// 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.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using CommunityToolkit.Mvvm.SourceGenerators.Extensions;
using static CommunityToolkit.Mvvm.SourceGenerators.Diagnostics.DiagnosticDescriptors;

namespace CommunityToolkit.Mvvm.SourceGenerators;

/// <summary>
/// A source generator for the <c>INotifyPropertyChangedAttribute</c> type.
/// </summary>
[Generator]
public sealed class INotifyPropertyChangedGenerator : TransitiveMembersGenerator
{
    /// <summary>
    /// Initializes a new instance of the <see cref="INotifyPropertyChangedGenerator"/> class.
    /// </summary>
    public INotifyPropertyChangedGenerator()
        : base("CommunityToolkit.Mvvm.ComponentModel.INotifyPropertyChangedAttribute")
    {
    }

    /// <inheritdoc/>
    protected override DiagnosticDescriptor TargetTypeErrorDescriptor => INotifyPropertyChangedGeneratorError;

    /// <inheritdoc/>
    protected override bool ValidateTargetType(
        GeneratorExecutionContext context,
        AttributeData attributeData,
        ClassDeclarationSyntax classDeclaration,
        INamedTypeSymbol classDeclarationSymbol,
        [NotNullWhen(false)] out DiagnosticDescriptor? descriptor)
    {
        INamedTypeSymbol iNotifyPropertyChangedSymbol = context.Compilation.GetTypeByMetadataName("System.ComponentModel.INotifyPropertyChanged")!;

        // Check if the type already implements INotifyPropertyChanged
        if (classDeclarationSymbol.AllInterfaces.Any(i => SymbolEqualityComparer.Default.Equals(i, iNotifyPropertyChangedSymbol)))
        {
            descriptor = DuplicateINotifyPropertyChangedInterfaceForINotifyPropertyChangedAttributeError;

            return false;
        }

        descriptor = null;

        return true;
    }

    /// <inheritdoc/>
    protected override IEnumerable<MemberDeclarationSyntax> FilterDeclaredMembers(
        GeneratorExecutionContext context,
        AttributeData attributeData,
        ClassDeclarationSyntax classDeclaration,
        INamedTypeSymbol classDeclarationSymbol,
        ClassDeclarationSyntax sourceDeclaration)
    {
        // If requested, only include the event and the basic methods to raise it, but not the additional helpers
        if (attributeData.HasNamedArgument("IncludeAdditionalHelperMethods", false))
        {
            return sourceDeclaration.Members.Where(static member =>
            {
                return member
                    is EventFieldDeclarationSyntax
                    or MethodDeclarationSyntax { Identifier: { ValueText: "OnPropertyChanged" } };
            });
        }

        return sourceDeclaration.Members;
    }
}