/*
    This file is part of Peers, a java SIP softphone.

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    any later version.

    This program 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 General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
    
    Copyright 2007, 2008, 2009, 2010 Yohann Martineau 
*/

package peers.sip;


import java.net.InetAddress;

import peers.sip.core.useragent.UAS;
import peers.sip.syntaxencoding.SipHeaderFieldMultiValue;
import peers.sip.syntaxencoding.SipHeaderFieldName;
import peers.sip.syntaxencoding.SipHeaderFieldValue;
import peers.sip.syntaxencoding.SipHeaders;
import peers.sip.transport.SipMessage;

@SuppressWarnings("unused")
public class Utils {

    public static final String PEERSHOME_SYSTEM_PROPERTY = "peers.home";
    public static final String DEFAULT_PEERS_HOME = ".";

    public static SipHeaderFieldValue getTopVia(SipMessage sipMessage) {
        SipHeaders sipHeaders = sipMessage.getSipHeaders();
        SipHeaderFieldName viaName = new SipHeaderFieldName(RFC3261.HDR_VIA);
        SipHeaderFieldValue via = sipHeaders.get(viaName);
        if (via instanceof SipHeaderFieldMultiValue) {
            via = ((SipHeaderFieldMultiValue)via).getValues().get(0);
        }
        return via;
    }
    
    public static String generateTag() {
        return randomString(8);
    }
    
    public static String generateCallID(InetAddress inetAddress) {
        //TODO make a hash using current time millis, public ip @, private @, and a random string
        return randomString(8) +
                '-' +
                System.currentTimeMillis() +
                '@' +
                inetAddress.getHostName();
    }
    
    public static String generateBranchId() {
        //TODO must be unique across space and time...
        return RFC3261.BRANCHID_MAGIC_COOKIE +
                //TODO must be unique across space and time...
                randomString(9);
    }
    
    public static String getMessageCallId(SipMessage sipMessage) {
        SipHeaderFieldValue callId = sipMessage.getSipHeaders().get(
                new SipHeaderFieldName(RFC3261.HDR_CALLID));
        return callId.getValue();
    }
    
    public static String randomString(int length) {
        String chars = "abcdefghijklmnopqrstuvwxyz" +
                       "ABCDEFGHIFKLMNOPRSTUVWXYZ" +
                       "0123456789";
        StringBuilder buf = new StringBuilder(length);
        for (int i = 0; i < length; ++i) {
            int pos = (int)Math.round(Math.random() * (chars.length() - 1));
            buf.append(chars.charAt(pos));
        }
        return buf.toString();
    }
    
    public static void copyHeader(SipMessage src, SipMessage dst, String name) {
        SipHeaderFieldName sipHeaderFieldName = new SipHeaderFieldName(name);
        SipHeaderFieldValue sipHeaderFieldValue = src.getSipHeaders().get(sipHeaderFieldName);
        if (sipHeaderFieldValue != null) {
            dst.getSipHeaders().add(sipHeaderFieldName, sipHeaderFieldValue);
        }
    }
    
    public static String getUserPart(String sipUri) {
        int start = sipUri.indexOf(RFC3261.SCHEME_SEPARATOR);
        int end = sipUri.indexOf(RFC3261.AT);
        return sipUri.substring(start + 1, end);
    }

    /**
     * adds Max-Forwards Supported and Require headers
     * @param headers the headers to add to
     */
    public static void addCommonHeaders(SipHeaders headers) {
        //Max-Forwards
        
        headers.add(new SipHeaderFieldName(RFC3261.HDR_MAX_FORWARDS),
                new SipHeaderFieldValue(
                        String.valueOf(RFC3261.DEFAULT_MAXFORWARDS)));
        
        //TODO Supported and Require
    }

    public static String generateAllowHeader() {
        StringBuilder buf = new StringBuilder();
        for (String supportedMethod: UAS.SUPPORTED_METHODS) {
            buf.append(supportedMethod);
            buf.append(", ");
        }
        int bufLength = buf.length();
        buf.delete(bufLength - 2, bufLength);
        return buf.toString();
    }

}