using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using SharpGen.Logging;
using SharpGen.Model;
using static Microsoft.CodeAnalysis.CSharp.SyntaxFactory;

namespace SharpGen.Generator
{
    internal sealed class NativeStructCodeGenerator : CodeGeneratorBase, IMultiCodeGenerator<CsStruct, MemberDeclarationSyntax>
    {
        private static readonly NameSyntax StructLayoutAttributeName = ParseName("System.Runtime.InteropServices.StructLayoutAttribute");
        private const string StructLayoutKindName = "System.Runtime.InteropServices.LayoutKind.";
        private static readonly AttributeArgumentSyntax StructLayoutExplicit = AttributeArgument(ParseName(StructLayoutKindName + "Explicit"));
        private static readonly AttributeArgumentSyntax StructLayoutSequential = AttributeArgument(ParseName(StructLayoutKindName + "Sequential"));
        private static readonly NameEqualsSyntax StructLayoutPackName = NameEquals(IdentifierName("Pack"));
        private static readonly SyntaxToken MarshalParameterRefName = Identifier("@ref");

        private static readonly AttributeArgumentSyntax StructLayoutCharset = AttributeArgument(
            ParseName("System.Runtime.InteropServices.CharSet.Unicode")
        ).WithNameEquals(NameEquals(IdentifierName("CharSet")));

        public IEnumerable<MemberDeclarationSyntax> GenerateCode(CsStruct csStruct)
        {
            yield return StructDeclaration("__Native")
                        .WithModifiers(TokenList(Token(SyntaxKind.InternalKeyword), Token(SyntaxKind.PartialKeyword)))
                        .WithAttributeLists(SingletonList(GenerateStructLayoutAttribute(csStruct)))
                        .WithMembers(List(csStruct.Fields.SelectMany(GenerateMarshalStructField)));

            if (csStruct.GenerateAsClass)
            {
                var methodName = IdentifierName("__MarshalFrom");
                var marshalArgument = Argument(IdentifierName(MarshalParameterRefName))
                   .WithRefOrOutKeyword(Token(SyntaxKind.RefKeyword));

                var invocationExpression = csStruct.IsStaticMarshal
                                               ? InvocationExpression(
                                                   methodName,
                                                   ArgumentList(
                                                       SeparatedList(
                                                           new[]
                                                           {
                                                               Argument(ThisExpression())
                                                                  .WithRefOrOutKeyword(Token(SyntaxKind.RefKeyword)),
                                                               marshalArgument
                                                           }
                                                       )
                                                   )
                                               )
                                               : InvocationExpression(
                                                   methodName,
                                                   ArgumentList(SingletonSeparatedList(marshalArgument))
                                               );

                yield return ConstructorDeclaration(csStruct.Name)
                            .WithModifiers(TokenList(Token(SyntaxKind.PublicKeyword)))
                            .WithBody(Block());

                yield return ConstructorDeclaration(csStruct.Name)
                            .WithModifiers(TokenList(Token(SyntaxKind.InternalKeyword)))
                            .WithParameterList(MarshalParameterListSyntax)
                            .WithBody(Block(ExpressionStatement(invocationExpression)));
            }

            yield return GenerateMarshalFree(csStruct);
            yield return GenerateMarshalFrom(csStruct);
            yield return GenerateMarshalTo(csStruct);

            IEnumerable<MemberDeclarationSyntax> GenerateMarshalStructField(CsField field)
            {
                var fieldDecl = FieldDeclaration(VariableDeclaration(ParseTypeName(field.MarshalType.QualifiedName)))
                   .WithModifiers(TokenList(Token(SyntaxKind.PublicKeyword)));

                if (csStruct.ExplicitLayout)
                    fieldDecl = AddFieldOffsetAttribute(fieldDecl, field.Offset);

                if (field.ArraySpecification is {} arraySpecification)
                {
                    yield return fieldDecl.WithDeclaration(
                        fieldDecl.Declaration.AddVariables(VariableDeclarator(field.Name))
                    );

                    if (arraySpecification.Dimension is { } dimension)
                        for (var i = 1; i < dimension; i++)
                        {
                            var declaration = fieldDecl.WithDeclaration(
                                fieldDecl.Declaration.AddVariables(VariableDeclarator($"__{field.Name}{i}"))
                            );

                            if (csStruct.ExplicitLayout)
                            {
                                var offset = field.Offset + i * field.Size / dimension;
                                declaration = AddFieldOffsetAttribute(declaration, offset, true);
                            }

                            yield return declaration;
                        }
                    else
                        Logger.Warning(
                            LoggingCodes.UnknownArrayDimension, "Unknown array dimensions for [{0}]",
                            field.QualifiedName
                        );
                }
                else if (field.HasNativeValueType)
                {
                    yield return fieldDecl.WithDeclaration(
                        VariableDeclaration(
                            ParseTypeName($"{field.MarshalType.QualifiedName}.__Native"),
                            SingletonSeparatedList(VariableDeclarator(field.Name))
                        )
                    );
                }
                else
                {
                    yield return fieldDecl.WithDeclaration(
                        fieldDecl.Declaration.AddVariables(VariableDeclarator(field.Name))
                    );
                }
            }
        }

        internal static AttributeListSyntax GenerateStructLayoutAttribute(CsStruct csElement) => AttributeList(
            SingletonSeparatedList(
                Attribute(
                    StructLayoutAttributeName,
                    AttributeArgumentList(
                        SeparatedList(
                            new[]
                            {
                                csElement.ExplicitLayout ? StructLayoutExplicit : StructLayoutSequential,
                                AttributeArgument(
                                        LiteralExpression(SyntaxKind.NumericLiteralExpression, Literal(csElement.Align))
                                    )
                                   .WithNameEquals(StructLayoutPackName),
                                StructLayoutCharset
                            }
                        )
                    )
                )
            )
        );

        private MethodDeclarationSyntax GenerateMarshalFree(CsStruct csStruct) => GenerateMarshalMethod(
            "__MarshalFree",
            csStruct.Fields.Where(field => !field.IsArray),
            field => GetMarshaller(field)?.GenerateNativeCleanup(field, false)
        );

        private MethodDeclarationSyntax GenerateMarshalTo(CsStruct csStruct)
        {
            IEnumerable<StatementSyntax> FieldMarshallers(CsField field)
            {
                if (field.Relations.Count == 0)
                {
                    yield return GetMarshaller(field).GenerateManagedToNative(field, false);
                    yield break;
                }

                foreach (var relation in field.Relations)
                {
                    var marshaller = GetRelationMarshaller(relation);
                    CsField publicElement = null;

                    if (relation is LengthRelation related)
                    {
                        var relatedMarshallableName = related.Identifier;

                        publicElement = csStruct.Fields.First(fld => fld.CppElementName == relatedMarshallableName);
                    }

                    yield return marshaller.GenerateManagedToNative(publicElement, field);
                }
            }

            return GenerateMarshalMethod(
                "__MarshalTo",
                csStruct.Fields,
                FieldMarshallers
            );
        }

        private static ParameterListSyntax MarshalParameterListSyntax => ParameterList(
            SingletonSeparatedList(Parameter(MarshalParameterRefName).WithType(RefType(ParseTypeName("__Native"))))
        );

        private MethodDeclarationSyntax GenerateMarshalMethod<T>(string name, IEnumerable<T> source,
                                                                 Func<T, StatementSyntax> transform)
            where T : CsMarshalBase
        {
            StatementSyntaxList list = new(Generators.Marshalling);
            list.AddRange(source, transform);
            return GenerateMarshalMethod(name, list);
        }

        private MethodDeclarationSyntax GenerateMarshalMethod<T>(string name, IEnumerable<T> source,
                                                                 Func<T, IEnumerable<StatementSyntax>> transform)
            where T : CsMarshalBase
        {
            StatementSyntaxList list = new(Generators.Marshalling);
            list.AddRange(source, transform);
            return GenerateMarshalMethod(name, list);
        }

        private static MethodDeclarationSyntax GenerateMarshalMethod(string name, StatementSyntaxList body) =>
            MethodDeclaration(PredefinedType(Token(SyntaxKind.VoidKeyword)), name)
               .WithParameterList(MarshalParameterListSyntax)
               .WithModifiers(TokenList(Token(SyntaxKind.InternalKeyword), Token(SyntaxKind.UnsafeKeyword)))
               .WithBody(body.ToBlock());

        private MethodDeclarationSyntax GenerateMarshalFrom(CsStruct csStruct) => GenerateMarshalMethod(
            "__MarshalFrom",
            csStruct.PublicFields,
            field => GetMarshaller(field).GenerateNativeToManaged(field, false)
        );

        public NativeStructCodeGenerator(Ioc ioc) : base(ioc)
        {
        }
    }
}