// 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.Immutable;
using System.Threading;
using Microsoft.CodeAnalysis.CSharp.Simplification.Simplifiers;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.Diagnostics;
using Microsoft.CodeAnalysis.RemoveUnnecessaryCast;
using Microsoft.CodeAnalysis.Text;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.CSharp.RemoveUnnecessaryCast
{
    /// <summary>
    /// Supports simplifying cast expressions like <c>(T)x</c> as well as try-cast expressions like <c>x as T</c>
    /// </summary>
    [DiagnosticAnalyzer(LanguageNames.CSharp)]
    internal sealed class CSharpRemoveUnnecessaryCastDiagnosticAnalyzer
        : AbstractRemoveUnnecessaryCastDiagnosticAnalyzer<SyntaxKind, ExpressionSyntax>
    {
        protected override ImmutableArray<SyntaxKind> SyntaxKindsOfInterest { get; } =
            ImmutableArray.Create(SyntaxKind.CastExpression, SyntaxKind.AsExpression);
 
        protected override bool IsUnnecessaryCast(SemanticModel model, ExpressionSyntax cast, CancellationToken cancellationToken)
            => CastSimplifier.IsUnnecessaryCast(cast, model, cancellationToken);
 
        protected override TextSpan GetFadeSpan(ExpressionSyntax node)
            => node is CastExpressionSyntax cast ? TextSpan.FromBounds(cast.OpenParenToken.SpanStart, cast.CloseParenToken.Span.End) :
               node is BinaryExpressionSyntax binary ? TextSpan.FromBounds(binary.OperatorToken.SpanStart, node.Span.End) : throw ExceptionUtilities.Unreachable();
    }
}