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);
        }
    }
}