TransientServiceFactory.cs

#region License
/* ************************************************************
 *
 *    @author Couchbase <info@couchbase.com>
 *    @copyright 2025 Couchbase, Inc.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 *
 * ************************************************************/
#endregion

using System.Diagnostics.CodeAnalysis;
using Couchbase.AnalyticsClient.Utils;

namespace Couchbase.AnalyticsClient.Internal.DI;

/// <summary>
/// Implementation of <see cref="IServiceFactory"/> which creates a transient
/// service for each request.
/// </summary>
internal sealed class TransientServiceFactory : IServiceFactory
{
    private readonly Func<IServiceProvider, object?> _factory;

    private IServiceProvider? _serviceProvider;

    /// <summary>
    /// Creates a new TransientServiceFactory which uses a lambda to create the service.
    /// </summary>
    /// <param name="factory">Lambda to invoke on each call to <see cref="CreateService"/>.</param>
    public TransientServiceFactory(Func<IServiceProvider, object?> factory)
    {
        // ReSharper disable once ConditionIsAlwaysTrueOrFalseAccordingToNullableAPIContract
        if (factory is null)
        {
            ThrowHelper.ThrowArgumentNullException(nameof(factory));
        }

        _factory = factory;
    }

    /// <summary>
    /// Creates a new TransientServiceFactory which uses a type's constructor on each call to <see cref="CreateService"/>.
    /// </summary>
    /// <param name="type">Type to create on each call to <seealso cref="CreateService"/>.</param>
    public TransientServiceFactory([DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors)] Type type)
        : this(CreateFactory(type))
    {
    }

    /// <inheritdoc />
    public void Initialize(IServiceProvider serviceProvider)
    {
        // ReSharper disable once ConditionIsAlwaysTrueOrFalseAccordingToNullableAPIContract
        if (serviceProvider is null)
        {
            ThrowHelper.ThrowArgumentNullException(nameof(serviceProvider));
        }

        _serviceProvider = serviceProvider;
    }

    /// <inheritdoc />
    public object? CreateService(Type requestedType)
    {
        if (_serviceProvider == null)
        {
            ThrowHelper.ThrowInvalidOperationException("Not initialized.");
        }

        return _factory(_serviceProvider);
    }

    private static Func<IServiceProvider, object> CreateFactory([DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicConstructors)] Type implementationType)
    {
        var constructor = ConstructorSelector.SelectConstructor(implementationType);

        return Factory;

        object Factory(IServiceProvider serviceProvider)
        {
            var constructorArgs = constructor.GetParameters()
                .Select(p => serviceProvider.GetRequiredService(p.ParameterType))
                .ToArray();

            return constructor.Invoke(constructorArgs);
        }
    }
}