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 * Copyright (c) 2005-2025 The OPC Foundation, Inc. All rights reserved.
 *
 * OPC Foundation MIT License 1.00
 *
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 * obtaining a copy of this software and associated documentation
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using System;
using System.Threading;
using System.Threading.Tasks;
using Opc.Ua.Client;

namespace Opc.Ua.Di.Client
{
    /// <summary>
    /// Client-side wrapper for the OPC 10000-100 §10.5 locking service.
    /// Composes (does <em>not</em> inherit) the source-generated
    /// <see cref="Opc.Ua.Di.LockingServicesTypeClient"/> proxy so that
    /// the four lock methods round-trip through the same typed OPC UA
    /// client surface as the rest of the Di model, eliminating the
    /// hand-rolled <c>CallMethodRequest</c> + <c>NodeId.Create</c>
    /// boilerplate.
    /// </summary>
    /// <remarks>
    /// <para>
    /// Each method targets a single <c>TopologyElementType.Lock</c>
    /// instance (a child of a device, sub-component, or topology
    /// element). The instance NodeId is supplied at construction time;
    /// pass the <c>Lock</c> child NodeId resolved via browse, not the
    /// owning device NodeId.
    /// </para>
    /// </remarks>
    public sealed class DiLockClient
    {
        private LockingServicesTypeClient? m_proxy;

        /// <summary>
        /// Creates a new lock client rooted at the supplied
        /// <c>LockingServicesType</c> instance.
        /// </summary>
        public DiLockClient(
            ISession session,
            NodeId lockNodeId,
            ITelemetryContext telemetry)
        {
            if (session is null)
            {
                throw new ArgumentNullException(nameof(session));
            }
            if (lockNodeId.IsNull)
            {
                throw new ArgumentException(
                    "Lock NodeId is required.", nameof(lockNodeId));
            }
            if (telemetry is null)
            {
                throw new ArgumentNullException(nameof(telemetry));
            }

            Session = session;
            LockNodeId = lockNodeId;
            Telemetry = telemetry;
        }

        /// <summary>
        /// The owning session.
        /// </summary>
        public ISession Session { get; }

        /// <summary>The NodeId of the <c>Lock</c> instance.</summary>
        public NodeId LockNodeId { get; }

        /// <summary>
        /// Telemetry context.
        /// </summary>
        public ITelemetryContext Telemetry { get; }

        private LockingServicesTypeClient Proxy
        {
            get
            {
                return m_proxy ??= new LockingServicesTypeClient(
                    Session, LockNodeId, Telemetry);
            }
        }

        /// <summary>
        /// Calls <c>InitLock</c> on the server. Returns the status code
        /// reported by the device (see
        /// <c>Opc.Ua.Di.Server.Locking.LockStatus</c>): 0 = OK,
        /// 1 = already locked, 2 = could not lock.
        /// </summary>
        public ValueTask<int> InitLockAsync(string context, CancellationToken ct = default)
        {
            return Proxy.InitLockAsync(context ?? string.Empty, ct);
        }

        /// <summary>
        /// Calls <c>RenewLock</c>. 0 = OK, 1 = not locked, 2 = wrong client.
        /// </summary>
        public ValueTask<int> RenewLockAsync(CancellationToken ct = default)
        {
            return Proxy.RenewLockAsync(ct);
        }

        /// <summary>
        /// Calls <c>ExitLock</c>. 0 = OK, 1 = not locked, 2 = wrong client.
        /// </summary>
        public ValueTask<int> ExitLockAsync(CancellationToken ct = default)
        {
            return Proxy.ExitLockAsync(ct);
        }

        /// <summary>
        /// Calls <c>BreakLock</c>. 0 = OK, 1 = not locked.
        /// </summary>
        public ValueTask<int> BreakLockAsync(CancellationToken ct = default)
        {
            return Proxy.BreakLockAsync(ct);
        }
    }
}