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 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
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package org.apache.cayenne.crypto.unit;

import java.security.Key;

import org.apache.cayenne.crypto.transformer.bytes.BytesDecryptor;
import org.apache.cayenne.crypto.transformer.bytes.BytesEncryptor;

/**
 * A fake "cipher" used for unit tests that does simple bytes swapping.
 */
public class SwapBytesTransformer implements BytesEncryptor, BytesDecryptor {

    private static final SwapBytesTransformer instance = new SwapBytesTransformer();

    public static BytesEncryptor encryptor() {
        return instance;
    }

    public static BytesDecryptor decryptor() {
        return instance;
    }

    private SwapBytesTransformer() {
    }

    @Override
    public byte[] decrypt(byte[] input, int inputOffset, Key key) {

        byte[] output = new byte[input.length - inputOffset];
        System.arraycopy(input, inputOffset, output, 0, input.length - inputOffset);

        swap(output, 0, output.length - 1);
        return output;
    }

    @Override
    public byte[] encrypt(byte[] input, int outputOffset, byte[] flags) {

        byte[] output = new byte[input.length + outputOffset];

        System.arraycopy(input, 0, output, outputOffset, input.length);

        swap(output, outputOffset, outputOffset + input.length - 1);

        return output;
    }

    private void swap(byte[] buffer, int start, int end) {

        if (start >= end) {
            return;
        }

        byte b = buffer[end];
        buffer[end] = buffer[start];
        buffer[start] = b;

        swap(buffer, ++start, --end);
    }
}