using System.Text.Json;

namespace AcDream.Launcher.Core.Updates;

internal static class AtomicJsonFile
{
    internal static async Task WriteAsync<T>(
        string path,
        T value,
        JsonSerializerOptions options,
        CancellationToken cancellationToken = default)
    {
        string fullPath = Path.GetFullPath(path);
        string directory = Path.GetDirectoryName(fullPath)
            ?? throw new InvalidOperationException("The JSON path has no parent directory.");
        Directory.CreateDirectory(directory);
        string temporaryPath = Path.Combine(
            directory,
            $".{Path.GetFileName(fullPath)}.{Guid.NewGuid():N}.tmp");
        try
        {
            await using (var stream = new FileStream(
                temporaryPath,
                FileMode.CreateNew,
                FileAccess.Write,
                FileShare.None,
                16 * 1024,
                FileOptions.Asynchronous | FileOptions.WriteThrough))
            {
                await JsonSerializer.SerializeAsync(
                        stream,
                        value,
                        options,
                        cancellationToken)
                    .ConfigureAwait(false);
                await stream.FlushAsync(cancellationToken).ConfigureAwait(false);
                stream.Flush(flushToDisk: true);
            }

            cancellationToken.ThrowIfCancellationRequested();
            File.Move(temporaryPath, fullPath, overwrite: true);
        }
        finally
        {
            VerifiedArtifactDownloader.TryDelete(temporaryPath);
        }
    }

    internal static async Task WriteBytesAsync(
        string path,
        ReadOnlyMemory<byte> bytes,
        CancellationToken cancellationToken = default)
    {
        string fullPath = Path.GetFullPath(path);
        string directory = Path.GetDirectoryName(fullPath)
            ?? throw new InvalidOperationException("The file path has no parent directory.");
        Directory.CreateDirectory(directory);
        string temporaryPath = Path.Combine(
            directory,
            $".{Path.GetFileName(fullPath)}.{Guid.NewGuid():N}.tmp");
        try
        {
            await using (var stream = new FileStream(
                temporaryPath,
                FileMode.CreateNew,
                FileAccess.Write,
                FileShare.None,
                16 * 1024,
                FileOptions.Asynchronous | FileOptions.WriteThrough))
            {
                await stream.WriteAsync(bytes, cancellationToken).ConfigureAwait(false);
                await stream.FlushAsync(cancellationToken).ConfigureAwait(false);
                stream.Flush(flushToDisk: true);
            }

            cancellationToken.ThrowIfCancellationRequested();
            File.Move(temporaryPath, fullPath, overwrite: true);
        }
        finally
        {
            VerifiedArtifactDownloader.TryDelete(temporaryPath);
        }
    }
}