// 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.CodeAnalysis;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Text;
using Roslyn.Utilities;

namespace Microsoft.CodeAnalysis;

/// <summary>
/// A source for <see cref="TextAndVersion"/> constructed from an syntax tree.
/// </summary>
internal sealed class TreeTextSource(AsyncLazy<SourceText> textSource, VersionStamp version) : ITextAndVersionSource
{
    private readonly VersionStamp _version = version;

    public bool CanReloadText
        => false;

    /// <summary>
    /// Not created from a text loader.
    /// </summary>
    public TextLoader? TextLoader
        => null;

    public async Task<TextAndVersion> GetValueAsync(LoadTextOptions options, CancellationToken cancellationToken)
    {
        var text = await textSource.GetValueAsync(cancellationToken).ConfigureAwait(false);
        return TextAndVersion.Create(text, _version);
    }

    public TextAndVersion GetValue(LoadTextOptions options, CancellationToken cancellationToken)
    {
        var text = textSource.GetValue(cancellationToken);
        return TextAndVersion.Create(text, _version);
    }

    public bool TryGetValue(LoadTextOptions options, [NotNullWhen(true)] out TextAndVersion? value)
    {
        if (textSource.TryGetValue(out var text))
        {
            value = TextAndVersion.Create(text, _version);
            return true;
        }
        else
        {
            value = null;
            return false;
        }
    }

    public bool TryGetVersion(LoadTextOptions options, out VersionStamp version)
    {
        version = _version;
        return version != default;
    }

    public async ValueTask<VersionStamp> GetVersionAsync(LoadTextOptions options, CancellationToken cancellationToken)
        => _version;
}