Effects inside main

Most of what a person does has a screen, and the screen pages show it. A few things have none: a privacy setting, the authenticator key, mentions in a story, the followers of an account. The Simulator offers these as effects. You call them inside the main of an entry, on the process the entry already launched, so you never need a session file or the app layer for them.

How

Inside main, write yield* in front of the effect.

import { AndroidIgpapi, FeedTimelineScreen, followersFeed, SettingsPrivacyMessagesGet } from '@igpapi/android';
import { Effect } from 'effect';
import { readFile } from 'node:fs/promises';

const saved = JSON.parse(await readFile('session.json', 'utf8'));

const result = await AndroidIgpapi.launch({
  checkpoint: saved,
  screen: FeedTimelineScreen,
  main: _feed =>
    Effect.gen(function* () {
      // An effect with no screen runs inside `main`, on the process the entry already launched.
      const settings = yield* SettingsPrivacyMessagesGet();

      // A list is a feed: open it, then load its first page.
      const followers = yield* followersFeed({ id: '123456' });
      const page = yield* followers.next;

      return { whoCanMessage: settings.ig_followers, followers: page.items.length };
    }).pipe(
      // These effects are not screen actions, so `otherwise` does not answer a challenge over them:
      // the challenge stays their own error, and you decide what to do with it here.
      Effect.catchTag('IgCheckpointError', () => Effect.succeed(undefined)),
    ),
});
console.log(result);

• SettingsPrivacyMessagesGet() reads who may message the account; the answer's ig_followers is the "Your followers on Instagram" setting.
• followersFeed({ id }) opens the list; followers.next loads one page and says whether there is more (Lists).
• The process is launched already, so nothing more is needed: no AndroidApp, no snapshot.

Challenges

A screen action that meets a challenge is answered by your otherwise branches, and the action runs again. These effects are not screen actions: a challenge over one of them stays its own error, IgCheckpointError. Answer it with Effect.catchTag('IgCheckpointError', …) as the program above does; the usual answer is to stop the program and let a person pass the challenge (Challenges).

The effects documented on this site

You want to	Effect	Page
Read or change who can message the account	SettingsPrivacyMessagesGet, SettingsPrivacyMessagesSet	Message controls
Turn on the authenticator app	SecurityInfo, GenerateTwoFactorTotpKey, EnableTotpTwoFactor, AddKeyTotpTwoFactor	Turn on the authenticator app
Mention accounts in a story	MediaAddMentionedUser	Mention users in a story
Read followers and following	followersFeed and the other feeds	Lists
Send the telemetry now	FlushTelemetry	Telemetry

When to use the app layer instead

When you need a request the Simulator has no effect for, or you run several programs over one process: Compose the app layer yourself.

Related

• Work with screens
• Challenges: answer them once with otherwise
• All recipes