feat: toggle between compact and full date format

2 files changed, 57 insertions, 4 deletions

diff --git a/src/components/DateString/DateString.tsx b/src/components/DateString/DateString.tsx
index e31b52e..3f2ceb2 100644
--- a/src/components/DateString/DateString.tsx
+++ b/src/components/DateString/DateString.tsx
@@ -1,9 +1,18 @@
-import React from 'react';
+import React, { useState, useMemo, useCallback } from 'react';
+import { makeStyles } from '@material-ui/core/styles';
+import compactDateString from './compactDateString';
 
 interface PropTypes {
   value: Date | string;
 }
 
+const useStyles = makeStyles({
+  root: {
+    display: 'block',
+    cursor: 'pointer'
+  }
+});
+
 const DATE_FORMAT = {
   month: 'long',
   day: 'numeric',
@@ -13,10 +22,20 @@ const DATE_FORMAT = {
 };
 
 const DateString: React.FC<PropTypes> = ({ value }) => {
-  const date = new Date(value);
-  const formatted = date.toLocaleString('default', DATE_FORMAT);
+  const [isCompact, setIsCompact] = useState<boolean>(true);
+  const classes = useStyles();
+
+  const toggleScompact = useCallback(() => setIsCompact(v => !v), [setIsCompact]);
+
+  const date = useMemo(() => new Date(value), [value]);
+  const formatted = useMemo(() => date.toLocaleString('default', DATE_FORMAT), [date]);
+  const compact = useMemo(() => compactDateString(date), [date]);
 
-  return <>{formatted}</>;
+  return (
+    <div className={classes.root} onClick={toggleScompact}>
+      {isCompact ? compact : formatted}
+    </div>
+  );
 };
 
 export default DateString;
diff --git a/src/components/DateString/compactDateString.ts b/src/components/DateString/compactDateString.ts
new file mode 100644
index 0000000..dffd912
--- /dev/null
+++ b/src/components/DateString/compactDateString.ts
@@ -0,0 +1,34 @@
+const metrics = [
+  { name: 'minute', ratio: 60 },
+  { name: 'hour', ratio: 60 },
+  { name: 'day', ratio: 24 },
+  { name: 'week', ratio: 7 },
+  { name: 'month', ratio: 4 },
+  { name: 'year', ratio: 12 }
+];
+
+const PRECISION = 0.75;
+
+const resolve = (value: number, metricIndex = 0): string => {
+  // Recursively divide value until it's ready to be presented as a string
+  const metric = metrics[metricIndex];
+  const nextMetric = metrics[metricIndex + 1];
+  const newValue = value / metric.ratio;
+
+  if (newValue < nextMetric.ratio * PRECISION) {
+    const rounded = Math.round(newValue);
+    const isPlural = rounded > 1;
+    const count = isPlural ? rounded : 'a';
+    const ending = isPlural ? 's' : '';
+    return `${count} ${metric.name}${ending} ago`;
+  }
+  return resolve(newValue, metricIndex + 1);
+};
+
+const compactDateString = (date: Date): string => {
+  const now = new Date();
+  const diff = (now.valueOf() - date.valueOf()) / 1000;
+  return resolve(diff);
+};
+
+export default compactDateString;