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 * Copyright (c) 2005-2025 The OPC Foundation, Inc. All rights reserved.
 *
 * OPC Foundation MIT License 1.00
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
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 *
 * The above copyright notice and this permission notice shall be
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 * ======================================================================*/

using System;
using Microsoft.Extensions.DependencyInjection.Extensions;
using Opc.Ua;
using Opc.Ua.Configuration;

namespace Microsoft.Extensions.DependencyInjection
{
    /// <summary>
    /// <see cref="IOpcUaBuilder"/> extensions provided by
    /// <c>Opc.Ua.Configuration</c>.
    /// </summary>
    public static class OpcUaConfigurationServiceCollectionExtensions
    {
        /// <summary>
        /// Registers the default
        /// <see cref="IApplicationInstanceFactory"/> implementation so
        /// hosted OPC UA servers (regular, GDS, LDS, WotCon) can each
        /// create their own <see cref="IApplicationInstance"/>.
        /// </summary>
        /// <remarks>
        /// Idempotent (<c>TryAddSingleton</c>). A consumer that registers
        /// a custom <see cref="IApplicationInstanceFactory"/> before this
        /// call wins.
        /// </remarks>
        /// <param name="builder">The OPC UA builder.</param>
        /// <returns>The same <paramref name="builder"/> instance.</returns>
        /// <exception cref="ArgumentNullException"><paramref name="builder"/> is <c>null</c>.</exception>
        public static IOpcUaBuilder AddApplicationInstance(this IOpcUaBuilder builder)
        {
            if (builder is null)
            {
                throw new ArgumentNullException(nameof(builder));
            }
            builder.Services.TryAddSingleton<IApplicationInstanceFactory,
                DefaultApplicationInstanceFactory>();
            return builder;
        }
    }
}