1 files changed, 182 insertions, 0 deletions
diff --git a/public/gapi.js b/public/gapi.js
new file mode 100644
index 0000000..f5ab73e
--- /dev/null
+++ b/public/gapi.js
@@ -0,0 +1,182 @@
+/* global chrome */
+const gapi_base = 'https://www.googleapis.com/calendar/v3';
+
+const GApiError = {
+    invalidSyncToken: 1,
+    otherError: 2,
+};
+
+function to_params(dict) {
+    return Object.entries(dict).map(([k, v]) => `${encodeURIComponent(k)}=${encodeURIComponent(v)}`).join('&');
+}
+
+function getAuthToken() {
+    return new Promise(resolver =>
+        chrome.identity.getAuthToken(
+            {interactive: true}, token => resolver(token)));
+}
+
+function getCalendars(token) {
+    return fetch(`${gapi_base}/users/me/calendarList?${to_params({access_token: token})}`,
+            { method: 'GET', async: true })
+        .then(response => response.json())
+        .then(data => data.items);
+}
+
+function getColors(token) {
+    return fetch(`${gapi_base}/colors?${to_params({access_token: token})}`,
+        { method: 'GET', async: true })
+        .then(response => response.json());
+}
+
+function getEvent(calId, eventId, token) {
+    return fetch(`${gapi_base}/calendars/${calId}/events/${eventId}?${to_params({access_token: token})}`,
+        { method: 'GET', async: true })
+        .then(response => response.json());
+}
+
+function getEvents(calId, token, syncToken, resultsPerRequest=100) {
+    let results = [];
+    const singleFetch = (pageToken, syncToken) => fetch(`${gapi_base}/calendars/${calId}/events?${to_params({
+            access_token: token,
+            pageToken,
+            syncToken,
+            maxResults: resultsPerRequest
+        })}`, { method: 'GET', async: true })
+            .then(response => {
+                if (response.status === 200)
+                    return response.json();
+                else if (response.status == 410)
+                    throw GApiError.invalidSyncToken;
+                else throw GApiError.otherErrors;
+            })
+            .then(data => {
+                results.push(...data.items);
+                if (data.nextPageToken) {
+                    return singleFetch(data.nextPageToken, '');
+                } else {
+                    return ({
+                        nextSyncToken: data.nextSyncToken,
+                        results
+                    });
+                }
+            })
+
+    return singleFetch('', syncToken);
+}
+
+class GCalendar {
+    constructor(calId, name) {
+        this.calId = calId;
+        this.name = name;
+        this.token = getAuthToken();
+        this.syncToken = '';
+        this.cache = {};
+    }
+
+    static dateToCacheKey(date) {
+        return Math.floor(date / 8.64e7);
+    }
+
+    getSlot(k) {
+        if (!this.cache[k])
+            this.cache[k] = {};
+        return this.cache[k];
+    }
+
+    static slotStartDate(k) { return new Date(k * 8.64e7); }
+    static slotEndDate(k) { return new Date((k + 1) * 8.64e7); }
+
+    addEvent(e) {
+        let ks = GCalendar.dateToCacheKey(e.start);
+        let ke = GCalendar.dateToCacheKey(new Date(e.end.getTime() - 1));
+        if (ks === ke)
+            this.getSlot(ks)[e.id] = {
+                start: e.start,
+                end: e.end,
+                id: e.id,
+                summary: e.summary};
+        else
+        {
+            this.getSlot(ks)[e.id] = {
+                start: e.start,
+                end: GCalendar.slotEndDate(ks),
+                id: e.id,
+                summary: e.summary};
+            this.getSlot(ke)[e.id] = {
+                start: GCalendar.slotStartDate(ke),
+                end: e.end,
+                id: e.id,
+                summary: e.summary};
+            for (let k = ks + 1; k < ke; k++)
+                this.getSlot(k)[e.id] = {
+                    start: GCalendar.slotStartDate(k),
+                    end: GCalendar.slotEndDate(k),
+                    id: e.id,
+                    summary: e.summary};
+        }
+    }
+
+    removeEvent(e) {
+        let ks = GCalendar.dateToCacheKey(e.start);
+        let ke = GCalendar.dateToCacheKey(new Date(e.end.getTime() - 1));
+        for (let k = ks; k <= ke; k++)
+            delete this.getSlot(k)[e.id];
+    }
+
+    getSlotEvents(k, start, end) {
+        let s = this.getSlot(k);
+        let results = [];
+        for (let id in s) {
+            if (!(s[id].start >= end || s[id].end <= start))
+            {
+                results.push({
+                    id,
+                    start: s[id].start < start ? start: s[id].start,
+                    end: s[id].end > end ? end: s[id].end,
+                    summary: s[id].summary
+                });
+            }
+        }
+        return results;
+    }
+
+    getCachedEvents(start, end) {
+        let ks = GCalendar.dateToCacheKey(start);
+        let ke = GCalendar.dateToCacheKey(new Date(end.getTime() - 1));
+        let results = this.getSlotEvents(ks, start, end);
+        for (let k = ks + 1; k < ke; k++)
+        {
+            let s = this.getSlot(k);
+            for (let id in s)
+                results.push(s[id]);
+        }
+        if (ke > ks)
+            results.push(...this.getSlotEvents(ke, start, end));
+        return results;
+    }
+
+    sync() {
+        return this.token.then(token => getEvents(this.calId, token, this.syncToken).then(r => {
+            this.syncToken = r.nextSyncToken;
+            let pm_results = r.results.map(e => e.start ? Promise.resolve(e) : getEvent(this.calId, e.id, token));
+            return Promise.all(pm_results).then(results => results.forEach(e => {
+                e.start = new Date(e.start.dateTime);
+                e.end = new Date(e.end.dateTime);
+                if (e.status === 'confirmed')
+                    this.addEvent(e);
+                else if (e.status === 'cancelled')
+                    this.removeEvent(e);
+            }));
+        })).catch(e => {
+            if (e == GApiError.invalidSyncToken) {
+                this.syncToken = '';
+                this.sync();
+            } else throw e;
+        });
+    }
+
+    getEvents(start, end) {
+        return this.sync().then(() => this.getCachedEvents(start, end));
+    }
+}