// 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.Immutable;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.PooledObjects;
using Microsoft.CodeAnalysis.Structure;
using Xunit;

namespace Microsoft.CodeAnalysis.Editor.UnitTests.Structure;

public abstract class AbstractSyntaxNodeStructureProviderTests<TSyntaxNode> : AbstractSyntaxStructureProviderTests
    where TSyntaxNode : SyntaxNode
{
    internal abstract AbstractSyntaxStructureProvider CreateProvider();

    internal sealed override async Task<ImmutableArray<BlockSpan>> GetBlockSpansWorkerAsync(Document document, BlockStructureOptions options, int position)
    {
        var root = await document.GetSyntaxRootAsync(CancellationToken.None);
        var token = root.FindToken(position, findInsideTrivia: true);
        var node = token.Parent.FirstAncestorOrSelf<TSyntaxNode>();
        Assert.NotNull(node);

        // We prefer ancestor nodes if the position is on the edge of the located node's span.
        while (node.Parent is TSyntaxNode)
        {
            if ((position == node.SpanStart && position == node.Parent.SpanStart) ||
                (position == node.Span.End && position == node.Parent.Span.End))
            {
                node = (TSyntaxNode)node.Parent;
            }
            else
            {
                break;
            }
        }

        var outliner = CreateProvider();
        using var _ = ArrayBuilder<BlockSpan>.GetInstance(out var actualRegions);
        // Calculate previousToken for tests the same way it is derived in production code
        var previousToken = root.DescendantNodesAndTokens(descendIntoTrivia: true).TakeWhile(nodeOrToken => nodeOrToken != node).LastOrDefault(nodeOrToken => nodeOrToken.IsToken).AsToken();
        outliner.CollectBlockSpans(previousToken, node, actualRegions, options, CancellationToken.None);

        // TODO: Determine why we get null outlining spans.
        return actualRegions.ToImmutableAndClear();
    }
}
