Define ReSpec processor for cross-reference to JSEP

Mechanics of #337

webrtc.js

@@ -89,4 +89,48 @@ var respecConfig = {
       ]
     }
   ],
+  preProcess: [
+      function linkToJsep() {
+          var xhr = new XMLHttpRequest();
+          xhr.open('GET', 'jsep-mapping/map.json');
+          xhr.onload = function(e) {
+              var data = JSON.parse(this.responseText);
+              if (respecConfig.localBiblio.JSEP.date !== data.metadata.date) {
+                  respecEvents.pub("warn", "Date of JSEP draft in localBiblio (" + respecConfig.localBiblio.date + ") does not match date of JSEP draft used in map.json (" + data.metadata.date + ").");
+              }
+              // Replace all
+              //    <span data-jsep="foo">[[!JSEP]]</a>
+              // with
+              //    <span>[[!JSEP]] (<a href="...#X.Y">section X.Y.</a>)
+              // based on mapping maintained in jsep.json
+              Array.prototype.forEach.call(
+                  document.querySelectorAll("*[data-jsep]"),
+                  function (el) {
+                      var sectionLink = document.createElement("a");
+                      var jsepSection = data.sections['sec.' + el.dataset.jsep];
+                      if (!jsepSection) {
+                          respecEvents.pub("warn", "Reference to inexistent JSEP section with anchor 'sec." + el.dataset.jsep + "'.");
+                          return;
+                      }
+                      el.removeAttribute("data-jsep");
+                      sectionLink.href = "https://tools.ietf.org/html/draft-ietf-rtcweb-jsep-" + data.metadata.version + "#section-" +  jsepSection.slice(0, jsepSection.length - 1);
+                      sectionLink.textContent = "section " + jsepSection;
+                      el.appendChild(document.createTextNode(" ("));
+                      el.appendChild(sectionLink);
+                      el.appendChild(document.createTextNode(")"));
+                  });
+          };
+          xhr.send();
+      }
+  ],
+    localBiblio: {
+        "JSEP": {
+            "authors":["Justin Uberti","Cullen Jennings","Eric Rescorla"],
+            "href": "http://datatracker.ietf.org/doc/draft-ietf-rtcweb-jsep/",
+            "publisher": "IETF",
+            "status": "Active Internet-Draft",
+            "title": "Javascript Session Establishment Protocol",
+            "date": "18 October 2015"
+        }
+    }
 };