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using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using Opc.Ua.Client.StateMachines;
using Opc.Ua.Client.Subscriptions.Streaming;
using MonitoringOptions = Opc.Ua.Client.Subscriptions.MonitoredItems.MonitoredItemOptions;

namespace Opc.Ua.Client.Alarms
{
    /// <summary>
    /// Part 16 state-machine helpers on <see cref="AlarmClient"/>.
    /// Surface the new generic state-machine API for the
    /// <c>ShelvingState</c> child of every Part 9 alarm condition,
    /// using the same proxy-delegation pattern as the rest of the
    /// client.
    /// </summary>
    public partial class AlarmClient
    {
        /// <summary>
        /// Reads the current shelving-state-machine snapshot for the
        /// supplied alarm condition. Equivalent to constructing a
        /// <see cref="ShelvedStateMachineTypeClient"/> with the
        /// condition's NodeId as the ObjectId and calling
        /// <see cref="FiniteStateMachineTypeClientExtensions.GetCurrentFiniteStateAsync"/>.
        /// </summary>
        /// <param name="conditionId">The alarm condition NodeId.</param>
        /// <param name="ct">Cancellation token.</param>
        public ValueTask<FiniteStateSnapshot> GetShelvingStateAsync(
            NodeId conditionId,
            CancellationToken ct = default)
        {
            return new ShelvedStateMachineTypeClient(m_session, conditionId, m_telemetry)
                        .GetCurrentFiniteStateAsync(ct);
        }

        /// <summary>
        /// Subscribes to the supplied alarm condition's
        /// <c>ShelvingState</c> machine and yields a fresh
        /// <see cref="FiniteStateSnapshot"/> every time the alarm
        /// shelves / unshelves.
        /// </summary>
        public IAsyncEnumerable<FiniteStateSnapshot> ObserveShelvingTransitionsAsync(
            NodeId conditionId,
            IStreamingSubscription streaming,
            MonitoringOptions? options = null,
            CancellationToken ct = default)
        {
            return new ShelvedStateMachineTypeClient(m_session, conditionId, m_telemetry)
                        .ObserveFiniteTransitionsAsync(streaming, options, ct);
        }
    }
}