// 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 System;
using System.Collections.Generic;
using System.ComponentModel.Composition;
using Microsoft.CodeAnalysis.Classification;
using Microsoft.CodeAnalysis.ErrorReporting;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.VisualStudio.Text.Classification;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.ExternalAccess.FSharp.Editor.Shared.Utilities;
 
[Export]
internal class FSharpClassificationTypeMap
{
    private readonly Dictionary<string, IClassificationType> _identityMap;
    private readonly IClassificationTypeRegistryService _registryService;
 
    [ImportingConstructor]
    [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
    public FSharpClassificationTypeMap(IClassificationTypeRegistryService registryService)
    {
        _registryService = registryService;
 
        // Prepopulate the identity map with the constant string values from ClassificationTypeNames
        var fields = typeof(ClassificationTypeNames).GetFields();
        _identityMap = new Dictionary<string, IClassificationType>(fields.Length, ReferenceEqualityComparer.Instance);
 
        foreach (var field in fields)
        {
            // The strings returned from reflection do not have reference-identity
            // with the string constants used by the compiler. Fortunately, a call
            // to string.Intern fixes them.
            var value = string.Intern((string)field.GetValue(null));
            _identityMap.Add(value, registryService.GetClassificationType(value));
        }
    }
 
    public IClassificationType GetClassificationType(string name)
    {
        var type = GetClassificationTypeWorker(name);
        if (type == null)
        {
            FatalError.ReportAndCatch(new Exception($"classification type doesn't exist for {name}"));
        }
 
        return type ?? GetClassificationTypeWorker(ClassificationTypeNames.Text);
    }
 
    private IClassificationType GetClassificationTypeWorker(string name)
    {
        return _identityMap.TryGetValue(name, out var result)
            ? result
            : _registryService.GetClassificationType(name);
    }
}