keep state and continue

scripts/background/task.js

@@ -0,0 +1,66 @@
+class Task {
+    // _manager = undefined;
+    // _id = 0;
+    // _urls = [];
+    _data = {};
+    /**
+     * 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(...args) {
+        if (!testArgs(...args))
+            throw new Error(`Invalid call arguments.\n\n${signitures}\n\n`);
+        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._urls.reduce((p, c) => {
+            return p.concat(this._data[c]);
+        }, []);
+    }
+    clean() {
+        this._data = {};
+    }
+    async execute(tab, upstreamData) {
+        if (!tab) throw new Error("No tab to execute the task.");
+        if (!this._urls.length) {
+            if (upstreamData) {
+                this._urls = parseUrls(upstreamData);
+            } else {
+                this._urls = [await queryUrl(tab)];
+            }
+        }
+        return this._urls.reduce((p, url, i) => p.then(
+            results => {
+                if (i > 0) {
+                    if (!MSG_URL_SKIPPED.isEqual(results)) {
+                        let lastURL = this._urls[i - 1];
+                        this._data[lastURL] = results;
+                    } 
+                }
+                return this._data[url] ? MSG_URL_SKIPPED : redirectTab(tab, url).then(
+                    () => extractTabData(tab, this._itemsSelector, this._fieldSelectors)
+                );
+            }
+        ), Promise.resolve(null)).then(
+            results => {
+                if (!MSG_URL_SKIPPED.isEqual(results)) {
+                    let lastURL = this._urls[this._urls.length - 1];
+                    this._data[lastURL] = results;
+                    return;
+                }
+            }
+        );
+    }
+}