import java.util.Arrays;
import java.util.BitSet;

import redis.clients.jedis.Jedis;

public class SieveOfEratosthenes {

	/**
	 * @param args
	 */
	public static void main(final String[] args) {

		// setup values
		final Jedis redis = new Jedis("localhost");
		final String sieveSetBit = "sieveSetBit";
		final String sieveSetKey = "sieveSetKey";
		final int length = 20;
		final BitSet sieve = new BitSet(length);
		sieve.flip(2, length);

		// create bitset of all values
		for (int i = 0; i < length; i++) {
			if (sieve.get(i)) {
				for (int j = i * 2; j < length; j += i) {
					sieve.set(j, false);
				}
			}
		}

		// Write 2 bitsets to redis
		// 1. setbit through redis
		for (int i = 0; i < sieve.length(); i++) {
			if (sieve.get(i)) {
				redis.setbit(sieveSetBit, i, true);
			}
		}

		// 2. Set entire bitset
		redis.set(sieveSetKey.getBytes(), sieve.toByteArray());

		// Compare bitsets from Redis when retrieved via getKey
		final String sieveBitString = redis.get(sieveSetBit);
		final String sieveKeyString = redis.get(sieveSetKey);
		final byte[] sieveBitBytes = redis.get(sieveSetBit.getBytes());
		final byte[] sieveKeyBytes = redis.get(sieveSetKey.getBytes());
		final BitSet setBitSieve = BitSet.valueOf(sieveBitString.getBytes());
		final BitSet setKeySieve = BitSet.valueOf(sieveKeyString.getBytes());
		final BitSet reverseSetBit = fromByteArray(sieveBitString.getBytes());
		final BitSet reverseSetKey = fromByteArray(sieveKeyString.getBytes());

		System.out.println(Arrays.toString(sieve.toByteArray()));
		System.out.println(sieve + " <== Original Sieve");
		System.out.println();
		System.out.println(Arrays.toString(sieveBitString.getBytes()));
		System.out.println(setBitSieve + " <== setbit/get (String) -> BitSet.valueOf()");
		System.out.println(reverseSetBit + " <== setbit/get (String) -> fromByteArray()");
		System.out.println();
		System.out.println(Arrays.toString(sieveKeyString.getBytes()));
		System.out.println(setKeySieve + " <== set/get (String) -> BitSet.valueOf()");
		System.out.println(reverseSetKey + " <== set/get (String) -> fromByteArray()");
		System.out.println();
		System.out.println(Arrays.toString(sieveKeyBytes));
		System.out.println(BitSet.valueOf(sieveKeyBytes) + " <== get/set (byte[] versions) -> BitSet.valueOf()");
		System.out.println();
		System.out.println(Arrays.toString(sieveBitBytes));
		System.out.println(BitSet.valueOf(sieveBitBytes) + " <== setbit/get (byte[] versions) -> BitSet.valueOf()");
		System.out.println(fromByteArrayReverse(sieveBitBytes) + " <== setbit/get (byte[] versions) -> fromByteArrayReverse()");

		System.out.println();
		System.out.println(Arrays.toString(sieveBitBytes));
		System.out.println(BitSet.valueOf(sieveBitBytes) + " <== setbit/get (byte[] versions) -> BitSet.valueOf()");
		System.out.println(toByteArrayReverse(sieve) + " <== reverse To Array before storages -> toByteArrayReverse()");
	}

	public static BitSet fromByteArrayReverse(final byte[] bytes) {
		final BitSet bits = new BitSet();
		for (int i = 0; i < bytes.length * 8; i++) {
			if ((bytes[i / 8] & (1 << (7 - (i % 8)))) != 0) {
				bits.set(i);
			}
		}
		return bits;
	}

	public static BitSet fromByteArray(final byte[] bytes) {
		final BitSet bits = new BitSet();
		for (int i = 0; i < bytes.length * 8; i++) {
			if ((bytes[bytes.length - i / 8 - 1] & (1 << (i % 8))) > 0) {
				bits.set(i);
			}
		}
		return bits;
	}

	public static byte[] toByteArrayReverse(BitSet bits) {
		final byte[] bytes = new byte[bits.length() / 8 + 1];
		for (int i = 0; i < bits.length(); i++) {
			if (bits.get(i)) {
				int value = bytes[i/8] | (1 <<( 7 -(i%8)));
				bytes[i/8] = (byte) value;
			}
		}
		return bytes;
	}
}