/*
 * otr4j, the open source java otr library.
 *
 * Distributable under LGPL license. See terms of license at gnu.org.
 */
package net.java.otr4j.io.messages;

import java.io.IOException;
import java.util.Arrays;

import net.java.otr4j.OtrException;
import net.java.otr4j.crypto.OtrCryptoEngineImpl;
import net.java.otr4j.io.SerializationUtils;

/** @author George Politis */
public class SignatureMessage extends AbstractEncodedMessage {
    // Fields.
    public byte[] xEncrypted;
    public byte[] xEncryptedMAC;

    // Ctor.
    protected SignatureMessage(int messageType, int protocolVersion, byte[] xEncrypted,
            byte[] xEncryptedMAC) {
        super(messageType, protocolVersion);
        this.xEncrypted = xEncrypted;
        this.xEncryptedMAC = xEncryptedMAC;
    }

    public SignatureMessage(int protocolVersion, byte[] xEncrypted, byte[] xEncryptedMAC) {
        this(MESSAGE_SIGNATURE, protocolVersion, xEncrypted, xEncryptedMAC);
    }

    // Memthods.
    public byte[] decrypt(byte[] key) throws OtrException {
        return new OtrCryptoEngineImpl().aesDecrypt(key, null, xEncrypted);
    }

    public boolean verify(byte[] key) throws OtrException {
        // Hash the key.
        byte[] xbEncrypted;
        try {
            xbEncrypted = SerializationUtils.writeData(xEncrypted);
        } catch (IOException e) {
            throw new OtrException(e);
        }

        byte[] xEncryptedMAC = new OtrCryptoEngineImpl().sha256Hmac160(xbEncrypted, key);
        // Verify signature.
        return Arrays.equals(this.xEncryptedMAC, xEncryptedMAC);
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = super.hashCode();
        result = prime * result + Arrays.hashCode(xEncrypted);
        result = prime * result + Arrays.hashCode(xEncryptedMAC);
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (!super.equals(obj))
            return false;
        if (getClass() != obj.getClass())
            return false;
        SignatureMessage other = (SignatureMessage) obj;
        if (!Arrays.equals(xEncrypted, other.xEncrypted))
            return false;
        if (!Arrays.equals(xEncryptedMAC, other.xEncryptedMAC))
            return false;
        return true;
    }
}