Add errors and warnings based on estimated due date (#163)

This adds some error messages if the estimated due date is highly likely
to be an error, and some warnings if the estimated due date is outside
the recommended period, but still possible.

## Errors

### Blank

<img width="812" alt="Screenshot 2025-01-14 at 15 02 12"
src="https://github.com/user-attachments/assets/9afe8356-536a-4713-96fe-052e8d2f271c"
/>

### Due date is more than 37 weeks after vaccination date

This is an error as also highly unlikely to know they are pregnant at
this point

![Screenshot 2025-01-16 at 14 18
36](https://github.com/user-attachments/assets/558dc3f2-ed70-4301-a66c-ef8dadb570d8)

### Due date is more than 4 weeks before vaccination date

This is an error as almost no pregnancies will go beyond 44 weeks

<img width="908" alt="Screenshot 2025-01-14 at 14 58 25"
src="https://github.com/user-attachments/assets/868d0ffd-f4d1-4315-a589-aec5c3aca4c8"
/>

## Warnings

These are shown on a subsequent page, and users can choose to either
continue, go back (eg to fix a mistake) or cancel the vaccination (by
navigating away).

### RSV

This is only shown if the patient is not yet 28 weeks pregnant

![Screenshot 2025-01-16 at 14 22
29](https://github.com/user-attachments/assets/02398ba6-611b-4e73-bbd2-be5b9f585094)

### Pertussis

This is only shown if the patient is not yet 16 weeks pregnant

![Screenshot 2025-01-16 at 14 21
30](https://github.com/user-attachments/assets/38445572-e68b-409f-ac1a-a11e114f90b5)

---------

Co-authored-by: Anna-Sutton <[email protected]>

Author: frankieroberto

app/routes/vaccinate.js

@@ -1,3 +1,33 @@
+// Returns a date object from a valid year, month, and day.
+// Note: inputs can be strings, and month is based on 1 = Jan
+// rather than 0 = Jan
+// Time is set to midday
+function dateFromYearMonthDay(year, month, day) {
+  const yearInt = parseInt(year)
+  const monthInt = parseInt(month)
+  const dayInt = parseInt(day)
+
+  if (yearInt > 0 && monthInt > 0 && dayInt > 0) {
+    return new Date(yearInt, (monthInt - 1), dayInt, 12)
+  } else {
+    return null
+  }
+}
+
+// If date2 is after date1 return positive number of days,
+// if it’s before then negative, if it’s the same then 0.
+function daysBetweenDates(date1, date2) {
+  if (!date1 || !date2) {
+    return null
+  }
+  const millisecondsInADay = (24 * 3600 * 1000)
+  const differenceInMilliseconds = date2.getTime() - date1.getTime()
+  const differenceInDays = differenceInMilliseconds / millisecondsInADay
+
+  return Math.floor(differenceInDays)
+}
+
+
 module.exports = router => {
 
   router.post('/vaccinate/answer-patient-nhs-number-known', (req, res) => {
@@ -16,7 +46,6 @@ module.exports = router => {
     } else {
       res.redirect('/vaccinate/patient?showError=yes')
     }
-
   })
 
 
@@ -80,6 +109,124 @@ module.exports = router => {
 
   })
 
+  router.get('/vaccinate/patient-estimated-due-date', (req, res) => {
+
+    const showError = req.query.showError
+    const data = req.session.data
+    const pregnancyDueDate = dateFromYearMonthDay(data.pregnancyDueDate?.year, data.pregnancyDueDate?.month, data.pregnancyDueDate?.day);
+
+    let dateErrorMessage = false
+
+    if (showError === 'yes') {
+
+      if (!pregnancyDueDate) {
+        dateErrorMessage = "Enter estimated due date"
+      } else if (data.vaccinationToday === "yes") {
+
+        const vaccinationDate = new Date()
+
+        // Estimated due date is based on 40 weeks (280 days) since last period
+        const numberOfDaysPregnant = 280 - daysBetweenDates(vaccinationDate, pregnancyDueDate)
+
+        if (numberOfDaysPregnant < 21) {
+          dateErrorMessage = "Estimated due date is too far in the future. Patient must be at least 21 days pregnant."
+        } else if (numberOfDaysPregnant > 308) {
+          dateErrorMessage = "Patient cannot be more than 44 weeks pregnant"
+        }
+
+      }
+    }
+
+    res.render('vaccinate/patient-estimated-due-date', {
+      dateErrorMessage
+    })
+  })
+
+
+  // Routing page after setting pregnancy estimated due date
+  router.post('/vaccinate/save-estimated-due-date', (req, res) => {
+
+    const data = req.session.data
+    const pregnancyDueDate = dateFromYearMonthDay(data.pregnancyDueDate?.year, data.pregnancyDueDate?.month, data.pregnancyDueDate?.day)
+
+    // Re-render with error if date is not set
+    if (!pregnancyDueDate) {
+      return res.redirect('/vaccinate/patient-estimated-due-date?showError=yes')
+    }
+
+    // Skip to consent page if the vaccination happened in the past
+    // as it’s then too late for any warnings
+    if (data.vaccinationToday != "yes") {
+      return res.redirect('/vaccinate/consent')
+    }
+
+    // Vaccination date is today
+    const vaccinationDate = new Date()
+
+    // Estimated due date is based on 40 weeks (280 days) since last period
+    const numberOfDaysPregnant = 280 - daysBetweenDates(vaccinationDate, pregnancyDueDate)
+
+    // Being less than 3 weeks or more than 44 weeks (308 days) pregnant
+    // results in an error
+    if (numberOfDaysPregnant < 21 || numberOfDaysPregnant > 308) {
+      return res.redirect('/vaccinate/patient-estimated-due-date?showError=yes')
+    }
+
+    // RSV is recommended from 28+ weeks (196 days)
+    if (data.vaccinationToday == 'yes' && data.vaccine === "RSV" && numberOfDaysPregnant < 196) {
+      res.redirect('/vaccinate/patient-estimated-due-date-rsv-warning')
+
+    // Pertussis is recommended between 16 weeks (112 days) and 32 weeks
+    } else if (data.vaccinationToday == 'yes' && data.vaccine === "Pertussis" && numberOfDaysPregnant < 112) {
+      res.redirect('/vaccinate/patient-estimated-due-date-pertussis-warning')
+    } else {
+      res.redirect('/vaccinate/consent')
+    }
+
+  });
+
+  router.get('/vaccinate/patient-estimated-due-date-rsv-warning', (req, res) => {
+
+    const data = req.session.data
+    const pregnancyDueDate = dateFromYearMonthDay(data.pregnancyDueDate?.year, data.pregnancyDueDate?.month, data.pregnancyDueDate?.day)
+
+    // Vaccination date is today
+    const vaccinationDate = new Date()
+
+    // Estimated due date is based on 40 weeks (280 days) since last period
+    const numberOfDaysPregnant = 280 - daysBetweenDates(vaccinationDate, pregnancyDueDate)
+
+    const fullWeeksPregnant = Math.floor(numberOfDaysPregnant / 7)
+    const remainderDaysPregnant = (numberOfDaysPregnant % 7)
+
+    res.render('vaccinate/patient-estimated-due-date-rsv-warning', {
+      fullWeeksPregnant,
+      remainderDaysPregnant
+    })
+
+  })
+
+  router.get('/vaccinate/patient-estimated-due-date-pertussis-warning', (req, res) => {
+
+    const data = req.session.data
+    const pregnancyDueDate = dateFromYearMonthDay(data.pregnancyDueDate?.year, data.pregnancyDueDate?.month, data.pregnancyDueDate?.day)
+
+    // Vaccination date is today
+    const vaccinationDate = new Date()
+
+    // Estimated due date is based on 40 weeks (280 days) since last period
+    const numberOfDaysPregnant = 280 - daysBetweenDates(vaccinationDate, pregnancyDueDate)
+
+    const fullWeeksPregnant = Math.floor(numberOfDaysPregnant / 7)
+    const remainderDaysPregnant = (numberOfDaysPregnant % 7)
+
+    res.render('vaccinate/patient-estimated-due-date-pertussis-warning', {
+      fullWeeksPregnant,
+      remainderDaysPregnant
+    })
+
+  })
+
   // Routing page after DONE
   router.post('/vaccinate/what-next', (req, res) => {
 

app/views/vaccinate/patient-estimated-due-date-pertussis-warning.html

@@ -0,0 +1,36 @@
+{% extends 'layout.html' %}
+
+{% block pageTitle %}
+  Vaccines
+{% endblock %}
+
+{% set currentSection = "vaccinate" %}
+
+{% block beforeContent %}
+  {{ backLink({ href: "/vaccinate/patient-estimated-due-date" }) }}
+{% endblock %}
+
+{% block content %}
+  <div class="nhsuk-grid-row">
+    <div class="nhsuk-grid-column-two-thirds">
+
+      <h1 class="nhsuk-heading-l">Are you sure you want to continue?</h1>
+
+      <p>{{ data.patientName }} is {{ fullWeeksPregnant | plural("week") }}{% if remainderDaysPregnant > 0 %} and {{ remainderDaysPregnant | plural("day") }}{% endif %} pregnant.
+      </p>
+
+      <p>The pertussis vaccine is recommended between 16 and 32 weeks of pregnancy.</p>
+
+      <p><a href="https://www.gov.uk/government/publications/vaccination-against-pertussis-whooping-cough-for-pregnant-women/pertussis-whooping-cough-vaccination-programme-for-pregnant-women" target="_blank">UKHSA guidance on pertussis vaccination of pregnant women (opens in new tab)</a>.
+
+
+    </div>
+  </div>
+
+  {{ button({
+    "text": "Continue",
+    "href": "/vaccinate/consent"
+  }) }}
+
+{% endblock %}
+

app/views/vaccinate/patient-estimated-due-date-rsv-warning.html

@@ -0,0 +1,37 @@
+{% extends 'layout.html' %}
+
+{% block pageTitle %}
+  Vaccines
+{% endblock %}
+
+{% set currentSection = "vaccinate" %}
+
+{% block beforeContent %}
+  {{ backLink({ href: "/vaccinate/patient-estimated-due-date" }) }}
+{% endblock %}
+
+{% block content %}
+  <div class="nhsuk-grid-row">
+    <div class="nhsuk-grid-column-two-thirds">
+
+      <h1 class="nhsuk-heading-l">Are you sure you want to continue?</h1>
+
+
+      <p>{{ data.patientName }} is {{ fullWeeksPregnant | plural("week") }}{% if remainderDaysPregnant > 0 %} and {{ remainderDaysPregnant | plural("day") }}{% endif %} pregnant.
+      </p>
+
+      <p>The {{ data.vaccine }} vaccine is not routinely recommended before 28 weeks of pregnancy.</p>
+
+      <p><a href="https://www.gov.uk/government/publications/respiratory-syncytial-virus-rsv-programme-information-for-healthcare-professionals/rsv-vaccination-of-pregnant-women-for-infant-protection-information-for-healthcare-practitioners" target="_blank">UKHSA guidance on RSV vaccination of pregnant women (opens in new tab)</a>.
+
+
+    </div>
+  </div>
+
+  {{ button({
+    "text": "Continue",
+    "href": "/vaccinate/consent"
+  }) }}
+
+{% endblock %}
+

app/views/vaccinate/patient-estimated-due-date.html

@@ -14,7 +14,20 @@
   <div class="nhsuk-grid-row">
     <div class="nhsuk-grid-column-two-thirds">
 
-      <form action="/vaccinate/consent" method="post" novalidate>
+      {% if dateErrorMessage %}
+        {{ errorSummary({
+          titleText: "There is a problem",
+          errorList: [{
+            text: dateErrorMessage,
+            href: "#pregnancyDueDate-day"
+          }]
+        }) }}
+      {% endif %}
+
+
+      <form action="/vaccinate/save-estimated-due-date" method="post" novalidate>
+        <!-- reset showError to false -->
+        <input type="hidden" name="showError" value="">
 
         {{ dateInput({
           id: "pregnancyDueDate",
@@ -26,22 +39,25 @@
               isPageHeading: true
             }
           },
+          errorMessage: {
+            text: dateErrorMessage
+          } if dateErrorMessage,
           values: data.pregnancyDueDate,
           hint: {
             text: "For example, 15 6 2025"
           },
           items: [
             {
               name: "day",
-              classes: "nhsuk-input--width-2"
+              classes: "nhsuk-input--width-2 " + ("nhsuk-input--error" if dateErrorMessage else "")
             },
             {
               name: "month",
-              classes: "nhsuk-input--width-2"
+              classes: "nhsuk-input--width-2 " + ("nhsuk-input--error" if dateErrorMessage else "")
             },
             {
               name: "year",
-              classes: "nhsuk-input--width-4"
+              classes: "nhsuk-input--width-4 " + ("nhsuk-input--error" if dateErrorMessage else "")
             }
           ]
         }) }}