rudeshark.net/src/server/api/endpoints/notes/watching/create.ts

import $ from 'cafy';
import ID, { transform } from '../../../../../misc/cafy-id';
import Note from '../../../../../models/note';
import define from '../../../define';
import watch from '../../../../../services/note/watch';

export const meta = {
	stability: 'stable',

	desc: {
		'ja-JP': '指定した投稿をウォッチします。',
		'en-US': 'Watch a note.'
	},

	requireCredential: true,

	kind: 'account-write',

	params: {
		noteId: {
			validator: $.type(ID),
			transform: transform,
			desc: {
				'ja-JP': '対象の投稿のID',
				'en-US': 'Target note ID.'
			}
		}
	}
};

export default define(meta, (ps, user) => new Promise(async (res, rej) => {
	// Get note
	const note = await Note.findOne({
		_id: ps.noteId
	});

	if (note === null) {
		return rej('note not found');
	}

	await watch(user._id, note);

	// Send response
	res();
}));