Tdd oct 13 2022

src/main/java/guru/springframework/Bank.java

@@ -0,0 +1,21 @@
+package guru.springframework;
+
+import java.util.HashMap;
+
+public class Bank {
+    private HashMap<Pair, Integer> rateMap = new HashMap<>();
+    public Money reduce(Expression source, String toCurrency) {
+        return source.reduce(this, toCurrency);
+    }
+
+    public int rate(String from, String to){
+        if (from.equals(to)) {
+            return 1;
+        }
+        return rateMap.get(new Pair(from, to));
+
+    }
+    public void addRate(String from, String to, int rate) {
+        rateMap.put(new Pair(from, to), rate);
+    }
+}

src/main/java/guru/springframework/Expression.java

@@ -0,0 +1,5 @@
+package guru.springframework;
+
+public interface Expression {
+    Money reduce(Bank bank, String to);
+}

src/main/java/guru/springframework/Money.java

@@ -0,0 +1,49 @@
+package guru.springframework;
+
+public class Money implements guru.springframework.Expression {
+    protected int amount;
+    protected String currency;
+    public Money(int amount, String currency) {
+        this.amount = amount;
+        this.currency = currency;
+    }
+
+    protected String currency() {
+        return currency;
+    }
+
+
+    public static Money franc(int amount){return new Money(amount, "CHF");}
+
+    public static Money dollar(int amount){
+        return new Money(amount, "USD");
+    }
+    public boolean equals(Object object){
+        Money money = (Money) object;
+        return amount == money.amount
+                && this.currency == money.currency;
+    }
+
+    @Override
+    public Money reduce(Bank bank, String to){
+        //return this;
+        //int rate = (currency.equals("CHF") && to.equals("USD")) ? 2 : 1;
+        return new Money(amount / bank.rate(this.currency, to), to);
+    }
+
+    @Override
+    public String toString() {
+        return "Money{" +
+                "amount=" + amount +
+                ", currency='" + currency + '\'' +
+                '}';
+    }
+
+    public Money times(int multiplier) {
+        return new Money(amount * multiplier, this.currency);
+    }
+
+    public Expression plus(Money addend) {
+        return new Sum(this, addend);
+    }
+}

src/main/java/guru/springframework/Pair.java

@@ -0,0 +1,27 @@
+package guru.springframework;
+
+import java.util.Objects;
+
+public class Pair {
+
+    private final String from;
+    private final String to;
+
+    public Pair(String from, String to) {
+        this.from = from;
+        this.to = to;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof Pair)) return false;
+        Pair pair = (Pair) o;
+        return Objects.equals(from, pair.from) && Objects.equals(to, pair.to);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(from, to);
+    }
+}

src/main/java/guru/springframework/Sum.java

@@ -0,0 +1,17 @@
+package guru.springframework;
+
+public class Sum implements Expression{
+    Money augmend;
+    Money addmend;
+
+    public Sum(Money augmend, Money addmend) {
+        this.augmend = augmend;
+        this.addmend = addmend;
+    }
+
+    @Override
+    public Money reduce(Bank bank, String to){
+        int amount = augmend.amount + addmend.amount;
+        return new Money(amount, to);
+    }
+}

src/test/java/guru/springframework/MoneyTest.java

@@ -0,0 +1,81 @@
+package guru.springframework;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+
+public class MoneyTest {
+//TODO on Dell 16, Project Structure was running Java 17. Had to be rolled back to Java 11 to avoid warnings
+//Dell 16, Project Structure was running Java 17. Had to be rolled back to Java 11 to avoid warnings
+    @Test
+    void testMultiplication(){
+        Money five = Money.dollar(5);
+        assertEquals(Money.dollar(10), five.times(2));
+        assertEquals(Money.dollar(15), five.times(3));
+        Money fiveF = Money.franc(5);
+        assertEquals(Money.franc(10), fiveF.times(2));
+
+    }
+
+    @Test
+    void testEquality(){
+        assertEquals(Money.dollar(5), Money.dollar(5));
+        assertNotEquals(Money.dollar(5), Money.dollar(8));
+        assertEquals(Money.franc(5), Money.franc(5));
+        assertNotEquals(Money.dollar(5), Money.franc(5));
+    }
+
+    @Test
+    void testCurrency(){
+        assertEquals("USD", Money.dollar(1).currency());
+        assertEquals("CHF", Money.franc(1).currency());
+    }
+
+    @Test
+    void testSimpleAddition(){
+        Money five = Money.dollar(5);
+        Expression sum = (Expression) five.plus(five);
+        Bank bank = new Bank();
+        Money reduced = bank.reduce(sum, "USD");
+        assertEquals(Money.dollar(10), reduced);
+    }
+
+    @Test
+    void testPlusReturnsSum() {
+        Money five = Money.dollar(5);
+        Expression result = five.plus(five);
+        Sum sum = (Sum) result;
+        assertEquals(five, sum.augmend);
+        assertEquals(five, sum.addmend);
+    }
+
+    @Test
+    void testReduceSum() {
+        Expression sum = new Sum(Money.dollar(3), Money.dollar(4));
+        Bank bank = new Bank();
+        Money result = bank.reduce(sum, "USD");
+        assertEquals(Money.dollar(7), result);
+    }
+
+    @Test
+    void testReduceMoney() {
+        Bank bank = new Bank();
+        Money result = bank.reduce(Money.dollar(1), "USD");
+        assertEquals(Money.dollar(1), result);
+    }
+
+    @Test
+    void testReduceMoneyDifferentCurrency() {
+        Bank bank = new Bank();
+        bank.addRate("CHF", "USD", 2);
+        Money result = bank.reduce(Money.franc(2), "USD");
+        assertEquals(Money.dollar(1), result);
+    }
+
+    @Test
+    void testIdentityRate() {
+        assertEquals(1, new Bank().rate("USD", "USD"));
+        assertEquals(1, new Bank().rate("CHF", "CHF"));
+    }
+}