package lk.ac.pdn.ceit.pos;

import lk.ac.pdn.ceit.pos.entities.Bill;
import lk.ac.pdn.ceit.pos.entities.Item;
import lk.ac.pdn.ceit.pos.entities.LineItem;

public class BillManagerImpl implements BillManager {
    private ItemManager itemManager;

    private Bill currentBill;

    // Just for demo purpose. In real world, a database call may be used for this purpose.
    private int lastBillId = 0;

    public BillManagerImpl(ItemManager itemManager) {
        this.itemManager = itemManager;
    }

    @Override
    public Bill createNewBill() {
        currentBill = new Bill();

        lastBillId++;
        currentBill.setId(lastBillId);

        return currentBill;
    }

    @Override
    public void addLineItem(String itemId, int quantity) {
        if (currentBill == null) {
            throw new IllegalStateException("A bill has not been created so far. Neither a checked exception is thrown.");    
        }

        Item item = itemManager.findById(itemId);
        
        if (item != null) {
            LineItem lineItem = new LineItem(item.getId(), item.getName(), quantity, item.getUnitPrice());
            currentBill.addLineItem(lineItem);
        }
    }

    @Override
    public void saveBill() {
        // TODO: Save the currentBill in DB.
    }

    @Override
    public void finishBillSession() {
        currentBill = null;
    }
}