1 files changed, 114 insertions, 0 deletions
diff --git a/comm/chat/protocols/matrix/lib/sdp-transform/writer.js b/comm/chat/protocols/matrix/lib/sdp-transform/writer.js
new file mode 100644
index 0000000000..decdf480a8
--- /dev/null
+++ b/comm/chat/protocols/matrix/lib/sdp-transform/writer.js
@@ -0,0 +1,114 @@
+var grammar = require('./grammar');
+
+// customized util.format - discards excess arguments and can void middle ones
+var formatRegExp = /%[sdv%]/g;
+var format = function (formatStr) {
+  var i = 1;
+  var args = arguments;
+  var len = args.length;
+  return formatStr.replace(formatRegExp, function (x) {
+    if (i >= len) {
+      return x; // missing argument
+    }
+    var arg = args[i];
+    i += 1;
+    switch (x) {
+    case '%%':
+      return '%';
+    case '%s':
+      return String(arg);
+    case '%d':
+      return Number(arg);
+    case '%v':
+      return '';
+    }
+  });
+  // NB: we discard excess arguments - they are typically undefined from makeLine
+};
+
+var makeLine = function (type, obj, location) {
+  var str = obj.format instanceof Function ?
+    (obj.format(obj.push ? location : location[obj.name])) :
+    obj.format;
+
+  var args = [type + '=' + str];
+  if (obj.names) {
+    for (var i = 0; i < obj.names.length; i += 1) {
+      var n = obj.names[i];
+      if (obj.name) {
+        args.push(location[obj.name][n]);
+      }
+      else { // for mLine and push attributes
+        args.push(location[obj.names[i]]);
+      }
+    }
+  }
+  else {
+    args.push(location[obj.name]);
+  }
+  return format.apply(null, args);
+};
+
+// RFC specified order
+// TODO: extend this with all the rest
+var defaultOuterOrder = [
+  'v', 'o', 's', 'i',
+  'u', 'e', 'p', 'c',
+  'b', 't', 'r', 'z', 'a'
+];
+var defaultInnerOrder = ['i', 'c', 'b', 'a'];
+
+
+module.exports = function (session, opts) {
+  opts = opts || {};
+  // ensure certain properties exist
+  if (session.version == null) {
+    session.version = 0; // 'v=0' must be there (only defined version atm)
+  }
+  if (session.name == null) {
+    session.name = ' '; // 's= ' must be there if no meaningful name set
+  }
+  session.media.forEach(function (mLine) {
+    if (mLine.payloads == null) {
+      mLine.payloads = '';
+    }
+  });
+
+  var outerOrder = opts.outerOrder || defaultOuterOrder;
+  var innerOrder = opts.innerOrder || defaultInnerOrder;
+  var sdp = [];
+
+  // loop through outerOrder for matching properties on session
+  outerOrder.forEach(function (type) {
+    grammar[type].forEach(function (obj) {
+      if (obj.name in session && session[obj.name] != null) {
+        sdp.push(makeLine(type, obj, session));
+      }
+      else if (obj.push in session && session[obj.push] != null) {
+        session[obj.push].forEach(function (el) {
+          sdp.push(makeLine(type, obj, el));
+        });
+      }
+    });
+  });
+
+  // then for each media line, follow the innerOrder
+  session.media.forEach(function (mLine) {
+    sdp.push(makeLine('m', grammar.m[0], mLine));
+
+    innerOrder.forEach(function (type) {
+      grammar[type].forEach(function (obj) {
+        if (obj.name in mLine && mLine[obj.name] != null) {
+          sdp.push(makeLine(type, obj, mLine));
+        }
+        else if (obj.push in mLine && mLine[obj.push] != null) {
+          mLine[obj.push].forEach(function (el) {
+            sdp.push(makeLine(type, obj, el));
+          });
+        }
+      });
+    });
+  });
+
+  return sdp.join('\r\n') + '\r\n';
+};