feat(04-03): implement DefineValidation helpers (name regex + componentwise min/max)

src/main/java/com/mythlane/gravityflip/command/DefineValidation.java

@@ -0,0 +1,53 @@
+package com.mythlane.gravityflip.command;
+
+import java.util.regex.Pattern;
+
+/**
+ * Pure-data validation helpers for {@code /gravityflip define <name>}.
+ *
+ * <p>No Hytale runtime dependency — same philosophy as {@code FallDamageGuard}
+ * and {@code WandSelectionStore}. Testable with JUnit alone.
+ *
+ * <p>Exposes :
+ * <ul>
+ *   <li>{@link #isValidName(String)} — region name regex gate.</li>
+ *   <li>{@link #componentwiseMin(int[], int[])} / {@link #componentwiseMax(int[], int[])}
+ *       — so the builder can click pos1/pos2 in any order.</li>
+ * </ul>
+ *
+ * <p>See {@code DefineValidationTest} for the accepted/rejected-name corpus and
+ * the rationale for the inflate-max-by-1 convention applied in
+ * {@code GravityFlipDefineSubCommand}.
+ */
+public final class DefineValidation {
+
+    private static final Pattern NAME = Pattern.compile("^[a-zA-Z0-9_-]{1,32}$");
+
+    private DefineValidation() {}
+
+    /**
+     * Returns {@code true} iff {@code n} matches {@code ^[a-zA-Z0-9_-]{1,32}$}.
+     * Rejects {@code null}, blank, spaces, path separators, non-ASCII.
+     */
+    public static boolean isValidName(String n) {
+        return n != null && NAME.matcher(n).matches();
+    }
+
+    /** Returns {@code {min(a.x,b.x), min(a.y,b.y), min(a.z,b.z)}}. */
+    public static int[] componentwiseMin(int[] a, int[] b) {
+        return new int[]{
+                Math.min(a[0], b[0]),
+                Math.min(a[1], b[1]),
+                Math.min(a[2], b[2])
+        };
+    }
+
+    /** Returns {@code {max(a.x,b.x), max(a.y,b.y), max(a.z,b.z)}}. */
+    public static int[] componentwiseMax(int[] a, int[] b) {
+        return new int[]{
+                Math.max(a[0], b[0]),
+                Math.max(a[1], b[1]),
+                Math.max(a[2], b[2])
+        };
+    }
+}