// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

#nullable disable

using System.Collections.Generic;
using System.Linq;
using Microsoft.CodeAnalysis.CSharp.Extensions;
using Microsoft.CodeAnalysis.CSharp.Symbols;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.CSharp.Utilities;
using Microsoft.CodeAnalysis.Shared.Extensions;

namespace Microsoft.CodeAnalysis.CSharp.Organizing.Organizers;

internal static partial class MemberDeclarationsOrganizer
{
    private sealed class Comparer : IComparer<MemberDeclarationSyntax>
    {
        // TODO(cyrusn): Allow users to specify the ordering they want
        private enum OuterOrdering
        {
            Fields,
            EventFields,
            Constructors,
            Destructors,
            Properties,
            Events,
            Indexers,
            Operators,
            ConversionOperators,
            Methods,
            Types,
            Remaining
        }

        private enum InnerOrdering
        {
            StaticInstance,
            Accessibility,
            Name
        }

        private enum Accessibility
        {
            Public,
            Protected,
            ProtectedOrInternal,
            Internal,
            Private
        }

        public int Compare(MemberDeclarationSyntax x, MemberDeclarationSyntax y)
        {
            if (x == y)
            {
                return 0;
            }

            var xOuterOrdering = GetOuterOrdering(x);
            var yOuterOrdering = GetOuterOrdering(y);

            var compare = xOuterOrdering - yOuterOrdering;
            if (compare != 0)
            {
                return compare;
            }

            if (xOuterOrdering == OuterOrdering.Remaining)
            {
                return 1;
            }
            else if (yOuterOrdering == OuterOrdering.Remaining)
            {
                return -1;
            }

            if (xOuterOrdering == OuterOrdering.Fields || yOuterOrdering == OuterOrdering.Fields)
            {
                // Fields with initializers can't be reordered relative to 
                // themselves due to ordering issues.
                var xHasInitializer = ((FieldDeclarationSyntax)x).Declaration.Variables.Any(v => v.Initializer != null);
                var yHasInitializer = ((FieldDeclarationSyntax)y).Declaration.Variables.Any(v => v.Initializer != null);
                if (xHasInitializer && yHasInitializer)
                {
                    return 0;
                }
            }

            var xIsStatic = x.GetModifiers().Any(SyntaxKind.StaticKeyword);
            var yIsStatic = y.GetModifiers().Any(SyntaxKind.StaticKeyword);

            if ((compare = Comparer<bool>.Default.Inverse().Compare(xIsStatic, yIsStatic)) != 0)
            {
                return compare;
            }

            var xAccessibility = GetAccessibility(x);
            var yAccessibility = GetAccessibility(y);
            if ((compare = xAccessibility - yAccessibility) != 0)
            {
                return compare;
            }

            var xName = ShouldCompareByName(x) ? x.GetNameToken() : default;
            var yName = ShouldCompareByName(y) ? y.GetNameToken() : default;

            if ((compare = TokenComparer.NormalInstance.Compare(xName, yName)) != 0)
            {
                return compare;
            }

            // Their names were the same.  Order them by arity at this point.
            return x.GetArity() - y.GetArity();
        }

        private static Accessibility GetAccessibility(MemberDeclarationSyntax x)
        {
            var xModifiers = x.GetModifiers();

            if (xModifiers.Any(SyntaxKind.PublicKeyword))
            {
                return Accessibility.Public;
            }
            else if (xModifiers.Any(SyntaxKind.ProtectedKeyword) && xModifiers.Any(SyntaxKind.InternalKeyword))
            {
                return Accessibility.ProtectedOrInternal;
            }
            else if (xModifiers.Any(SyntaxKind.InternalKeyword))
            {
                return Accessibility.Internal;
            }
            else if (xModifiers.Any(SyntaxKind.ProtectedKeyword))
            {
                return Accessibility.Protected;
            }
            else
            {
                return Accessibility.Private;
            }
        }

        private static OuterOrdering GetOuterOrdering(MemberDeclarationSyntax x)
        {
            switch (x.Kind())
            {
                case SyntaxKind.FieldDeclaration:
                    return OuterOrdering.Fields;
                case SyntaxKind.EventFieldDeclaration:
                    return OuterOrdering.EventFields;
                case SyntaxKind.ConstructorDeclaration:
                    return OuterOrdering.Constructors;
                case SyntaxKind.DestructorDeclaration:
                    return OuterOrdering.Destructors;
                case SyntaxKind.PropertyDeclaration:
                    return OuterOrdering.Properties;
                case SyntaxKind.EventDeclaration:
                    return OuterOrdering.Events;
                case SyntaxKind.IndexerDeclaration:
                    return OuterOrdering.Indexers;
                case SyntaxKind.OperatorDeclaration:
                    return OuterOrdering.Operators;
                case SyntaxKind.ConversionOperatorDeclaration:
                    return OuterOrdering.ConversionOperators;
                case SyntaxKind.MethodDeclaration:
                    return OuterOrdering.Methods;
                case SyntaxKind.ClassDeclaration:
                case SyntaxKind.InterfaceDeclaration:
                case SyntaxKind.StructDeclaration:
                case SyntaxKind.EnumDeclaration:
                case SyntaxKind.DelegateDeclaration:
                case SyntaxKind.RecordDeclaration:
                case SyntaxKind.RecordStructDeclaration:
                    return OuterOrdering.Types;
                default:
                    return OuterOrdering.Remaining;
            }
        }

        private static bool ShouldCompareByName(MemberDeclarationSyntax x)
        {
            // Constructors, destructors, indexers and operators should not be sorted by name.
            // Note:  Conversion operators should not be sorted by name either, but it's not
            //        necessary to deal with that here, because GetNameToken cannot return a
            //        name for them (there's only a NameSyntax, not a Token).
            switch (x.Kind())
            {
                case SyntaxKind.ConstructorDeclaration:
                case SyntaxKind.DestructorDeclaration:
                case SyntaxKind.IndexerDeclaration:
                case SyntaxKind.OperatorDeclaration:
                    return false;
                default:
                    return true;
            }
        }
    }
}