/*
 * TeleStax, Open Source Cloud Communications
 * Copyright 2011-2013, Telestax Inc and individual contributors
 * by the @authors tag.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.mobicents.protocols.ss7.sccp.impl.parameter;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import javolution.xml.XMLSerializable;
import org.mobicents.protocols.ss7.sccp.message.ParseException;
import org.mobicents.protocols.ss7.sccp.parameter.EncodingScheme;
import org.mobicents.protocols.ss7.sccp.parameter.EncodingSchemeType;

/**
 * Default impl which supports simple encoding.
 * @author baranowb
 * @author sergey vetyutnev
 */
public class DefaultEncodingScheme implements EncodingScheme, XMLSerializable {
    public static final EncodingScheme INSTANCE = new DefaultEncodingScheme();
    public static final int SCHEMA_CODE = 0;

    public DefaultEncodingScheme() {
    }

    @Override
    public EncodingSchemeType getType() {
        return EncodingSchemeType.UNKNOWN;
    }

    @Override
    public byte getSchemeCode() {
        return SCHEMA_CODE;
    }

    protected boolean isOdd() {
        //Trick for single codebase
        return false;
    }

    @Override
    public void encode(String digits, OutputStream out) throws ParseException {
        try {
            boolean odd;
            if (getSchemeCode() != 0) {
                odd = isOdd();
            } else {
                odd = digits.length() % 2 != 0;
            }

            int b = 0;

            int count = odd ? digits.length() - 1 : digits.length();

            for (int i = 0; i < count - 1; i += 2) {
                String ds1 = digits.substring(i, i + 1);
                String ds2 = digits.substring(i + 1, i + 2);

                int d1 = Integer.parseInt(ds1, 16);
                int d2 = Integer.parseInt(ds2, 16);

                b = (byte) (d2 << 4 | d1);
                out.write(b);
            }

            // if number is odd append last digit with filler
            if (odd) {
                String ds1 = digits.substring(count, count + 1);
                int d = Integer.parseInt(ds1, 16);

                b = (byte) (d & 0x0f);
                out.write(b);
            }
        } catch (IOException e) {
            throw new ParseException(e);
        }
    }

    @Override
    public String decode(InputStream is) throws ParseException {
        try {
            int b;
            StringBuilder digits = new StringBuilder();

            while (is.available() > 0) {
                b = is.read() & 0xff;

                digits.append(Integer.toHexString(b & 0x0f));
                digits.append(Integer.toHexString((b & 0xf0) >> 4));
            }

            if (isOdd()) {
                digits.deleteCharAt(digits.length() - 1);
            }

            return digits.toString().toLowerCase();
        } catch (IOException e) {
            throw new ParseException(e);
        }
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = getSchemeCode();
        result = prime * result;
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        if(this.getSchemeCode() == ((EncodingScheme)obj).getSchemeCode())
            return true;
        return false;
    }

    @Override
    public String toString() {
        return getClass().getSimpleName()+"[type=" + getType() + ", code=" + getSchemeCode() + "]";
    }
}