using Grpc.Core;

namespace MxGateway.Client;

/// <summary>
/// Maps low-level <see cref="RpcException"/>s raised by the gRPC stack to the client's
/// native exception hierarchy. Shared by every gateway and Galaxy Repository transport
/// so the gRPC-to-native translation has exactly one implementation.
/// </summary>
internal static class RpcExceptionMapper
{
    /// <summary>
    /// Translates a <see cref="RpcException"/> into the most specific native exception type.
    /// </summary>
    /// <param name="exception">The gRPC exception to translate.</param>
    /// <param name="cancellationToken">
    /// The cancellation token of the originating call; used to distinguish a caller-driven
    /// cancellation from a server-side <see cref="StatusCode.Cancelled"/> status.
    /// </param>
    /// <returns>
    /// An <see cref="OperationCanceledException"/> when the call was cancelled, a typed
    /// authentication/authorization exception for auth statuses, or an
    /// <see cref="MxGatewayException"/> carrying the originating gRPC <see cref="StatusCode"/>.
    /// </returns>
    public static Exception Map(
        RpcException exception,
        CancellationToken cancellationToken)
    {
        ArgumentNullException.ThrowIfNull(exception);

        if (cancellationToken.IsCancellationRequested || exception.StatusCode == StatusCode.Cancelled)
        {
            return new OperationCanceledException(
                exception.Status.Detail,
                exception,
                cancellationToken);
        }

        return exception.StatusCode switch
        {
            StatusCode.Unauthenticated => new MxGatewayAuthenticationException(
                exception.Status.Detail,
                statusCode: exception.StatusCode,
                innerException: exception),
            StatusCode.PermissionDenied => new MxGatewayAuthorizationException(
                exception.Status.Detail,
                statusCode: exception.StatusCode,
                innerException: exception),
            _ => new MxGatewayException(
                exception.Status.Detail,
                exception.StatusCode,
                exception),
        };
    }
}