package betsy.bpel.virtual.common.messages.deploy;

import java.io.Serializable;
import java.util.zip.CRC32;

/**
 * A checksum representation of the given data.<br>
 * Can be used to compare if sent and received data are equal or if information
 * has been lost or corrupted. <br>
 *
 * @author Cedric Roeck
 * @version 1.0
 */
public class Checksum implements Serializable {

    /**
     * SerialVersionUID.
     */
    private static final long serialVersionUID = 1L;

    private final long data;

    /**
     * Create a new instance of the object. <br>
     *
     * @param data {@link Checksum} is created based on the given data
     */
    private Checksum(final byte... data) {
        if (data == null) {
            throw new IllegalArgumentException("data must not be null");
        }

        CRC32 crc = new CRC32();
        crc.update(data);
        this.data = crc.getValue();
    }

    /**
     * Create a {@link Checksum} based on the given data.
     *
     * @param data used to calculate the checksum
     * @return the calculated checksum
     */
    public static Checksum createChecksum(final byte... data) {
        return new Checksum(data);
    }

    /**
     * Check whether the given data does match the given checksum.
     *
     * @param data     will be used to calculate a new checksum
     * @param checksum comparison reference, data must match this checksum
     * @return true if data matches checksum, false if checksum belongs to
     *         different data
     */
    public static boolean isValid(final byte[] data, Checksum checksum) {
        return checksum.equals(new Checksum(data));
    }

    @Override
    public boolean equals(Object otherO) {
        if (this == otherO) {
            return true;
        }
        if (otherO == null) {
            return false;
        }
        if (!(otherO instanceof Checksum)) {
            return false;
        }

        Checksum other = (Checksum) otherO;

        return this.data == other.getValue();
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + Float.floatToIntBits(data);
        return result;
    }

    @Override
    public String toString() {
        return Long.toString(getValue());
    }

    /**
     * Get the checksum value as primitive long representation.
     *
     * @return raw checksum value
     */
    private long getValue() {
        return this.data;
    }
}