// 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.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using Microsoft.CodeAnalysis.Shared.Extensions;

namespace Microsoft.CodeAnalysis.CodeFixes.FullyQualify;

internal abstract partial class AbstractFullyQualifyService<TSimpleNameSyntax> where TSimpleNameSyntax : SyntaxNode
{
    private readonly struct SymbolResult : IEquatable<SymbolResult>, IComparable<SymbolResult>
    {
        public readonly INamespaceOrTypeSymbol Symbol;
        public readonly int Weight;
        public readonly INamespaceOrTypeSymbol? OriginalSymbol;
        public readonly IReadOnlyList<string> NameParts;

        public SymbolResult(INamespaceOrTypeSymbol symbol, int weight)
            : this(symbol, weight, originalSymbol: null)
        {
        }

        private SymbolResult(INamespaceOrTypeSymbol symbol, int weight, INamespaceOrTypeSymbol? originalSymbol)
        {
            Symbol = symbol;
            Weight = weight;
            NameParts = INamespaceOrTypeSymbolExtensions.GetNameParts(symbol);
            OriginalSymbol = originalSymbol;
        }

        public override bool Equals(object? obj)
            => obj is SymbolResult result && Equals(result);

        public bool Equals(SymbolResult other)
            => Equals(Symbol, other.Symbol);

        public override int GetHashCode()
            => Symbol.GetHashCode();

        public SymbolResult WithSymbol(INamespaceOrTypeSymbol other)
            => new(other, Weight, Symbol);

        public int CompareTo(SymbolResult other)
        {
            Debug.Assert(Symbol is INamespaceSymbol || !((INamedTypeSymbol)Symbol).IsGenericType);
            Debug.Assert(other.Symbol is INamespaceSymbol || !((INamedTypeSymbol)other.Symbol).IsGenericType);

            var diff = Weight - other.Weight;
            if (diff != 0)
            {
                return diff;
            }

            return INamespaceOrTypeSymbolExtensions.CompareNameParts(
                NameParts, other.NameParts, placeSystemNamespaceFirst: true);
        }
    }
}