Support compiling templates in the browser.

extension/background.js

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Glue code that interacts with dwc_compiler.dart to proxy arbitrary content
+// for urls.
+
+
+var existingRuleIds = {};
+var onParse = null;
+
+// TODO(jacobr): set the onParse property directly from Dart.
+function setOnParseCallback(cb) {
+  onParse = cb;
+}
+
+function proxyUrls(port, requests) {
+  // Unfortunately we have to create the data urls from the content script due
+  // to chrome security restrictions.
+  port.postMessage({type: 'CREATE_DATA_URLS', requests: requests});
+}
+
+function onProxyUrls(requests) {
+  var rulesToAdd = [];
+  var ruleIdsToRemove = [];
+  for (var i = 0; i < requests.length; i++) {
+    var request = requests[i];
+    var url = request.url;
+    var redirectUrl = request.redirectUrl;
+    var rule = {
+      conditions: [
+        new chrome.declarativeWebRequest.RequestMatcher(
+            {url: {urlEquals: url}})
+      ],
+      actions: [
+        new chrome.declarativeWebRequest.RedirectRequest(
+          {redirectUrl: redirectUrl})
+      ]};
+    if (existingRuleIds[url]) {
+      ruleIdsToRemove.push(existingRuleIds[url]);
+    }
+    rulesToAdd.push(rule);
+  }
+
+  if (ruleIdsToRemove.length > 0) {
+    chrome.declarativeWebRequest.onRequest.removeRules(ruleIdsToRemove);
+  }
+  chrome.declarativeWebRequest.onRequest.addRules(rulesToAdd, function(added) {
+    for(var i = 0; i < added.length; i++) {
+      var r = added[i];
+      existingRuleIds[r.conditions[0].url.urlEquals] = r.id;
+    }
+    // TODO(jacobr): notify caller that the proxy server is ready to use.
+  })
+}
+chrome.extension.onConnect.addListener(function(port) {
+  if (port.name == "parse") {
+    // Listen to requests from chrome tabs to parse templates.
+    port.onMessage.addListener(function(msg) {
+      onParse(port, msg.url);
+    });
+  } else if (port.name == "proxy") {
+    // Listen for requests to proxy urls.
+    port.onMessage.addListener(function(msg) {
+      onProxyUrls(msg.requests);
+    });
+  }
+});