Add classes for drawing snowflakes

app/src/main/java/ch/nuth/zhaw/exbox/SnowflakeServer.java

@@ -0,0 +1,39 @@
+package ch.nuth.zhaw.exbox;
+
+/**
+ * Provides the functionality to draw a snowflake.
+ */
+public class SnowflakeServer implements CommandExecutor {
+    @Override
+    public String execute(String command) {
+        int recursionLevel = Integer.parseInt(command);
+        Turtle turtle = Turtle.instance();
+        drawSnowflake(turtle, recursionLevel);
+        return turtle.getTrace();
+    }
+
+    public void drawSnowflake(Turtle turtle, int recursionLevel) {
+        turtle.reset(0.1, 0.266);
+        turtle.turn(60);
+
+        for (int i = 0; i < 3; i++) {
+            drawLine(turtle, recursionLevel, 0.8);
+            turtle.turn(-120);
+        }
+    }
+
+    public void drawLine(Turtle turtle, int recursionLevel, double destination) {
+        if (recursionLevel == 0) {
+            turtle.move(destination);
+        } else {
+            double distance = destination / 3;
+
+            for (int i = 0; i < 3; i++) {
+                drawLine(turtle, recursionLevel - 1, distance);
+                turtle.turn(i % 2 == 0 ? 60 : -120);
+            }
+
+            drawLine(turtle, recursionLevel - 1, distance);
+        }
+    }
+}

app/src/main/java/ch/nuth/zhaw/exbox/TestGraphicServer.java

@@ -0,0 +1,17 @@
+package ch.nuth.zhaw.exbox;
+
+public class TestGraphicServer implements CommandExecutor {
+    String figure = "<line x1=\"0.1\" y1 = \"0.8\" x2=\"0.9\" y2 = \"0.8\" />\n" +
+            "<line x1=\"0.2\" y1 = \"0.4\" x2=\"0.2\" y2 = \"0.8\" />\n" +
+            "<line x1=\"0.3\" y1 = \"0.4\" x2=\"0.3\" y2 = \"0.8\" />\n" +
+            "<line x1=\"0.3\" y1 = \"0.4\" x2=\"0.7\" y2 = \"0.4\" />\n" +
+            "<line x1=\"0.3\" y1 = \"0.6\" x2=\"0.4\" y2 = \"0.6\" />\n" +
+            "<line x1=\"0.5\" y1 = \"0.8\" x2=\"0.5\" y2 = \"0.6\" />\n" +
+            "<line x1=\"0.5\" y1 = \"0.6\" x2=\"0.7\" y2 = \"0.6\" />\n" +
+            "<line x1=\"0.7\" y1 = \"0.6\" x2=\"0.7\" y2 = \"0.4\" />\n" +
+            "<line x1=\"0.8\" y1 = \"0.4\" x2=\"0.8\" y2 = \"0.8\" />\n";
+
+    public String execute(String command) {
+        return figure;
+    }
+}

app/src/main/java/ch/nuth/zhaw/exbox/Turtle.java

@@ -0,0 +1,63 @@
+package ch.nuth.zhaw.exbox;
+
+public class Turtle {
+    private static StringBuffer b;
+    private static double x, y;
+    private static double angle;
+    private static Turtle theTurtle;
+
+    public static Turtle instance() {
+        if (theTurtle == null) {
+            theTurtle = new Turtle();
+        }
+
+        return theTurtle;
+    }
+
+    public Turtle() {
+        this(0, 0);
+    }
+
+    public Turtle(double x, double y) {
+        reset(x, y);
+        theTurtle = this;
+    }
+
+    public void reset(double x, double y) {
+        b = new StringBuffer();
+        Turtle.x = x;
+        Turtle.y = y;
+        angle = 0;
+    }
+
+    public void clear() {
+        reset(0, 0);
+    }
+
+    public String getTrace() {
+        return b.toString();
+    }
+
+    private double round(double d) {
+        return Math.round(d * 10000) / 10000.0;
+    }
+
+    public void move(double dist) {
+        b.append("<line x1=\"");
+        b.append(Double.toString(round(x)));
+        b.append("\" y1=\"");
+        b.append(Double.toString(round(y)));
+        b.append("\" ");
+        x += Math.cos(angle) * dist;
+        y += Math.sin(angle) * dist;
+        b.append("x2=\"");
+        b.append(Double.toString(round(x)));
+        b.append("\" y2=\"");
+        b.append(Double.toString(round(y)));
+        b.append("\"/>\n");
+    }
+
+    public void turn(double turnAngle) {
+        angle += turnAngle * Math.PI / 180;
+    }
+}