111 lines
3.8 KiB
JavaScript
111 lines
3.8 KiB
JavaScript
class Extractor {
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constructor() {
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this._tasks = [];
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this._results = {};
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}
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/**
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* Add a task to Extractor. \n
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* One Extractor could has multiple tasks, which orgnized in a task chian.
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* Later task will use previous task result as input (target url list).
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* So only the first task can have target url arguments, while later tasks can't.
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* @param {...any} args itemsSelector, fieldSelectors, and more args to specify target urls.
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*/
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task(...args) {
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if (!testArgs(...args))
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throw new Error(`Invalid call arguments.\n\n${signitures}\n\n`);
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// given >2 arguments means the task specifies target page,
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// so it won't accept last task result as url list.
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// in this case, former tasks are useless, can be cleared.
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if (args.length > 2) this.clear();
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this._tasks.push(args);
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return this;
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}
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/**
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* Clear tasks and caches.
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*/
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clear() {
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this._tasks = [];
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this._results = [];
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}
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/**
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* Start the task chain.
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*/
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async start() {
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if (!this._tasks.length) {
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console.log('No task to run.');
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return;
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}
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return this._tasks.reduce((pms, args, i, tasks) => {
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return pms.then(
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result => {
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if (result === undefined) return getData(...args);
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this._results[tasks[i - 1]] = result;
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return getData(...args, result);
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});
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}, Promise.resolve(undefined)).then(
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result => {
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this._results[this._tasks[this._tasks.length - 1]] = result;
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this.save();
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}
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).catch(err => console.log(err));
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}
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/**
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* restart from specified task, but don't restart the previous tasks.
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* @param {number} taskid from which restart the tasks
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*/
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async restart(taskid) {
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taskid = this._checkTaskId(taskid, 1);
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if (!taskid) return;
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if (taskid == 1) {
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this.start();
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return;
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}
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let cache = this._results[this._tasks[taskid - 2]];
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if (!cache) {
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console.log(`No result cache for task (id ${taskid}). \nMake sure call ".start()" before ".restart()"?`);
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return;
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}
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return this._tasks.slice(taskid - 1).reduce((pms, args, i, tasks) => {
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return pms.then(
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result => {
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this._results[tasks[i - 1]] = result;
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return getData(...args, result);
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});
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}, Promise.resolve(cache)).then(
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result => {
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this._results[this._tasks[this._tasks.length - 1]] = result;
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this.save();
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}
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).catch(err => console.log(err));
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}
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/**
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* Save result of a task
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* @param {number} taskid which task id to save.
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*/
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save(taskid) {
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taskid = this._checkTaskId(taskid, this._tasks.length);
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if (!taskid) return;
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const result = this._results[this._tasks[taskid - 1]];
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if (!result) {
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console.log(`No task result for id (${taskid}). Forget to call ".start()"?`);
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return;
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}
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if (confirm(
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`Click confirm to download if the sample data looks good (${result.data.length} items)：\n\n${result.toString(50) || "- Empty -"}`
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)) {
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saveFile(result, "text/csv");
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}
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}
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_checkTaskId(id, defaultId) {
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if (!this._tasks.length) {
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console.log("No task found.");
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return 0;
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}
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if (defaultId && id === undefined || this.task === null) id = defaultId;
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if (isNaN(id) || id < 1 || id > this._tasks.length) {
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console.log(`Invalid task id. Rang(1-${this._tasks.length})`);
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return 0;
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}
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return id
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}
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} |