// 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 Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.CSharp.Utilities;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.Simplification;
 
namespace Microsoft.CodeAnalysis.CSharp.Simplification
{
    internal partial class CSharpVarReducer
    {
        private class Rewriter : AbstractReductionRewriter
        {
            public Rewriter(ObjectPool<IReductionRewriter> pool)
                : base(pool)
            {
            }
 
            private SyntaxNode ProcessTypeSyntax(TypeSyntax typeSyntax)
            {
                this.CancellationToken.ThrowIfCancellationRequested();
 
                // Only simplify if us, or a parent, was marked as needing simplification.
                if (!alwaysSimplify && !typeSyntax.HasAnnotation(Simplifier.Annotation))
                {
                    return typeSyntax;
                }
 
                // Definitely do not simplify us if we were told to not simplify.
                if (typeSyntax.HasAnnotation(SimplificationHelpers.DontSimplifyAnnotation))
                {
                    return typeSyntax;
                }
 
                var typeStyle = CSharpUseImplicitTypeHelper.Instance.AnalyzeTypeName(
                    typeSyntax, this.SemanticModel, this.Options, this.CancellationToken);
 
                if (!typeStyle.IsStylePreferred || !typeStyle.CanConvert())
                {
                    return typeSyntax;
                }
 
                return SyntaxFactory.IdentifierName("var")
                    .WithLeadingTrivia(typeSyntax.GetLeadingTrivia())
                    .WithTrailingTrivia(typeSyntax.GetTrailingTrivia());
            }
 
            public override SyntaxNode VisitAliasQualifiedName(AliasQualifiedNameSyntax node) => ProcessTypeSyntax(node);
            public override SyntaxNode VisitArrayType(ArrayTypeSyntax node) => ProcessTypeSyntax(node);
            public override SyntaxNode VisitGenericName(GenericNameSyntax node) => ProcessTypeSyntax(node);
            public override SyntaxNode VisitIdentifierName(IdentifierNameSyntax node) => ProcessTypeSyntax(node);
            public override SyntaxNode VisitNullableType(NullableTypeSyntax node) => ProcessTypeSyntax(node);
            public override SyntaxNode VisitPointerType(PointerTypeSyntax node) => ProcessTypeSyntax(node);
            public override SyntaxNode VisitPredefinedType(PredefinedTypeSyntax node) => ProcessTypeSyntax(node);
            public override SyntaxNode VisitQualifiedName(QualifiedNameSyntax node) => ProcessTypeSyntax(node);
            public override SyntaxNode VisitTupleType(TupleTypeSyntax node) => ProcessTypeSyntax(node);
        }
    }
}