Check for updates and update public calendars

Fetch the open calendars every 20 seconds
and check if they have changed since they were loaded.

If a calendar changed remove all it's data from the store
and thereby effectively trigger a reload.

This is a fairly brute force approach as it drops all known data
rather than fetching only the data that changed via the caldav sync API.

However Caldav sync is yet to be implemented. (nextcloud/cdav-library#9)
So this serves as a workaround for the time being.

See #31.

src/store/calendars.js

@@ -427,6 +427,17 @@ const getters = {
 			return true
 		})
 	},
+
+	/**
+	 * Gets all calendarObjects for a given calendar.
+	 *
+	 * @param {Object} state the store data
+	 * @param {String} calendarId the id of the calendar
+	 * @returns {function({String}): {Object}}
+	 */
+	getAllCalendarObjectsForCalendar: (state) => (calendarId) =>
+		state.calendarsById[calendarId].calendarObjects
+	,
 }
 
 const actions = {
@@ -469,6 +480,23 @@ const actions = {
 		return calendarObjects
 	},
 
+	/**
+	 *
+	 * @param {Object} vuex The destructuring object for vuex
+	 * @param {Object} vuex.getters The Vuex getters Object
+	 * @param {Object} data The data destructuring object
+	 * @param {String[]} data.tokens The tokens to load
+	 * @returns {Promise<Object[]>}
+	 */
+	async getUpdatedPublicCalendars({ getters }, { tokens }) {
+		const calendars = await findPublicCalendarsByTokens(tokens)
+		return calendars.map(mapDavCollectionToCalendar)
+			.filter(retrieved => {
+				const stored = getters.getCalendarById(retrieved.id)
+				return (stored.dav.syncToken !== retrieved.dav.syncToken)
+			})
+	},
+
 	/**
 	 * Append a new calendar to array of existing calendars
 	 *
@@ -567,6 +595,37 @@ const actions = {
 		context.commit('renameCalendar', { calendar, newName })
 	},
 
+	/**
+	 * Update a calendar to a new state as fetched from the server
+	 *
+	 * This will primarily update the syncToken of the calendar
+	 * and clear all cached data so that the calendar effectively
+	 * reloads.
+	 *
+	 * @param {Object} vuex The destructuring object for vuex
+	 * @param {Function} vuex.commit The Vuex commit function
+	 * @param {Object} vuex.getters The Vuex getters Object
+	 * @param {Object} context the store mutations Current context
+	 * @param {Object} data destructuring object
+	 * @param {Object} data.calendar the calendar to delete
+	 * @returns {Promise}
+	 */
+	async updateCalendar({ commit, getters }, { calendar }) {
+		commit('markCalendarAsLoading', { calendar })
+		getters.getAllTimeRangesForCalendar(calendar.id)
+			.forEach(timeRange => {
+				commit('removeTimeRange', { timeRangeId: timeRange.id })
+			})
+		getters.getAllCalendarObjectsForCalendar(calendar.id)
+			.forEach(id => {
+				const calendarObject = { id }
+				commit('deleteCalendarObject', { calendarObject })
+			})
+		commit('deleteCalendar', { calendar })
+		commit('addCalendar', { calendar })
+		commit('markCalendarAsNotLoading', { calendar })
+	},
+
 	/**
 	 * Change a calendar's color
 	 *

src/store/fetchedTimeRanges.js

@@ -151,7 +151,7 @@ const mutations = {
 	},
 
 	/**
-	 * Adds a calendar-object-id to all time-ranges of a given caloendar
+	 * Adds a calendar-object-id to all time-ranges of a given calendar
 	 *
 	 * @param {Object} state The vuex state
 	 * @param {Object} data The destructuring object
@@ -171,7 +171,7 @@ const mutations = {
 	},
 
 	/**
-	 * Removes a calendar-object-id to all time-ranges of a given caloendar
+	 * Removes a calendar-object-id from all time-ranges of a given calendar
 	 *
 	 * @param {Object} state The vuex state
 	 * @param {Object} data The destructuring object

src/views/Calendar.vue

@@ -114,6 +114,7 @@ export default {
 			updateTodayJob: null,
 			updateTodayJobPreviousDate: null,
 			showEmptyCalendarScreen: false,
+			checkForUpdatesJob: null,
 		}
 	},
 	computed: {
@@ -183,6 +184,18 @@ export default {
 				})
 			}
 		}, 1000 * 60)
+		this.checkForUpdatesJob = setInterval(async() => {
+			const tokens = this.$route.params.tokens.split('-')
+			const updated = await this.$store.dispatch('getUpdatedPublicCalendars', { tokens })
+			updated.forEach(calendar => {
+				this.$store.dispatch('updateCalendar', { calendar })
+			})
+		}, 1000 * 20)
+
+	},
+	destroy() {
+		clearInterval(this.timeFrameCahceExpiryJob)
+		clearInterval(this.checkForUpdatesJob)
 	},
 	async beforeMount() {
 		this.$store.commit('loadSettingsFromServer', {