Timeline date headers

ts/util/timestamp.ts

@@ -1,7 +1,15 @@
-// Copyright 2021 Signal Messenger, LLC
+// Copyright 2021-2022 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
-const ONE_DAY = 24 * 3600 * 1000;
+import type { Moment } from 'moment';
+import moment from 'moment';
+import type { LocalizerType } from '../types/Util';
+import * as log from '../logging/log';
+import { DAY, HOUR, MINUTE, MONTH, WEEK } from './durations';
+
+const MAX_FORMAT_STRING_LENGTH = 50;
+
+type RawTimestamp = Readonly<number | Date | Moment>;
 
 export function isMoreRecentThan(timestamp: number, delta: number): boolean {
   return timestamp > Date.now() - delta;
@@ -20,5 +28,124 @@ export function isInFuture(timestamp: number): boolean {
 }
 
 export function toDayMillis(timestamp: number): number {
-  return timestamp - (timestamp % ONE_DAY);
+  return timestamp - (timestamp % DAY);
+}
+
+const isSameDay = (a: RawTimestamp, b: RawTimestamp): boolean =>
+  moment(a).isSame(b, 'day');
+
+const isToday = (rawTimestamp: RawTimestamp): boolean =>
+  isSameDay(rawTimestamp, Date.now());
+
+const isYesterday = (rawTimestamp: RawTimestamp): boolean =>
+  isSameDay(rawTimestamp, moment().subtract(1, 'day'));
+
+// This sanitization is probably unnecessary, but we do it just in case someone translates
+//   a super long format string and causes performance issues.
+function sanitizeFormatString(
+  rawFormatString: string,
+  fallback: string
+): string {
+  if (rawFormatString.length > MAX_FORMAT_STRING_LENGTH) {
+    log.error(
+      `Format string ${JSON.stringify(
+        rawFormatString
+      )} is too long. Falling back to ${fallback}`
+    );
+    return fallback;
+  }
+  return rawFormatString;
+}
+
+export function formatDateTimeShort(
+  i18n: LocalizerType,
+  rawTimestamp: RawTimestamp
+): string {
+  const timestamp = rawTimestamp.valueOf();
+
+  const now = Date.now();
+  const diff = now - timestamp;
+
+  if (diff < MINUTE) {
+    return i18n('justNow');
+  }
+
+  if (diff < HOUR) {
+    return i18n('minutesAgo', [Math.floor(diff / MINUTE).toString()]);
+  }
+
+  const m = moment(timestamp);
+
+  if (isToday(timestamp)) {
+    return m.format('LT');
+  }
+
+  if (diff < WEEK && m.isSame(now, 'month')) {
+    return m.format('ddd');
+  }
+
+  if (m.isSame(now, 'year')) {
+    return m.format(i18n('timestampFormat_M') || 'MMM D');
+  }
+
+  return m.format('ll');
+}
+
+export function formatDateTimeLong(
+  i18n: LocalizerType,
+  rawTimestamp: RawTimestamp
+): string {
+  let rawFormatString: string;
+  if (isToday(rawTimestamp)) {
+    rawFormatString = i18n('timestampFormat__long__today');
+  } else if (isYesterday(rawTimestamp)) {
+    rawFormatString = i18n('timestampFormat__long__yesterday');
+  } else {
+    rawFormatString = 'lll';
+  }
+  const formatString = sanitizeFormatString(rawFormatString, 'lll');
+
+  return moment(rawTimestamp).format(formatString);
+}
+
+export function formatTime(
+  i18n: LocalizerType,
+  rawTimestamp: RawTimestamp
+): string {
+  const timestamp = rawTimestamp.valueOf();
+  const diff = Date.now() - timestamp;
+
+  if (diff < MINUTE) {
+    return i18n('justNow');
+  }
+
+  if (diff < HOUR) {
+    return i18n('minutesAgo', [Math.floor(diff / MINUTE).toString()]);
+  }
+
+  return moment(timestamp).format('LT');
+}
+
+export function formatDate(
+  i18n: LocalizerType,
+  rawTimestamp: RawTimestamp
+): string {
+  if (isToday(rawTimestamp)) {
+    return i18n('today');
+  }
+
+  if (isYesterday(rawTimestamp)) {
+    return i18n('yesterday');
+  }
+
+  const m = moment(rawTimestamp);
+
+  const formatI18nKey =
+    Math.abs(m.diff(Date.now())) < 6 * MONTH
+      ? 'TimelineDateHeader--date-in-last-6-months'
+      : 'TimelineDateHeader--date-older-than-6-months';
+  const rawFormatString = i18n(formatI18nKey);
+  const formatString = sanitizeFormatString(rawFormatString, 'LL');
+
+  return m.format(formatString);
 }