// 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;
using System.Collections.Generic;
using System.Linq;
 
namespace Microsoft.CodeAnalysis.Shared.Utilities;
 
internal sealed class SignatureComparer
{
    public static readonly SignatureComparer Instance = new(SymbolEquivalenceComparer.Instance);
    public static readonly SignatureComparer IgnoreAssembliesInstance = new(SymbolEquivalenceComparer.IgnoreAssembliesInstance);
 
    private readonly SymbolEquivalenceComparer _symbolEquivalenceComparer;
 
    private SignatureComparer(SymbolEquivalenceComparer symbolEquivalenceComparer)
        => _symbolEquivalenceComparer = symbolEquivalenceComparer;
 
    private IEqualityComparer<IParameterSymbol> ParameterEquivalenceComparer => _symbolEquivalenceComparer.ParameterEquivalenceComparer;
 
    private IEqualityComparer<ITypeSymbol> SignatureTypeEquivalenceComparer => _symbolEquivalenceComparer.SignatureTypeEquivalenceComparer;
 
    public bool HaveSameSignature(ISymbol symbol1, ISymbol symbol2, bool caseSensitive)
    {
        // NOTE - we're deliberately using reference equality here for speed.
        if (symbol1 == symbol2)
            return true;
 
        if (symbol1 == null || symbol2 == null)
            return false;
 
        if (symbol1.Kind != symbol2.Kind)
            return false;
 
        return symbol1.Kind switch
        {
            SymbolKind.Method => HaveSameSignature((IMethodSymbol)symbol1, (IMethodSymbol)symbol2, caseSensitive),
            SymbolKind.Property => HaveSameSignature((IPropertySymbol)symbol1, (IPropertySymbol)symbol2, caseSensitive),
            SymbolKind.Event => HaveSameSignature((IEventSymbol)symbol1, (IEventSymbol)symbol2, caseSensitive),
            _ => true,
        };
    }
 
    private static bool HaveSameSignature(IEventSymbol event1, IEventSymbol event2, bool caseSensitive)
        => IdentifiersMatch(event1.Name, event2.Name, caseSensitive);
 
    public bool HaveSameSignature(IPropertySymbol property1, IPropertySymbol property2, bool caseSensitive)
    {
        if (!IdentifiersMatch(property1.Name, property2.Name, caseSensitive) ||
            property1.Parameters.Length != property2.Parameters.Length ||
            property1.IsIndexer != property2.IsIndexer)
        {
            return false;
        }
 
        return property1.Parameters.SequenceEqual(
            property2.Parameters,
            this.ParameterEquivalenceComparer);
    }
 
    private static bool BadPropertyAccessor(IMethodSymbol method1, IMethodSymbol method2)
    {
        return method1 != null &&
            (method2 == null || method2.DeclaredAccessibility != Accessibility.Public);
    }
 
    public bool HaveSameSignature(IMethodSymbol method1,
        IMethodSymbol method2,
        bool caseSensitive,
        bool compareParameterName = false,
        bool isParameterCaseSensitive = false)
    {
        if ((method1.MethodKind == MethodKind.AnonymousFunction) !=
            (method2.MethodKind == MethodKind.AnonymousFunction))
        {
            return false;
        }
 
        if (method1.MethodKind != MethodKind.AnonymousFunction)
        {
            if (!IdentifiersMatch(method1.Name, method2.Name, caseSensitive))
                return false;
        }
 
        if (method1.MethodKind != method2.MethodKind ||
            method1.Arity != method2.Arity)
        {
            return false;
        }
 
        return HaveSameSignature(method1.Parameters, method2.Parameters, compareParameterName, isParameterCaseSensitive);
    }
 
    private static bool IdentifiersMatch(string identifier1, string identifier2, bool caseSensitive)
    {
        return caseSensitive
            ? identifier1 == identifier2
            : string.Equals(identifier1, identifier2, StringComparison.OrdinalIgnoreCase);
    }
 
    public bool HaveSameSignature(
        IList<IParameterSymbol> parameters1,
        IList<IParameterSymbol> parameters2)
    {
        if (parameters1.Count != parameters2.Count)
        {
            return false;
        }
 
        return parameters1.SequenceEqual(parameters2, this.ParameterEquivalenceComparer);
    }
 
    public bool HaveSameSignature(
        IList<IParameterSymbol> parameters1,
        IList<IParameterSymbol> parameters2,
        bool compareParameterName,
        bool isCaseSensitive)
    {
        if (parameters1.Count != parameters2.Count)
        {
            return false;
        }
 
        for (var i = 0; i < parameters1.Count; ++i)
        {
            if (!_symbolEquivalenceComparer.ParameterEquivalenceComparer.Equals(parameters1[i], parameters2[i], compareParameterName, isCaseSensitive))
            {
                return false;
            }
        }
 
        return true;
    }
 
    public bool HaveSameSignatureAndConstraintsAndReturnTypeAndAccessors(ISymbol symbol1, ISymbol symbol2, bool caseSensitive)
    {
        // NOTE - we're deliberately using reference equality here for speed.
        if (symbol1 == symbol2)
            return true;
 
        if (!HaveSameSignature(symbol1, symbol2, caseSensitive))
            return false;
 
        switch (symbol1.Kind)
        {
            case SymbolKind.Method:
                var method1 = (IMethodSymbol)symbol1;
                var method2 = (IMethodSymbol)symbol2;
 
                return HaveSameSignatureAndConstraintsAndReturnType(method1, method2);
            case SymbolKind.Property:
                var property1 = (IPropertySymbol)symbol1;
                var property2 = (IPropertySymbol)symbol2;
 
                return property1.ReturnsByRef == property2.ReturnsByRef &&
                       property1.ReturnsByRefReadonly == property2.ReturnsByRefReadonly &&
                       this.SignatureTypeEquivalenceComparer.Equals(property1.Type, property2.Type) &&
                       HaveSameAccessors(property1, property2);
            case SymbolKind.Event:
                var ev1 = (IEventSymbol)symbol1;
                var ev2 = (IEventSymbol)symbol2;
 
                return HaveSameReturnType(ev1, ev2);
        }
 
        return true;
    }
 
    private static bool HaveSameAccessors(IPropertySymbol property1, IPropertySymbol property2)
    {
        if (property1.ContainingType == null ||
            property1.ContainingType.TypeKind == TypeKind.Interface)
        {
            if (BadPropertyAccessor(property1.GetMethod, property2.GetMethod) ||
                BadPropertyAccessor(property1.SetMethod, property2.SetMethod))
            {
                return false;
            }
        }
 
        if (property2.ContainingType == null ||
            property2.ContainingType.TypeKind == TypeKind.Interface)
        {
            if (BadPropertyAccessor(property2.GetMethod, property1.GetMethod) ||
                BadPropertyAccessor(property2.SetMethod, property1.SetMethod))
            {
                return false;
            }
        }
 
        return true;
    }
 
    private bool HaveSameSignatureAndConstraintsAndReturnType(IMethodSymbol method1, IMethodSymbol method2)
    {
        if (method1.ReturnsVoid != method2.ReturnsVoid ||
            method1.ReturnsByRef != method2.ReturnsByRef ||
            method1.ReturnsByRefReadonly != method2.ReturnsByRefReadonly)
        {
            return false;
        }
 
        if (!method1.ReturnsVoid && !this.SignatureTypeEquivalenceComparer.Equals(method1.ReturnType, method2.ReturnType))
            return false;
 
        for (var i = 0; i < method1.TypeParameters.Length; i++)
        {
            var typeParameter1 = method1.TypeParameters[i];
            var typeParameter2 = method2.TypeParameters[i];
 
            if (!HaveSameConstraints(typeParameter1, typeParameter2))
                return false;
        }
 
        return true;
    }
 
    private bool HaveSameConstraints(ITypeParameterSymbol typeParameter1, ITypeParameterSymbol typeParameter2)
    {
        if (typeParameter1.HasConstructorConstraint != typeParameter2.HasConstructorConstraint ||
            typeParameter1.HasReferenceTypeConstraint != typeParameter2.HasReferenceTypeConstraint ||
            typeParameter1.HasValueTypeConstraint != typeParameter2.HasValueTypeConstraint ||
            typeParameter1.AllowsRefLikeType != typeParameter2.AllowsRefLikeType)
        {
            return false;
        }
 
        if (typeParameter1.ConstraintTypes.Length != typeParameter2.ConstraintTypes.Length)
        {
            return false;
        }
 
        return typeParameter1.ConstraintTypes.SetEquals(
            typeParameter2.ConstraintTypes, this.SignatureTypeEquivalenceComparer);
    }
 
    private bool HaveSameReturnType(IEventSymbol ev1, IEventSymbol ev2)
        => this.SignatureTypeEquivalenceComparer.Equals(ev1.Type, ev2.Type);
}