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+// Copyright (c) 2014 The Chromium Authors. All rights reserved.
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+// Use of this source code is governed by a BSD-style license that can be
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+// found in the LICENSE file.
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+
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+/**
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+ * Get the current URL.
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+ *
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+ * @param {function(string)} callback - called when the URL of the current tab
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+ * is found.
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+ */
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+function getCurrentTabUrl(callback) {
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+ // Query filter to be passed to chrome.tabs.query - see
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+ // https://developer.chrome.com/extensions/tabs#method-query
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+ var queryInfo = {
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+ active: true,
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+ currentWindow: true
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+ };
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+
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+ chrome.tabs.query(queryInfo, function(tabs) {
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+ // chrome.tabs.query invokes the callback with a list of tabs that match the
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+ // query. When the popup is opened, there is certainly a window and at least
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+ // one tab, so we can safely assume that |tabs| is a non-empty array.
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+ // A window can only have one active tab at a time, so the array consists of
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+ // exactly one tab.
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+ var tab = tabs[0];
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+
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+ // A tab is a plain object that provides information about the tab.
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+ // See https://developer.chrome.com/extensions/tabs#type-Tab
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+ var url = tab.url;
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+
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+ // tab.url is only available if the "activeTab" permission is declared.
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+ // If you want to see the URL of other tabs (e.g. after removing active:true
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+ // from |queryInfo|), then the "tabs" permission is required to see their
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+ // "url" properties.
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+ console.assert(typeof url == 'string', 'tab.url should be a string');
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+
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+ callback(url);
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+ });
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+
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+ // Most methods of the Chrome extension APIs are asynchronous. This means that
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+ // you CANNOT do something like this:
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+ //
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+ // var url;
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+ // chrome.tabs.query(queryInfo, function(tabs) {
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+ // url = tabs[0].url;
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+ // });
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+ // alert(url); // Shows "undefined", because chrome.tabs.query is async.
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+}
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+
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+/**
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+ * @param {string} searchTerm - Search term for Google Image search.
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+ * @param {function(string,number,number)} callback - Called when an image has
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+ * been found. The callback gets the URL, width and height of the image.
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+ * @param {function(string)} errorCallback - Called when the image is not found.
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+ * The callback gets a string that describes the failure reason.
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+ */
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+function getImageUrl(searchTerm, callback, errorCallback) {
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+ // Google image search - 100 searches per day.
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+ // https://developers.google.com/image-search/
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+ var searchUrl = 'https://ajax.googleapis.com/ajax/services/search/images' +
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+ '?v=1.0&q=' + encodeURIComponent(searchTerm);
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+ var x = new XMLHttpRequest();
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+ x.open('GET', searchUrl);
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+ // The Google image search API responds with JSON, so let Chrome parse it.
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+ x.responseType = 'json';
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+ x.onload = function() {
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+ // Parse and process the response from Google Image Search.
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+ var response = x.response;
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+ if (!response || !response.responseData || !response.responseData.results ||
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+ response.responseData.results.length === 0) {
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+ errorCallback('No response from Google Image search!');
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+ return;
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+ }
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+ var firstResult = response.responseData.results[0];
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+ // Take the thumbnail instead of the full image to get an approximately
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+ // consistent image size.
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+ var imageUrl = firstResult.tbUrl;
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+ var width = parseInt(firstResult.tbWidth);
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+ var height = parseInt(firstResult.tbHeight);
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+ console.assert(
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+ typeof imageUrl == 'string' && !isNaN(width) && !isNaN(height),
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+ 'Unexpected respose from the Google Image Search API!');
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+ callback(imageUrl, width, height);
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+ };
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+ x.onerror = function() {
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+ errorCallback('Network error.');
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+ };
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+ x.send();
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+}
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+
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+function renderStatus(statusText) {
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+ document.getElementById('status').textContent = statusText;
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+}
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+
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+document.addEventListener('DOMContentLoaded', function() {
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+ getCurrentTabUrl(function(url) {
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+ // Put the image URL in Google search.
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+ renderStatus('Performing Google Image search for ' + url);
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+
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+ getImageUrl(url, function(imageUrl, width, height) {
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+
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+ renderStatus('Search term: ' + url + '\n' +
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+ 'Google image search result: ' + imageUrl);
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+ var imageResult = document.getElementById('image-result');
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+ // Explicitly set the width/height to minimize the number of reflows. For
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+ // a single image, this does not matter, but if you're going to embed
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+ // multiple external images in your page, then the absence of width/height
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+ // attributes causes the popup to resize multiple times.
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+ imageResult.width = width;
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+ imageResult.height = height;
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+ imageResult.src = imageUrl;
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+ imageResult.hidden = false;
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+
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+ }, function(errorMessage) {
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+ renderStatus('Cannot display image. ' + errorMessage);
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+ });
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+ });
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+});
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