Add manifest.json and basic redirecting

Author: Nateowami

manifest.json

@@ -0,0 +1,18 @@
+{
+  "manifest_version": 2,
+
+  "name": "Backloader",
+  "version": "0.1.0",
+  "description": "A Chrome extension to redirect CDN requests to another CDN or local resource",
+
+  "permissions": [
+    "storage",
+    "webRequest",
+    "webRequestBlocking",
+    "*://*/*"
+  ],
+
+  "background": {
+    "scripts": ["scripts/background.js", "scripts/list.js"]
+  }
+}

scripts/background.js

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+//register an event listener for all web requests
+chrome.webRequest.onBeforeRequest.addListener(manageRequest, {urls: ["<all_urls>"]}, ["blocking"]);
+
+/**
+ * Manages a webrequest, redirecting or blocking as necessary. Called 
+ * directly by Chrome when the onBeforeRequest even fires.
+ * @param request - The webrequest.
+ */
+function manageRequest(request){
+	var list = completeFilterList();
+	for(var i in list){
+		if(match(list[i].source, request.url)){
+		
+			//block or redirect
+			var redirect = 
+				redirectUrl(list[i].source, list[i].target, request.url);
+				
+			if(redirect){
+				console.log("Redirecting "+request.url+" to " + redirect);
+				return {redirectUrl: redirect};
+			}
+			
+			else {
+				//block the request
+				console.log("Blocking " + request.url);
+				return {cancel: true};
+			}
+			
+		}
+	}
+}
+
+/**
+ * Returns a complete list of URLs to filter.
+ */
+function completeFilterList(){
+	return standardList;
+}
+
+/**
+ * Tells if the parameters source and target match, including wildcards 
+ * which may be present in the source.
+ * @param {String} source - The URL to match, which may include '*' as 
+ * wildcards, matching one or more of any character.
+ * @param {String} target - The URL to test against.
+ * @return {Boolean} Tells if target matches source.
+ */
+function match(source, target){
+	return new RegExp(escapeUrl(source)).test(target);
+}
+
+/**
+ * Calculates a redirect URL given source and target (optionally 
+ * containing wildcards), and the URL requested, by replaceing wildcards 
+ * in target with their respective matches in url. For example, 
+ * redirectUrl("*nowhere*", "*somewhere*", "http://nowhere.nil") returns 
+ * "http://somewhere.nil".
+ * @param {String} source - A string optionally with wildcards, matching 
+ * url.
+ * @param {String} target - A string optionally with wildcards matching 
+ * url.
+ * @param {String} url - The string from which to find matches for 
+ * wildcards.  
+ * @return A string like url, with values matching source chagned to those 
+ * in target. Or, if no target is provided, false.
+ */
+function redirectUrl(source, target, url){
+	if(!target) return false;
+	//a list of concrete values for the wildcards
+	var matches = url.match(new RegExp(escapeUrl(source)));
+	//a list of the non-wildcard parts of target
+	var targetSplit = target.split("*");
+	//now we join the two, taking every other, starting with targetSplit
+	var joined = targetSplit[0];
+	//i = 1 because targetSplit[0] has been appended above, and because
+	//matches[0] is the same as url
+	for(var i = 1; i < targetSplit.length; i++){
+		joined += matches[i] + targetSplit[i];
+	}
+	return joined;
+}
+
+/**
+ * Escape the match URL to make it safe for regex parsing, and convert all
+ * wildcards '*' to regex syntax.
+ * @param {String} url - the URL to be escaped
+ * @return {String} - The escaped URL.
+ **/
+function escapeUrl(url) {
+	//regex from http://stackoverflow.com/questions/2593637/how-to-escape-regular-expression-in-javascript
+	return url.replace(/([.?+^$[\]\\(){}|-])/g, '\\$1')
+		.split('*').join('(.+)');
+}

scripts/list.js

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+var standardList = [
+  {source: "*://ajax.googleapis.com/ajax/libs/jqueryui/*", target: "*://cdnjs.cloudflare.com/ajax/libs/jqueryui/*"},
+  {source: "*://ajax.googleapis.com/ajax/libs/jquery/*", target: "*://cdn.jsdelivr.net/jquery/*"},
+  
+  {source: "*://html5shiv.googlecode.com/svn/trunk/html5.js"},
+  
+  {source: "*://fonts.googleapis.com/css?family=*"},
+  
+  {source: "*://use.typekit.net/acm5rxh.js"},
+  {source: "*://use.typekit.net/num2ubd.js"},
+  {source: "*://sdk.spritzinc.com/js/1.0/css/spritz.min.css"}
+];