import de.maxhenkel.voicechat.voice.common.Secret;
import java.nio.ByteBuffer;
import java.security.SecureRandom;
import java.util.Arrays;
import java.util.UUID;
import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

public class ProtocolCryptoSelfTest {
    public static void main(String[] args) throws Exception {
        byte[] key = new byte[16];
        for (int i = 0; i < key.length; i++) key[i] = (byte) (i * 13 + 7);
        UUID legacyKey = uuidFromBytes(key);
        Secret hybridSecret = Secret.fromBytes(key);
        byte[] message = "SVC dual-protocol crypto self-test".getBytes("UTF-8");

        hybridSecret.setLegacyProtocol(true);
        for (int i = 0; i < 100; i++) {
            byte[] oldClientPacket = legacyEncrypt(legacyKey, message);
            if (!Arrays.equals(message, hybridSecret.decrypt(oldClientPacket))) {
                throw new AssertionError("Hybrid server failed to decrypt a 2.5 CBC packet");
            }
            byte[] hybridServerPacket = hybridSecret.encrypt(message);
            if (!Arrays.equals(message, legacyDecrypt(legacyKey, hybridServerPacket))) {
                throw new AssertionError("2.5 client failed to decrypt a hybrid server CBC packet");
            }
        }

        hybridSecret.setLegacyProtocol(false);
        for (int i = 0; i < 100; i++) {
            byte[] packet = hybridSecret.encrypt(message);
            if (!Arrays.equals(message, hybridSecret.decrypt(packet))) {
                throw new AssertionError("Hybrid server AES-GCM round-trip failed");
            }
        }
        System.out.println("PASS: 100 CBC client/server interop cycles and 100 GCM round-trips");
    }

    private static UUID uuidFromBytes(byte[] bytes) {
        ByteBuffer buffer = ByteBuffer.wrap(bytes);
        return new UUID(buffer.getLong(), buffer.getLong());
    }

    private static byte[] legacyEncrypt(UUID secret, byte[] data) throws Exception {
        byte[] iv = new byte[16];
        new SecureRandom().nextBytes(iv);
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, key(secret), new IvParameterSpec(iv));
        byte[] encrypted = cipher.doFinal(data);
        byte[] payload = Arrays.copyOf(iv, iv.length + encrypted.length);
        System.arraycopy(encrypted, 0, payload, iv.length, encrypted.length);
        return payload;
    }

    private static byte[] legacyDecrypt(UUID secret, byte[] payload) throws Exception {
        byte[] iv = Arrays.copyOfRange(payload, 0, 16);
        byte[] encrypted = Arrays.copyOfRange(payload, 16, payload.length);
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.DECRYPT_MODE, key(secret), new IvParameterSpec(iv));
        return cipher.doFinal(encrypted);
    }

    private static SecretKeySpec key(UUID secret) {
        byte[] key = ByteBuffer.allocate(16)
                .putLong(secret.getMostSignificantBits())
                .putLong(secret.getLeastSignificantBits())
                .array();
        return new SecretKeySpec(key, "AES");
    }
}