availablity check before run on active tab

manifest.json

@@ -22,6 +22,7 @@
       "scripts/background/result.js",
       "scripts/background/signiture.js",
       "scripts/background/actions.js",
+      "scripts/background/task.js",
       "scripts/background/extractor.js",
       "scripts/background/helpers.js"
     ],

readme.md

@@ -50,17 +50,14 @@ function (itemsSelector:string, fieldSelectors:string[], urls:string[])
 function (itemsSelector:string, fieldSelectors:string[], urls:ExtractResult)
 ```
 
-## Advanced Usage
+## Stop Tasks
 
-### Stop Tasks
+The only way to stop tasks before its finish, is `Closing the target tab`.
 
-Tasks wait for their target elements' appearance, given some elements were loaded asynchronously.
+> Tasks wait for their target elements' appearance, given some elements were loaded asynchronously.  
+> If you typed wrong selectors, the task waits forever for  elements which don't exists.
 
-But if you typed wrong selectors, the task waits forever for  elements which don't exists.
+## Extract Attributes.
-
-The only way to stop tasks before its finish, is `Closing the host tab`.
-
-### Extract Attributes.
 
 e.g.: link text and target (use 'selector@attribute')
 
@@ -68,20 +65,43 @@ e.g.: link text and target (use 'selector@attribute')
 new Extractor().task('.item', ['a', 'a@href']).start();
 ```
 
+## Advanced Usage
+
 ### Use Task Chain.
 
 e.g.: Collect links from `http://sample.com/abc`, then, Extract data of each link
 
 ```js
-new Extractor()
+e = new Extractor()
-    .task('.search-list-item', ['a@href'], ["http://sample.com/abc"])
+e.task('.search-list-item', ['a@href'], ["http://sample.com/abc"])
     .task('list-item', ["a.title", "p.content"])
     .start();
 ```
 
+### Continue Tasks
+
+You can always continue tasks (with following), even it stops in the middle of a task:
+
+```js
+e.start()
+```
+
+The `Extractor` kept the state of last execution, and starts from where it stopped.
+
+### Restart Tasks
+
+What should I do, if I don't like to continue from last state, but restart from certain task?
+
+```js
+// restart all tasks
+e.restart(0)
+// restart from 2nd task
+e.restart(1)
+```
+
 ### Save Result of Any Task
 
-To a multiple task (chain) Extractor `e`:
+To a multiple task Extractor `e`:
 
 ```js
 e = new Extractor()
@@ -98,37 +118,12 @@ Incase you want to save it again, use:
 e.save()
 ```
 
-You may want to save another task's result, other than the final:
+To save another task result, other than the final one:
 
 ```js
 // save the result of first task
 // to the example above, that is a list of urls
+e.save(0)
+// save the result of second task
 e.save(1)
 ```
-
-### Restart Tasks
-
-In cases some later task fails, you don't need to restart all task.
-
-Here we have 2 tasks:
-
-```js
-e = new Extractor()
-e.task('.search-list-item', ['a@href'], ["http://sample.com/abc"])
-    .task('list-item', ["a.title", "p.content"])
-    .start();
-```
-
-Suppose the second task fails, we can restart and continue from the task 2:
-
-```js
-e.restart(2);
-```
-
-If you'd like restart all task, use:
-
-```js
-e.start();
-// or
-e.restart();
-```

scripts/background/actions.js

@@ -55,7 +55,7 @@ function parseUrls(...args) {
     if (arg instanceof Array) {
         return arg;
     } else if (arg instanceof ExtractResult) {
-        return arg.squash().filter(v => !!v);
+        return arg.squash().filter(v => URL_REG.test(v));
     } else {
         let urlTempl = arg;
         if (urlTempl) {
@@ -86,10 +86,10 @@ function redirectTab(tab, url) {
                     action: ACTION_GOTO_URL,
                     url: url
                 }
-                sendMessage(tab, req, `Goto url: ${url}`);
+                return sendMessage(tab, req, `Goto url: ${url}`);
             }
         })
-        .then(() => queryUrl(tab, curUrl, 'Check if tab url matches expected...'))
+        .then(() => queryUrl(tab, url, 'Check if tab url matches expected...'))
 }
 
 /**
@@ -110,32 +110,46 @@ function extractTabData(tab, itemsSelector, fieldSelectors) {
 }
 
 /**
- * get report in from the target tab, usually used to detect if the content script is ready.
+ * ping target tab, usually used to detect if the content script is ready.
  * @param {any} tab target tab
- * @returns {Promise<string>} a promise of the report in message
+ * @returns {Promise<boolean>} a promise of boolean value indicates if ping success
  */
-function reportIn(tab) {
+async function ping(tab, count = 1) {
     let req = {
         action: ACTION_REPORT_IN
     }
     let cond = r => r == req.action;
-    return sendMessage(tab, req, 'Check tab availability...', cond);
+    let pong = await sendMessage(tab, req, 'Check tab availability...', cond, 1000, count).catch(() => { });
+    return pong == ACTION_REPORT_IN;
 }
 
 /**
  * get the url of the target tab
  * @param {any} tab target tab
- * @param {string} urlExcluded if specified, queryUrl resolves only when response not equals to urlExcluded
+ * @param {string} expected if specified, queryUrl resolves only when tab url equals to expected
  * @returns {Promise<string>} a promise of the url
  */
-function queryUrl(tab, urlExcluded, log) {
+function queryUrl(tab, expected, log) {
     let req = {
         action: ACTION_QUERY_URL
     }
-    let cond = url => url && (!urlExcluded || (urlExcluded && urlExcluded != url));
+    let cond = url => url && (!expected || (expected && expected == url));
     return sendMessage(tab, req, log, cond);
 }
 
+/**
+ * get the url of the target tab
+ * @param {any} tab target tab
+ * @param {string} expected if specified, queryUrl resolves only when tab url equals to expected
+ * @returns {Promise<string>} a promise of the url
+ */
+function scrollToBottom(tab) {
+    let req = {
+        action: ACTION_SCROLL_BOTTOM
+    }
+    return sendMessage(tab, req, 'Scroll to page bottom...');
+}
+
 async function createTab(url, active) {
     return new Promise((resolve, reject) => {
         chrome.tabs.create({

scripts/background/extractor.js

@@ -1,41 +1,45 @@
 class Extractor {
-    constructor() {
+    constructor(options) {
         this._tasks = [];
-        this._tab = undefined;
         this._running = false;
-        this._results = {};
+        this._options = options;
     }
     /**
      * Add a task to Extractor. \n
      * One Extractor could has multiple tasks, which orgnized in a task chian.
-     * Later task will use previous task result as input (target url list).
+     * If url arguments not given within later tasks, they will use previous task result as input (target url list).
-     * So only the first task can have target url arguments, while later tasks can't.
      * @param {...any} args itemsSelector, fieldSelectors, and more args to specify target urls.
      */
     task(...args) {
-        if (!testArgs(...args)) {
+        this._tasks.push(new Task(this._options, ...args));
-            console.log(`Invalid task arguments: ${argsToString(...args)}\n\n${signitures}\n`);
-            return this;
-        }
-        // given >2 arguments means the task specifies target page, 
-        // so it won't accept last task result as url list.
-        // in this case, former tasks are useless, can be cleared.
-        if (args.length > 2) this.clear();
-        this._tasks.push(args);
         return this;
     }
     /**
-     * Clear tasks and caches.
+     * Clear tasks and task caches.
      */
     clear() {
         this._tasks = [];
-        this._results = [];
         return this;
     }
     /**
      * Start the task chain.
      */
     async start() {
+        return this._startTasks(0);
+    }
+    /**
+     * restart from specified task, but don't restart the previous tasks.
+     * @param {number} from where to restart the tasks, begins with 0
+     */
+    async restart(from = 0) {
+        let id = this._checkTaskId(from, 0);
+        if (id < 0) return;
+        for (let i = id; i < this._tasks.length; i++) {
+            this._tasks[i].clean();
+        }
+        return this._startTasks(0);
+    }
+    async _startTasks(from) {
         if (this._running) {
             console.log('The Extractor is running. Please wait..');
             return;
@@ -44,107 +48,75 @@ class Extractor {
             console.log('No task to run.');
             return;
         }
-        let firstTaskArgs = this._tasks[0];
+
-        if (firstTaskArgs.length > 2) {
+        let tab;
+        let task = this._tasks[0];
+        if (task.urls.length) {
             // task specifies target urls, create new tab with first url for it
-            let urls = parseUrls(...firstTaskArgs.slice(2, firstTaskArgs.length));
+            tab = await createTab(task.urls[0], false);
-            this._tab = await createTab(urls[0], false);
         } else {
-            this._tab = await getActiveTab(false);
+            tab = await getActiveTab(true) || await getActiveTab(false);
+            let succ = await ping(tab);
+            if (!succ) {
+                console.log('Cannot contact with active tab.');
+                return;
+            }
         }
         this._running = true;
-        return this._tasks.reduce((pms, args, i, tasks) => {
+        return this._tasks.reduce((pms, task, i) => {
             return pms.then(
-                result => {
+                () => {
-                    if (result === undefined) return getData(this._tab, ...args);
+                    if (i < from) return;
-                    this._results[tasks[i - 1]] = result;
+                    if (i > 0) {
-                    return getData(this._tab, ...args, result);
+                        let prevTask = this._tasks[i - 1];
+                        return task.execute(tab, new ExtractResult(prevTask.results));
+                    }
+                    return task.execute(tab, undefined);
                 });
         }, Promise.resolve(undefined)).then(
-            result => {
+            () => {
-                this._results[this._tasks[this._tasks.length - 1]] = result;
-                this._running = false;
-                console.log("Tasks are all done.")
-                this.save();
-            }
-        ).catch(err => {
-            this._running = false;
-            console.log(err)
-        });
-    }
-    /**
-     * restart from specified task, but don't restart the previous tasks.
-     * @param {number} taskid from which restart the tasks
-     */
-    async restart(taskid) {
-        if (this._running) {
-            console.log('The Extractor is running. Please wait..');
-            return;
-        }
-        taskid = this._checkTaskId(taskid, 1);
-        if (!taskid) return;
-        if (taskid == 1) {
-            this.start();
-            return;
-        }
-        let cache = this._results[this._tasks[taskid - 2]];
-        if (!cache) {
-            console.log(`No result cache for task (id ${taskid}). \nMake sure call ".start()" before ".restart()"?`);
-            return;
-        }
-        this._running = true;
-        this._tab = await createTab(parseUrls(cache)[0], false)
-        return this._tasks.slice(taskid - 1).reduce((pms, args, i, tasks) => {
-            return pms.then(
-                result => {
-                    this._results[tasks[i - 1]] = result;
-                    return getData(this._tab, ...args, result);
-                });
-        }, Promise.resolve(cache)).then(
-            result => {
-                this._results[this._tasks[this._tasks.length - 1]] = result;
                 this._running = false;
                 this.save();
             }
         ).catch(err => {
             this._running = false;
-            console.log(err)
+            console.log(err);
         });
     }
     /**
      * Save result of a task
-     * @param {number} taskid which task id to save.
+     * @param {number} taskid which task id to save, begins with 0
      */
     save(taskid) {
-        taskid = this._checkTaskId(taskid, this._tasks.length);
+        let id = this._checkTaskId(taskid, this._tasks.length - 1);
-        if (!taskid) return;
+        if (id < 0) return;
-        const result = this._results[this._tasks[taskid - 1]];
+        let results = this._tasks[id].results
-        if (!result) {
+        results.unshift(this._tasks[id].fieldSelectors);
-            console.log(`No result for task #${taskid}. Forget to call ".start()"?`);
+
-            return;
+        let exResults = new ExtractResult(results);
-        }
+
-        if (result.data.length <= 1) { // 1 for selector headers
+        if (!results.length) {
-            console.log(`No result for task #${taskid}. Forget to call ".start()"?`);
+            console.log(`No result for task #${id}. Forget to call ".start()"?`);
             return;
         }
         let msg = `
-Please confirm to download (${result.data.length - 1} items)：
+Please confirm to download (${results.length - 1} items)：
 
-${result.toString(50) || "- Empty -"}
+${exResults.toString(50) || "- Empty -"}
 `.trim();
         if (confirm(msg)) {
-            saveFile(result, "text/csv");
+            saveFile(exResults, "text/csv");
         }
     }
     _checkTaskId(id, defaultId) {
         if (!this._tasks.length) {
             console.log("No task found.");
-            return 0;
+            return -1;
         }
-        if (defaultId && id === undefined || this.task === null) id = defaultId;
+        if (!isNaN(defaultId) && id === undefined) id = defaultId;
-        if (isNaN(id) || id < 1 || id > this._tasks.length) {
+        if (isNaN(id) || id < 0 || id >= this._tasks.length) {
-            console.log(`Invalid task id. Rang(1-${this._tasks.length})`);
+            console.log(`Invalid task id. Rang(0-${this._tasks.length - 1})`);
-            return 0;
+            return -1;
         }
         return id
     }

scripts/background/messaging.js

@@ -4,12 +4,15 @@
  * @param {object} tab the table where to send the message
  * @param {object} req the request data.
  * @param {function} cond success condition function, r:any=>boolean
- * @param {number} interval interval for detecting
+ * @param {number} interval retry interval, default: 500ms.
+ * @param {number} limit retry limit, default: 0, no limit.
  * @param {string} log messages logged to console.
  * @return {Promise} a promise of the response.
  */
-function sendMessage(tab, req, log, cond, interval) {
+function sendMessage(tab, req, log, cond, interval, limit = 0) {
     interval = interval || 500;
+    limit = limit && !isNaN(limit) ? limit : 0;
+    count = 0;
     return new Promise((resolve, reject) => {
 
         loop();
@@ -22,11 +25,17 @@ function sendMessage(tab, req, log, cond, interval) {
                 return;
             }
 
-            chrome.tabs.sendMessage(tab.id, req, r => {
+            if (limit && count >= limit) {
-                if (chrome.runtime.lastError) {
+                reject(`sendMessage loop limit ${limit} reached.`);
-                    reject(chrome.runtime.lastError.message);
                 return;
             }
+            count++;
+            chrome.tabs.sendMessage(tab.id, req, r => {
+                // check error but do nothing.
+                // do not interrupt promise chains even if error, or the task always fail when:
+                // a tab is newly created, and the content scripts won't have time to initialize
+                chrome.runtime.lastError;
+
                 let flag = !cond || cond(r);
                 if (log) console.log(log, flag ? '(OK)' : '(failed)');
                 if (flag) {

scripts/background/task.js

@@ -0,0 +1,78 @@
+class Task {
+    _data = {};
+    _data_keys = [];
+    /**
+     * Create a task.
+     * constructor(itemsSelector:string, fieldSelectors:string[])
+     * constructor(itemsSelector:string, fieldSelectors:string[], url:string, from:number, to:number, interval:number)
+     * constructor(itemsSelector:string, fieldSelectors:string[], url:string, pages:number[])
+     * constructor(itemsSelector:string, fieldSelectors:string[], urls:string[])
+     * @param {...any} args
+     */
+    constructor(options, ...args) {
+        if (!testArgs(...args))
+            throw new Error(`Invalid call arguments.\n\n${signitures}\n\n`);
+        this._options = options;
+        this._itemsSelector = args.shift();
+        this._fieldSelectors = args.shift();
+        this._urls = parseUrls(...args);
+    }
+    get urls() {
+        return this._urls;
+    }
+    get data() {
+        return this._data;
+    }
+    get results() {
+        return this._data_keys.reduce((p, c) => {
+            return p.concat(this._data[c]);
+        }, []);
+    }
+    get fieldSelectors() {
+        return this._fieldSelectors;
+    }
+    clean() {
+        this._data = {};
+    }
+    async execute(tab, upstreamData) {
+        if (!tab) return Promise.reject("No tab to execute the task.");
+        let urls = this._urls
+        if (!urls.length) {
+            if (upstreamData) {
+                urls = parseUrls(upstreamData);
+            } else {
+                urls = [await queryUrl(tab)];
+            }
+        }
+        let saveResult = (results, key) => {
+            this._data[key] = results;
+            this._data_keys.push(key);
+        }
+        return urls.reduce((p, url, i) => p.then(
+            results => {
+                if (i > 0) {
+                    if (!MSG_URL_SKIPPED.isEqual(results)) {
+                        let lastURL = urls[i - 1];
+                        saveResult(results, lastURL);
+                    }
+                }
+                if (this._data[url]) return MSG_URL_SKIPPED;
+                let pms = redirectTab(tab, url);
+                if (this._options["scrollToBottom"]) {
+                    pms = pms.then(() => scrollToBottom(tab));
+                }
+                return pms.then(
+                    () => extractTabData(tab, this._itemsSelector, this._fieldSelectors)
+                );
+            }
+        ), Promise.resolve(null)).then(
+            results => {
+                if (!MSG_URL_SKIPPED.isEqual(results)) {
+                    let lastURL = urls[urls.length - 1];
+                    saveResult(results, lastURL);
+                    return;
+                }
+            }
+        );
+    }
+}

scripts/content/content.js

@@ -1,29 +1,40 @@
-chrome.runtime.onMessage.addListener(
+(function () {
+    chrome.runtime.onMessage.addListener(
         function (request, sender, sendResponse) {
             if (!request.action) return;
             // console.log("Recieved request:",request);
+            doAction(request, sender).then(r => sendResponse && sendResponse(r));
+            // return true to indicate you wish to send a response asynchronously
+            return true;
+        }
+    );
+
+    async function doAction(request, sender) {
         switch (request.action) {
             case ACTION_EXTRACT:
                 let data = extract(request.itemsSelector, request.fieldSelectors);
-                if (sendResponse) sendResponse(data);
+                return data;
-                break;
             case ACTION_GOTO_URL:
                 window.location.replace(request.url);
-                if (sendResponse) sendResponse(request.url);
+                return request.url;
-                break;
             case ACTION_REPORT_IN:
-                if (sendResponse) sendResponse(request.action);
+                return request.action;
-                break;
             case ACTION_QUERY_URL:
-                if (sendResponse) sendResponse(window.location.href);
+                return window.location.href;
-                break;
+            case ACTION_SCROLL_BOTTOM:
+                return executeUntil(
+                    () => window.scrollTo(0, document.body.clientHeight),
+                    () => document.body.clientHeight - window.scrollY - window.innerHeight < 20,
+                    "Scroll to page bottom...",
+                    1000,
+                    10
+                )
             default:
                 break;
         }
     }
-);
 
-function extract(itemsSelector, fieldSelectors) {
+    function extract(itemsSelector, fieldSelectors) {
         // since some elements may be loaded asynchronously.
         // if one field is never found, we should return undefined,
         // so that senders can detect to retry until elements loaded.
@@ -50,4 +61,41 @@ function extract(itemsSelector, fieldSelectors) {
         // if it exists a field, which is not found in any row, the sender should retry.
         let shouldWait = fieldSelectors.reduce((p, c) => p || !fieldFound[c], false);
         return shouldWait ? MSG_ELEMENT_NOT_FOUND : results
-}
+    }
+
+    /**
+     * Repeatedly execute an function until the the detector returns true.
+     * @param {object} fn the function to execute
+     * @param {object} detector the detector.
+     * @param {string} log messages logged to console.
+     * @param {number} interval interval for detecting
+     * @param {number} limit max execute times of a function
+     * @return {Promise} a promise of the response.
+     */
+    function executeUntil(fn, detector, log, interval, limit) {
+        interval = interval || 500;
+        let count = 0;
+        return new Promise((resolve, reject) => {
+
+            loop();
+
+            async function loop() {
+                fn();
+                limit++;
+                if (limit && count >= limit) {
+                    reject(false);
+                }
+                setTimeout(() => {
+                    let flag = !detector || detector();
+                    if (log) console.log(log, flag ? '(OK)' : '(failed)');
+                    if (flag) {
+                        resolve(true);
+                    } else {
+                        loop();
+                    }
+                }, interval);
+            }
+        });
+    }
+
+})();

scripts/shared/common.js

@@ -1,8 +1,12 @@
 const EXT_NAME = "DataExtracter";
 
+const URL_REG = getWebUrl();
+
 const ACTION_EXTRACT = `${EXT_NAME}:Extract`;
 const ACTION_GOTO_URL = `${EXT_NAME}:GoToTUL`;
 const ACTION_REPORT_IN = `${EXT_NAME}:ReportIn`;
 const ACTION_QUERY_URL = `${EXT_NAME}:QueryURL`;
+const ACTION_SCROLL_BOTTOM = `${EXT_NAME}:ScrollToBottom`;
 
 const MSG_ELEMENT_NOT_FOUND = new ConstMessage(1, "No element found for at least one selector, maybe it's not loaded yet");
+const MSG_URL_SKIPPED = new ConstMessage(100, "Skipped current URL");