Building A Complex Task (Optional)

Building a more complex task

Tasks prompt users to complete activities on a programmatic schedule. This tutorial will guide you through the development of an advanced task. This is an optional tutorial and is not required to get started with CHT Application development.

  • Create a task with a complex follow-up schedule
  • Use a 3rd party JavaScript library luxon to make Date/Time calculations easier
  • Pass information from the task into the action app form
  • Custom logic for resolving a task

Prerequisites

Scenario

This scenario is loosely based on the Pregnancy Visit Task from the Maternal and Newborn Health Reference App.

We expectations for the task are:

  1. Only CHW users should be prompted to complete pregnancy visits
  2. Pregnancy visits should appear for pregnant patients after their pregnancy registration
  3. Pregnancy visits should be scheduled eight times between the last mentrual period (LMP) and delivery.
  4. A pregnancy visit should be skipped if an assessment followup is completed within the scheduled window for the pregancy visit.
  5. The first pregnancy visit should prompt the CHW to ask some additional questions

Developing the task

This solution relies on the library luxon for parsing and manipulating dates and times. Let’s start by installing it locally:

npm install --save-dev luxon

And then in tasks.js we can analyse this solution:

const { DateTime } = require('luxon');

module.exports = {
  name: 'pnc-after-pregnancy',
  icon: 'icon-follow-up',
  title: 'task.pnc_followup',
  appliesTo: 'contacts',
  appliesToType: ['patient'],
  appliesIf: function (contact) {
    const userIsChw = user.parent && user.parent.contact_type === 'chw_area';
    const isDead = contact.contact.date_of_death;
    const isMuted = contact.contact.muted;

    if (userIsChw && !isDead && !isMuted) {
      const mostRecentPregnancy = Utils.getMostRecentReport(contact.reports, 'pregnancy');
      const calculatedLmp = mostRecentPregnancy && Utils.getField(mostRecentPregnancy, 'g_details.estimated_lmp');
      this.lmp = calculatedLmp && DateTime.fromFormat(calculatedLmp, 'yyyy-MM-dd');
      
      return this.lmp && this.lmp.isValid;
    }
  },
  events: [12, 20, 26, 30, 34, 36, 38, 40] // follow-up weeks after LMP
    .map(weekAfterLmp => ({
      id: `pnc-week-${weekAfterLmp}`,
      start: weekAfterLmp > 30 ? 6 : 7,
      end: weekAfterLmp > 30 ? 7 : 14,
      dueDate: function () {
        return this.lmp.plus({ weeks: weekAfterLmp }).toJsDate();
      }
    })),
  resolvedIf: function (contact, report, event, dueDate) {
    const start = Utils.addDate(dueDate, -event.start).getTime();
    const end = Utils.addDate(dueDate, event.end + 1).getTime();
    const pncInWindow = Utils.isFormSubmittedInWindow(contact.reports, 'pnc_followup', start, end);
    const assessmentInWindow = Utils.isFormSubmittedInWindow(contact.reports, 'assessment_followup', start, end);
    return pncInWindow || assessmentInWindow;
  },
  actions: [{
    form: 'pnc_followup',
    modifyContent: function (content, contact, report, event) {
      const followupCount = this.definition.events.findIndex(e => event.id === e.id) + 1;
      content.t_followup_count = followupCount.toString();
    }
  }]
};

What is this code doing?

AppliesIf

1. Only CHW users should be prompted to complete pregnancy visits
2. Pregnancy visits should appear for pregnant patients after their pregnancy registration

This function starts with the standard stuff from the Configuring Tasks Tutorial. We want to confirm the user is a CHW, and the patient is alive and unmuted.

Then, the code searches through each contact’s reports to find the most recent (newest) pregnancy registration using the Utils helper library. It gets that report’s value for report.fields.g_details.estimated_lmp, which is a date string calculated by the app form. It parses that string using the luxon library and returns true if it is a valid date.

Defining lmp as a property of this, stores the LMP DateTime and we will use that value later.

Events

3. Pregnancy visits should be scheduled eight times between the last mentrual period (LMP) and delivery.

This is a recurring task, unlike the one-time task we wrote in Configuring Tasks Tutorial. This task is going to appear once 12 weeks after the estimated LMP date, again after 20 weeks, and again 6 more times. The dueDate on the event says that the task event is due a variable number of weeks after the estimated LMP. The time the CHW has to complete the visit is shorter toward the end of the schedule.

We’re using the this.lmp value which was calculated and saved in the appliesIf function.

ResolvedIf

4. A pregnancy visit should be skipped if an _assessment followup_ is completed within the scheduled window for the pregancy visit.

resolvedIf captures the conditions when the task event should disappear because it has been completed. Since we want the task schedule to appear if the user completes an assessment followup or the pnc followup, we can’t use the default resolvedIf definition.

This function calculates timestamps for the start and end of each event. Then, it uses the Utils helper library to see if either a pnc or an assessment followup is present within those timestamps.

We will be looking at resolvedIf and the concept of task completion in more depth in [Configuring Tasks - Part 4]({{ < ref “apps/tutorials/tasks-4” >}}).

Actions

5. The first pregnancy visit should prompt the CHW to ask some additional questions

The modifyContent attribute allows the task to pass data from the task (in JavaScript) into the action app form (xlsx). Check out the guide for Passing data from a task into the app form.


CHT Applications > Tutorials > Tasks

Writing and testing a simple task

CHT Applications > Reference > tasks.js

Tasks: Definition of tasks shown to app users

CHT Applications > Reference > Utils Functions

CHT Applications > Examples > Maternal & Newborn Health

Reference application for maternal and newborn care for CHW’s using a mobile app