Transform into a web extension

src/background/main.js

+var NO_DATA = {
+	badge: "",
+	syntax: "",
+	fetch: function () {
+		return new Promise(function (resolve, reject) {
+			reject("No data!");
+		});
+	}
+};
+
 var allTabs = {};
 
 function getTabData(id) {
 	if (!allTabs.hasOwnProperty(id)) {
 		allTabs[id] = {
 			isActive: false,
-			hasData: ""
+			linkedData: NO_DATA
 		};
 	}
 	return allTabs[id];
@@ -25,7 +35,7 @@ function updateIcon(tabId) {
 		tabId: tabId
 	});
 	chrome.browserAction.setBadgeText({
-		text: data.hasData,
+		text: data.linkedData.badge,
 		tabId: tabId
 	});
 }
@@ -48,9 +58,102 @@ chrome.tabs.onUpdated.addListener(function (tabId, changeInfo, tab) { onTabActiv
 chrome.tabs.onActivated.addListener(function (activeInfo) { onTabActivated(activeInfo.tabId); });
 
 
+function fetchAt(uri) {
+	return new Promise(function (resolve, reject) {
+		reject("No data!");
+	});
+}
+
+function fetchContent(tabId) {
+	return new Promise(function (resolve, reject) {
+		reject("No data!");
+	});
+}
+
+function parseLinkTags(content) {
+	var tags = [];
+	var regexp = RegExp("([a-zA-Z_0-9]+)\\s*=\\s*('[^']*'|\"[^\"]*\")", "g");
+	var match;
+	while ((match = regexp.exec(content)) !== null) {
+		tags.push({
+			name: match[1],
+			value: match[2].substring(1, match[2].length - 1)
+		});
+	}
+	return tags;
+}
+
+function parseLinks(content) {
+	var links = [];
+	var regexp = RegExp("<([^>]*)>(?:\\s*;\\s*([a-zA-Z_0-9]+)\\s*=\\s*('[^']*'|\"[^\"]*\"))*", "g");
+	var match;
+	while ((match = regexp.exec(content)) !== null) {
+		var link = { url: match[1] };
+		var tags = parseLinkTags(match[0]);
+		for (var i = 0; i != tags.length; i++) {
+			link[tags[i].name] = tags[i].value;
+		}
+		links.push(link);
+	}
+	return links;
+}
+
+function getHeader(headers, name) {
+	for (var i = 0; i != headers.length; i++) {
+		if (headers[i].name == name) {
+			return headers[i].value;
+		}
+	}
+	return null;
+}
+
+function detectDataOnLinks(headers) {
+	linksContent = getHeader(headers, "Link");
+	if (linksContent == null)
+		return NO_DATA;
+	var links = parseLinks(linksContent);
+	for (var j = 0; j != links.length; j++) {
+		if (links[j].rel == "alternate" && links[j].type == "text/n3") {
+			return {
+				badge: "N3",
+				syntax: links[j].type,
+				fetch: function (url = links[j].url) {
+					return fetchAt(url);
+				}
+			};
+		}
+	}
+	return NO_DATA;
+}
+
+function detectDataOnContent(tabId, headers) {
+	var contentType = getHeader(headers, "Content-Type");
+	if (contentType == null)
+		return NO_DATA;
+	contentType = contentType.split(";")[0];
+	if (contentType == "text/n3") {
+		return {
+			badge: "N3",
+			syntax: "text/n3",
+			fetch: function (tabId = tabId) {
+				return fetchContent(tabId);
+			}
+		};
+	}
+	return NO_DATA;
+}
+
+function detectData(tabId, headers) {
+	var linkedData = detectDataOnContent(tabId, headers);
+	if (linkedData == NO_DATA)
+		linkedData = detectDataOnLinks(headers);
+	data = getTabData(tabId);
+	data.linkedData = linkedData;
+	updateIcon(tabId);
+}
 
 function onHeaders(details) {
-	console.log(details);
+	detectData(details.tabId, details.responseHeaders);
 }
 
 // listen to received headers