Add character count on edit document page

app/assets/stylesheets/application.scss

@@ -11,5 +11,6 @@ $govuk-global-styles: true;
 @import "components/markdown-toolbar";
 @import "components/summary";
 @import "components/metadata";
+@import "components/character-count";
 
 @import "utilities/display";

app/assets/stylesheets/components/_character-count.scss

@@ -0,0 +1,23 @@
+@import "../../../node_modules/govuk-frontend/settings/all";
+@import "../../../node_modules/govuk-frontend/helpers/all";
+@import "../../../node_modules/govuk-frontend/tools/all";
+
+.govuk-textarea[data-module="character-count"],
+.govuk-input[data-module="character-count"] {
+  display: block;
+  margin-bottom: govuk-spacing(1);
+}
+
+.govuk-textarea--error[data-module="character-count"],
+.govuk-input--error[data-module="character-count"] {
+  padding: govuk-spacing(1) - 2; // stop a "jump" when width of border changes
+}
+
+.govuk-character-count__message {
+  margin-top: govuk-spacing(1);
+  margin-bottom: 0;
+}
+
+.govuk-character-count__message--disabled {
+  visibility: hidden;
+}

app/javascript/components/character-count.js

@@ -0,0 +1,166 @@
+function CharacterCount ($module) {
+  this.$module = $module
+}
+
+// Initialize component
+CharacterCount.prototype.init = function (options) {
+  // Check for module
+  var $module = this.$module
+  if (!$module) {
+    return
+  }
+
+  // Read options set using dataset ('data-' values) and merge them with options
+  var dataset = this.getDataset($module)
+  this.options = this.merge(options || {}, dataset)
+
+  // Read the limit attribute
+  var countAttribute = 'data-maxlength'
+
+  // Set the element limit
+  if ($module.getAttribute) {
+    this.maxLength = $module.getAttribute(countAttribute)
+  } else {
+    return
+  }
+
+  // Generate and reference message
+  var boundCreateCountMessage = this.createCountMessage.bind(this)
+  this.countMessage = boundCreateCountMessage()
+
+  // If there's a maximum length defined and the count message was successfully applied
+  if (this.maxLength && this.countMessage) {
+    // Replace maxlength attribute with data-maxlength to avoid hard limit
+    $module.setAttribute('maxlength', '')
+    $module.setAttribute('data-maxlength', $module.maxLength)
+
+    // Bind event changes to the textarea
+    var boundChangeEvents = this.bindChangeEvents.bind(this)
+    boundChangeEvents()
+
+    // Update count message
+    var boundUpdateCountMessage = this.updateCountMessage.bind(this)
+    boundUpdateCountMessage()
+  }
+}
+
+// Fills in default values
+CharacterCount.prototype.merge = function (obj) {
+  for (var i = 1; i < arguments.length; i++) {
+    var def = arguments[i]
+    for (var n in def) {
+      if (obj[n] === undefined) obj[n] = def[n]
+    }
+  }
+  return obj
+}
+
+CharacterCount.prototype.getDataset = function (element) {
+  var dataset = {}
+  var attributes = element.attributes
+  if (attributes) {
+    for (var i = 0; i < attributes.length; i++) {
+      var attribute = attributes[i]
+      var match = attribute.name.match(/^data-(.+)/)
+      if (match) {
+        dataset[match[1]] = attribute.value
+      }
+    }
+  }
+  return dataset
+}
+
+// Generate count message and bind it to the input
+// returns reference to the generated element
+CharacterCount.prototype.createCountMessage = function () {
+  var countElement = this.$module
+  var elementId = countElement.id
+  // Check for existing info count message
+  var countMessage = document.getElementById(elementId + '-info')
+  // If there is no existing info count message we add one right after the field
+  if (elementId && !countMessage) {
+    countElement.insertAdjacentHTML('afterend', '<span id="' + elementId + '-info" class="govuk-hint govuk-character-count__message" aria-live="polite"></span>')
+    this.describedBy = countElement.getAttribute('aria-describedby')
+    this.describedByInfo = this.describedBy + ' ' + elementId + '-info'
+    countElement.setAttribute('aria-describedby', this.describedByInfo)
+    countMessage = document.getElementById(elementId + '-info')
+  }
+  return countMessage
+}
+
+// Bind input propertychange to the elements and update based on the change
+CharacterCount.prototype.bindChangeEvents = function () {
+  var $module = this.$module
+  $module.addEventListener('keyup', this.updateCountMessage.bind(this))
+
+  // Bind focus/blur events to start/stop polling
+  $module.addEventListener('focus', this.handleFocus.bind(this))
+  $module.addEventListener('blur', this.handleBlur.bind(this))
+}
+
+// Speech recognition software such as Dragon NaturallySpeaking will modify the
+// fields by directly changing its `value`. These changes don't trigger events
+// in JavaScript, so we need to poll to handle when and if they occur.
+CharacterCount.prototype.checkIfValueChanged = function () {
+  if (!this.oldValue) this.oldValue = ''
+  if (this.$module.value !== this.oldValue) {
+    this.oldValue = this.$module.value
+    var boundUpdateCountMessage = this.updateCountMessage.bind(this)
+    boundUpdateCountMessage()
+  }
+}
+
+// Update message box
+CharacterCount.prototype.updateCountMessage = function () {
+  var countElement = this.$module
+  var options = this.options
+  var countMessage = this.countMessage
+
+  // Determine the remaining number of characters/words
+  var currentLength = countElement.value.length
+  var maxLength = this.maxLength
+  var remainingNumber = maxLength - currentLength
+
+  // Set threshold if presented in options
+  var thresholdPercent = options.threshold ? options.threshold : 0
+  var thresholdValue = maxLength * thresholdPercent / 100
+  if (thresholdValue > currentLength) {
+    countMessage.classList.add('govuk-character-count__message--disabled')
+  } else {
+    countMessage.classList.remove('govuk-character-count__message--disabled')
+  }
+
+  // Update styles
+  if (remainingNumber < 0) {
+    countElement.classList.add('govuk-textarea--error')
+    countMessage.classList.remove('govuk-hint')
+    countMessage.classList.add('govuk-error-message')
+  } else {
+    countElement.classList.remove('govuk-textarea--error')
+    countMessage.classList.remove('govuk-error-message')
+    countMessage.classList.add('govuk-hint')
+  }
+
+  // Update message
+  var charVerb = 'remaining'
+  var charNoun = 'character'
+  var displayNumber = remainingNumber
+  charNoun = charNoun + ((remainingNumber === -1 || remainingNumber === 1) ? '' : 's')
+
+  charVerb = (remainingNumber < 0) ? 'too many' : 'remaining'
+  displayNumber = Math.abs(remainingNumber)
+
+  countMessage.innerHTML = 'You have ' + displayNumber + ' ' + charNoun + ' ' + charVerb
+}
+
+CharacterCount.prototype.handleFocus = function () {
+  // Check if value changed on focus
+  this.valueChecker = setInterval(this.checkIfValueChanged.bind(this), 1000)
+}
+
+CharacterCount.prototype.handleBlur = function () {
+  // Cancel value checking on blur
+  clearInterval(this.valueChecker)
+}
+
+export default CharacterCount

app/javascript/packs/application.js

@@ -11,6 +11,7 @@ import restrict from '../restrict'
 import editDocumentForm from '../documents/edit'
 import MarkdownEditor from '../components/markdown-editor'
 import ContextualGuidance from '../components/contextual-guidance'
+import CharacterCount from '../components/character-count'
 import Raven from 'raven-js'
 
 var $sentryDsn = document.querySelector('meta[name=sentry-dsn]')
@@ -25,6 +26,7 @@ if ($sentryDsn && $sentryCurrentEnv) {
 
 restrict('edit-document-form', editDocumentForm)
 restrict('markdown-editor', ($el) => new MarkdownEditor($el).init())
+restrict('character-count', ($el) => new CharacterCount($el).init())
 
 // Initialise guidance at document level
 var guidance = new ContextualGuidance()

app/views/documents/edit.html.erb

@@ -12,6 +12,8 @@
         name: "document[title]",
         value: @document.title,
         data: {
+          "module": "character-count",
+          "maxlength": "65",
           "contextual-guidance": "document-title-guidance"
         }
       } %>
@@ -55,6 +57,8 @@
         value: @document.summary,
         rows: 4,
         data: {
+          "module": "character-count",
+          "maxlength": "160",
           "contextual-guidance": "document-summary-guidance"
         }
       } %>