// 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.Formatting;
using Microsoft.CodeAnalysis.Simplification;
 
namespace Microsoft.CodeAnalysis.CSharp.Simplification;
 
internal static class CSharpSimplificationHelpers
{
    public static SyntaxToken TryEscapeIdentifierToken(SyntaxToken syntaxToken, SyntaxNode parentOfToken)
    {
        // do not escape an already escaped identifier
        if (syntaxToken.IsVerbatimIdentifier())
        {
            return syntaxToken;
        }
 
        if (SyntaxFacts.GetKeywordKind(syntaxToken.ValueText) == SyntaxKind.None && SyntaxFacts.GetContextualKeywordKind(syntaxToken.ValueText) == SyntaxKind.None)
        {
            return syntaxToken;
        }
 
        if (SyntaxFacts.GetContextualKeywordKind(syntaxToken.ValueText) == SyntaxKind.UnderscoreToken)
        {
            return syntaxToken;
        }
 
        var parent = parentOfToken.Parent;
        if (parentOfToken is SimpleNameSyntax && parent.Kind() == SyntaxKind.XmlNameAttribute)
        {
            // do not try to escape XML name attributes
            return syntaxToken;
        }
 
        // do not escape global in a namespace qualified name
        if (parent.Kind() == SyntaxKind.AliasQualifiedName &&
            syntaxToken.ValueText == "global")
        {
            return syntaxToken;
        }
 
        // safe to escape identifier
        return syntaxToken.CopyAnnotationsTo(
            SyntaxFactory.VerbatimIdentifier(
                syntaxToken.LeadingTrivia,
                syntaxToken.ToString(),
                syntaxToken.ValueText,
                syntaxToken.TrailingTrivia))
                    .WithAdditionalAnnotations(Simplifier.Annotation);
    }
 
    public static T AppendElasticTriviaIfNecessary<T>(T rewrittenNode, T originalNode) where T : SyntaxNode
    {
        var firstRewrittenToken = rewrittenNode.GetFirstToken(true, false, true, true);
        var firstOriginalToken = originalNode.GetFirstToken(true, false, true, true);
        if (TryAddLeadingElasticTriviaIfNecessary(firstRewrittenToken, firstOriginalToken, out var rewrittenTokenWithLeadingElasticTrivia))
        {
            return rewrittenNode.ReplaceToken(firstRewrittenToken, rewrittenTokenWithLeadingElasticTrivia);
        }
 
        return rewrittenNode;
    }
 
    public static bool TryAddLeadingElasticTriviaIfNecessary(SyntaxToken token, SyntaxToken originalToken, out SyntaxToken tokenWithLeadingWhitespace)
    {
        tokenWithLeadingWhitespace = default;
 
        if (token.HasLeadingTrivia)
        {
            return false;
        }
 
        var previousToken = originalToken.GetPreviousToken();
 
        if (previousToken.HasTrailingTrivia)
        {
            return false;
        }
 
        tokenWithLeadingWhitespace = token.WithLeadingTrivia(SyntaxFactory.ElasticMarker).WithAdditionalAnnotations(Formatter.Annotation);
        return true;
    }
}