feat: Add Unix pipe support for draw command

README.md

@@ -68,6 +68,15 @@ L' F B2 L F2 B2 L' F2 L2 R B2 U' B' D' L2 D' F2 B2 R2 Fw2 U Rw2 Uw2 R' U' Rw2 R
 ```
 ![Image of a WCA 3x3 Scramble](docs/resources/images/three.svg)
 
+#### Piping Scrambles to Draw
+
+You can directly pipe the output of the `scramble` command to the `draw` command. This is useful for quickly visualizing a freshly generated scramble. When providing the scramble via standard input (stdin) like this, you can omit the `-s` or `--scramble` option for the `draw` command.
+
+```bash
+tnoodle scramble -p three | tnoodle draw -p three > output.svg
+```
+This command will generate a scramble for the 3x3x3 cube (`three`), send that scramble directly to the `draw` command (which also expects a 3x3x3 cube scramble), and save the resulting SVG image to `output.svg`.
+
 ## Legal
 ***Disclaimer:** This CLI tool is an **unofficial** project currently unaffiliated with the WCA. Scrambles generated by this tool are NOT authorized for use in any official WCA event. All such scrambles must be generated using the [official TNoodle program](https://www.worldcubeassociation.org/regulations/scrambles/).*
 

src/main/java/tnoodlecli/commands/DrawCommand.java

@@ -19,7 +19,9 @@
 
 import java.io.File;
 import java.io.FileNotFoundException;
+import java.io.IOException;
 import java.io.PrintWriter;
+import java.util.Scanner;
 
 import com.beust.jcommander.Parameter;
 import com.beust.jcommander.Parameters;
@@ -47,7 +49,7 @@ public class DrawCommand implements Runnable {
     @Parameter(
         names = { "-s", "--scramble" },
         description = "The scramble to draw.",
-        required = true
+        required = false
     )
     private String scramble;
 
@@ -56,6 +58,40 @@ public class DrawCommand implements Runnable {
 
     public void run() {
         try {
+            if (scramble == null || scramble.isEmpty()) {
+                try {
+                    if (System.in.available() > 0) {
+                        Scanner scanner = new Scanner(System.in);
+                        if (scanner.hasNextLine()) {
+                            scramble = scanner.nextLine();
+                            if (scramble.trim().isEmpty()) {
+                                System.err.println("Error: Received empty scramble from standard input.");
+                                System.exit(1);
+                            }
+                        } else {
+                            // This case means stdin had available bytes but nothing was read by nextLine (e.g. only EOF)
+                            System.err.println("Error: Standard input was open but no scramble string was provided.");
+                            System.exit(1);
+                        }
+                        // We don't close the scanner for System.in here
+                    } else {
+                        // System.in.available() <= 0 means no input from stdin when -s is not used
+                        System.err.println("Error: No scramble provided via -s/--scramble and no input detected on standard input.");
+                        System.exit(1);
+                    }
+                } catch (IOException e) {
+                    // Handle IOException from System.in.available()
+                    System.err.println("Error accessing standard input: " + e.getMessage());
+                    System.exit(1);
+                }
+            }
+
+            // This check is now more of a safeguard, as the logic above should handle most empty/null cases.
+            if (scramble == null || scramble.trim().isEmpty()) {
+                System.err.println("Error: Scramble string not provided or is empty.");
+                System.exit(1);
+            }
+
             Svg svg = PuzzleRegistry.valueOf(puzzle.toUpperCase()).getScrambler().drawScramble(scramble, null);
             if (output == null) {
                 System.out.println(svg.toString());
@@ -64,11 +100,13 @@ public void run() {
                 try (PrintWriter writer = new PrintWriter(outputFile)){
                     writer.print(svg.toString());
                 } catch (FileNotFoundException e) {
-                    e.printStackTrace();
+                    e.printStackTrace(); // Or a more user-friendly message + System.exit(1)
                 }
             }
         } catch (InvalidScrambleException e1) {
-            e1.printStackTrace();
+            System.err.println("Error: Invalid scramble string: " + e1.getMessage());
+            // e1.printStackTrace(); // Optionally print stack trace for more detail
+            System.exit(1);
         } 
     }
 }

src/test/java/tnoodlecli/commands/DrawCommandTest.java

@@ -0,0 +1,125 @@
+package tnoodlecli.commands;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.InputStream;
+import java.io.PrintStream;
+
+import com.beust.jcommander.JCommander;
+import tnoodlecli.commands.ScrambleCommand; // Added import
+
+/**
+ * Unit tests for the DrawCommand class.
+ */
+public class DrawCommandTest {
+
+    @Test
+    void testDrawCommand_readsFromStdin() {
+        String scrambleString = "R U R' U'";
+        String puzzleName = "THREE"; // Corresponds to 3x3x3 cube
+
+        InputStream originalIn = System.in;
+        PrintStream originalOut = System.out;
+
+        try {
+            // Simulate stdin
+            System.setIn(new ByteArrayInputStream(scrambleString.getBytes()));
+
+            // Capture stdout
+            ByteArrayOutputStream baos = new ByteArrayOutputStream();
+            System.setOut(new PrintStream(baos));
+
+            // Execute the command
+            DrawCommand drawCommand = new DrawCommand();
+
+            // Use JCommander to parse arguments and set the 'puzzle' field.
+            // 'scramble' field will remain null as it's not provided.
+            JCommander.newBuilder()
+                .addObject(drawCommand)
+                .build()
+                .parse("-p", puzzleName);
+
+            drawCommand.run();
+
+            // Assert the output
+            String output = baos.toString();
+            assertNotNull(output, "Output should not be null.");
+            assertFalse(output.isEmpty(), "Output should not be empty.");
+            assertTrue(output.contains("<svg"), "Output should contain '<svg'.");
+            assertTrue(output.contains("</svg>"), "Output should contain '</svg>'.");
+            assertTrue(output.contains("width="), "Output should contain 'width='.");
+            assertTrue(output.contains("height="), "Output should contain 'height='.");
+            // Check for potential error messages instead of SVG content
+            assertFalse(output.contains("Error:"), "Output should not contain 'Error:'.");
+
+        } finally {
+            // Restore System.in and System.out
+            System.setIn(originalIn);
+            System.setOut(originalOut);
+        }
+    }
+}
+
+    @Test
+    void testFullPipeWorkflow_scrambleToDraw() {
+        String puzzleName = "THREE"; // Corresponds to 3x3x3 cube
+
+        InputStream originalIn = System.in;
+        PrintStream originalOut = System.out;
+        ByteArrayOutputStream scrambleBaos = new ByteArrayOutputStream();
+        ByteArrayOutputStream drawBaos = new ByteArrayOutputStream();
+
+        try {
+            // === ScrambleCommand Phase ===
+            System.setOut(new PrintStream(scrambleBaos));
+
+            ScrambleCommand scrambleCommand = new ScrambleCommand();
+            JCommander.newBuilder()
+                .addObject(scrambleCommand)
+                .build()
+                .parse("-p", puzzleName, "-c", "1"); // Set puzzle and count to 1
+
+            scrambleCommand.run();
+            String generatedScramble = scrambleBaos.toString().trim(); // Trim to remove trailing newline
+
+            // Restore System.out before DrawCommand potentially prints errors to console during setup
+            System.setOut(originalOut); 
+
+            // Ensure scramble is not empty
+            assertNotNull(generatedScramble, "Generated scramble should not be null.");
+            assertFalse(generatedScramble.isEmpty(), "Generated scramble should not be empty.");
+
+            // === DrawCommand Phase ===
+            System.setIn(new ByteArrayInputStream(generatedScramble.getBytes()));
+            System.setOut(new PrintStream(drawBaos)); // Capture DrawCommand output
+
+            DrawCommand drawCommand = new DrawCommand();
+            JCommander.newBuilder()
+                .addObject(drawCommand)
+                .build()
+                .parse("-p", puzzleName); // Set puzzle, scramble comes from stdin
+
+            drawCommand.run();
+            String svgOutput = drawBaos.toString();
+
+            // Assert the SVG output
+            assertNotNull(svgOutput, "SVG output should not be null.");
+            assertFalse(svgOutput.isEmpty(), "SVG output should not be empty.");
+            assertTrue(svgOutput.contains("<svg"), "SVG output should contain '<svg'.");
+            assertTrue(svgOutput.contains("</svg>"), "SVG output should contain '</svg>'.");
+            assertTrue(svgOutput.contains("width="), "SVG output should contain 'width='.");
+            assertTrue(svgOutput.contains("height="), "SVG output should contain 'height='.");
+            assertFalse(svgOutput.contains("Error:"), "SVG output should not contain 'Error:'.");
+
+        } finally {
+            // Restore System.in and System.out
+            System.setIn(originalIn);
+            System.setOut(originalOut);
+        }
+    }
+}