Improved live timezone updates, access to timezone transitions. (#18)

* Add Timezone.getAllTransitions() function.
* Improve retrieval of timezone updates, taking advantage of tzexplorer.org.

Author: kshetline

README.md

@@ -1513,6 +1513,12 @@ For a given `wallTime`, expressed in milliseconds, find the most recent change i
 findTransitionByWallTime(wallTime: number): Transition | null
 ```
 
+Get all transitions in a timezone. Returns null for simple, single-UTC-offset timezones which have no transitions.
+
+```typescript
+getAllTransitions(): Transition[] | null
+```
+
 Get the short-form name for the timezone, dependent upon `utcTime` in milliseconds, such as the America/New_York timezone returning `'EST'` during the winter, but `'EDT'` during the summer.
 
 ```typescript

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "@tubular/time",
-  "version": "3.3.2",
+  "version": "3.4.0",
   "description": "Date/time, IANA timezones, leap seconds, TAI/UTC conversions, calendar with settable Julian/Gregorian switchover",
   "main": "dist/cjs/index.js",
   "module": "dist/fesm2015/index.js",
@@ -47,7 +47,8 @@
   "license": "MIT",
   "dependencies": {
     "@tubular/math": "^3.1.0",
-    "@tubular/util": "^4.3.1"
+    "@tubular/util": "^4.3.1",
+    "json-z": "^3.3.2"
   },
   "optionalDependencies": {
     "by-request": "^1.2.7"

package.json

@@ -1,3 +1,4 @@
 export interface IZonePoller {
+  getLatestVersion(url: string): Promise<string>
   getTimezones(url: string): Promise<Record<string, string>>
 }

src/i-zone-poller.ts

@@ -26,7 +26,7 @@ import timezoneSmall from './timezone-small';
 import timezoneLarge from './timezone-large';
 import timezoneLargeAlt from './timezone-large-alt';
 import { parse } from './format-parse';
-import { forEach, isString, toNumber } from '@tubular/util';
+import { forEach, isBoolean, isString, toNumber } from '@tubular/util';
 import { CalendarType, DayOfWeek, Month, LAST } from './calendar';
 import { getDeltaTAtJulianDate, tdtToUt, utToTdt } from './ut-converter';
 import { defaultLocale, getMinDaysInWeek, getStartOfWeek, getWeekend, hasDateTimeStyle, hasIntlDateTime } from './locale-data';
@@ -105,8 +105,12 @@ export function initTimezoneLargeAlt(failQuietly = false): void {
 }
 
 let pollingInterval: any;
+let lastUpdateName = 'small';
+let currentTzVersion = Timezone.version === 'unspecified' ? '' : Timezone.version;
 
-const zonesUrl = 'https://unpkg.com/@tubular/time/dist/data/timezone-{name}.js';
+const versionCheckUrl = 'https://tzexplorer.org/api/tz-version';
+const zonesUrl1 = 'https://unpkg.com/@tubular/time/dist/data/timezone-{name}.js';
+const zonesUrl2 = 'https://tzexplorer.org/tzdata/timezone-{name}.js';
 
 export type ZoneOptions = 'small' | 'large' | 'large-alt';
 
@@ -115,15 +119,50 @@ export function pollForTimezoneUpdates(zonePoller: IZonePoller | false, name: Zo
     clearInterval(pollingInterval);
 
   if (zonePoller && name && intervalDays >= 0) {
-    const url = zonesUrl.replace('{name}', name);
-    const poll = (): void => {
-      zonePoller.getTimezones(url).then(zones => {
-        dispatchUpdateNotification(Timezone.defineTimezones(zones));
-      })
-        .catch(err => dispatchUpdateNotification(err instanceof Error ? err : new Error(err)));
+    const poll = async (): Promise<void> => {
+      let latestTzVersion: string;
+
+      try {
+        latestTzVersion = await zonePoller.getLatestVersion(versionCheckUrl);
+      }
+      catch (e) {
+        dispatchUpdateNotification(e);
+        return;
+      }
+
+      if (latestTzVersion <= currentTzVersion && lastUpdateName === name) {
+        dispatchUpdateNotification(false);
+        return;
+      }
+
+      let zones: any;
+      let updated = false;
+
+      try {
+        zones = await zonePoller.getTimezones(zonesUrl1.replace('{name}', name));
+        updated = Timezone.defineTimezones(zones);
+      }
+      catch {}
+
+      if (!updated) {
+        try {
+          zones = await zonePoller.getTimezones(zonesUrl2.replace('{name}', name));
+          updated = Timezone.defineTimezones(zones);
+        }
+        catch (e) {
+          dispatchUpdateNotification(e);
+          return;
+        }
+      }
+
+      if (updated)
+        currentTzVersion = latestTzVersion;
+
+      lastUpdateName = name;
+      dispatchUpdateNotification(updated);
     };
 
-    poll();
+    poll().finally();
 
     if (intervalDays > 0) {
       pollingInterval = setInterval(poll, Math.max(intervalDays * DAY_MSEC, 3600000));
@@ -154,6 +193,9 @@ export async function getTimezones(zonePoller: IZonePoller, name: ZoneOptions =
 const listeners = new Set<(result: boolean | Error) => void>();
 
 function dispatchUpdateNotification(result: boolean | Error): void {
+  if (!(result instanceof Error) && !isBoolean(result))
+    result = new Error(String(result)); // Oddly, some errors come through as numbers like 404.
+
   listeners.forEach(listener => {
     try {
       listener(result);

src/index.ts

@@ -1195,6 +1195,10 @@ export class Timezone {
     }
   }
 
+  getAllTransitions(): Transition[] | null {
+    return !this.transitions || this.transitions.length === 0 ? null : clone(this.transitions);
+  }
+
   findTransitionByUtc(utcTime: number): Transition | null {
     if (!this.transitions || this.transitions.length === 0)
       return null;

src/timezone.ts

@@ -1,6 +1,38 @@
 import { IZonePoller } from './i-zone-poller';
 
 export const zonePollerBrowser: IZonePoller = {
+  getLatestVersion(url: string): Promise<string> {
+    return new Promise<string>((resolve, reject) => {
+      const head = document.querySelector('head');
+      const script = document.createElement('script');
+      const callbackName = 'tt_zp_callback_' + (1000000 + Math.floor(Math.random() * 9000000));
+      let version: Error | string = '';
+
+      window[callbackName] = (data: any): void => {
+        if (typeof data === 'string')
+          version = data;
+        else
+          version = new Error('Invalid data for tz version from ' + url);
+      };
+
+      head.appendChild(script);
+      script.onload = (): void => {
+        script.remove();
+        window[callbackName] = undefined;
+
+        if (version instanceof Error)
+          reject(version);
+        else
+          resolve(version);
+      };
+      script.onerror = (): void => {
+        script.remove();
+        reject(new Error('Failed to retrieve latest tz version from ' + url));
+      };
+      script.src = `${url}?callback=${callbackName}`;
+    });
+  },
+
   getTimezones(url: string): Promise<{ [p: string]: string }> {
     return new Promise<Record<string, string>>((resolve, reject) => {
       const head = document.querySelector('head');

src/zone-poller-browser.ts

@@ -1,28 +1,41 @@
 import { IZonePoller } from './i-zone-poller';
+import JSONZ from 'json-z';
 
 let requestText: (url: string, options?: any) => Promise<string>;
 let byRequestCheckDone = false;
 
-export const zonePollerNode: IZonePoller = {
-  async getTimezones(url: string): Promise<{ [p: string]: string }> {
-    if (!byRequestCheckDone && !requestText) {
-      byRequestCheckDone = true;
-
-      try { // Obscure name of by-request package to prevent webpack from generating a dependency.
-        // @ts-ignore
-        requestText = (await import(/* webpackIgnore: true */ 'tseuqer-yb'.split('').reverse().join(''))).requestText;
-      }
-      catch {}
+async function checkForRequestText(): Promise<void> {
+  if (!byRequestCheckDone && !requestText) {
+    byRequestCheckDone = true;
+
+    try { // Obscure name of by-request package to prevent webpack from generating a dependency.
+      // @ts-ignore
+      requestText = (await import(/* webpackIgnore: true */ 'tseuqer-yb'.split('').reverse().join(''))).requestText;
     }
+    catch {}
 
     if (!requestText) {
       const msg = 'npm package "by-request" should be installed to use zonePollerNode';
       console.error(msg);
       throw new Error(msg);
     }
+  }
+}
+
+export const zonePollerNode: IZonePoller = {
+  async getLatestVersion(url: string): Promise<string> {
+    await checkForRequestText();
+
+    return (await requestText(url, { timeout: 60000 })).replace(/"/g, '');
+  },
+
+  async getTimezones(url: string): Promise<{ [p: string]: string }> {
+    await checkForRequestText();
 
-    const zones = (await requestText(url, { timeout: 60000 })).replace(/^.*?=\s*/, '');
+    const zones = (await requestText(url, { timeout: 60000 }))
+      .replace(/^.*?=\s*/s, '')
+      .replace(/}.*$/s, '}');
 
-    return JSON.parse(zones);
+    return JSONZ.parse(zones);
   }
 };