Zetlyn

End a watch. It is deleted with its history.

The account: its address, how many watches it has and runs, and on zetlyn.com its subscription and how many watches the plan holds.

One watch with its last 20 changes (before and after) and its recent checks.

The changes on all of the account's watches since a moment, newest first: which watch, when, before and after. Use it to answer what changed lately.

List the account's watches: what each watches, what it read last, its state and when it was checked.

Read a public web page (or JSON, an RSS or Atom feed, XML or plain text, each read as a page of its own: one line per value, the field's path beside it) and list the places on it that can be watched, each with the selector that marks it, what it says now, and the text beside it: the page's own content first, its menus, header and footer last. Call this before watch_page to choose a place. If the place the person means is not among them, call it again with find (a word or sign the place says, such as "€", "In stock" or "Version"), which searches the whole page. If it fails saying the site does not let programs read the page, that page cannot be watched: tell the person, and do not call watch_page for it.

Read what one or more places on a page say now, without watching anything. Use it to try selectors before watch_page or update_watch instead of making and ending watches. Each place is read twice a few seconds apart; steady: false means the site shows something else on its own from one read to the next (an A/B test, a box that guesses where the reader is), so prefer a narrower place inside it.

A link for the person to subscribe to Zetlyn by (9.99 € a month for up to 10 watches, 0.50 € for each one more). Call it when a watch is waiting for a subscription or the person wants one. Give the person the link and the price; they open it themselves and pay at Stripe. You cannot pay or agree for them. Afterwards get_account says subscribed: true and waiting watches run.

Change a watch in place: watch another place on the same page (selector), the whole page (whole_page: true), or check it at another interval (every_minutes). The watch keeps its id and history and does not start a new free trial. To watch a different page, make a new watch.

Start watching a page: one place on it (give the selector from preview_page) or the whole page (no selector). A JSON field is a place like any other; a feed watched whole is told by its new entries. Zetlyn checks it every hour (with a subscription as often as every minute, see every_minutes) and notifies the account when it changes.