Merge pull request #84 from kwong21/74-string-calculator

[TDD] Kata - String Calculator

src/main/java/com/ordestiny/tdd/kata/StringCalculator.java

@@ -0,0 +1,92 @@
+package com.ordestiny.tdd.kata;
+
+import java.text.DecimalFormat;
+import java.util.Arrays;
+import java.util.regex.Pattern;
+
+public class StringCalculator {
+
+ private static final String NEWLINE = "\n";
+ private static final String CUSTOM_DELIMITER_SUFFIX = NEWLINE;
+ private static final String DEFAULT_DELIMITERS = ",|" + NEWLINE;
+ private static final String CUSTOM_DELIMITER_PREFIX = "//";
+
+ public String add(String number) {
+ String delimiter = DEFAULT_DELIMITERS;
+ String numbers = number;
+
+ if (number.startsWith(CUSTOM_DELIMITER_PREFIX)) {
+ delimiter = getCustomDelimiter(number);
+ numbers = getNumbersInput(number);
+ validateInput(numbers, delimiter);
+ }
+
+ if (numbers.isEmpty()) {
+ return "0";
+ }
+
+ if (isInvalidLastCharacterIn(numbers)) {
+ throw new IllegalArgumentException("Number expected but found EOF");
+ }
+
+ double result = getSum(numbers, delimiter);
+ return format(result);
+ }
+
+ private String getCustomDelimiter(String input) {
+ int indexOfDelimiterStart = input.lastIndexOf(CUSTOM_DELIMITER_PREFIX) + 2;
+ int indexOfNumbersStart = input.indexOf(CUSTOM_DELIMITER_SUFFIX);
+
+ String unquotedDelimiter = input.substring(indexOfDelimiterStart, indexOfNumbersStart);
+
+ return unquotedDelimiter;
+ }
+
+ private String getNumbersInput(String input) {
+ return input.substring(input.lastIndexOf(NEWLINE) + 1);
+ }
+
+ private boolean isInvalidLastCharacterIn(String numbers) {
+ return Character.digit(numbers.charAt(numbers.length() - 1), 10) < 0;
+ }
+
+ private void validateInput(String input, String delimiter) {
+ for (int i = 1; i < input.length(); i += 2) {
+ int expectedDelimiterIndex = i + delimiter.length();
+
+ if (expectedDelimiterIndex < input.length()) {
+ String delimiterInString = input.substring(i, expectedDelimiterIndex);
+
+ if (!delimiterInString.equals(delimiter)) {
+ String exceptionMessage = String.format("'%s' expected but '%s', found at position %d", delimiter,
+ delimiterInString, i);
+ throw new IllegalArgumentException(exceptionMessage);
+ }
+ }
+ }
+ }
+
+ private double getSum(String numbers, String delimiter) {
+ if (delimiter.matches("[^A-Za-z0-9]")) {
+ // Quote any delimiter that is a special character, such as `|`
+ delimiter = Pattern.quote(delimiter);
+ }
+
+ String[] arrayOfStringNumbers = numbers.split(delimiter);
+
+ return sum(arrayOfStringNumbers);
+ }
+
+ private double sum(String[] numbers) {
+ Double sum = Arrays.stream(numbers)
+ .map(number-> Double.valueOf(number))
+ .reduce(0.0, Double::sum);
+
+ return sum;
+ }
+
+ private String format(double value) {
+ DecimalFormat format = new DecimalFormat("0.#");
+ return format.format(value);
+ }
+}

src/test/java/com/ordestiny/tdd/kata/StringCalculatorTest.java

@@ -0,0 +1,41 @@
+package com.ordestiny.tdd.kata;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+import org.junit.jupiter.params.provider.ValueSource;
+
+public class StringCalculatorTest {
+
+ private static StringCalculator fixture;
+
+ @BeforeAll
+ public static void setup() {
+ fixture = new StringCalculator();
+ }
+
+ @ParameterizedTest
+ @CsvSource({ "'',0", "1,1", "'1.1,2.2',3.3", "'1\n2,3', 6", "'//;\n1;2',3", "'//|\n1|2|3', 6", "'//sep\n2sep3',5",
+ "'//;\n',0" })
+ public void add_WithValidNumber_SumOfNumbers(String input, String expected) {
+ final String actual = fixture.add(input);
+
+ assertEquals(expected, actual);
+ }
+
+ @ParameterizedTest
+ @ValueSource(strings = { "//|\n1|2,3", "//a\n1a2a3a4b5", "//%\n1%4$5", "//c\n1c2c" })
+ public void add_WithInvalidInput_ThrowException(String input) {
+ Exception exception = assertThrows(IllegalArgumentException.class, () -> {
+ fixture.add(input);
+ });
+
+ String expectedMessage = "expected but";
+ String actualMessage = exception.getMessage();
+ assertTrue(actualMessage.contains(expectedMessage));
+ }
+}