// 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.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Text;
 
namespace Microsoft.CodeAnalysis.BraceMatching
{
    internal abstract class AbstractDirectiveTriviaBraceMatcher<TDirectiveTriviaSyntax,
        TIfDirectiveTriviaSyntax, TElseIfDirectiveTriviaSyntax,
        TElseDirectiveTriviaSyntax, TEndIfDirectiveTriviaSyntax,
        TRegionDirectiveTriviaSyntax, TEndRegionDirectiveTriviaSyntax> : IBraceMatcher
            where TDirectiveTriviaSyntax : SyntaxNode
            where TIfDirectiveTriviaSyntax : TDirectiveTriviaSyntax
            where TElseIfDirectiveTriviaSyntax : TDirectiveTriviaSyntax
            where TElseDirectiveTriviaSyntax : TDirectiveTriviaSyntax
            where TEndIfDirectiveTriviaSyntax : TDirectiveTriviaSyntax
            where TRegionDirectiveTriviaSyntax : TDirectiveTriviaSyntax
            where TEndRegionDirectiveTriviaSyntax : TDirectiveTriviaSyntax
    {
        internal abstract List<TDirectiveTriviaSyntax> GetMatchingConditionalDirectives(TDirectiveTriviaSyntax directive, CancellationToken cancellationToken);
        internal abstract TDirectiveTriviaSyntax GetMatchingDirective(TDirectiveTriviaSyntax directive, CancellationToken cancellationToken);
        internal abstract TextSpan GetSpanForTagging(TDirectiveTriviaSyntax directive);
 
        public async Task<BraceMatchingResult?> FindBracesAsync(Document document, int position, BraceMatchingOptions options, CancellationToken cancellationToken)
        {
            var root = await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);
            var token = root.FindToken(position, findInsideTrivia: true);
 
            if (token.Parent is not TDirectiveTriviaSyntax directive)
            {
                return null;
            }
 
            TDirectiveTriviaSyntax matchingDirective = null;
            if (IsConditionalDirective(directive))
            {
                // #if/#elif/#else/#endif directive cases.
                var matchingDirectives = GetMatchingConditionalDirectives(directive, cancellationToken);
                if (matchingDirectives?.Count > 0)
                {
                    matchingDirective = matchingDirectives[(matchingDirectives.IndexOf(directive) + 1) % matchingDirectives.Count];
                }
            }
            else
            {
                // #region/#endregion or other directive cases.
                matchingDirective = GetMatchingDirective(directive, cancellationToken);
            }
 
            if (matchingDirective == null)
            {
                // one line directives, that do not have a matching begin/end directive pair.
                return null;
            }
 
            return new BraceMatchingResult(
                LeftSpan: GetSpanForTagging(directive),
                RightSpan: GetSpanForTagging(matchingDirective));
        }
 
        private static bool IsConditionalDirective(TDirectiveTriviaSyntax directive)
        {
            return directive is TIfDirectiveTriviaSyntax or
                   TElseIfDirectiveTriviaSyntax or
                   TElseDirectiveTriviaSyntax or
                   TEndIfDirectiveTriviaSyntax;
        }
    }
}