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;
                }
            }
        );
    }
}