Add killpage support

lib/api/mediawiki.js

@@ -18,9 +18,15 @@ export class MediaWikiClient {
 	 * @param {string} wikiURL Target wiki's MediaWiki path (i.e. the path that
 	 * contains `index.php` and `api.php`) without a trailing slash. For example
 	 * for English Wikipedia this would be `'https://en.wikipedia.org/w'`.
+     * @param {object} options
+     * @param {string} [options.killPage] Name of a page that, if provided, will
+     * be read periodically. If the page ever contains text, the process will be
+     * killed. This is a safety measure allowing other editors to kill an
+     * unattended script if it misbehaves.
 	 */
-	constructor (wikiURL) {
+	constructor (wikiURL, {killPage}) {
 		this.wikiURL = wikiURL;
+		this.killPage = killPage;
 		this.fetch = makeFetchCookie(fetch);
 	}
 
@@ -122,6 +128,20 @@ export class MediaWikiClient {
 		if (body.login.result === 'Failed') {
 			throw new Error(body.login.reason);
 		}
+
+		if (this.killPage) {
+			// start the kill page check loop as soon as we're logged in
+			const checkKillPage = async () => {
+				let content = await this.readPage(this.killPage);
+				if (content.trim()) {
+					console.error('*** Kill page is not empty; stopping ***\n');
+					console.error(content);
+					process.exit(1);
+				}
+				setTimeout(checkKillPage, 30 * 1000); // every 30 seconds
+			};
+			checkKillPage();
+		}
 	}
 
 	/**