Завершить инженерный кандидат Stage 5

app/src/main/java/com/projectsacrifice/game/ReplayStateSignature.java

@@ -0,0 +1,28 @@
+package com.projectsacrifice.game;
+
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+/** Stable compact fingerprint for exact deterministic replay comparisons. */
+public final class ReplayStateSignature {
+    private ReplayStateSignature() {}
+
+    public static String of(byte[] puzzleState, boolean completed, boolean allDoorsOpen) {
+        if (puzzleState == null) throw new IllegalArgumentException("Puzzle state is required");
+        try {
+            MessageDigest digest = MessageDigest.getInstance("SHA-256");
+            digest.update((byte) (completed ? 1 : 0));
+            digest.update((byte) (allDoorsOpen ? 1 : 0));
+            digest.update(puzzleState);
+            byte[] bytes = digest.digest();
+            StringBuilder hex = new StringBuilder(32);
+            for (int i = 0; i < 16; i++) {
+                hex.append(Character.forDigit((bytes[i] >>> 4) & 0xf, 16));
+                hex.append(Character.forDigit(bytes[i] & 0xf, 16));
+            }
+            return hex.toString();
+        } catch (NoSuchAlgorithmException impossible) {
+            throw new IllegalStateException("SHA-256 unavailable", impossible);
+        }
+    }
+}