// 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;
 
internal partial class DocumentState
{
    /// <summary>
    /// A source for <see cref="TextAndVersion"/> constructed from an syntax tree.
    /// </summary>
    private 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 ValueTask<VersionStamp> GetVersionAsync(LoadTextOptions options, CancellationToken cancellationToken)
            => new(_version);
    }
}