Extract line IO abstractions into shared library

.gitignore

@@ -12,4 +12,8 @@ out/
 !**/src/main/**/out/
 !**/src/test/**/out/
 
+# macOS
+**/.DS_Store
 .DS_Store
+
+.worktrees/

area-rectangular-room/build.gradle

@@ -3,6 +3,8 @@ plugins {
 }
 
 dependencies {
+    implementation(project(':line-io'))
+    testImplementation(testFixtures(project(':line-io')))
     testImplementation(libs.assertj.core)
     testImplementation(libs.junit.jupiter)
 }

area-rectangular-room/src/main/java/dev/delivercraft/rectangular/AreaRectangularRoomCalculator.java

@@ -1,5 +1,8 @@
 package dev.delivercraft.rectangular;
 
+import dev.delivercraft.io.LineReader;
+import dev.delivercraft.io.LineWriter;
+
 class AreaRectangularRoomCalculator {
 
     private static final double CONVERSION_FACTOR = 0.092_903_04;

area-rectangular-room/src/main/java/dev/delivercraft/rectangular/Main.java

@@ -1,5 +1,10 @@
 package dev.delivercraft.rectangular;
 
+import dev.delivercraft.io.InputStreamLineReader;
+import dev.delivercraft.io.LineReader;
+import dev.delivercraft.io.LineWriter;
+import dev.delivercraft.io.OutputStreamLineWriter;
+
 public final class Main {
 
     void main() {

area-rectangular-room/src/test/java/dev/delivercraft/rectangular/AreaRectangularRoomCalculatorTest.java

@@ -1,11 +1,13 @@
 package dev.delivercraft.rectangular;
 
+import dev.delivercraft.io.CapturingLineWriter;
+import dev.delivercraft.io.LineReader;
+import dev.delivercraft.io.LineWriter;
+import dev.delivercraft.io.StubLineReader;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.NullAndEmptySource;
 
-import java.util.StringJoiner;
-
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
 
@@ -16,7 +18,7 @@ class AreaRectangularRoomCalculatorTest {
     void calculateArea_GivenNoInput_ShouldThrowException(String input) {
         LineReader lineReader = () -> input;
         AreaRectangularRoomCalculator calculator = new AreaRectangularRoomCalculator(lineReader,
-                new InMemoryLineWriter());
+                new CapturingLineWriter());
 
         assertThatIllegalArgumentException()
                 .isThrownBy(calculator::calculateArea)
@@ -26,7 +28,7 @@ void calculateArea_GivenNoInput_ShouldThrowException(String input) {
     @Test
     void calculateArea_ShouldAskForLength() {
         LineReader lineReader = () -> "123";
-        LineWriter lineWriter = new InMemoryLineWriter();
+        LineWriter lineWriter = new CapturingLineWriter();
         AreaRectangularRoomCalculator calculator = new AreaRectangularRoomCalculator(lineReader, lineWriter);
 
         calculator.calculateArea();
@@ -38,7 +40,7 @@ void calculateArea_ShouldAskForLength() {
     @Test
     void calculateArea_ShouldAskForWidth() {
         LineReader lineReader = () -> "123";
-        LineWriter lineWriter = new InMemoryLineWriter();
+        LineWriter lineWriter = new CapturingLineWriter();
         AreaRectangularRoomCalculator calculator = new AreaRectangularRoomCalculator(lineReader, lineWriter);
 
         calculator.calculateArea();
@@ -50,7 +52,7 @@ void calculateArea_ShouldAskForWidth() {
     @Test
     void calculateArea_GivenLengthAndWidth_ShouldDisplayDimensions() {
         LineReader lineReader = new StubLineReader("15", "20");
-        LineWriter lineWriter = new InMemoryLineWriter();
+        LineWriter lineWriter = new CapturingLineWriter();
         AreaRectangularRoomCalculator calculator = new AreaRectangularRoomCalculator(lineReader, lineWriter);
 
         calculator.calculateArea();
@@ -62,7 +64,7 @@ void calculateArea_GivenLengthAndWidth_ShouldDisplayDimensions() {
     @Test
     void calculateArea_GivenValidInput_ShouldDisplayTheAreaInSquareFeet() {
         LineReader lineReader = new StubLineReader("15", "20");
-        LineWriter lineWriter = new InMemoryLineWriter();
+        LineWriter lineWriter = new CapturingLineWriter();
         AreaRectangularRoomCalculator calculator = new AreaRectangularRoomCalculator(lineReader, lineWriter);
 
         calculator.calculateArea();
@@ -75,7 +77,7 @@ void calculateArea_GivenValidInput_ShouldDisplayTheAreaInSquareFeet() {
     @Test
     void calculateArea_GivenValidInput_ShouldDisplayTheAreaInSquareMeters() {
         LineReader lineReader = new StubLineReader("15", "20");
-        LineWriter lineWriter = new InMemoryLineWriter();
+        LineWriter lineWriter = new CapturingLineWriter();
         AreaRectangularRoomCalculator calculator = new AreaRectangularRoomCalculator(lineReader, lineWriter);
 
         calculator.calculateArea();
@@ -87,47 +89,11 @@ void calculateArea_GivenValidInput_ShouldDisplayTheAreaInSquareMeters() {
     @Test
     void calculateArea_GivenNonNumericInput_ShouldThrowException() {
         LineReader lineReader = new StubLineReader("asdf");
-        LineWriter lineWriter = new InMemoryLineWriter();
+        LineWriter lineWriter = new CapturingLineWriter();
         AreaRectangularRoomCalculator calculator = new AreaRectangularRoomCalculator(lineReader, lineWriter);
 
         assertThatIllegalArgumentException()
                 .isThrownBy(calculator::calculateArea)
                 .withMessage("Please enter a numeric value! Input: asdf");
     }
-
-    private static final class StubLineReader implements LineReader {
-
-        private final String[] inputs;
-
-        private int index;
-
-        private StubLineReader(String... inputs) {
-            this.inputs = inputs;
-        }
-
-        @Override
-        public String readLine() {
-            return this.inputs[this.index++];
-        }
-    }
-
-    private static final class InMemoryLineWriter implements LineWriter {
-
-        private final StringJoiner stringJoiner = new StringJoiner("");
-
-        @Override
-        public void write(String text) {
-            this.stringJoiner.add(text);
-        }
-
-        @Override
-        public void writeLine(String line) {
-            this.stringJoiner.add(line).add(System.lineSeparator());
-        }
-
-        @Override
-        public String toString() {
-            return this.stringJoiner.toString();
-        }
-    }
 }

line-io/build.gradle

@@ -0,0 +1,10 @@
+plugins {
+    id 'dev.delivercraft.common-conventions'
+    id 'java-library'
+    id 'java-test-fixtures'
+}
+
+dependencies {
+    testImplementation(libs.assertj.core)
+    testImplementation(libs.junit.jupiter)
+}

line-io/src/main/java/dev/delivercraft/io/InputStreamLineReader.java

@@ -0,0 +1,45 @@
+package dev.delivercraft.io;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.UncheckedIOException;
+import java.util.Objects;
+
+/**
+ * Reads lines from an {@link InputStream}.
+ *
+ * <p>This implementation uses the platform default charset, returns {@code null} when the stream is exhausted, and
+ * wraps checked {@link IOException} failures in {@link UncheckedIOException}.
+ */
+public final class InputStreamLineReader implements LineReader {
+
+    private final BufferedReader bufferedReader;
+
+    /**
+     * Creates a line reader backed by the supplied input stream.
+     *
+     * @param inputStream the stream to read from
+     * @throws NullPointerException when {@code inputStream} is {@code null}
+     */
+    public InputStreamLineReader(InputStream inputStream) {
+        Objects.requireNonNull(inputStream, "inputStream must not be null");
+        this.bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
+    }
+
+    /**
+     * Reads the next line from the stream.
+     *
+     * @return the next line without a line separator, or {@code null} when the stream is exhausted
+     * @throws UncheckedIOException when the underlying stream cannot be read
+     */
+    @Override
+    public String readLine() {
+        try {
+            return this.bufferedReader.readLine();
+        } catch (IOException e) {
+            throw new UncheckedIOException(e);
+        }
+    }
+}

line-io/src/main/java/dev/delivercraft/io/LineReader.java

@@ -0,0 +1,14 @@
+package dev.delivercraft.io;
+
+/**
+ * Reads one line of text.
+ */
+public interface LineReader {
+
+    /**
+     * Reads one line of text.
+     *
+     * @return the line without a line separator, or {@code null} when no input remains
+     */
+    String readLine();
+}

line-io/src/main/java/dev/delivercraft/io/LineWriter.java

@@ -0,0 +1,21 @@
+package dev.delivercraft.io;
+
+/**
+ * Writes text and lines of text.
+ */
+public interface LineWriter {
+
+    /**
+     * Writes text without appending a line separator.
+     *
+     * @param text the text to write
+     */
+    void write(String text);
+
+    /**
+     * Writes text followed by the platform line separator.
+     *
+     * @param line the line to write
+     */
+    void writeLine(String line);
+}

line-io/src/main/java/dev/delivercraft/io/OutputStreamLineWriter.java

@@ -0,0 +1,48 @@
+package dev.delivercraft.io;
+
+import java.io.OutputStream;
+import java.io.PrintWriter;
+import java.util.Objects;
+
+/**
+ * Writes text and lines to an {@link OutputStream}.
+ *
+ * <p>This implementation writes text without validation or formatting, flushes prompt text written through
+ * {@link #write(String)}, and uses {@link PrintWriter#println(String)} for line output.
+ */
+public final class OutputStreamLineWriter implements LineWriter {
+
+    private final PrintWriter printWriter;
+
+    /**
+     * Creates a line writer backed by the supplied output stream.
+     *
+     * @param outputStream the stream to write to
+     * @throws NullPointerException when {@code outputStream} is {@code null}
+     */
+    public OutputStreamLineWriter(OutputStream outputStream) {
+        Objects.requireNonNull(outputStream, "outputStream must not be null");
+        this.printWriter = new PrintWriter(outputStream, true);
+    }
+
+    /**
+     * Writes text without appending a line separator and flushes the underlying writer.
+     *
+     * @param text the text to write
+     */
+    @Override
+    public void write(String text) {
+        this.printWriter.print(text);
+        this.printWriter.flush();
+    }
+
+    /**
+     * Writes text followed by the platform line separator.
+     *
+     * @param line the line to write
+     */
+    @Override
+    public void writeLine(String line) {
+        this.printWriter.println(line);
+    }
+}