using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using Microsoft.EntityFrameworkCore;
using xCommons.Extensions;
using xDataService.Interfaces;

namespace xDataService.Providers
{
    public class XEntityRegisterarHandlerService
    {
        /// <summary>
        /// a Collection for Extract Registerars Services ...
        /// </summary>
        private readonly List<IXEntityRegisterar> registerars = [];

        /// <summary>
        /// a Collection for Holding all Entity Types ...
        /// </summary>
        public IReadOnlyList<Type> AllEntityTypes { get; private set; }

        /// <summary>
        /// Retrieve Specified Registerars Entity Types ...
        /// </summary>
        /// <param name="names"></param>
        /// <returns></returns>
        public IReadOnlyList<Type> GetEntityTypes(string[] names = null)
        {
            //
            var items = new List<Type>();

            //
            if (!names.IsNull() && names.HasChild())
            {
                //
                items = [.. registerars
                    .Where(r => names.Contains(r.Name))
                    .SelectMany(r => r.GetEntityTypes())];
            }

            //
            return items.AsReadOnly();
        }

        /// <summary>
        /// Load all Dynamically Registered Entities ...
        /// </summary>
        public void HandleRegisteredEntities()
        {
            //
            var entityTypes = new List<Type>();
            // path = Path.Combine (Directory.GetCurrentDirectory ());
            var path = Path.Combine (AppContext.BaseDirectory);
            var files = Directory.GetFiles(path, "*.dll");
            foreach (var dll in files)
            {
                //
                // Retrieve DLL Assembly ...
                var assembly = Assembly.LoadFrom(dll);

                //
                // Extract Registerar Types ...
                var registerarTypes = assembly
                    .GetExportedTypes()
                    .Where(t =>
                        !t.IsAbstract &&
                        typeof(IXEntityRegisterar).IsAssignableFrom(t));
                foreach (var registerarType in registerarTypes)
                {
                    //
                    // Create Instance of Registerar Type ...
                    var registerar = (IXEntityRegisterar)Activator.CreateInstance(registerarType);
                    if (!registerar.IsNull())
                    {
                        //
                        // Add Registerar Instance to Collection ...
                        registerars.Add(registerar);

                        //
                        // Add Registerar Provided Entities to Collection ...
                        entityTypes.AddRange(registerar.GetEntityTypes());
                    }
                }

                //
                // Converts to Readonly List ...
                AllEntityTypes = entityTypes.AsReadOnly();
            }
        }

        /// <summary>
        /// Configure all Dynamically Registered Entities ...
        /// </summary>
        /// <param name="modelBuilder"></param>
        /// <param name="names"></param>
        public void HandleApplyRegisteredEntitiesConfigurations(
            ModelBuilder modelBuilder,
            string[] names = null
        )
        {
            //
            var selectedRegisterars = 
                !names.IsNull() &&
                names.HasChild()
                ? registerars
                    .Where(r => names.Contains(r.Name))
                : registerars;

            //
            // Loop Through Extracted Registerars ... 
            foreach(var registerar in selectedRegisterars)
            {
                //
                // Configure Specified Registerars Entities ...
                registerar.ConfigureEntities(modelBuilder);
            }
        }
    }
}