ReC/src/ReC.Application/DependencyInjection.cs

using FluentValidation;
using MediatR;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using ReC.Application.Common.Behaviors;
using ReC.Application.Common.Constants;
using ReC.Application.Common.Options;
using System.Reflection;

namespace ReC.Application;

public static class DependencyInjection
{
    public static IServiceCollection AddRecServices(this IServiceCollection services, Action<ConfigurationOptions> options)
    {
        var configOpt = new ConfigurationOptions();
        options.Invoke(configOpt);

        configOpt.EnsureRequiredServices();

        configOpt.ApplyConfigurations(services);

        services.AddValidatorsFromAssembly(Assembly.GetExecutingAssembly());

        services.AddAutoMapper(cfg =>
        {
            cfg.AddMaps(Assembly.GetExecutingAssembly());
            cfg.LicenseKey = configOpt.LuckyPennySoftwareLicenseKey;
        });

        services.AddMediatR(cfg =>
        {
            cfg.RegisterServicesFromAssembly(Assembly.GetExecutingAssembly());
            cfg.AddOpenBehaviors([typeof(BodyQueryBehavior<,>), typeof(HeaderQueryBehavior<,>)]);
            cfg.AddBehavior(typeof(IPipelineBehavior<,>), typeof(ValidationBehavior<,>));
            cfg.LicenseKey = configOpt.LuckyPennySoftwareLicenseKey;
        });

        services.AddHttpClient(Http.ClientName)
            .ConfigurePrimaryHttpMessageHandler(() => new HttpClientHandler
            {
                UseDefaultCredentials = false
            });

        return services;
    }

    public class ConfigurationOptions
    {

        #region Required Services
        private readonly Dictionary<string, bool> _requiredServices = new()
        {
            { nameof(ConfigureRecActions), false },
            { nameof(LuckyPennySoftwareLicenseKey), false }
        };

        internal void EnsureRequiredServices()
        {
            var missingServices = _requiredServices
                .Where(kvp => !kvp.Value)
                .Select(kvp => kvp.Key.Replace("Configure", string.Empty));
            if (missingServices.Any())
                throw new InvalidOperationException($"The following required services were not configured: {string.Join(", ", missingServices)}");
        }
        #endregion Required Services

        #region Configuration
        private readonly Queue<Action<IServiceCollection>> _configActions = new();

        internal void ApplyConfigurations(IServiceCollection services)
        {
            while (_configActions.Count > 0)
            {
                var action = _configActions.Dequeue();
                action(services);
            }
        }
        #endregion Configuration

        #region LuckyPennySoftwareLicenseKey
        private string? _luckyPennySoftwareLicenseKey;

        public string? LuckyPennySoftwareLicenseKey 
        { 
            get => _luckyPennySoftwareLicenseKey; 
            set
            {
                _luckyPennySoftwareLicenseKey = value;
                if (value is not null)
                    _requiredServices[nameof(LuckyPennySoftwareLicenseKey)] = true;
            }
        }
        #endregion LuckyPennySoftwareLicenseKey

        #region ConfigureRecActions
        public ConfigurationOptions ConfigureRecActions(Action<RecActionOptions> configure)
        {
            _configActions.Enqueue(services => services.Configure(configure));

            if(_requiredServices[nameof(ConfigureRecActions)])
                throw new InvalidOperationException("RecActionOptions have already been configured.");
            _requiredServices[nameof(ConfigureRecActions)] = true;
            
            return this;
        }

        public ConfigurationOptions ConfigureRecActions(IConfiguration configuration)
        {
            _configActions.Enqueue(services => services.Configure<RecActionOptions>(configuration));

            if (_requiredServices[nameof(ConfigureRecActions)])
                throw new InvalidOperationException("RecActionOptions have already been configured.");
            _requiredServices[nameof(ConfigureRecActions)] = true;

            return this;
        }
        #endregion ConfigureRecActions
    }
}