// 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.Diagnostics;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Host;
using Microsoft.CodeAnalysis.LanguageService;
using Microsoft.CodeAnalysis.Shared.Extensions;
using Roslyn.Utilities;

namespace Microsoft.CodeAnalysis.QuickInfo;

/// <summary>
/// A service that is used to determine the appropriate quick info for a position in a document.
/// </summary>
public abstract class QuickInfoService : ILanguageService
{
    // Prevent inheritance outside of Roslyn.
    internal QuickInfoService()
    {
    }

    /// <summary>
    /// Gets the appropriate <see cref="QuickInfoService"/> for the specified document.
    /// </summary>
    public static QuickInfoService? GetService(Document? document)
        => document?.GetLanguageService<QuickInfoService>();

    /// <summary>
    /// Gets the <see cref="QuickInfoItem"/> associated with position in the document.
    /// </summary>
    public Task<QuickInfoItem?> GetQuickInfoAsync(
        Document document,
        int position,
        CancellationToken cancellationToken = default)
    {
        Debug.Fail("For backwards API compat only, should not be called");
        return GetQuickInfoAsync(document, position, SymbolDescriptionOptions.Default, cancellationToken);
    }

    internal virtual Task<QuickInfoItem?> GetQuickInfoAsync(
        Document document,
        int position,
        SymbolDescriptionOptions options,
        CancellationToken cancellationToken)
    {
        return SpecializedTasks.Null<QuickInfoItem>();
    }
}