceIndent();

                // Generate all the function declarations.
                foreach (var function in context.Functions)
                    GenerateFunction(function);

                WriteCloseBraceIndent();
            }

            foreach(var childNamespace in context.Namespaces)
                GenerateDeclContext(childNamespace);

            if (shouldGenerateNamespace)
                WriteCloseBraceIndent();
        }

        public void GenerateDeclarationCommon(Declaration decl)
        {
            GenerateSummary(decl.BriefComment);
            GenerateDebug(decl);
        }

        public void GenerateDebug(Declaration decl)
        {
            if (Options.OutputDebug && !String.IsNullOrWhiteSpace(decl.DebugText))
                WriteLine("// DEBUG: " + decl.DebugText);
        }

        public void GenerateSummary(string comment)
        {
            if (String.IsNullOrWhiteSpace(comment))
                return;

            WriteLine("/// <summary>");
            WriteLine("/// {0}", comment);
            WriteLine("/// </summary>");
        }

        public void GenerateInlineSummary(string comment)
        {
            if (String.IsNullOrWhiteSpace(comment))
                return;

            WriteLine("/// <summary>{0}</summary>", comment);
        }

        #region Classes

        public void GenerateClass(Class @class)
        {
            if (@class.Ignore || @class.IsIncomplete)
                return;

            GenerateDeclarationCommon(@class);

            if (@class.IsUnion)
            {
                // TODO: How to do wrapping of unions?
                throw new NotImplementedException();
            }

            GenerateClassProlog(@class);

            NewLine();
            WriteStartBraceIndent();

            if (!@class.IsOpaque)
            {
                GenerateClassInternals(@class);

                GenerateDeclContext(@class);

                if (ShouldGenerateClassNativeField(@class))
                {
                    NewLineIfNeeded();
                    WriteLine("public System.IntPtr {0} {{ get; protected set; }}",
                        Helpers.InstanceIdentifier);
                    NeedNewLine();
                }

                GenerateClassConstructors(@class);
                GenerateClassFields(@class);
                GenerateClassMethods(@class);
                GenerateClassVariables(@class);
                GenerateClassProperties(@class);
            }

            WriteCloseBraceIndent();
        }

        public void GenerateClassInternals(Class @class)
        {
            var typePrinter = TypePrinter as CSharpTypePrinter;
            typePrinter.PushContext(CSharpTypePrinterContextKind.Native);

            WriteLine("[StructLayout(LayoutKind.Explicit, Size = {0})]",
                @class.Layout.Size);

            Write("internal ");

            if (@class.HasBaseClass)
                Write("new ");

            WriteLine("struct Internal");
            WriteStartBraceIndent();

            ResetNewLine();

        GenerateClassFields(@class, isInternal: true);

            foreach (var ctor in @class.Constructors)
            {
                if (ctor.IsCopyConstructor || ctor.IsMoveConstructor)
                    continue;

                NewLineIfNeeded();
                GenerateFunction(ctor, @class);
            }

            foreach (var method in @class.Methods)
            {
                if (CheckIgnoreMethod(@class, method))
                    continue;

                if (method.IsConstructor)
                    continue;

                if (method.IsSynthetized)
                    continue;

                NewLineIfNeeded();
                GenerateFunction(method, @class);
            }

            WriteCloseBraceIndent();
            NeedNewLine();

            typePrinter.PopContext();
        }

        private void GenerateStructMarshalingFields(Class @class)
        {
            foreach (var @base in @class.Bases)
            {
                if (!@base.IsClass || @base.Class.Ignore)
                    continue;

                GenerateStructMarshalingFields(@base.Class);
            }

            foreach (var field in @class.Fields)
            {
                if (CheckIgnoreField(@class, field)) continue;

                var nativeField = string.Format("{0}->{1}",
                    Helpers.GeneratedIdentifier("ptr"), field.OriginalName);

                var ctx = new CSharpMarshalContext(Driver)
                {
                    Kind = CSharpMarshalKind.NativeField,
                    ArgName = field.Name,
                    ReturnVarName = nativeField,
                    ReturnType = field.QualifiedType
                };

                var marshal = new CSharpMarshalNativeToManagedPrinter(ctx);
                field.Visit(marshal);

                if (!string.IsNullOrWhiteSpace(marshal.Context.SupportBefore))
                    Write(marshal.Context.SupportBefore);

                WriteLine("{0} = {1};", field.Name, marshal.Context.Return);
            }
        }

        public bool ShouldGenerateClassNativeField(Class @class)
        {
            if (!@class.IsRefType)
                return false;

            Class baseClass = null;

            if (@class.HasBaseClass)
                baseClass = @class.Bases[0].Class;

            var hasRefBase = baseClass != null && baseClass.IsRefType
                             && !baseClass.Ignore;

            var hasIgnoredBase = baseClass != null && baseClass.Ignore;

            return !@class.HasBase || !hasRefBase || hasIgnoredBase;
        }

        public void GenerateClassProlog(Class @class)
        {
            if (@class.IsUnion)
                WriteLine("[StructLayout(LayoutKind.Explicit)]");

            Write("public unsafe ");

            if (Options.GeneratePartialClasses)
                Write("partial ");

            Write(@class.IsValueType ? "struct " : "class ");
            Write("{0}", SafeIdentifier(@class.Name));

            var needsBase = @class.HasBaseClass && !@class.IsValueType
                && !@class.Bases[0].Class.IsValueType
                && !@class.Bases[0].Class.Ignore;

            if (needsBase || @class.IsRefType)
                Write(" : ");

            if (needsBase)
            {
                var qualifiedBase = QualifiedIdentifier(@class.Bases[0].Class);
                Write("{0}", qualifiedBase);

                if (@class.IsRefType)
                    Write(", ");
            }

            if (@class.IsRefType)
                Write("IDisposable");
        }

        public void GenerateClassFields(Class @class, bool isInternal = false)
        {
            // Handle value-type inheritance
            if (@class.IsValueType)
            {
                foreach (var @base in @class.Bases)
                {
                    if (!@base.IsClass)
                        continue;

                    var baseClass = @base.Class;

                    if (!baseClass.IsValueType || baseClass.Ignore)
                        continue;

                    GenerateClassFields(baseClass, isInternal);
                }
            }

            foreach (var field in @class.Fields)
            {
                if (CheckIgnoreField(@class, field)) continue;

                NewLineIfNeeded();

                if (isInternal)
                {
                    WriteLine("[FieldOffset({0})]", field.OffsetInBytes);

                    var result = field.Type.Visit(TypePrinter, field.QualifiedType.Qualifiers);

                    Write("public {0} {1}", result.Type, SafeIdentifier(field.OriginalName));

                    if (!string.IsNullOrWhiteSpace(result.NameSuffix))
                        Write(result.NameSuffix);

                    WriteLine(";");
                }
                else if (@class.IsRefType)
                {
                    GenerateFieldProperty(field);
                }
                else
                {
                    GenerateDeclarationCommon(field);
                    if (@class.IsUnion)
                        WriteLine("[FieldOffset({0})]", field.Offset);
                    WriteLine("public {0} {1};", field.Type, SafeIdentifier(field.Name));
                }

                NeedNewLine();
            }
        }

        private void GenerateFieldProperty(Field field)
        {
            var @class = field.Class;

            GenerateDeclarationCommon(field);
            WriteLine("public {0} {1}", field.Type, SafeIdentifier(field.Name));
            WriteStartBraceIndent();

            GeneratePropertyGetter(field, @class);
            NewLine();

            GeneratePropertySetter(field, @class);

            WriteCloseBraceIndent();
        }

        enum PropertyMethodKind
        {
            Getter,
            Setter
        }

        private string GetPropertyLocation<T>(T decl, PropertyMethodKind kind,
            out bool isRefClass) where T : Declaration, ITypedDecl
        {
            isRefClass = false;

            if (decl is Variable)
            {
                var @var = decl as Variable;

                string symbol;
                if (!FindMangledDeclSymbol(@var, out symbol))
                    return string.Empty;

                NativeLibrary library;
                Driver.LibrarySymbols.FindLibraryBySymbol(symbol, out library);

                return string.Format("CppSharp.SymbolResolver.ResolveSymbol(\"{0}\", \"{1}\")",
                    Path.GetFileNameWithoutExtension(library.FileName), symbol);
            }

            throw new NotSupportedException();
        }

        private void GeneratePropertySetter<T>(T decl, Class @class)
            where T : Declaration, ITypedDecl
        {
            WriteLine("set");
            WriteStartBraceIndent();

            var param = new Parameter
            {
                Name = "value",
                QualifiedType = decl.QualifiedType
            };

            var ctx = new CSharpMarshalContext(Driver)
            {
                Parameter = param,
                ArgName = param.Name,
            };

            if (decl is Function)
            {
                var function = decl as Function;
                var parameters = new List<Parameter> { param };
                GenerateInternalFunctionCall(function, @class, parameters);
            }
            else if (decl is Field)
            {
                var field = decl as Field;

                WriteLine("var {0} = (Internal*){1}.ToPointer();",
                    Helpers.GeneratedIdentifier("ptr"), Helpers.InstanceIdentifier);

                var marshal = new CSharpMarshalManagedToNativePrinter(ctx);
                param.Visit(marshal);

                if (!string.IsNullOrWhiteSpace(marshal.Context.SupportBefore))
                    Write(marshal.Context.SupportBefore);

                Write("{0}->{1} = {2}", Helpers.GeneratedIdentifier("ptr"),
                    Helpers.SafeIdentifier(field.OriginalName), marshal.Context.Return);

                WriteLine(";");
            }

            WriteCloseBraceIndent();
        }

        private void GeneratePropertyGetter<T>(T decl, Class @class)
            where T : Declaration, ITypedDecl
        {
            WriteLine("get");
            WriteStartBraceIndent();

            var @return = string.Empty;

            if (decl is Function)
            {
                var function = decl as Function;
                GenerateInternalFunctionCall(function, @class);
                @return = "ret";
            }
            else if (decl is Field)
            {
                var field = decl as Field;

                WriteLine("var {0} = (Internal*){1}.ToPointer();",
                    Helpers.GeneratedIdentifier("ptr"), Helpers.InstanceIdentifier);

                var ctx = new CSharpMarshalContext(Driver)
                {
                    Kind = CSharpMarshalKind.NativeField,
                    ArgName = decl.Name,
                    ReturnVarName = string.Format("{0}->{1}", Helpers.GeneratedIdentifier("ptr"),
                        Helpers.SafeIdentifier(field.OriginalName)),
                    ReturnType = decl.QualifiedType
                };

                var marshal = new CSharpMarshalNativeToManagedPrinter(ctx);
                decl.Visit(marshal);

                if (!string.IsNullOrWhiteSpace(marshal.Context.SupportBefore))
                    Write(marshal.Context.SupportBefore);

                WriteLine("return {0};", marshal.Context.Return);
            }
            else
            {
                bool isRefClass;
                @return = GetPropertyLocation(decl, PropertyMethodKind.Getter,
                    out isRefClass);

                var ctx = new CSharpMarshalContext(Driver)
                {
                    ArgName = decl.Name,
                    ReturnVarName = @return,
                    ReturnType = decl.QualifiedType
                };

                var marshal = new CSharpMarshalNativeToManagedPrinter(ctx);
                decl.Visit(marshal);

                if (!string.IsNullOrWhiteSpace(marshal.Context.SupportBefore))
                    Write(marshal.Context.SupportBefore);

                WriteLine("return {0};", marshal.Context.Return);
            }

            WriteCloseBraceIndent();
        }

        public void GenerateClassMethods(Class @class)
        {
            var staticMethods = new List<Method>();
            foreach (var method in @class.Methods)
            {
                if (CheckIgnoreMethod(@class, method))
                    continue;

                if (method.IsConstructor)
                    continue;

                if (method.IsStatic)
                {
                    staticMethods.Add(method);
                    continue;
                }

                NewLineIfNeeded();
                GenerateMethod(method, @class);
                NeedNewLine();
            }

            foreach (var method in staticMethods)
            {
                NewLineIfNeeded();
                GenerateMethod(method, @class);
                NeedNewLine();
            }
        }

        public void GenerateClassVariables(Class @class)
        {
            foreach (var variable in @class.Variables)
            {
                if (variable.Ignore) continue;

                if (variable.Access != AccessSpecifier.Public)
                    continue;

                var type = variable.Type;

                NewLineIfNeeded();
                GenerateVariable(@class, type, variable);
                NeedNewLine();
            }
        }

        private void GenerateClassProperties(Class @class)
        {
            foreach (var prop in @class.Properties)
            {
                if (prop.Ignore) continue;

                NewLineIfNeeded();
                WriteLine("public {0} {1}", prop.Type, prop.Name);
                WriteStartBraceIndent();

                GeneratePropertyGetter(prop.GetMethod, @class);
                NeedNewLine();

                if (prop.SetMethod != null)
                {
                    NewLineIfNeeded();
                    GeneratePropertySetter(prop.SetMethod, @class);
                }

                WriteCloseBraceIndent();
                NeedNewLine();
            }
        }

        private void GenerateVariable(Class @class, Type type, Variable variable)
        {
            WriteLine("public static {0} {1}", type, variable.Name);
            WriteStartBraceIndent();

            GeneratePropertyGetter(variable, @class);

            if (!variable.QualifiedType.Qualifiers.IsConst)
                GeneratePropertySetter(variable, @class);

            WriteCloseBraceIndent();
        }

        #endregion

        #region Constructors

        public void GenerateClassConstructors(Class @class)
        {
            NewLineIfNeeded();

            // Output a default constructor that takes the native pointer.
            GenerateNativeConstructor(@class);
            NeedNewLine();

            foreach (var ctor in @class.Constructors)
            {
                if (CheckIgnoreMethod(@class, ctor))
                    continue;

                NewLineIfNeeded();
                GenerateMethod(ctor, @class);
                NeedNewLine();
            }

            if (@class.IsRefType)
                GenerateDisposeMethods(@class);
        }

        private void GenerateDisposeMethods(Class @class)
        {
            var hasBaseClass = @class.HasBaseClass && @class.BaseClass.IsRefType;

            // Generate the IDispose Dispose() method.
            if (!hasBaseClass)
            {
                NewLineIfNeeded();
                WriteLine("public void Dispose()");
                WriteStartBraceIndent();

                WriteLine("Dispose(disposing: true);");
                WriteLine("GC.SuppressFinalize(this);");

                WriteCloseBraceIndent();
                NeedNewLine();
            }

            // Generate Dispose(bool) method
            NewLineIfNeeded();
            Write("protected ");

            Write(hasBaseClass ? "override " : "virtual ");

            WriteLine("void Dispose(bool disposing)");
            WriteStartBraceIndent();

            if (ShouldGenerateClassNativeField(@class))
                WriteLine("Marshal.FreeHGlobal({0});", Helpers.InstanceIdentifier);

            if (hasBaseClass)
                WriteLine("base.Dispose(disposing);");

            WriteCloseBraceIndent();
            NeedNewLine();
        }

        private void GenerateNativeConstructor(Class @class)
        {
            WriteLine("internal {0}(System.IntPtr native)", SafeIdentifier(@class.Name));

            var hasBaseClass = @class.HasBaseClass && @class.BaseClass.IsRefType;
            if (hasBaseClass)
                WriteLineIndent(": base(native)");

            WriteStartBraceIndent();

            if (@class.IsRefType)
            {
                if (ShouldGenerateClassNativeField(@class))
                    WriteLine("{0} = native;", Helpers.InstanceIdentifier);
            }
            else
            {
                WriteLine("var {0} = (Internal*){1}.ToPointer();",
                    Helpers.GeneratedIdentifier("ptr"), "native");

                GenerateStructMarshalingFields(@class);
            }

            WriteCloseBraceIndent();
        }

        private bool GenerateClassConstructorBase(Class @class, Method method)
        {
            var hasBase = @class.HasBaseClass && !@class.Bases[0].Class.Ignore;

            if (hasBase && !@class.IsValueType)
            {
                PushIndent();
                Write(": this(", QualifiedIdentifier(@class.Bases[0].Class));

                if (method != null)
                    Write("IntPtr.Zero");
                else
                    Write("native");

                WriteLine(")");
                PopIndent();
            }

            return hasBase;
        }

        #endregion

        #region Methods / Functions

        public void GenerateMethod(Method method, Class @class)
        {
            GenerateDeclarationCommon(method);

            Write("public ");

            if (method.IsStatic ||
                method.Kind == CXXMethodKind.Operator)
                Write("static ");

            var functionName = GetFunctionIdentifier(method);

            if (method.IsConstructor || method.IsDestructor)
                Write("{0}(", functionName);
            else
                Write("{0} {1}(", method.ReturnType, functionName);

            GenerateMethodParameters(method, @class);

            WriteLine(")");

            if (method.Kind == CXXMethodKind.Constructor)
                GenerateClassConstructorBase(@class, method);

            WriteStartBraceIndent();

            if (@class.IsRefType)
            {
                if (method.IsConstructor)
                {
                    GenerateClassConstructor(method, @class);
                }
                else if (method.IsOperator)
                {
                    GenerateOperator(method, @class);
                }
                else
                {
                    GenerateInternalFunctionCall(method, @class);
                }
            }
            else if (@class.IsValueType)
            {
                if (method.IsConstructor)
                {
                    GenerateInternalFunctionCall(method, @class);
                }
                else if (method.IsOperator)
                {
                    GenerateOperator(method, @class);
                }
                else
                {
                    GenerateInternalFunctionCall(method, @class);
                }
            }

            WriteCloseBraceIndent();
        }

        private static string GetOperatorOverloadPair(CXXOperatorKind kind)
        {
            switch (kind)
            {
            case CXXOperatorKind.EqualEqual:
                return "!=";
            case CXXOperatorKind.ExclaimEqual:
                return "==";

            case CXXOperatorKind.Less:
                return ">";
            case CXXOperatorKind.Greater:
                return "<";

            case CXXOperatorKind.LessEqual:
                return ">=";
            case CXXOperatorKind.GreaterEqual:
                return "<=";

            default:
                throw new NotSupportedException();
            }
        }

        private void GenerateOperator(Method method, Class @class)
        {
            if (method.IsSynthetized)
            {
                var @operator = GetOperatorOverloadPair(method.OperatorKind);

                WriteLine("return !({0} {1} {2});", method.Parameters[0].Name,
                          @operator, method.Parameters[1].Name);
                return;
            }

            GenerateInternalFunctionCall(method, @class);
        }

        private void GenerateClassConstructor(Method method, Class @class)
        {
            var @params = GenerateFunctionParamsMarshal(method.Parameters, method);

            WriteLine("{0} = Marshal.AllocHGlobal({1});", Helpers.InstanceIdentifier,
                @class.Layout.Size);
            Write("Internal.{0}({1}", GetFunctionNativeIdentifier(method),
                Helpers.InstanceIdentifier);
            if (@params.Any())
                Write(", ");
            GenerateFunctionParams(@params);
            WriteLine(");");
        }

        public void GenerateInternalFunctionCall(Function function, Class @class,
            List<Parameter> parameters = null)
        {
            if (parameters == null)
                parameters = function.Parameters;

            var functionName = string.Format("Internal.{0}",
                GetFunctionNativeIdentifier(function));
            GenerateFunctionCall(functionName, parameters, function, @class);
        }

        public void GenerateFunctionCall(string functionName, List<Parameter> parameters,
            Function function, Class @class = null)
        {
            var retType = function.ReturnType;
            var needsReturn = !retType.Type.IsPrimitiveType(PrimitiveType.Void);

            var method = function as Method;
            var needsInstance = method != null && !method.IsStatic && !method.IsOperator;

            var isValueType = @class != null && @class.IsValueType;
            var needsFixedThis = needsInstance && isValueType;

            Class retClass = null;
            if (function.HasHiddenStructParameter)
            {
                function.ReturnType.Type.IsTagDecl(out retClass);

                WriteLine("var {0} = new {1}.Internal();", GeneratedIdentifier("udt"),
                    retClass.OriginalName);

                retType.Type = new BuiltinType(PrimitiveType.Void);
                needsReturn = false;
            }

            var @params = GenerateFunctionParamsMarshal(parameters, function);

            var names = (from param in @params
                         where !param.Param.Ignore
                         select param.Name).ToList();

            if (function.HasHiddenStructParameter)
            {
                var name = string.Format("new IntPtr(&{0})", GeneratedIdentifier("udt"));
                names.Insert(0, name);
            }

            if (needsInstance)
            {
                names.Insert(0, needsFixedThis ? string.Format("new System.IntPtr({0})",
                    GeneratedIdentifier("instance")) : Helpers.InstanceIdentifier);
            }

            if (needsFixedThis)
            {
                WriteLine("fixed({0}* {1} = &this)", @class.QualifiedName,
                    GeneratedIdentifier("instance"));
                WriteStartBraceIndent();
            }

            if (needsReturn)
                Write("var ret = ");

            WriteLine("{0}({1});", functionName, string.Join(", ", names));

            var cleanups = new List<TextGenerator>();
            GenerateFunctionCallOutParams(@params, cleanups);

            foreach (var param in @params)
            {
                var context = param.Context;
                if (context == null) continue;

                if (!string.IsNullOrWhiteSpace(context.Cleanup))
                    cleanups.Add(context.Cleanup);
            }

            foreach (var cleanup in cleanups)
            {
                Write(cleanup);
            }

            if (needsReturn)
            {
                var ctx = new CSharpMarshalContext(Driver)
                {
                    ArgName = "ret",
                    ReturnVarName = "ret",
                    ReturnType = retType
                };

                var marshal = new CSharpMarshalNativeToManagedPrinter(ctx);
                function.ReturnType.Type.Visit(marshal, function.ReturnType.Qualifiers);

                if (!string.IsNullOrWhiteSpace(marshal.Context.SupportBefore))
                    Write(marshal.Context.SupportBefore);

                WriteLine("return {0};", marshal.Context.Return);
            }

            if (function.HasHiddenStructParameter)
            {
                WriteLine("var ret = new {0}();", retClass.Name);

                if (retClass.IsValueType)
                    WriteLine("*({0}.Internal*) &ret = {1};", retClass.Name,
                        GeneratedIdentifier("udt"));
                else
                    WriteLine("*({0}.Internal*) ret.{1}.ToPointer() = {2};",
                        retClass.Name, Helpers.InstanceIdentifier,
                        GeneratedIdentifier("udt"));

                WriteLine("return ret;");
            }

            if (needsFixedThis)
                WriteCloseBraceIndent();
        }

        private void GenerateFunctionCallOutParams(IEnumerable<ParamMarshal> @params,
            ICollection<TextGenerator> cleanups)
        {
            foreach (var paramInfo in @params)
            {
                var param = paramInfo.Param;
                if (param.Usage != ParameterUsage.Out && param.Usage != ParameterUsage.InOut)
                    continue;

                var nativeVarName = paramInfo.Name;

                var ctx = new CSharpMarshalContext(Driver)
                {
                    ArgName = nativeVarName,
                    ReturnVarName = nativeVarName,
                    ReturnType = param.QualifiedType
                };

                var marshal = new CSharpMarshalNativeToManagedPrinter(ctx);
                param.Visit(marshal);

                if (!string.IsNullOrWhiteSpace(marshal.Context.SupportBefore))
                    Write(marshal.Context.SupportBefore);

                WriteLine("{0} = {1};", param.Name, marshal.Context.Return);

                if (!string.IsNullOrWhiteSpace(marshal.CSharpContext.Cleanup))
                    cleanups.Add(marshal.CSharpContext.Cleanup);
            }
        }

        private static bool IsInstanceFunction(Function function)
        {
            var isInstanceFunction = false;

            var method = function as Method;
            if (method != null)
                isInstanceFunction = method.Conversion == MethodConversionKind.None;
            return isInstanceFunction;
        }

        public struct ParamMarshal
        {
            public string Name;
            public Parameter Param;
            public CSharpMarshalContext Context;
        }

        public void GenerateFunctionParams(List<ParamMarshal> @params)
        {
            var names = @params.Select(param => param.Name).ToList();
            Write(string.Join(", ", names));
        }

        public List<ParamMarshal> GenerateFunctionParamsMarshal(IEnumerable<Parameter> @params,
                                                                Function function = null)
        {
            var marshals = new List<ParamMarshal>();

            var paramIndex = 0;
            foreach (var param in @params)
            {
                marshals.Add(GenerateFunctionParamMarshal(param, paramIndex, function));
                paramIndex++;
            }

            return marshals;
        }

        private ParamMarshal GenerateFunctionParamMarshal(Parameter param, int paramIndex,
            Function function = null)
        {
            if (param.Type is BuiltinType)
            {
                return new ParamMarshal { Name = param.Name, Param = param };
            }

            var argName = "arg" + paramIndex.ToString(CultureInfo.InvariantCulture);
            var paramMarshal = new ParamMarshal { Name = argName, Param = param };

            if (param.Usage == ParameterUsage.Out)
            {
                var paramType = param.Type;

                Class @class;
                if (paramType.Desugar().IsTagDecl(out @class) && @class.IsRefType)
                {
                    WriteLine("{0} = new {1}();", param.Name, paramType);
                }
            }

            var ctx = new CSharpMarshalContext(Driver)
            {
                Parameter = param,
                ParameterIndex = paramIndex,
                ArgName = argName,
                Function = function
            };

            paramMarshal.Context = ctx;

            var marshal = new CSharpMarshalManagedToNativePrinter(ctx);
            param.Visit(marshal);

            if (string.IsNullOrEmpty(marshal.Context.Return))
                throw new Exception("Cannot marshal argument of function");

            if (!string.IsNullOrWhiteSpace(marshal.Context.SupportBefore))
                Write(marshal.Context.SupportBefore);

            WriteLine("var {0} = {1};", SafeIdentifier(argName), marshal.Context.Return);

            return paramMarshal;
        }

        static string GetParameterUsage(ParameterUsage usage)
        {
            switch (usage)
            {
                case ParameterUsage.Out:
                    return "out ";
                case ParameterUsage.InOut:
                    return "ref";
                default:
                    return string.Empty;
            }
        }

        private void GenerateMethodParameters(Method method, Class @class)
        {
            var @params = new List<string>();

            for (var i = 0; i < method.Parameters.Count; ++i)
            {
                var param = method.Parameters[i];

                if (param.Kind == ParameterKind.HiddenStructureReturn)
                    continue;

                @params.Add(string.Format("{0}{1} {2}", GetParameterUsage(param.Usage),
                    param.Type, SafeIdentifier(param.Name)));
            }

            Write(string.Join(", ", @params));
        }

        #endregion

        public bool GenerateTypedef(TypedefDecl typedef)
        {
            if (typedef.Ignore)
                return false;

            GenerateDeclarationCommon(typedef);

            FunctionType function;
            TagType tag;

            if (typedef.Type.IsPointerToPrimitiveType(PrimitiveType.Void)
                || typedef.Type.IsPointerTo<TagType>(out tag))
            {
                WriteLine("public class " + SafeIdentifier(typedef.Name) + @" { }");
            }
            else if (typedef.Type.IsPointerTo<FunctionType>(out function))
            {
                WriteLine("public {0};",
                    string.Format(TypePrinter.VisitDelegate(function).Type,
                        SafeIdentifier(typedef.Name)));
                NeedNewLine();
            }
            else if (typedef.Type.IsEnumType())
            {
                // Already handled in the parser.
                return false;
            }
            else
            {
                Console.WriteLine("Unhandled typedef type: {0}", typedef);
                return false;
            }

            return true;
        }

        public void GenerateEnum(Enumeration @enum)
        {
            if (@enum.Ignore) return;
            GenerateDeclarationCommon(@enum);

            if (@enum.IsFlags)
                WriteLine("[Flags]");

            Write("public enum {0}", SafeIdentifier(@enum.Name));

            var typeName = TypePrinter.VisitPrimitiveType(@enum.BuiltinType.Type,
                                                          new TypeQualifiers());

            if (@enum.BuiltinType.Type != PrimitiveType.Int32)
                Write(" : {0}", typeName);

            NewLine();

            WriteStartBraceIndent();
            for (var i = 0; i < @enum.Items.Count; ++i)
            {
                var item = @enum.Items[i];
                GenerateInlineSummary(item.Comment);

                Write(item.ExplicitValue
                          ? string.Format("{0} = {1}", SafeIdentifier(item.Name), item.Value)
                          : string.Format("{0}", SafeIdentifier(item.Name)));

                if (i < @enum.Items.Count - 1)
                    Write(",");

                NewLine();
            }
            WriteCloseBraceIndent();
        }

        public static string GetOperatorIdentifier(CXXOperatorKind kind)
        {
            // These follow the order described in MSDN (Overloadable Operators).

            switch (kind)
            {
                // These unary operators can be overloaded
                case CXXOperatorKind.Plus: return "operator +";
                case CXXOperatorKind.Minus: return "operator -";
                case CXXOperatorKind.Exclaim: return "operator !";
                case CXXOperatorKind.Tilde: return "operator ~";
                case CXXOperatorKind.PlusPlus: return "operator ++";
                case CXXOperatorKind.MinusMinus: return "operator --";

                // These binary operators can be overloaded
                case CXXOperatorKind.Star: return "operator *";
                case CXXOperatorKind.Slash: return "operator /";
                case CXXOperatorKind.Percent: return "operator +";
                case CXXOperatorKind.Amp: return "operator &";
                case CXXOperatorKind.Pipe: return "operator |";
                case CXXOperatorKind.Caret: return "operator ^";
                case CXXOperatorKind.LessLess: return "operator <<";
                case CXXOperatorKind.GreaterGreater: return "operator >>";

                // The comparison operators can be overloaded
                case CXXOperatorKind.EqualEqual: return "operator ==";
                case CXXOperatorKind.ExclaimEqual: return "operator !=";
                case CXXOperatorKind.Less: return "operator <";
                case CXXOperatorKind.Greater: return "operator >";
                case CXXOperatorKind.LessEqual: return "operator <=";
                case CXXOperatorKind.GreaterEqual: return "operator >=";

                // Assignment operators cannot be overloaded
                case CXXOperatorKind.PlusEqual:
                case CXXOperatorKind.MinusEqual:
                case CXXOperatorKind.StarEqual:
                case CXXOperatorKind.SlashEqual:
                case CXXOperatorKind.PercentEqual:
                case CXXOperatorKind.AmpEqual:
                case CXXOperatorKind.PipeEqual:
                case CXXOperatorKind.CaretEqual:
                case CXXOperatorKind.LessLessEqual:
                case CXXOperatorKind.GreaterGreaterEqual:

                // The array indexing operator cannot be overloaded
                case CXXOperatorKind.Subscript:

                // The conditional logical operators cannot be overloaded
                case CXXOperatorKind.AmpAmp:
                case CXXOperatorKind.PipePipe:

                // These operators cannot be overloaded.
                case CXXOperatorKind.Equal:
                case CXXOperatorKind.Comma:
                case CXXOperatorKind.ArrowStar:
                case CXXOperatorKind.Arrow:
                case CXXOperatorKind.Call:
                case CXXOperatorKind.Conditional:
                case CXXOperatorKind.New:
                case CXXOperatorKind.Delete:
                case CXXOperatorKind.Array_New:
                case CXXOperatorKind.Array_Delete:
                default: throw new NotImplementedException();
            }
        }

        public string GetFunctionIdentifier(Function function)
        {
            var printer = TypePrinter as CSharpTypePrinter;
            var isNativeContext = printer.ContextKind == CSharpTypePrinterContextKind.Native;

            string identifier;

            var method = function as Method;
            if (method != null && method.IsOperator)
            {
                if (isNativeContext)
                    identifier = "Operator" + method.OperatorKind.ToString();
                else
                    identifier = GetOperatorIdentifier(method.OperatorKind);
            }
            else
            {
                identifier = SafeIdentifier(function.Name);
            }

            var overloads = function.Namespace.GetFunctionOverloads(function).ToList();
            var index = overloads.IndexOf(function);

            if (isNativeContext && index >= 0)
                identifier += index.ToString(CultureInfo.InvariantCulture);

            return identifier;
        }

        public string GetFunctionNativeIdentifier(Function function)
        {
            var typePrinter = TypePrinter as CSharpTypePrinter;
            typePrinter.PushContext(CSharpTypePrinterContextKind.Native);

            var name = GetFunctionIdentifier(function);

            typePrinter.PopContext();

            return name;
        }

        bool FindMangledDeclLibrary(IMangledDecl decl, out NativeLibrary library)
        {
            string symbol;
            if (!FindMangledDeclSymbol(decl, out symbol))
            {
                library = null;
                return false;
            }

            Driver.LibrarySymbols.FindLibraryBySymbol(symbol, out library);
            return true;
        }

        bool FindMangledDeclSymbol(IMangledDecl decl, out string symbol)
        {
            symbol = decl.Mangled;
            if (!Driver.LibrarySymbols.FindSymbol(ref symbol))
            {
                Driver.Diagnostics.EmitError(DiagnosticId.SymbolNotFound,
                    "Symbol not found: {0}", symbol);
                symbol = null;
                return false;
            }

            return true;
        }

        public void GenerateFunction(Function function, Class @class = null)
        {
            if(function.Ignore) return;

            GenerateDeclarationCommon(function);
            WriteLine("[SuppressUnmanagedCodeSecurity]");

            NativeLibrary library;
            FindMangledDeclLibrary(function, out library);

            var libName = (library != null) ? library.FileName : "SymbolNotFound";
            Write("[DllImport(\"{0}\", ", libName);

            var callConv = Helpers.ToCSharpCallConv(function.CallingConvention);
            WriteLine("CallingConvention = CallingConvention.{0},", callConv);

            WriteLineIndent("EntryPoint=\"{0}\")]", function.Mangled);

            if (function.ReturnType.Type.Desugar().IsPrimitiveType(PrimitiveType.Bool))
                WriteLine("[return: MarshalAsAttribute(UnmanagedType.I1)]");

            var @params = new List<string>();

            var typePrinter = TypePrinter as CSharpTypePrinter;
            var retType = typePrinter.VisitParameterDecl(new Parameter()
                {
                    QualifiedType = function.ReturnType
                });

            var method = function as Method;
            if (method != null && !method.IsStatic)
            {
                @params.Add("System.IntPtr instance");

                if (method.IsConstructor && Options.IsMicrosoftAbi)
                    retType = "System.IntPtr";
            }

            for(var i = 0; i < function.Parameters.Count; ++i)
            {
                var param = function.Parameters[i];

                if (param.Kind == ParameterKind.OperatorParameter)
                    continue;

                var typeName = param.Visit(typePrinter);

                var paramName = param.IsSynthetized ?
                    GeneratedIdentifier(param.Name) : SafeIdentifier(param.Name);

                @params.Add(string.Format("{0} {1}", typeName, paramName));
            }

            if (method != null && method.IsConstructor)
                if (Options.IsMicrosoftAbi && @class.Layout.HasVirtualBases)
                    @params.Add("int " + GeneratedIdentifier("forBases"));

            WriteLine("public unsafe static extern {0} {1}({2});", retType,
                      GetFunctionIdentifier(function),
                      string.Join(", ", @params));
            NeedNewLine();
        }
    }

    internal class SymbolNotFoundException : Exception
    {
        public SymbolNotFoundException(string msg) : base(msg)
        {}
    }
}