// 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.Immutable;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.SpellCheck;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.LanguageServer.Handler.SpellCheck;
 
internal record struct SpellCheckState(ISpellCheckSpanService Service, Document Document);
 
/// <summary>
/// Simplified version of <see cref="VersionedPullCache{TCheapVersion, TExpensiveVersion, TState, TComputedData}"/> that only uses a 
/// single cheap key to check results against.
/// </summary>
internal sealed class SpellCheckPullCache(string uniqueKey) : VersionedPullCache<(Checksum parseOptionsChecksum, Checksum textChecksum)?, object?, SpellCheckState, SpellCheckSpan>(uniqueKey)
{
    public override async Task<(Checksum parseOptionsChecksum, Checksum textChecksum)?> ComputeCheapVersionAsync(SpellCheckState state, CancellationToken cancellationToken)
    {
        var project = state.Document.Project;
        var parseOptionsChecksum = project.State.GetParseOptionsChecksum();
 
        var documentChecksumState = await state.Document.State.GetStateChecksumsAsync(cancellationToken).ConfigureAwait(false);
        var textChecksum = documentChecksumState.Text;
 
        return (parseOptionsChecksum, textChecksum);
    }
 
    public override Checksum ComputeChecksum(ImmutableArray<SpellCheckSpan> data)
    {
        var checksums = data.SelectAsArray(s => Checksum.Create(s, SerializeSpellCheckSpan)).Sort();
        return Checksum.Create(checksums);
    }
 
    public override async Task<ImmutableArray<SpellCheckSpan>> ComputeDataAsync(SpellCheckState state, CancellationToken cancellationToken)
    {
        var spans = await state.Service.GetSpansAsync(state.Document, cancellationToken).ConfigureAwait(false);
        return spans;
    }
 
    public override Task<object?> ComputeExpensiveVersionAsync(SpellCheckState state, CancellationToken cancellationToken)
    {
        // Spell check does not need an expensive version check - we return null to effectively skip this check.
        return SpecializedTasks.Null<object>();
    }
 
    private void SerializeSpellCheckSpan(SpellCheckSpan span, ObjectWriter writer)
    {
        writer.WriteInt32(span.TextSpan.Start);
        writer.WriteInt32(span.TextSpan.Length);
        writer.WriteInt32((int)span.Kind);
    }
}