Support custom event/filter background colors

src/components/organisms/Calendar/Calendar.js

@@ -95,13 +95,44 @@ class Calendar extends HTMLElement {
       // eslint-disable-next-line no-console
       console.error(`Failed to parse list of events:\n${eventsJSON}`);
     }
+    events = this.applyEventPropertyRules(events);
     const eventSource = {
       id: 'eventsArray',
       events: events,
     };
     return eventSource;
   }
 
+  /**
+   * Apply additional event properties as defined by event
+   * property rules supplied in the `event-property-rules` attribute.
+   *
+   * @param {Object[]} events - An array of pre-parsed
+   *        event objects. See https://fullcalendar.io/docs/event-parsing.
+   * @returns {Object[]} An array of pre-parsed event objects.
+   */
+  applyEventPropertyRules(events) {
+    const eventPropertyRules = this.getEventPropertyRules();
+    for (const property in eventPropertyRules) {
+      events = events.map((event) => {
+        const eventPropertyValue = event[property];
+        if (
+          !Object.prototype.hasOwnProperty.call(
+            eventPropertyRules[property],
+            eventPropertyValue,
+          )
+        ) {
+          return event;
+        }
+        return {
+          ...event,
+          ...eventPropertyRules[property][eventPropertyValue],
+        };
+      });
+    }
+    return events;
+  }
+
   /**
    * Replaces the 'eventsArray' event source with a new event source.
    *
@@ -132,7 +163,6 @@ class Calendar extends HTMLElement {
    * @param {string} [newFiltersJSON=null] - A JSON serialized array of event filter definitions.
    *        If null, filters will be fetched from the 'event-filters' attribute on the
    *        component instead.
-   * @returns void
    */
   buildEventFilters(newFiltersJSON = null) {
     const calendarFilterElt = this.shadowRoot.getElementById('calendarFilters');
@@ -164,7 +194,6 @@ class Calendar extends HTMLElement {
    * @param {HTMLElement} calendarFilterElt - An HTML element to be used
    *        as the container for the event filter created.
    * @param {Object} filter - A single event filter object.
-   * @returns void
    */
   buildEventFilter(calendarFilterElt, filter) {
     switch (filter.type) {
@@ -198,6 +227,8 @@ class Calendar extends HTMLElement {
           const radioButtonLabel = document.createElement('label');
           radioButtonLabel.setAttribute('for', value);
           radioButtonLabel.classList.add('btn', 'btn-primary');
+          const eventRule = this.getEventPropertyRule(filter.key, value);
+          this.applyFilterPropertyRule(radioButtonLabel, eventRule);
           radioButtonLabel.innerText = value;
           radioButtonContainer.appendChild(radioButtonLabel);
           radioFiltersContainer.appendChild(radioButtonContainer);
@@ -214,6 +245,31 @@ class Calendar extends HTMLElement {
     }
   }
 
+  /**
+   * Applies necessary styles based on the event property rule supplied.
+   *
+   * @param {HTMLElement} filterElement - The HTML element where the filter
+   *        property rule will be applied.
+   * @param {Object} eventPropertyRule - An event property rule to be used as
+   *        the filter property.
+   */
+  applyFilterPropertyRule(filterElement, eventPropertyRule) {
+    for (const property in eventPropertyRule) {
+      switch (property) {
+        case 'backgroundColor': {
+          filterElement.style.backgroundColor = eventPropertyRule[property];
+          break;
+        }
+        default: {
+          // TODO: Introduce proper error logging.
+          // eslint-disable-next-line no-console
+          console.warn(`Ignoring unsupported filter property: ${property}`);
+          return;
+        }
+      }
+    }
+  }
+
   /**
    * Handles filter element events by filter down events to the
    * user-selected criteria.
@@ -237,6 +293,44 @@ class Calendar extends HTMLElement {
     this.updateEventArraySource(JSON.stringify(events));
   }
 
+  /**
+   * Get an event/filter property and value for a given event/filter key and
+   * value.
+   * @param {string} eventKey - The event key used to filter down filters
+   *        and events for rules.
+   * @param {string} eventKeyValue - The value at the sepcified event key
+   *        used to filter down filters and events for rules.
+   * @returns Object - An event property rule consisting of
+   *          property keys and values to be applied to events and filters.
+   */
+  getEventPropertyRule(eventKey, eventKeyValue) {
+    const rules = this.getEventPropertyRules();
+    return rules[eventKey][eventKeyValue] ?? {};
+  }
+
+  /**
+   * Get all the event property rules from the `event-property-rules`
+   * attribute.
+   * @returns Object - All event property rules.
+   */
+  getEventPropertyRules() {
+    const eventPropertyRulesJSON = this.getAttribute('event-property-rules');
+    if (!eventPropertyRulesJSON) {
+      return {};
+    }
+    let eventPropertyRules = {};
+    try {
+      eventPropertyRules = JSON.parse(eventPropertyRulesJSON ?? '{}');
+    } catch (error) {
+      // TODO: Introduce proper error logging.
+      // eslint-disable-next-line no-console
+      console.error(
+        `Failed to parse event property rules:\n${eventPropertyRulesJSON}`,
+      );
+    }
+    return eventPropertyRules;
+  }
+
   attributeChangedCallback(name, oldValue, newValue) {
     if (name in Calendar.observedAttributeCbs) {
       this.handleObservedAttribute(

src/stories/calendar.stories.js

@@ -25,6 +25,23 @@ export default {
           }
         }`,
     },
+    eventPropertyRules: {
+      control: { type: 'text' },
+      description: `A JSON object of event properties to be applied to events matching
+          a specific criteria. The keys and value of the object correspond to keys and
+          values of the event and filters where the properties are applied. The object
+          associated with each key is a list of event properties and their values
+          as defined in https://fullcalendar.io/docs/event-object.
+          The rules should take the following form:
+          {
+            event_field_key: {
+              event_field_key_value: {
+                backgroundColor: '#000',
+              }
+            }
+          }
+        `,
+    },
   },
   args: {
     events: JSON.stringify([
@@ -60,6 +77,19 @@ export default {
         ],
       },
     }),
+    eventPropertyRules: JSON.stringify({
+      location: {
+        'Say Detroit Play Center': {
+          backgroundColor: '#ff6c37',
+        },
+        'Senior Facility': {
+          backgroundColor: '#1f71bf',
+        },
+        'Detroit Housing Commission': {
+          backgroundColor: '#1ed760',
+        },
+      },
+    }),
   },
 };
 
@@ -70,6 +100,9 @@ const Template = (args) => {
   if (args.eventFilters) {
     calendarElt.setAttribute('event-filters', args.eventFilters);
   }
+  if (args.eventPropertyRules) {
+    calendarElt.setAttribute('event-property-rules', args.eventPropertyRules);
+  }
   return calendarElt;
 };