UA-.NETStandard/Libraries/Opc.Ua.WotCon.Server/Hosting/OpcUaWotConServerBuilderExtensions.cs

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using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection.Extensions;
using Microsoft.Extensions.Options;
using Opc.Ua;
using Opc.Ua.Server.Hosting;
using Opc.Ua.WotCon.Server;
using Opc.Ua.WotCon.Server.Hosting;

namespace Microsoft.Extensions.DependencyInjection
{
    /// <summary>
    /// <see cref="IOpcUaBuilder"/> extensions provided by
    /// <c>Opc.Ua.WotCon.Server</c>: register an OPC UA WoT Connectivity
    /// (OPC 10100-1) node manager that attaches to the regular OPC UA
    /// server hosted via <c>.AddServer(...)</c>.
    /// </summary>
    /// <remarks>
    /// The WoT Connectivity feature is <strong>not</strong> a standalone
    /// server. <c>.AddServer(...)</c> must be called first on the same
    /// <see cref="IOpcUaBuilder"/>; the hosted server will then pick up
    /// the <see cref="OpcUaServerNodeManagerRegistration"/> registered
    /// by <see cref="AddWotConServer(IOpcUaBuilder, Action{WotConnectivityServerOptions})"/>
    /// and attach a <see cref="WotConnectivityNodeManagerFactory"/> at
    /// start.
    /// </remarks>
    public static class OpcUaWotConServerBuilderExtensions
    {
        /// <summary>
        /// Default <see cref="IConfiguration"/> section name used by the
        /// <see cref="AddWotConServer(IOpcUaBuilder, IConfiguration)"/>
        /// overload.
        /// </summary>
        public const string DefaultConfigurationSection = "OpcUa:WotCon:Server";

        /// <summary>
        /// Registers a WoT Connectivity node manager (OPC 10100-1)
        /// attached to the regular OPC UA server, returning an
        /// <see cref="IWotConServerBuilder"/> for chaining
        /// asset-provider / discovery-provider registrations.
        /// </summary>
        /// <remarks>
        /// <para>
        /// Calling this method twice on the same
        /// <see cref="IServiceCollection"/> throws
        /// <see cref="InvalidOperationException"/>: at most one WoT
        /// Connectivity feature may be registered per service collection.
        /// </para>
        /// <para>
        /// At server start the registered
        /// <see cref="IWotAssetProviderFactory"/> services are merged
        /// into <see cref="WotConnectivityServerOptions.Bindings"/> and
        /// the registered <see cref="IWotAssetDiscoveryProvider"/>
        /// service (if any) is assigned to
        /// <see cref="WotConnectivityServerOptions.Discovery"/> when
        /// the option has not already been set.
        /// </para>
        /// </remarks>
        /// <param name="builder">The OPC UA builder.</param>
        /// <param name="configure">Required callback used to populate
        /// <see cref="WotConnectivityServerOptions"/>.</param>
        /// <returns>An <see cref="IWotConServerBuilder"/> for chaining.</returns>
        /// <exception cref="ArgumentNullException"><paramref name="builder"/>
        /// or <paramref name="configure"/> is <c>null</c>.</exception>
        /// <exception cref="InvalidOperationException">A WoT Connectivity
        /// feature is already registered.</exception>
        public static IWotConServerBuilder AddWotConServer(
            this IOpcUaBuilder builder,
            Action<WotConnectivityServerOptions> configure)
        {
            if (builder is null)
            {
                throw new ArgumentNullException(nameof(builder));
            }
            if (configure is null)
            {
                throw new ArgumentNullException(nameof(configure));
            }
            EnsureFirstRegistration(builder.Services);

            builder.Services.AddOptions<WotConnectivityServerOptions>().Configure(configure);
            RegisterCommonServices(builder.Services);

            return new WotConServerBuilder(builder.Services);
        }

        /// <summary>
        /// Registers a WoT Connectivity node manager with options bound
        /// from the supplied <paramref name="configuration"/> section
        /// <see cref="DefaultConfigurationSection"/>
        /// (<c>OpcUa:WotCon:Server</c>).
        /// </summary>
        /// <remarks>
        /// AOT-safe: bound by the .NET 8+ configuration binding source
        /// generator (<c>EnableConfigurationBindingGenerator</c>).
        /// </remarks>
        /// <param name="builder">The OPC UA builder.</param>
        /// <param name="configuration">Configuration root containing
        /// the <c>OpcUa:WotCon:Server</c> section.</param>
        /// <exception cref="ArgumentNullException"><paramref name="builder"/>
        /// or <paramref name="configuration"/> is <c>null</c>.</exception>
        /// <exception cref="InvalidOperationException">A WoT Connectivity
        /// feature is already registered.</exception>
        public static IWotConServerBuilder AddWotConServer(
            this IOpcUaBuilder builder,
            IConfiguration configuration)
        {
            if (configuration is null)
            {
                throw new ArgumentNullException(nameof(configuration));
            }
            return builder.AddWotConServer(configuration.GetSection(DefaultConfigurationSection));
        }

        /// <summary>
        /// Registers a WoT Connectivity node manager with options bound
        /// from the supplied <paramref name="section"/>.
        /// </summary>
        /// <remarks>
        /// AOT-safe: bound by the .NET 8+ configuration binding source
        /// generator (<c>EnableConfigurationBindingGenerator</c>).
        /// </remarks>
        /// <param name="builder">The OPC UA builder.</param>
        /// <param name="section">Configuration section to bind.</param>
        /// <exception cref="ArgumentNullException"><paramref name="builder"/>
        /// or <paramref name="section"/> is <c>null</c>.</exception>
        /// <exception cref="InvalidOperationException">A WoT Connectivity
        /// feature is already registered.</exception>
        public static IWotConServerBuilder AddWotConServer(
            this IOpcUaBuilder builder,
            IConfigurationSection section)
        {
            if (builder is null)
            {
                throw new ArgumentNullException(nameof(builder));
            }
            if (section is null)
            {
                throw new ArgumentNullException(nameof(section));
            }
            EnsureFirstRegistration(builder.Services);

            builder.Services.AddOptions<WotConnectivityServerOptions>().Bind(section);
            RegisterCommonServices(builder.Services);

            return new WotConServerBuilder(builder.Services);
        }

        private static void EnsureFirstRegistration(IServiceCollection services)
        {
            foreach (ServiceDescriptor d in services)
            {
                if (d.ServiceType == typeof(WotConServerRegistrationMarker))
                {
                    throw new InvalidOperationException(
                        "AddWotConServer has already been called. At most one WoT Connectivity feature may be registered per service collection.");
                }
            }
            services.AddSingleton<WotConServerRegistrationMarker>();
        }

        private static void RegisterCommonServices(IServiceCollection services)
        {
            services.TryAddSingleton<ITelemetryContext>(
                sp => new ServiceProviderTelemetryContext(sp));

            services.AddSingleton(sp =>
            {
                WotConnectivityServerOptions configured =
                    sp.GetRequiredService<IOptions<WotConnectivityServerOptions>>().Value
                    ?? throw new InvalidOperationException(
                        "WotConnectivityServerOptions could not be resolved.");

                var merged = new WotConnectivityServerOptions
                {
                    AssetNamespaceUri = configured.AssetNamespaceUri,
                    ThingDescriptionStorageFolder = configured.ThingDescriptionStorageFolder,
                    MaxThingDescriptionSize = configured.MaxThingDescriptionSize,
                    MaxOpenFileHandlesPerAsset = configured.MaxOpenFileHandlesPerAsset,
                    Discovery = configured.Discovery,
                    License = configured.License
                };
                foreach (IWotAssetProviderFactory binding in configured.Bindings)
                {
                    merged.Bindings.Add(binding);
                }
                foreach (KeyValuePair<string, WotConfigurationParameter> kvp in configured.Configuration)
                {
                    merged.Configuration[kvp.Key] = kvp.Value;
                }

                foreach (IWotAssetProviderFactory binding in sp.GetServices<IWotAssetProviderFactory>())
                {
                    merged.Bindings.Add(binding);
                }
                if (merged.Discovery is null)
                {
                    IWotAssetDiscoveryProvider? discovery =
                        sp.GetService<IWotAssetDiscoveryProvider>();
                    if (discovery is not null)
                    {
                        merged.Discovery = discovery;
                    }
                }

                return new WotConnectivityNodeManagerFactory(merged);
            });

            services.AddSingleton(sp =>
                new OpcUaServerNodeManagerRegistration(
                    sp.GetRequiredService<WotConnectivityNodeManagerFactory>()));

            services.AddOpcUa();
        }

        private sealed class WotConServerBuilder : IWotConServerBuilder
        {
            public WotConServerBuilder(IServiceCollection services)
            {
                Services = services;
            }

            public IServiceCollection Services { get; }

            public IWotConServerBuilder AddAssetProvider<
                [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors)] TFactory>()
                where TFactory : class, IWotAssetProviderFactory
            {
                Services.AddSingleton<TFactory>();
                Services.AddSingleton<IWotAssetProviderFactory>(
                    sp => sp.GetRequiredService<TFactory>());
                return this;
            }

            public IWotConServerBuilder AddAssetProvider(
                Func<IServiceProvider, IWotAssetProviderFactory> factory)
            {
                if (factory is null)
                {
                    throw new ArgumentNullException(nameof(factory));
                }
                Services.AddSingleton(factory);
                return this;
            }

            public IWotConServerBuilder AddDiscoveryProvider<
                [DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors)] T>()
                where T : class, IWotAssetDiscoveryProvider
            {
                Services.TryAddSingleton<IWotAssetDiscoveryProvider, T>();
                return this;
            }
        }

        private sealed class WotConServerRegistrationMarker;
    }
}