using Microsoft.eShopOnContainers.Services.Ordering.Domain.Seedwork;
using Ordering.Domain.Events;
using Ordering.Domain.Exceptions;
using System;
using System.Collections.Generic;
using System.Linq;

namespace Microsoft.eShopOnContainers.Services.Ordering.Domain.AggregatesModel.OrderAggregate
{
    public class Order
        : Entity, IAggregateRoot
    {
        // DDD Patterns comment
        // Using private fields, allowed since EF Core 1.1, is a much better encapsulation
        // aligned with DDD Aggregates and Domain Entities (Instead of properties and property collections)
        private DateTime _orderDate;

        public Address Address { get; private set; }

        private int? _buyerId;

        public OrderStatus OrderStatus { get; private set; }
        private int _orderStatusId;

        private string _description;

        // DDD Patterns comment
        // Using a private collection field, better for DDD Aggregate's encapsulation
        // so OrderItems cannot be added from "outside the AggregateRoot" directly to the collection,
        // but only through the method OrderAggrergateRoot.AddOrderItem() which includes behaviour.
        private readonly List<OrderItem> _orderItems;

        public IEnumerable<OrderItem> OrderItems => _orderItems.AsReadOnly();
        // Using List<>.AsReadOnly() 
        // This will create a read only wrapper around the private list so is protected against "external updates".
        // It's much cheaper than .ToList() because it will not have to copy all items in a new collection. (Just one heap alloc for the wrapper instance)
        //https://msdn.microsoft.com/en-us/library/e78dcd75(v=vs.110).aspx 

        private int? _paymentMethodId;

        protected Order() { _orderItems = new List<OrderItem>(); }

        public Order(string userId, Address address, int cardTypeId, string cardNumber, string cardSecurityNumber,
                string cardHolderName, DateTime cardExpiration, int? buyerId = null, int? paymentMethodId = null)
        {
            _orderItems = new List<OrderItem>();
            _buyerId = buyerId;
            _paymentMethodId = paymentMethodId;
            _orderStatusId = OrderStatus.Submited.Id;
            _orderDate = DateTime.UtcNow;
            Address = address;

            // Add the OrderStarterDomainEvent to the domain events collection 
            // to be raised/dispatched when comitting changes into the Database [ After DbContext.SaveChanges() ]
            AddOrderStartedDomainEvent(userId, cardTypeId, cardNumber,
                                       cardSecurityNumber, cardHolderName, cardExpiration);
        }

        // DDD Patterns comment
        // This Order AggregateRoot's method "AddOrderitem()" should be the only way to add Items to the Order,
        // so any behavior (discounts, etc.) and validations are controlled by the AggregateRoot 
        // in order to maintain consistency between the whole Aggregate. 
        public void AddOrderItem(int productId, string productName, decimal unitPrice, decimal discount, string pictureUrl, int units = 1)
        {
            var existingOrderForProduct = _orderItems.Where(o => o.ProductId == productId)
                .SingleOrDefault();

            if (existingOrderForProduct != null)
            {
                //if previous line exist modify it with higher discount  and units..

                if (discount > existingOrderForProduct.GetCurrentDiscount())
                {
                    existingOrderForProduct.SetNewDiscount(discount);
                    existingOrderForProduct.AddUnits(units);
                }
            }
            else
            {
                //add validated new order item

                var orderItem = new OrderItem(productId, productName, unitPrice, discount, pictureUrl, units);
                _orderItems.Add(orderItem);
            }
        }

        public void SetPaymentId(int id)
        {
            _paymentMethodId = id;
        }

        public void SetBuyerId(int id)
        {
            _buyerId = id;
        }

        #region Status Changes
        public void SetSubmitedStatus()
        {
            _orderStatusId = OrderStatus.Submited.Id;
        }

        public void SetAwaitingValidationStatus()
        {
            if (_orderStatusId != OrderStatus.Submited.Id)
            {
                StatusChangeException();
            }  

            _orderStatusId = OrderStatus.AwaitingValidation.Id;

            AddDomainEvent(new OrderStatusChangedToAwaitingValidationDomainEvent(Id, OrderItems));
        }

        public void SetStockConfirmedStatus(IEnumerable<int> orderStockNotConfirmedItems = null)
        {
            if (_orderStatusId != OrderStatus.AwaitingValidation.Id)
            {
                StatusChangeException();
            }

            if (orderStockNotConfirmedItems is null)
            {
                OrderStatus = OrderStatus.StockConfirmed;

                _description = "All the items were confirmed with available stock.";

                AddDomainEvent(new OrderStatusChangedToStockConfirmedDomainEvent(Id));
            }
            else
            {
                OrderStatus = OrderStatus.Cancelled;

                var itemsStockNotConfirmedProductNames = OrderItems
                    .Where(c => orderStockNotConfirmedItems.Contains(c.ProductId))
                    .Select(c => c.GetOrderItemProductName());

                var itemsStockNotConfirmedDescription = string.Join(", ", itemsStockNotConfirmedProductNames);
                _description = $"The product items don't have stock: ({itemsStockNotConfirmedDescription}).";   
            }
        }

        public void SetPaidStatus()
        {
            if (_orderStatusId != OrderStatus.StockConfirmed.Id)
            {
                StatusChangeException();
            }

            _orderStatusId = OrderStatus.Paid.Id;
            _description = "The payment was performed at a simulated \"American Bank checking bank account endinf on XX35071\"";

            AddDomainEvent(new OrderStatusChangedToPaidDomainEvent(Id, OrderItems));
        }

        public void SetShippedStatus()
        {
            if (_orderStatusId != OrderStatus.Paid.Id)
            {
                StatusChangeException();
            }

            _orderStatusId = OrderStatus.Shipped.Id;
            _description = "";

            //Call Domain Event
        }

        #endregion

        private void AddOrderStartedDomainEvent(string userId, int cardTypeId, string cardNumber,
                string cardSecurityNumber, string cardHolderName, DateTime cardExpiration)
        {
            var orderStartedDomainEvent = new OrderStartedDomainEvent(
                this, userId, cardTypeId, cardNumber, cardSecurityNumber,
                cardHolderName, cardExpiration);

            this.AddDomainEvent(orderStartedDomainEvent);
        }

        private void StatusChangeException()
        {
            throw new OrderingDomainException("Not able to process order event. Reason: no valid order status change");
        }
    }
}