/// A single warehouse fulfilling the complete order should always be more optimal than split orders (In my current understanding)
private bool TryFulfillCompleteOrder(Order order, WarehouseNetwork warehouseNetwork, out OrderFulfillment orderFulfillment)
{
foreach (var warehouse in warehouseNetwork)
{
var canFulfill = true;
foreach (var orderItem in order)
{
if (!warehouse.Inventory.ContainsKey(orderItem.Key) ||
warehouse.Inventory[orderItem.Key] < orderItem.Value)
{
canFulfill = false;
break;
}
}
if (canFulfill)
{
orderFulfillment = new OrderFulfillment
{
{ warehouse.Name, order }
};
return(true);
}
}
orderFulfillment = null;
return(false);
}
/// The main entry-point for this single responsibility class
public OrderFulfillment Allocate(Order order, WarehouseNetwork warehouseNetwork)
{
if (order == null)
{
throw new ArgumentNullException("order");
}
if (warehouseNetwork == null)
{
throw new ArgumentNullException("warehouseNetwork");
}
if (order.Values.Any(x => x < 0))
{
throw new ArgumentException("Invalid order");
}
// <comment for reviewers only:> going to assume the warehouse data is from a trusted data source, but assuming the order data may not be
if (!CanFulfillOrder(order, warehouseNetwork))
{
//None of the attempts resulted in a fulfilled order (DesignChoice: return null for this)
return(null);
}
// <comment for reviewers only:> the inline out variable is a newer C# feature, and makes the TryX pattern much nicer to read
// My original thought was I might be using multiple algorithms to find optimal shipment methods, but I ended up with only the greedy implementation
//Ideally we can fulfill an order from a single warehouse, if we can, this function will find that.
if (TryFulfillCompleteOrder(order, warehouseNetwork, out var fulfillment))
{
return(fulfillment);
}
return(FulfillWithGreedyMultipleShipments(order, warehouseNetwork));
}
///Use a greedy algorithm to fulfill the order
private OrderFulfillment FulfillWithGreedyMultipleShipments(Order order, WarehouseNetwork warehouseNetwork)
{
var orderFulfillment = new OrderFulfillment();
// <comment for reviewers only:> This is a semi-hacky way to get around "Collection was modified; enumeration operation may not execute." exceptions. It is safe here as long as I know this is the only code modifying the collection
var orderKeys = new List <string>(order.Keys);
foreach (var warehouse in warehouseNetwork)
{
var partialOrder = new Order();
foreach (var itemName in orderKeys)
{
if (!warehouse.Inventory.ContainsKey(itemName))
{
continue;
}
var orderItemQuantity = order[itemName];
var warehouseItemCount = warehouse.Inventory[itemName];
var amountCanFullfill = Math.Min(orderItemQuantity, warehouseItemCount);
if (amountCanFullfill > 0)
{
partialOrder.Add(itemName, amountCanFullfill);
//No need to update warehouse inventory directly here
//Do need to update order quantity remaining to fulfill, BUT the KeyValuePair object in C# is immutable... need to update the order dictionary itself
order[itemName] -= amountCanFullfill;
}
}
if (partialOrder.Count > 0)
{
orderFulfillment.Add(warehouse.Name, partialOrder);
}
}
return(orderFulfillment);
}
/// Is it possible ot fulfill the given order with our inventory
private bool CanFulfillOrder(Order order, WarehouseNetwork warehouseNetwork)
{
//This could be pre-computed, or cached, but the set operations are quite quick for even very large networks
var globalInventory = warehouseNetwork.SelectMany(x => x.Inventory)
.GroupBy(x => x.Key)
.Select(x => new
{
Item = x.Key,
GlobalCount = x.Sum(i => i.Value)
}).ToDictionary(k => k.Item, v => v.GlobalCount);
foreach (var orderItem in order)
{
if (!globalInventory.ContainsKey(orderItem.Key) ||
globalInventory[orderItem.Key] < orderItem.Value)
{
return(false);
}
}
return(true);
}