/*
 * Spreed Speak Freely.
 * Copyright (C) 2013-2014 struktur AG
 *
 * This file is part of Spreed Speak Freely.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
define(['jquery', 'underscore'], function($, _) {

  var Utils = function() {
  }

  Utils.prototype.mergeConstraints = function(cons1, cons2) {
    var merged = cons1;
    var name;
    for (name in cons2.mandatory) {
      merged.mandatory[name] = cons2.mandatory[name];
    }
    merged.optional.concat(cons2.optional);
    return merged;
  };

  Utils.prototype.extractSdp = function(sdpLine, pattern) {
    var result = sdpLine.match(pattern);
    return (result && result.length == 2)? result[1]: null;
  };

  Utils.prototype.addStereo = function(sdp) {
    // Set Opus in Stereo.

    var sdpLines = sdp.split('\r\n');
    var opusPayload = "";
    var fmtpLineIndex = null;
    var i;

    // Find opus payload.
    for (i=0; i < sdpLines.length; i++) {
      if (sdpLines[i].search('opus/48000') !== -1) {
        opusPayload = this.extractSdp(sdpLines[i], /:(\d+) opus\/48000/i);
        break;
      }
    }

    // Find the payload in fmtp line.
    for (i=0; i < sdpLines.length; i++) {
      if (sdpLines[i].search('a=fmtp') !== -1) {
        var payload = this.extractSdp(sdpLines[i], /a=fmtp:(\d+)/ );
        if (payload === opusPayload) {
          fmtpLineIndex = i;
          break;
        }
      }
    }
    // No fmtp line found.
    if (fmtpLineIndex === null) {
      console.log("Unable to add stereo (no fmtp line for opus payload)", opusPayload);
      return sdp;
    }

    // Append stereo=1 to fmtp line.
    sdpLines[fmtpLineIndex] = sdpLines[fmtpLineIndex].concat(' stereo=1');

    sdp = sdpLines.join('\r\n');
    console.log("Enabled opus stereo.");
    return sdp;

  };

  Utils.prototype.preferOpus = function(sdp) {
    // Set Opus as the preferred codec in SDP if Opus is present.

    var sdpLines = sdp.split('\r\n');
    var mLineIndex = null;
    var i;

    // Search for m line.
    for (i=0; i < sdpLines.length; i++) {
        if (sdpLines[i].search('m=audio') !== -1) {
          mLineIndex = i;
          break;
        }
    }
    if (mLineIndex === null) {
      return sdp;
    }

    // If Opus is available, set it as the default in m line.
    for (i=0; i < sdpLines.length; i++) {
      if (sdpLines[i].search('opus/48000') !== -1) {
        var opusPayload = this.extractSdp(sdpLines[i], /:(\d+) opus\/48000/i);
        if (opusPayload) {
          sdpLines[mLineIndex] = this.setDefaultCodec(sdpLines[mLineIndex], opusPayload);
        }
        break;
      }
    }

    // Remove CN in m line and sdp.
    sdpLines = this.removeCN(sdpLines, mLineIndex);

    sdp = sdpLines.join('\r\n');
    return sdp;

  };

  Utils.prototype.setDefaultCodec = function (mLine, payload) {
    // Set the selected codec to the first in m line.
    var elements = mLine.split(' ');
    var newLine = [];
    var index = 0;
    for (var i = 0; i < elements.length; i++) {
      // Format of media starts from the fourth.
      if (index === 3) {
        newLine[index++] = payload; // Put target payload to the first.
      }
      if (elements[i] !== payload) {
        newLine[index++] = elements[i];
      }
    }
    return newLine.join(' ');
  };

  Utils.prototype.removeCN = function(sdpLines, mLineIndex) {
    // Strip CN from sdp before CN constraints is ready.
    var mLineElements = sdpLines[mLineIndex].split(' ');
    // Scan from end for the convenience of removing an item.
    for (var i = sdpLines.length-1; i >= 0; i--) {
      var payload = this.extractSdp(sdpLines[i], /a=rtpmap:(\d+) CN\/\d+/i);
      if (payload) {
        var cnPos = mLineElements.indexOf(payload);
        if (cnPos !== -1) {
          // Remove CN payload from m line.
          mLineElements.splice(cnPos, 1);
        }
        // Remove CN line in sdp
        sdpLines.splice(i, 1);
      }
    }
    sdpLines[mLineIndex] = mLineElements.join(' ');
    return sdpLines;
  };

  var utils = new Utils();
  return utils;

});