added some comments, made code more DRY

Signed-off-by: Konstantin Läufer <[email protected]>

Author: klaeufer

src/main/java/edu/luc/cs/consoleapp/Main.java

@@ -37,6 +37,8 @@ public static void main(final String[] args) {
     final var input = new Scanner(System.in).useDelimiter("(?U)[^\\p{Alpha}0-9']+");
     final var queue = new CircularFifoQueue<String>(lastNWords);
 
+    // this is the core functionality, but it mixes 
+    // I/O and core processing logic and therefore is hard to test
     input.forEachRemaining(
       word -> {
         queue.add(word); // the oldest item automatically gets evicted

src/main/java/edu/luc/cs/consoleapp/MainLeaky.java

@@ -1,5 +1,6 @@
 package edu.luc.cs.consoleapp;
 
+import java.util.Collections;
 import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
@@ -8,6 +9,8 @@
 
 import org.apache.commons.collections4.queue.CircularFifoQueue;
 
+import edu.luc.cs.consoleapp.MainLeaky.LeakyQueue;
+
 // see https://stackoverflow.com/questions/1963806/#21699069
 // why we're using this implementation instead of java.util.ArrayQueue!
 
@@ -16,9 +19,6 @@ public class MainLeaky {
   public static final int LAST_N_WORDS = 10;
 
   public static void main(final String[] args) {
-
-    // TODO consider using a command-line option library
-
     // perform argument validity checking
     if (args.length > 1) {
       System.err.println("usage: ./target/universal/stage/bin/consoleapp [ last_n_words ]");
@@ -51,6 +51,11 @@ public static void main(final String[] args) {
       });
   }
 
+  /** 
+   * A sliding window queue that retains the last N elements. 
+   * This component is independent of the user interface and can be tested independently.
+   * Nevertheless, it violates an important nonfunctional requirement: it leaks memory.
+   */
   static class LeakyQueue {
 
     private final Queue<String> queue;
@@ -70,7 +75,7 @@ public List<Queue<String>> process() {
           final var snapshot = new LinkedList<>(queue);
           result.add(snapshot);
         });
-      return result;
+      return Collections.unmodifiableList(result);
     }
   }
 }

src/main/java/edu/luc/cs/consoleapp/MainStream.java

@@ -12,9 +12,6 @@ public class MainStream {
   public static final int LAST_N_WORDS = 10;
 
   public static void main(final String[] args) {
-
-    // TODO consider using a command-line option library
-
     // perform argument validity checking
     if (args.length > 1) {
       System.err.println("usage: ./target/universal/stage/bin/consoleapp [ last_n_words ]");

src/main/java/edu/luc/cs/consoleapp/MainTestable.java

@@ -10,9 +10,6 @@ public class MainTestable {
   public static final int LAST_N_WORDS = 10;
 
   public static void main(final String[] args) {
-
-    // TODO consider using a command-line option library
-
     // perform argument validity checking
     if (args.length > 1) {
       System.err.println("usage: ./target/universal/stage/bin/consoleapp [ last_n_words ]");
@@ -42,8 +39,10 @@ public static void main(final String[] args) {
           System.exit(1);
         }
       };
+    // the main functionality (excluding I/O) is now implemented in SlidingQueue
     final var slidingQueue = new SlidingQueue(lastNWords, input, outputToConsole);
 
+    // finally invoke the main functionality
     slidingQueue.process();
   }
 }

src/main/java/edu/luc/cs/consoleapp/OutputHandler.java

@@ -4,7 +4,7 @@
 import java.util.function.Consumer;
 
 /**
- * Observer for decoupling sliding window logic from routing updates. The consumer processes the
- * output and returns void.
+ * Observer for decoupling sliding window logic from routing updates. 
+ * The consumer processes the output and returns void.
  */
 interface OutputHandler extends Consumer<Queue<String>> {}

src/main/java/edu/luc/cs/consoleapp/SlidingQueue.java

@@ -5,6 +5,11 @@
 
 import org.apache.commons.collections4.queue.CircularFifoQueue;
 
+/** 
+ * A sliding window queue that retains the last N elements. 
+ * This component is independent of the user interface and can be tested independently.
+ * It takes an OutputHandler to route updates to the appropriate destination.
+ */
 class SlidingQueue {
 
   protected final Queue<String> queue;

src/test/java/edu/luc/cs/consoleapp/TestMainNotDRY.java

@@ -44,15 +44,4 @@ public void testSlidingWindowNonempty() {
     assertEquals(List.of("asdf", "qwer", "oiui"), result.get(2));
     assertEquals(List.of("qwer", "oiui", "zxcv"), result.get(3));
   }
-
-  private static class OutputToList implements OutputHandler {
-
-    final List<Queue<String>> result = new ArrayList<>();
-
-    @Override
-    public void accept(final Queue<String> value) {
-      final var snapshot = new LinkedList<>(value);
-      result.add(snapshot);
-    }
-  }
 }

src/test/java/edu/luc/cs/consoleapp/TestSlidingQueue.java

@@ -34,15 +34,4 @@ public void testSlidingWindowNonempty() {
     assertEquals(List.of("asdf", "qwer", "oiui"), result.get(2));
     assertEquals(List.of("qwer", "oiui", "zxcv"), result.get(3));
   }
-
-  private static class OutputToList implements OutputHandler {
-
-    final List<Queue<String>> result = new ArrayList<>();
-
-    @Override
-    public void accept(final Queue<String> value) {
-      final var snapshot = new LinkedList<>(value);
-      result.add(snapshot);
-    }
-  }
 }

src/test/java/edu/luc/cs/consoleapp/TestSlidingQueueInteractive.java

@@ -1,5 +1,7 @@
 package edu.luc.cs.consoleapp;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
@@ -16,7 +18,7 @@ public void testInteractiveBehavior() {
     // the test input
     final var input = List.of("asdf", "qwer", "oiui", "zxcv");
     // the expected interaction trace
-    final var expectedTrace = List.<TraceEvent>of(
+    final var expectedTrace = List.<IOEvent>of(
       new InputEvent("asdf"),
       new OutputEvent("asdf"),
       new InputEvent("qwer"),
@@ -31,23 +33,25 @@ public void testInteractiveBehavior() {
     sut.process();
     // // make sure the expected and actual traces match
     final var actualTrace = sut.getTrace();
+    assertEquals(expectedTrace, actualTrace);
   }
 }
 
 // A mini-framework for trace-based testing of interactive behavior (WIP)
 
-interface TraceEvent {}
+/** A common interface for user I/O events. */
+interface IOEvent {}
 
 /** A trace event representing user input. */
-record InputEvent(String value) implements TraceEvent {
+record InputEvent(String value) implements IOEvent {
   @Override
   public String toString() {
     return "InputEvent(" + value + ")";
   }
 }
 
 /** A trace event representing system output. */
-record OutputEvent(List<String> value) implements TraceEvent {
+record OutputEvent(List<String> value) implements IOEvent {
   public OutputEvent(String... values) {
     this(Arrays.asList(values));
   }
@@ -68,7 +72,7 @@ public String toString() {
 class SUTWithTracing {
   private final SlidingQueue sut;
 
-  private final LinkedList<TraceEvent> trace = new LinkedList<>();
+  private final LinkedList<IOEvent> trace = new LinkedList<>();
 
   SUTWithTracing(final int capacity, final Collection<String> input) {
     this.sut = new SlidingQueue(capacity, wrapInput(input), outputToTrace());
@@ -78,7 +82,7 @@ void process() {
     sut.process();
   }
 
-  List<TraceEvent> getTrace() {
+  List<IOEvent> getTrace() {
     return Collections.unmodifiableList(trace);
   }