using System;
using System.Collections;
using System.Collections.Generic;
using Microsoft.Extensions.DependencyInjection;
using xCommons.Helpers;

namespace xCommons.Extensions {
    public static class ServiceProviderExtensions {
        /// <summary>
        /// Get all registered <see cref="ServiceDescriptor"/>
        /// </summary>
        /// <param name="provider"></param>
        /// <returns></returns>
        public static Dictionary<Type, ServiceDescriptor> GetAllServiceDescriptors (this IServiceProvider provider) {
            //
            if (provider is ServiceProvider serviceProvider) {
                //
                var result = new Dictionary<Type, ServiceDescriptor> ();

                //
                var engine = serviceProvider.GetFieldValue ("_engine");
                var callSiteFactory = engine.GetPropertyValue ("CallSiteFactory");
                var descriptorLookup = callSiteFactory.GetFieldValue ("_descriptorLookup");
                if (descriptorLookup is IDictionary dictionary) {
                    foreach (DictionaryEntry entry in dictionary) {
                        result.Add ((Type) entry.Key, (ServiceDescriptor) entry.Value.GetPropertyValue ("Last"));
                    }
                }

                //
                return result;
            }

            //
            throw new NotSupportedException ($"Type '{provider.GetType()}' is not supported!");
        }
    }
}