add amp-live-list manager (#3094)

extensions/amp-live-list/0.1/live-list-manager.js

@@ -0,0 +1,158 @@
+/**
+ * Copyright 2016 The AMP HTML Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS-IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {Poller} from './poller';
+import {getService} from '../../../src/service';
+import {user} from '../../../src/log';
+import {viewerFor} from '../../../src/viewer';
+import {whenDocumentReady} from '../../../src/document-ready';
+import {xhrFor} from '../../../src/xhr';
+
+
+/**
+ * Manages registered AmpLiveList components.
+ * Primarily handles network requests and updates the components
+ * if necessary.
+ *
+ * @visibleForTesting
+ */
+export class LiveListManager {
+
+  constructor(win) {
+    this.win = win;
+
+    /** @private @const {!Object<string, !AmpLiveList>} */
+    this.liveLists_ = Object.create(null);
+
+    /** @private @const {!Viewer} */
+    this.viewer_ = viewerFor(this.win);
+
+    /** @private {number} */
+    this.interval_ = 15000;
+
+    /** @private @const {!Array<number>} */
+    this.intervals_ = [this.interval_];
+
+    /** @private {?Poller} */
+    this.poller_ = null;
+
+    /** @private @const {string} */
+    this.url_ = this.win.location.href;
+
+    /** @private @const {function(): Promise} */
+    this.work_ = this.fetchDocument_.bind(this, this.url_);
+
+    // Only start polling when doc is ready and when the viewer is visible.
+    this.whenDocReady_().then(() => {
+      // Switch out the poller interval if we can find a lower one and
+      // then make sure to stop polling if viewer is not visible.
+      this.interval_ = Math.min.apply(Math, this.intervals_);
+      this.poller_ = new Poller(this.win, this.interval_, this.work_);
+
+      if (this.viewer_.isVisible()) {
+        this.poller_.start();
+      }
+      this.setupVisibilityHandler_();
+    });
+  }
+
+  /**
+   * Makes a request to the given url for the latest document.
+   *
+   * @param {string} url
+   * @private
+   */
+  fetchDocument_(url) {
+    return xhrFor(this.win)
+        // TODO(erwinm): add update time here when possible.
+        .fetchDocument(url)
+        .then(this.getLiveLists_.bind(this));
+  }
+
+  /**
+   * Queries the document for all `amp-live-list` tags.
+   *
+   * @param {!HTMLDocument} doc
+   */
+  getLiveLists_(doc) {
+    const lists = Array.prototype.slice.call(
+        doc.getElementsByTagName('amp-live-list'));
+    lists.forEach(this.updateLiveList_.bind(this));
+  }
+
+  /**
+   * Updates the appropriate `amp-live-list` with its updates from the server.
+   *
+   * @param {!HTMLElement} liveList
+   */
+  updateLiveList_(liveList) {
+    const id = liveList.getAttribute('id');
+    user.assert(id, 'amp-live-list must have an id.');
+    user.assert(id in this.liveLists_, `amp-live-ist#${id} found but did not ` +
+        `exist on original page load`);
+    this.liveLists_[id].update(liveList);
+  }
+
+  /**
+   * Register an `amp-live-list` instance for updates.
+   *
+   * @param {number} id
+   * @param {!AmpLiveList} liveList
+   */
+  register(id, liveList) {
+    const isNotRegistered = !(id in this.liveLists_);
+    if (isNotRegistered) {
+      this.liveLists_[id] = liveList;
+      this.intervals_.push(liveList.getInterval());
+    }
+  }
+
+  /**
+   * Returns a promise that is resolved when the document is ready.
+   * @return {!Promise}
+   * @private
+   */
+  whenDocReady_() {
+    return whenDocumentReady(this.win.document);
+  }
+
+  /**
+   * Listens to he viewer visibility changed event.
+   * @private
+   */
+  setupVisibilityHandler_() {
+    // Polling should always be stopped when document is no longer visible.
+    this.viewer_.onVisibilityChanged(() => {
+      if (this.viewer_.isVisible()) {
+        // We use immediate so that the user starts getting updates
+        // right away when they've switched back to the page.
+        this.poller_.start(/** immediate */ true);
+      } else {
+        this.poller_.stop();
+      }
+    });
+  }
+}
+
+/**
+ * @param {!Window} window
+ * @return {!LiveListManager}
+ */
+export function installLiveListManager(win) {
+  return getService(win, 'liveListManager', () => {
+    return new LiveListManager(win);
+  });
+}

extensions/amp-live-list/0.1/poller.js

@@ -72,14 +72,16 @@ export class Poller {
 
   /**
    * Initalize any work needed to start polling.
+   * @param {boolean=} opt_immediate execute current work instead of queueing
+   *     it in a timeout.
    */
-  start() {
+  start(opt_immediate) {
     if (this.isRunning_) {
       return;
     }
 
     this.isRunning_ = true;
-    this.poll_();
+    this.poll_(opt_immediate);
   }
 
   /**
@@ -107,14 +109,16 @@ export class Poller {
   /**
    * Queues a timeout that executes the work and recursively calls
    * itself on success.
+   * @param {boolean=} opt_immediate execute current work instead of queueing
+   *     it in a timeout.
    * @private
    */
-  poll_() {
+  poll_(opt_immediate) {
     if (!this.isRunning_) {
       return;
     }
 
-    this.lastTimeoutId_ = timer.delay(() => {
+    const work = () => {
       this.lastWorkPromise_ = this.work_()
           .then(() => {
             if (this.backoffClock_) {
@@ -131,6 +135,12 @@ export class Poller {
               throw err;
             }
           });
-    }, this.getTimeout_());
+    };
+
+    if (opt_immediate) {
+      work();
+    } else {
+      this.lastTimeoutId_ = timer.delay(work, this.getTimeout_());
+    }
   }
 }