// 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.Generic;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Host;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Microsoft.CodeAnalysis.Text;

namespace Microsoft.CodeAnalysis.BracePairs;

internal readonly record struct BracePairData(
    TextSpan Start,
    TextSpan End);

internal interface IBracePairsService : ILanguageService
{
    Task AddBracePairsAsync(Document document, TextSpan textSpan, ArrayBuilder<BracePairData> bracePairs, CancellationToken cancellationToken);
}

internal abstract class AbstractBracePairsService : IBracePairsService
{
    private readonly Dictionary<int, int> _bracePairKinds = [];

    protected AbstractBracePairsService(
        ISyntaxKinds syntaxKinds)
    {
        Add(syntaxKinds.OpenBraceToken, syntaxKinds.CloseBraceToken);
        Add(syntaxKinds.OpenBracketToken, syntaxKinds.CloseBracketToken);
        Add(syntaxKinds.OpenParenToken, syntaxKinds.CloseParenToken);
        Add(syntaxKinds.LessThanToken, syntaxKinds.GreaterThanToken);

        return;

        void Add(int? open, int? close)
        {
            if (open != null && close != null)
                _bracePairKinds[open.Value] = close.Value;
        }
    }

    public async Task AddBracePairsAsync(
        Document document, TextSpan span, ArrayBuilder<BracePairData> bracePairs, CancellationToken cancellationToken)
    {
        var root = await document.GetSyntaxRootAsync(cancellationToken).ConfigureAwait(false);

        using var pooledStack = SharedPools.Default<Stack<SyntaxNodeOrToken>>().GetPooledObject();
        var stack = pooledStack.Object;

        stack.Push(root);

        while (stack.TryPop(out var current))
        {
            if (current.IsNode)
            {
                // Ignore nodes that have no intersection at all with the span we're being asked with. Note: if
                // there is any node intersection, then we want to process it.  We specifically don't check token
                // intersection as the start token might not be in the span we're asked about, but the close token
                // may be.
                if (!current.Span.IntersectsWith(span))
                    continue;

                foreach (var child in current.ChildNodesAndTokens().Reverse())
                    stack.Push(child);
            }
            else if (current.IsToken)
            {
                if (_bracePairKinds.TryGetValue(current.AsToken().RawKind, out var closeKind))
                {
                    // hit an open token.  Try to find the corresponding close token in the parent.
                    if (current.Parent != null)
                    {
                        foreach (var sibling in current.Parent.ChildNodesAndTokens())
                        {
                            if (sibling.IsToken && sibling.RawKind == closeKind)
                                bracePairs.Add(new BracePairData(current.Span, sibling.Span));
                        }
                    }
                }
            }
        }
    }
}
