// 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 Microsoft.CodeAnalysis.EmbeddedLanguages;
using Microsoft.CodeAnalysis.Shared.Collections;
 
namespace Microsoft.CodeAnalysis.Classification;
 
internal abstract class AbstractFallbackEmbeddedLanguageClassifier : IEmbeddedLanguageClassifier
{
    private readonly EmbeddedLanguageInfo _info;
    private readonly ImmutableArray<int> _supportedKinds;
 
    protected AbstractFallbackEmbeddedLanguageClassifier(EmbeddedLanguageInfo info)
    {
        _info = info;
 
        using var array = TemporaryArray<int>.Empty;
 
        array.Add(info.SyntaxKinds.CharacterLiteralToken);
        array.Add(info.SyntaxKinds.StringLiteralToken);
        array.Add(info.SyntaxKinds.InterpolatedStringTextToken);
 
        array.AsRef().AddIfNotNull(info.SyntaxKinds.Utf8StringLiteralToken);
 
        _supportedKinds = array.ToImmutableAndClear();
    }
 
    public void RegisterClassifications(EmbeddedLanguageClassificationContext context)
    {
        var token = context.SyntaxToken;
        if (!_supportedKinds.Contains(token.RawKind))
            return;
 
        var virtualChars = _info.VirtualCharService.TryConvertToVirtualChars(token);
        if (virtualChars.IsDefaultOrEmpty)
            return;
 
        // Can avoid any work if we got the same number of virtual characters back as characters in the string. In
        // that case, there are clearly no escaped characters.
        if (virtualChars.Length == token.Text.Length)
            return;
 
        foreach (var vc in virtualChars)
        {
            // utf-16 virtual char might have either one or two in text span
            if (vc.Span.Length > vc.Rune.Utf16SequenceLength)
                context.AddClassification(ClassificationTypeNames.StringEscapeCharacter, vc.Span);
        }
    }
}