Procedural approach refactor in String Calculator kata. Short description of the kata in the main README.

Author: Jonarzz

README.md

@@ -26,13 +26,19 @@
 * [Fizz Buzz kata](fizz-buzz)
   * JMH
   * 11 implementations of a simple algorithm with performance comparison
+* [String Calculator kata](string-calculator)
+  * Spock
+  * incremental development (9 steps of discovering new requirements)
+  * the same algorithm written using object-oriented and procedural approach
+  * strategy (policy) pattern
+  * value objects
+  * regular expressions
 
 ## In progress
-* [String Calculator kata](string-calculator)
+* [Unusual Spending kata](unusual-spending)
 
 ## To do
 ### Katas
-* [Unusual Spending kata](unusual-spending)
 * [Manhattan Distance kata](manhattan-distance)
 * [The Lift kata](the-lift)
 * [Social Network kata](social-network)

string-calculator/src/main/java/io/github/jonarzz/kata/string/calculator/procedural/SplitStreamStringCalculator.java

@@ -21,23 +21,15 @@ public class SplitStreamStringCalculator implements StringCalculator {
     public int add(String numbers) {
         var valueToSplit = numbers;
         var delimiterRegex = "[\\n,]";
-        if (numbers.startsWith(DELIMITER_PREFIX)) {
-            var split = numbers.split("\\n", -1);
-            if (split.length == 2) {
-                var unescapedDelimiter = split[0].replaceFirst("^" + DELIMITER_PREFIX, "");
-                var matcher = EXTENDED_DELIMITER_PATTERN.matcher(unescapedDelimiter);
-                if (matcher.find()) {
-                    Set<String> delimiters = new HashSet<>();
-                    do {
-                        delimiters.add(quote(matcher.group(1)));
-                    } while (matcher.find());
-                    delimiterRegex = join("|", delimiters);
-                } else {
-                    delimiterRegex = Pattern.quote(unescapedDelimiter);
-                }
-                valueToSplit = split[1];
-            }
+        if (!numbers.startsWith(DELIMITER_PREFIX)) {
+            return calculateSum(valueToSplit, delimiterRegex);
+        }
+        var split = numbers.split("\\n", -1);
+        if (split.length != 2) {
+            return calculateSum(valueToSplit, delimiterRegex);
         }
+        delimiterRegex = calculateDelimitersFrom(split[0]);
+        valueToSplit = split[1];
         return calculateSum(valueToSplit, delimiterRegex);
     }
 
@@ -64,4 +56,17 @@ private int calculateSum(String valueToSplit, String delimiterRegex) {
         return sum;
     }
 
+    private String calculateDelimitersFrom(String delimitersInput) {
+        var unescapedDelimiter = delimitersInput.replaceFirst("^" + DELIMITER_PREFIX, "");
+        var matcher = EXTENDED_DELIMITER_PATTERN.matcher(unescapedDelimiter);
+        if (!matcher.find()) {
+            return quote(unescapedDelimiter);
+        }
+        Set<String> delimiters = new HashSet<>();
+        do {
+            delimiters.add(quote(matcher.group(1)));
+        } while (matcher.find());
+        return join("|", delimiters);
+    }
+
 }