Add `useGetTimeAgo` and utils (#4556)

* Create a testable version of ago() and re-enable the disabled test (#4364)

* Enable the test of ago()

* Use test cases

This puts the input and the expected values next to each other.

* Create dateDiff function

This is a copy of ago(), but with the ability to specify the second date instead of using Date.now().

* Let ago() use dateDiff()

* Move constants close to usage

* Test dateDiff instead of ago

This makes it possible to test the dates without being forced to rely on what the current date is.

The commented out tests do not yet pass. This is fixed in later commits.

* Update dateDiff and enable the remaining tests

* Split up tests, use date-fns as helpers

* Remove old test

* Add long format

* Add hook

* Migrate to hooks

* Delete old code

* Or equal to

* Update comment

---------

Co-authored-by: Jan Aagaard <jan@aagaard.net>

5 files changed, 216 insertions, 59 deletions

diff --git a/src/lib/hooks/__tests__/useTimeAgo.test.ts b/src/lib/hooks/__tests__/useTimeAgo.test.ts
new file mode 100644
index 000000000..e74f9c62d
--- /dev/null
+++ b/src/lib/hooks/__tests__/useTimeAgo.test.ts
@@ -0,0 +1,102 @@
+import {describe, expect, it} from '@jest/globals'
+import {MessageDescriptor} from '@lingui/core'
+import {addDays, subDays, subHours, subMinutes, subSeconds} from 'date-fns'
+
+import {dateDiff} from '../useTimeAgo'
+
+const lingui: any = (obj: MessageDescriptor) => obj.message
+
+const base = new Date('2024-06-17T00:00:00Z')
+
+describe('dateDiff', () => {
+  it(`works with numbers`, () => {
+    expect(dateDiff(subDays(base, 3), Number(base), {lingui})).toEqual('3d')
+  })
+  it(`works with strings`, () => {
+    expect(dateDiff(subDays(base, 3), base.toString(), {lingui})).toEqual('3d')
+  })
+  it(`works with dates`, () => {
+    expect(dateDiff(subDays(base, 3), base, {lingui})).toEqual('3d')
+  })
+
+  it(`equal values return now`, () => {
+    expect(dateDiff(base, base, {lingui})).toEqual('now')
+  })
+  it(`future dates return now`, () => {
+    expect(dateDiff(addDays(base, 3), base, {lingui})).toEqual('now')
+  })
+
+  it(`values < 5 seconds ago return now`, () => {
+    const then = subSeconds(base, 4)
+    expect(dateDiff(then, base, {lingui})).toEqual('now')
+  })
+  it(`values >= 5 seconds ago return seconds`, () => {
+    const then = subSeconds(base, 5)
+    expect(dateDiff(then, base, {lingui})).toEqual('5s')
+  })
+
+  it(`values < 1 min return seconds`, () => {
+    const then = subSeconds(base, 59)
+    expect(dateDiff(then, base, {lingui})).toEqual('59s')
+  })
+  it(`values >= 1 min return minutes`, () => {
+    const then = subSeconds(base, 60)
+    expect(dateDiff(then, base, {lingui})).toEqual('1m')
+  })
+  it(`minutes round down`, () => {
+    const then = subSeconds(base, 119)
+    expect(dateDiff(then, base, {lingui})).toEqual('1m')
+  })
+
+  it(`values < 1 hour return minutes`, () => {
+    const then = subMinutes(base, 59)
+    expect(dateDiff(then, base, {lingui})).toEqual('59m')
+  })
+  it(`values >= 1 hour return hours`, () => {
+    const then = subMinutes(base, 60)
+    expect(dateDiff(then, base, {lingui})).toEqual('1h')
+  })
+  it(`hours round down`, () => {
+    const then = subMinutes(base, 119)
+    expect(dateDiff(then, base, {lingui})).toEqual('1h')
+  })
+
+  it(`values < 1 day return hours`, () => {
+    const then = subHours(base, 23)
+    expect(dateDiff(then, base, {lingui})).toEqual('23h')
+  })
+  it(`values >= 1 day return days`, () => {
+    const then = subHours(base, 24)
+    expect(dateDiff(then, base, {lingui})).toEqual('1d')
+  })
+  it(`days round down`, () => {
+    const then = subHours(base, 47)
+    expect(dateDiff(then, base, {lingui})).toEqual('1d')
+  })
+
+  it(`values < 30 days return days`, () => {
+    const then = subDays(base, 29)
+    expect(dateDiff(then, base, {lingui})).toEqual('29d')
+  })
+  it(`values >= 30 days return months`, () => {
+    const then = subDays(base, 30)
+    expect(dateDiff(then, base, {lingui})).toEqual('1mo')
+  })
+  it(`months round down`, () => {
+    const then = subDays(base, 59)
+    expect(dateDiff(then, base, {lingui})).toEqual('1mo')
+  })
+  it(`values are rounded by increments of 30`, () => {
+    const then = subDays(base, 61)
+    expect(dateDiff(then, base, {lingui})).toEqual('2mo')
+  })
+
+  it(`values < 360 days return months`, () => {
+    const then = subDays(base, 359)
+    expect(dateDiff(then, base, {lingui})).toEqual('11mo')
+  })
+  it(`values >= 360 days return the earlier value`, () => {
+    const then = subDays(base, 360)
+    expect(dateDiff(then, base, {lingui})).toEqual(then.toLocaleDateString())
+  })
+})
diff --git a/src/lib/hooks/useTimeAgo.ts b/src/lib/hooks/useTimeAgo.ts
new file mode 100644
index 000000000..5f0782f96
--- /dev/null
+++ b/src/lib/hooks/useTimeAgo.ts
@@ -0,0 +1,95 @@
+import {useCallback, useMemo} from 'react'
+import {msg, plural} from '@lingui/macro'
+import {I18nContext, useLingui} from '@lingui/react'
+import {differenceInSeconds} from 'date-fns'
+
+export type TimeAgoOptions = {
+  lingui: I18nContext['_']
+  format?: 'long' | 'short'
+}
+
+export function useGetTimeAgo() {
+  const {_} = useLingui()
+  return useCallback(
+    (
+      date: number | string | Date,
+      options?: Omit<TimeAgoOptions, 'lingui'>,
+    ) => {
+      return dateDiff(date, Date.now(), {lingui: _, format: options?.format})
+    },
+    [_],
+  )
+}
+
+export function useTimeAgo(
+  date: number | string | Date,
+  options?: Omit<TimeAgoOptions, 'lingui'>,
+): string {
+  const timeAgo = useGetTimeAgo()
+  return useMemo(() => {
+    return timeAgo(date, {...options})
+  }, [date, options, timeAgo])
+}
+
+const NOW = 5
+const MINUTE = 60
+const HOUR = MINUTE * 60
+const DAY = HOUR * 24
+const MONTH_30 = DAY * 30
+
+/**
+ * Returns the difference between `earlier` and `later` dates, formatted as a
+ * natural language string.
+ *
+ * - All month are considered exactly 30 days.
+ * - Dates assume `earlier` <= `later`, and will otherwise return 'now'.
+ * - Differences >= 360 days are returned as the "M/D/YYYY" string
+ * - All values round down
+ */
+export function dateDiff(
+  earlier: number | string | Date,
+  later: number | string | Date,
+  options: TimeAgoOptions,
+): string {
+  const _ = options.lingui
+  const format = options?.format || 'short'
+  const long = format === 'long'
+  const diffSeconds = differenceInSeconds(new Date(later), new Date(earlier))
+
+  if (diffSeconds < NOW) {
+    return _(msg`now`)
+  } else if (diffSeconds < MINUTE) {
+    return `${diffSeconds}${
+      long ? ` ${plural(diffSeconds, {one: 'second', other: 'seconds'})}` : 's'
+    }`
+  } else if (diffSeconds < HOUR) {
+    const diff = Math.floor(diffSeconds / MINUTE)
+    return `${diff}${
+      long ? ` ${plural(diff, {one: 'minute', other: 'minutes'})}` : 'm'
+    }`
+  } else if (diffSeconds < DAY) {
+    const diff = Math.floor(diffSeconds / HOUR)
+    return `${diff}${
+      long ? ` ${plural(diff, {one: 'hour', other: 'hours'})}` : 'h'
+    }`
+  } else if (diffSeconds < MONTH_30) {
+    const diff = Math.floor(diffSeconds / DAY)
+    return `${diff}${
+      long ? ` ${plural(diff, {one: 'day', other: 'days'})}` : 'd'
+    }`
+  } else {
+    const diff = Math.floor(diffSeconds / MONTH_30)
+    if (diff < 12) {
+      return `${diff}${
+        long ? ` ${plural(diff, {one: 'month', other: 'months'})}` : 'mo'
+      }`
+    } else {
+      const str = new Date(earlier).toLocaleDateString()
+
+      if (long) {
+        return _(msg`on ${str}`)
+      }
+      return str
+    }
+  }
+}
diff --git a/src/lib/strings/time.ts b/src/lib/strings/time.ts
index 8de4b52ae..1194e0240 100644
--- a/src/lib/strings/time.ts
+++ b/src/lib/strings/time.ts
@@ -1,45 +1,3 @@
-const NOW = 5
-const MINUTE = 60
-const HOUR = MINUTE * 60
-const DAY = HOUR * 24
-const MONTH_30 = DAY * 30
-const MONTH = DAY * 30.41675 // This results in 365.001 days in a year, which is close enough for nearly all cases
-export function ago(date: number | string | Date): string {
-  let ts: number
-  if (typeof date === 'string') {
-    ts = Number(new Date(date))
-  } else if (date instanceof Date) {
-    ts = Number(date)
-  } else {
-    ts = date
-  }
-  const diffSeconds = Math.floor((Date.now() - ts) / 1e3)
-  if (diffSeconds < NOW) {
-    return `now`
-  } else if (diffSeconds < MINUTE) {
-    return `${diffSeconds}s`
-  } else if (diffSeconds < HOUR) {
-    return `${Math.floor(diffSeconds / MINUTE)}m`
-  } else if (diffSeconds < DAY) {
-    return `${Math.floor(diffSeconds / HOUR)}h`
-  } else if (diffSeconds < MONTH_30) {
-    return `${Math.round(diffSeconds / DAY)}d`
-  } else {
-    let months = diffSeconds / MONTH
-    if (months % 1 >= 0.9) {
-      months = Math.ceil(months)
-    } else {
-      months = Math.floor(months)
-    }
-
-    if (months < 12) {
-      return `${months}mo`
-    } else {
-      return new Date(ts).toLocaleDateString()
-    }
-  }
-}
-
 export function niceDate(date: number | string | Date) {
   const d = new Date(date)
   return `${d.toLocaleDateString('en-us', {
diff --git a/src/view/com/util/TimeElapsed.tsx b/src/view/com/util/TimeElapsed.tsx
index a5d3a5372..d939b3163 100644
--- a/src/view/com/util/TimeElapsed.tsx
+++ b/src/view/com/util/TimeElapsed.tsx
@@ -1,26 +1,26 @@
 import React from 'react'
 
+import {useGetTimeAgo} from '#/lib/hooks/useTimeAgo'
 import {useTickEveryMinute} from '#/state/shell'
-import {ago} from 'lib/strings/time'
 
 export function TimeElapsed({
   timestamp,
   children,
-  timeToString = ago,
+  timeToString,
 }: {
   timestamp: string
   children: ({timeElapsed}: {timeElapsed: string}) => JSX.Element
   timeToString?: (timeElapsed: string) => string
 }) {
+  const ago = useGetTimeAgo()
+  const format = timeToString ?? ago
   const tick = useTickEveryMinute()
-  const [timeElapsed, setTimeAgo] = React.useState(() =>
-    timeToString(timestamp),
-  )
+  const [timeElapsed, setTimeAgo] = React.useState(() => format(timestamp))
 
   const [prevTick, setPrevTick] = React.useState(tick)
   if (prevTick !== tick) {
     setPrevTick(tick)
-    setTimeAgo(timeToString(timestamp))
+    setTimeAgo(format(timestamp))
   }
 
   return children({timeElapsed})
diff --git a/src/view/screens/Log.tsx b/src/view/screens/Log.tsx
index e727a1fb8..e10aa83ab 100644
--- a/src/view/screens/Log.tsx
+++ b/src/view/screens/Log.tsx
@@ -1,18 +1,19 @@
 import React from 'react'
 import {StyleSheet, TouchableOpacity, View} from 'react-native'
-import {useFocusEffect} from '@react-navigation/native'
 import {FontAwesomeIcon} from '@fortawesome/react-native-fontawesome'
-import {NativeStackScreenProps, CommonNavigatorParams} from 'lib/routes/types'
-import {ScrollView} from '../com/util/Views'
-import {s} from 'lib/styles'
-import {ViewHeader} from '../com/util/ViewHeader'
-import {Text} from '../com/util/text/Text'
-import {usePalette} from 'lib/hooks/usePalette'
-import {getEntries} from '#/logger/logDump'
-import {ago} from 'lib/strings/time'
-import {useLingui} from '@lingui/react'
 import {msg} from '@lingui/macro'
+import {useLingui} from '@lingui/react'
+import {useFocusEffect} from '@react-navigation/native'
+
+import {useGetTimeAgo} from '#/lib/hooks/useTimeAgo'
+import {getEntries} from '#/logger/logDump'
 import {useSetMinimalShellMode} from '#/state/shell'
+import {usePalette} from 'lib/hooks/usePalette'
+import {CommonNavigatorParams, NativeStackScreenProps} from 'lib/routes/types'
+import {s} from 'lib/styles'
+import {Text} from '../com/util/text/Text'
+import {ViewHeader} from '../com/util/ViewHeader'
+import {ScrollView} from '../com/util/Views'
 
 export function LogScreen({}: NativeStackScreenProps<
   CommonNavigatorParams,
@@ -22,6 +23,7 @@ export function LogScreen({}: NativeStackScreenProps<
   const {_} = useLingui()
   const setMinimalShellMode = useSetMinimalShellMode()
   const [expanded, setExpanded] = React.useState<string[]>([])
+  const timeAgo = useGetTimeAgo()
 
   useFocusEffect(
     React.useCallback(() => {
@@ -70,7 +72,7 @@ export function LogScreen({}: NativeStackScreenProps<
                     />
                   ) : undefined}
                   <Text type="sm" style={[styles.ts, pal.textLight]}>
-                    {ago(entry.timestamp)}
+                    {timeAgo(entry.timestamp)}
                   </Text>
                 </TouchableOpacity>
                 {expanded.includes(entry.id) ? (