Enhancement/31 salecalculator class

src/main/java/edu/ntnu/idi/idatt2003/g40/mappe/SaleCalculator.java

@@ -0,0 +1,78 @@
+package edu.ntnu.idi.idatt2003.g40.mappe;
+
+import java.math.BigDecimal;
+
+/**
+ * Calculator for sale transactions.
+ * <p>
+ * Calculates gross value, commission, tax and total sale value
+ * based on the share's purchase price, current sales price and quantity.
+ * </p>
+ */
+public class SaleCalculator implements TransactionCalculator {
+
+    private static final BigDecimal COMMISSION_RATE = new BigDecimal("0.01"); // 1%
+    private static final BigDecimal TAX_RATE = new BigDecimal("0.30");        // 30%
+
+    private final BigDecimal purchasePrice;
+    private final BigDecimal salesPrice;
+    private final BigDecimal quantity;
+
+    /**
+     * Creates a new {@code SaleCalculator} based on a share.
+     *
+     * @param share the share to base calculations on
+     */
+    public SaleCalculator(Share share) {
+        this.purchasePrice = share.getPurchasePrice();
+        this.salesPrice = share.getStock().getSalesPrice();
+        this.quantity = share.getQuantity();
+    }
+
+    /**
+     * {@inheritDoc}
+     * Gross value = salesPrice * quantity.
+     */
+    @Override
+    public BigDecimal calculateGross() {
+        return salesPrice.multiply(quantity);
+    }
+
+    /**
+     * {@inheritDoc}
+     * Commission = 1% of gross value.
+     */
+    @Override
+    public BigDecimal calculateCommission() {
+        return calculateGross().multiply(COMMISSION_RATE);
+    }
+
+    /**
+     * {@inheritDoc}
+     * Tax = 30% of profit.
+     * Profit = gross - commission - (purchasePrice * quantity).
+     * If profit is negative or zero, tax is zero.
+     */
+    @Override
+    public BigDecimal calculateTax() {
+        BigDecimal purchaseCost = purchasePrice.multiply(quantity);
+        BigDecimal profit = calculateGross()
+                .subtract(calculateCommission())
+                .subtract(purchaseCost);
+
+        return profit.signum() > 0
+                ? profit.multiply(TAX_RATE)
+                : BigDecimal.ZERO;
+    }
+
+    /**
+     * {@inheritDoc}
+     * Total value = gross - commission - tax.
+     */
+    @Override
+    public BigDecimal calculateTotal() {
+        return calculateGross()
+                .subtract(calculateCommission())
+                .subtract(calculateTax());
+    }
+}