var toIntIfInt = function (v) {
  return String(Number(v)) === v ? Number(v) : v;
};

var attachProperties = function (match, location, names, rawName) {
  if (rawName && !names) {
    location[rawName] = toIntIfInt(match[1]);
  }
  else {
    for (var i = 0; i < names.length; i += 1) {
      if (match[i+1] != null) {
        location[names[i]] = toIntIfInt(match[i+1]);
      }
    }
  }
};

var parseReg = function (obj, location, content) {
  var needsBlank = obj.name && obj.names;
  if (obj.push && !location[obj.push]) {
    location[obj.push] = [];
  }
  else if (needsBlank && !location[obj.name]) {
    location[obj.name] = {};
  }
  var keyLocation = obj.push ?
    {} :  // blank object that will be pushed
    needsBlank ? location[obj.name] : location; // otherwise, named location or root

  attachProperties(content.match(obj.reg), keyLocation, obj.names, obj.name);

  if (obj.push) {
    location[obj.push].push(keyLocation);
  }
};

var validLine = RegExp.prototype.test.bind(/^([a-z])=(.*)/);

function parseSDP(sdp) {
  var session = {}
    , media = []
    , location = session; // points at where properties go under (one of the above)

  // parse lines we understand
  sdp.split(/(\r\n|\r|\n)/).filter(validLine).forEach(function (l) {
    var type = l[0];
    var content = l.slice(2);
    if (type === 'm') {
      media.push({rtp: [], fmtp: []});
      location = media[media.length-1]; // point at latest media line
    }

    for (var j = 0; j < (grammar[type] || []).length; j += 1) {
      var obj = grammar[type][j];
      if (obj.reg.test(content)) {
        return parseReg(obj, location, content);
      }
    }
  });

  session.media = media; // link it up
  return session;
};

var paramReducer = function (acc, expr) {
  var s = expr.split(/=(.+)/, 2);
  if (s.length === 2) {
    acc[s[0]] = toIntIfInt(s[1]);
  }
  return acc;
};

function parseParamsSDP(str) {
  return str.split(/\;\s?/).reduce(paramReducer, {});
};

function parsePayloadsSDP(str) {
  return str.split(' ').map(Number);
};

function parseRemoteCandidatesSDP(str) {
  var candidates = [];
  var parts = str.split(' ').map(toIntIfInt);
  for (var i = 0; i < parts.length; i += 3) {
    candidates.push({
      component: parts[i],
      ip: parts[i + 1],
      port: parts[i + 2]
    });
  }
  return candidates;
};

function parseImageAttributesSDP(str) {
  return str.split(' ').map(function (item) {
    return item.substring(1, item.length-1).split(',').reduce(paramReducer, {});
  });
};

function parseSimulcastStreamListSDP(str) {
  return str.split(';').map(function (stream) {
    return stream.split(',').map(function (format) {
      var scid, paused = false;

      if (format[0] !== '~') {
        scid = toIntIfInt(format);
      } else {
        scid = toIntIfInt(format.substring(1, format.length));
        paused = true;
      }

      return {
        scid: scid,
        paused: paused
      };
    });
  });
};