1 files changed, 147 insertions, 0 deletions
diff --git a/app/javascript/flavours/glitch/components/relative_timestamp.js b/app/javascript/flavours/glitch/components/relative_timestamp.js
new file mode 100644
index 000000000..51588e78c
--- /dev/null
+++ b/app/javascript/flavours/glitch/components/relative_timestamp.js
@@ -0,0 +1,147 @@
+import React from 'react';
+import { injectIntl, defineMessages } from 'react-intl';
+import PropTypes from 'prop-types';
+
+const messages = defineMessages({
+  just_now: { id: 'relative_time.just_now', defaultMessage: 'now' },
+  seconds: { id: 'relative_time.seconds', defaultMessage: '{number}s' },
+  minutes: { id: 'relative_time.minutes', defaultMessage: '{number}m' },
+  hours: { id: 'relative_time.hours', defaultMessage: '{number}h' },
+  days: { id: 'relative_time.days', defaultMessage: '{number}d' },
+});
+
+const dateFormatOptions = {
+  hour12: false,
+  year: 'numeric',
+  month: 'short',
+  day: '2-digit',
+  hour: '2-digit',
+  minute: '2-digit',
+};
+
+const shortDateFormatOptions = {
+  month: 'numeric',
+  day: 'numeric',
+};
+
+const SECOND = 1000;
+const MINUTE = 1000 * 60;
+const HOUR   = 1000 * 60 * 60;
+const DAY    = 1000 * 60 * 60 * 24;
+
+const MAX_DELAY = 2147483647;
+
+const selectUnits = delta => {
+  const absDelta = Math.abs(delta);
+
+  if (absDelta < MINUTE) {
+    return 'second';
+  } else if (absDelta < HOUR) {
+    return 'minute';
+  } else if (absDelta < DAY) {
+    return 'hour';
+  }
+
+  return 'day';
+};
+
+const getUnitDelay = units => {
+  switch (units) {
+  case 'second':
+    return SECOND;
+  case 'minute':
+    return MINUTE;
+  case 'hour':
+    return HOUR;
+  case 'day':
+    return DAY;
+  default:
+    return MAX_DELAY;
+  }
+};
+
+@injectIntl
+export default class RelativeTimestamp extends React.Component {
+
+  static propTypes = {
+    intl: PropTypes.object.isRequired,
+    timestamp: PropTypes.string.isRequired,
+  };
+
+  state = {
+    now: this.props.intl.now(),
+  };
+
+  shouldComponentUpdate (nextProps, nextState) {
+    // As of right now the locale doesn't change without a new page load,
+    // but we might as well check in case that ever changes.
+    return this.props.timestamp !== nextProps.timestamp ||
+      this.props.intl.locale !== nextProps.intl.locale ||
+      this.state.now !== nextState.now;
+  }
+
+  componentWillReceiveProps (nextProps) {
+    if (this.props.timestamp !== nextProps.timestamp) {
+      this.setState({ now: this.props.intl.now() });
+    }
+  }
+
+  componentDidMount () {
+    this._scheduleNextUpdate(this.props, this.state);
+  }
+
+  componentWillUpdate (nextProps, nextState) {
+    this._scheduleNextUpdate(nextProps, nextState);
+  }
+
+  componentWillUnmount () {
+    clearTimeout(this._timer);
+  }
+
+  _scheduleNextUpdate (props, state) {
+    clearTimeout(this._timer);
+
+    const { timestamp }  = props;
+    const delta          = (new Date(timestamp)).getTime() - state.now;
+    const unitDelay      = getUnitDelay(selectUnits(delta));
+    const unitRemainder  = Math.abs(delta % unitDelay);
+    const updateInterval = 1000 * 10;
+    const delay          = delta < 0 ? Math.max(updateInterval, unitDelay - unitRemainder) : Math.max(updateInterval, unitRemainder);
+
+    this._timer = setTimeout(() => {
+      this.setState({ now: this.props.intl.now() });
+    }, delay);
+  }
+
+  render () {
+    const { timestamp, intl } = this.props;
+
+    const date  = new Date(timestamp);
+    const delta = this.state.now - date.getTime();
+
+    let relativeTime;
+
+    if (delta < 10 * SECOND) {
+      relativeTime = intl.formatMessage(messages.just_now);
+    } else if (delta < 3 * DAY) {
+      if (delta < MINUTE) {
+        relativeTime = intl.formatMessage(messages.seconds, { number: Math.floor(delta / SECOND) });
+      } else if (delta < HOUR) {
+        relativeTime = intl.formatMessage(messages.minutes, { number: Math.floor(delta / MINUTE) });
+      } else if (delta < DAY) {
+        relativeTime = intl.formatMessage(messages.hours, { number: Math.floor(delta / HOUR) });
+      } else {
+        relativeTime = intl.formatMessage(messages.days, { number: Math.floor(delta / DAY) });
+      }
+    } else {
+      relativeTime = intl.formatDate(date, shortDateFormatOptions);
+    }
+
+    return (
+      <time dateTime={timestamp} title={intl.formatDate(date, dateFormatOptions)}>
+        {relativeTime}
+      </time>
+    );
+  }
+
+}