// 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;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
 
namespace Microsoft.CodeAnalysis.EmbeddedLanguages;
 
/// <summary>
/// Helps match patterns of the form: language=name,option1,option2,option3
/// <para/>
/// All matching is case insensitive, with spaces allowed between the punctuation. Option values will be or'ed
/// together to produce final options value.  If an unknown option is encountered, processing will stop with
/// whatever value has accumulated so far.
/// <para/>
/// Option names are the values from the TOptions enum.
/// </summary>
internal static class EmbeddedLanguageCommentOptions<TOptions> where TOptions : struct, Enum
{
    private static readonly Dictionary<string, TOptions> s_nameToOption =
        typeof(TOptions).GetTypeInfo().DeclaredFields
            .Where(f => f.FieldType == typeof(TOptions))
            .ToDictionary(f => f.Name, f => (TOptions)f.GetValue(null)!, StringComparer.OrdinalIgnoreCase);
 
    public static bool TryGetOptions(IEnumerable<string> captures, out TOptions options)
    {
        options = default;
 
        foreach (var capture in captures)
        {
            if (!s_nameToOption.TryGetValue(capture, out var specificOption))
            {
                // hit something we don't understand.  bail out.  that will help ensure
                // users don't have weird behavior just because they misspelled something.
                // instead, they will know they need to fix it up.
                return false;
            }
 
            options = CombineOptions(options, specificOption);
        }
 
        return true;
    }
 
    private static TOptions CombineOptions(TOptions options, TOptions specificOption)
    {
        var int1 = (int)(object)options;
        var int2 = (int)(object)specificOption;
        return (TOptions)(object)(int1 | int2);
    }
}