SECURE BY DESIGN DAY 06

import static org.apache.commons.lang3.Validate.*;
import java.util.Collections;
import java.util.List;
import java.util.ArrayList;

public final class Order {
    private final OrderId id;           // Partially Immutable: ห้ามแก้หลังสร้าง
    private final CustomerId customerId;
    private final Address shippingAddress;
    private final List<OrderLine> items;
    private OrderStatus status;

    // 1. Mandatory Constructor: ข้อมูลครบถ้วนแต่วินาทีแรก (Consistent on Creation)
    public Order(OrderId id, CustomerId customerId, Address shippingAddress, List<OrderLine> initialItems) {
        this.id = notNull(id, "OrderId is required");
        this.customerId = notNull(customerId, "CustomerId is required");
        this.shippingAddress = notNull(shippingAddress, "ShippingAddress is required");
        notNull(initialItems, "Initial items required");
        isTrue(!initialItems.isEmpty(), "Order must contain at least one item");

        // Defensive Copy เพื่อตัดการเชื่อมโยงกับ List ภายนอก
        this.items = new ArrayList<>(initialItems);
        this.status = OrderStatus.CREATED;
    }

    // 2. Intent-Revealing Domain Operations แทน Unrestricted Setters
    public void cancel() {
        validState(this.status == OrderStatus.CREATED, 
            "Cannot cancel an order that is already processed");
        this.status = OrderStatus.CANCELLED;
    }

    public void addOrderLine(OrderLine item) {
        notNull(item, "Item cannot be null");
        validState(this.status == OrderStatus.CREATED, 
            "Cannot add items to a finalized order");
        this.items.add(item);
    }

    // 3. Guarded Collections: ส่งออกเฉพาะ Unmodifiable List ป้องกัน Escaping Reference
    public List<OrderLine> items() {
        return Collections.unmodifiableList(items);
    }
}