import java.util.ArrayList;

public class PearsonHash implements HashFunction<String> {
	private Character[] charArray1 = new Character[256];
	private Character[] charArray2 = new Character[256];

	public PearsonHash() {
		charArray1 = createTable();
		charArray2 = createTable();
	}

	private Character[] createTable() {
		ArrayList<Character> myArrayList = new ArrayList<Character>(256);
		for (int i = 0; i < 256; i++) {
			char charact = (char) i;
			myArrayList.add(charact);
		}
		java.util.Collections.shuffle(myArrayList);
		Character[] characterArray = new Character[256];
		myArrayList.toArray(characterArray);
		return  characterArray;
	}

	@Override
	public int hash(String key) {
		int len =  key.length();
		int hash1 = len;
		int hash2 = len;

		for (int i = 0; i < len; i++) {
			char curChar = ((String) key).charAt(i);
			int index1 = hash1 ^ curChar;
			hash1 = charArray1[index1];
			int index2 = hash2 ^ curChar;
			hash2 = charArray2[index2];
		}

		return ((hash1 << 16) | (hash2 << 8) | hash1);
	}

}