/**
 * @fileoverview Incoming SIP Message Sanity Check
 */

/**
 * SIP message sanity check.
 * @augments JsSIP
 * @function
 * @param {JsSIP.IncomingMessage} message
 * @param {JsSIP.UA} ua
 * @param {JsSIP.Transport} transport
 * @returns {Boolean}
 */
(function(JsSIP) {
var sanityCheck,
 LOG_PREFIX = JsSIP.name +' | '+ 'SANITY CHECK' +' | ',

 message, ua, transport,
 requests = [],
 responses = [],
 all = [];

/*
 * Sanity Check for incoming Messages
 *
 * Requests:
 *  - _rfc3261_8_2_2_1_ Receive a Request with a non supported URI scheme
 *  - _rfc3261_16_3_4_ Receive a Request already sent by us
 *   Does not look at via sent-by but at jssip_id, which is inserted as
 *   a prefix in all initial requests generated by the ua
 *  - _rfc3261_18_3_request_ Body Content-Length
 *  - _rfc3261_8_2_2_2_ Merged Requests
 *
 * Responses:
 *  - _rfc3261_8_1_3_3_ Multiple Via headers
 *  - _rfc3261_18_1_2_ sent-by mismatch
 *  - _rfc3261_18_3_response_ Body Content-Length
 *
 * All:
 *  - Minimum headers in a SIP message
 */

// Sanity Check functions for requests
function rfc3261_8_2_2_1() {
  if(message.s('to').uri.scheme !== 'sip') {
    reply(416);
    return false;
  }
}

function rfc3261_16_3_4() {
  if(!message.to_tag) {
    if(message.call_id.substr(0, 5) === ua.configuration.jssip_id) {
      reply(482);
      return false;
    }
  }
}

function rfc3261_18_3_request() {
  var len = JsSIP.Utils.str_utf8_length(message.body),
  contentLength = message.getHeader('content-length');

  if(len < contentLength) {
    reply(400);
    return false;
  }
}

function rfc3261_8_2_2_2() {
  var tr, idx,
    fromTag = message.from_tag,
    call_id = message.call_id,
    cseq = message.cseq;

  if(!message.to_tag) {
    if(message.method === JsSIP.C.INVITE) {
      tr = ua.transactions.ist[message.via_branch];
      if(!tr) {
        return;
      } else {
        for(idx in ua.transactions.ist) {
          tr = ua.transactions.ist[idx];
          if(tr.request.from_tag === fromTag && tr.request.call_id === call_id && tr.request.cseq === cseq) {
            reply(482);
            return false;
          }
        }
      }
    } else {
      tr = ua.transactions.nist[message.via_branch];
      if(!tr) {
        return;
      } else {
        for(idx in ua.transactions.nist) {
          tr = ua.transactions.nist[idx];
          if(tr.request.from_tag === fromTag && tr.request.call_id === call_id && tr.request.cseq === cseq) {
            reply(482);
            return false;
          }
        }
      }
    }
  }
}

// Sanity Check functions for responses
function rfc3261_8_1_3_3() {
  if(message.countHeader('via') > 1) {
    console.warn(LOG_PREFIX +'More than one Via header field present in the response. Dropping the response');
    return false;
  }
}

function rfc3261_18_1_2() {
  var via_host = ua.configuration.via_host;
  if(message.via.host !== via_host) {
    console.warn(LOG_PREFIX +'Via host in the response does not match UA Via host value. Dropping the response');
    return false;
  }
}

function rfc3261_18_3_response() {
  var
    len = JsSIP.Utils.str_utf8_length(message.body),
    contentLength = message.getHeader('content-length');

    if(len < contentLength) {
      console.warn(LOG_PREFIX +'Message body length is lower than the value in Content-Length header field. Dropping the response');
      return false;
    }
}

// Sanity Check functions for requests and responses
function minimumHeaders() {
  var
    mandatoryHeaders = ['from', 'to', 'call_id', 'cseq', 'via'],
    idx = mandatoryHeaders.length;

  while(idx--) {
    if(!message.hasHeader(mandatoryHeaders[idx])) {
      console.warn(LOG_PREFIX +'Missing mandatory header field : '+ mandatoryHeaders[idx] +'. Dropping the response');
      return false;
    }
  }
}

// Reply
function reply(status_code) {
  var to,
    response = "SIP/2.0 " + status_code + " " + JsSIP.C.REASON_PHRASE[status_code] + "\r\n",
    via_length = message.countHeader('via'),
    idx = 0;

  for(idx; idx < via_length; idx++) {
    response += "Via: " + message.getHeader('via', idx) + "\r\n";
  }

  to = message.getHeader('To');

  if(!message.to_tag) {
    to += ';tag=' + JsSIP.Utils.newTag();
  }

  response += "To: " + to + "\r\n";
  response += "From: " + message.getHeader('From') + "\r\n";
  response += "Call-ID: " + message.call_id + "\r\n";
  response += "CSeq: " + message.cseq + " " + message.method + "\r\n";
  response += "\r\n";

  transport.send(response);
}

requests.push(rfc3261_8_2_2_1);
requests.push(rfc3261_16_3_4);
requests.push(rfc3261_18_3_request);
requests.push(rfc3261_8_2_2_2);

responses.push(rfc3261_8_1_3_3);
responses.push(rfc3261_18_1_2);
responses.push(rfc3261_18_3_response);

all.push(minimumHeaders);

sanityCheck = function(m, u, t) {
  var len, pass;

  message = m;
  ua = u;
  transport = t;

  len = all.length;
  while(len--) {
    pass = all[len](message);
    if(pass === false) {
      return false;
    }
  }

  if(message instanceof JsSIP.IncomingRequest) {
    len = requests.length;
    while(len--) {
      pass = requests[len](message);
      if(pass === false) {
        return false;
      }
    }
  }

  else if(message instanceof JsSIP.IncomingResponse) {
    len = responses.length;
    while(len--) {
      pass = responses[len](message);
      if(pass === false) {
        return false;
      }
    }
  }

  //Everything is OK
  return true;
};

JsSIP.sanityCheck = sanityCheck;
}(JsSIP));