initial commit v2

integration/OrderBookDomain/OrderBook.cs

@@ -0,0 +1,69 @@
+namespace OrderBookDomain;
+
+public class OrderBook
+{
+    private readonly TimeSpan _paymentWindow;
+    private readonly Dictionary<int, Order> _ordersById = new();
+    private int _nextId = 1;
+
+    public OrderBook(TimeSpan? paymentWindow = null)
+        => _paymentWindow = paymentWindow ?? TimeSpan.FromDays(14);
+
+    public IReadOnlyList<Order> Orders => _ordersById.Values.ToList();
+
+    public Order OpenOrder(string customer)
+    {
+        var order = new Order(_nextId++, customer);
+        _ordersById[order.Id] = order;
+        return order;
+    }
+
+    public Order GetOrder(int orderId)
+        => _ordersById.TryGetValue(orderId, out var order)
+            ? order
+            : throw new InvalidOperationException($"Unknown order id {orderId}.");
+
+    public void FinalizeOrder(int orderId, DateTimeOffset finalizedAt)
+    {
+        var order = GetOrder(orderId);
+        RequireStatus(order, OrderStatus.Pending, "finalize");
+        order.Status = OrderStatus.WaitingForPayment;
+        order.FinalizedAt = finalizedAt;
+    }
+
+    public void PayOrder(int orderId, DateTimeOffset paidAt)
+    {
+        var order = GetOrder(orderId);
+        RequireStatus(order, OrderStatus.WaitingForPayment, "pay");
+        if (paidAt - order.FinalizedAt > _paymentWindow)
+        {
+            order.Status = OrderStatus.Cancelled;
+            throw new InvalidOperationException(
+                $"Payment for order {orderId} arrived after the payment window; the order was cancelled.");
+        }
+        order.Status = OrderStatus.Fulfilling;
+    }
+
+    public void ShipOrder(int orderId)
+    {
+        var order = GetOrder(orderId);
+        RequireStatus(order, OrderStatus.Fulfilling, "ship");
+        order.Status = OrderStatus.Delivered;
+    }
+
+    public void CancelOrder(int orderId)
+    {
+        var order = GetOrder(orderId);
+        if (order.Status is not (OrderStatus.Pending or OrderStatus.WaitingForPayment))
+            throw new InvalidOperationException(
+                $"Cannot cancel order {orderId} in status {order.Status}.");
+        order.Status = OrderStatus.Cancelled;
+    }
+
+    private static void RequireStatus(Order order, OrderStatus expected, string action)
+    {
+        if (order.Status != expected)
+            throw new InvalidOperationException(
+                $"Cannot {action} order {order.Id} in status {order.Status} (expected {expected}).");
+    }
+}