traQ上のメッセージの投稿・編集日時に年月日を適宜省略しつつ付け足す

src/lib/basic/date.ts

@@ -42,12 +42,25 @@ export const getDateRepresentationWithoutSameDate = (
 }
 
 export const getDisplayDate = (createdAt: string, updatedAt: string) => {
-  const createdDate = new Date(createdAt)
-  if (createdAt === updatedAt) {
-    return getTimeString(createdDate)
+  let displayDate = new Date(createdAt)
+  if (createdAt !== updatedAt) {
+    displayDate = new Date(updatedAt)
+  }
+  const today = new Date()
+  const timeString = getTimeString(displayDate)
+  const yesterday = new Date(today)
+  yesterday.setDate(today.getDate() - 1)
+
+  if (getFullDayString(displayDate) === getFullDayString(today)) {
+    return '今日' + ' ' + timeString
+  }
+  if (getFullDayString(displayDate) === getFullDayString(yesterday)) {
+    return '昨日' + ' ' + timeString
+  }
+  if (displayDate.getFullYear() === today.getFullYear()) {
+    return getDayString(displayDate) + ' ' + timeString
   } else {
-    const updatedDate = new Date(updatedAt)
-    return getDateRepresentationWithoutSameDate(updatedDate, createdDate)
+    return getFullDayString(displayDate) + ' ' + timeString
   }
 }
 

tests/unit/lib/basic/date.spec.ts

@@ -94,18 +94,33 @@ describe('getDateRepresentationWithoutSameDate', () => {
 })
 
 describe('getDisplayDate', () => {
-  const dateISO = '2001-04-04T05:20:34'
-
-  it('should get time string when not modified', () => {
-    expect(getDisplayDate(dateISO, dateISO)).toBe('05:20')
+  beforeEach(() => {
+    vi.useFakeTimers()
   })
-  it('should get time string when same date', () => {
-    const dateISO2 = '2001-04-04T08:25:34'
-    expect(getDisplayDate(dateISO, dateISO2)).toBe('08:25')
+  afterEach(() => {
+    vi.useRealTimers()
   })
-  it('should get date string when not same date', () => {
-    const dateISO2 = '2001-06-04T08:25:34'
-    expect(getDisplayDate(dateISO, dateISO2)).toBe('06/04 08:25')
+
+  const createdDateISO = '2010-04-01T12:34:56'
+  const updatedDateISO = '2010-05-02T14:28:57'
+
+  it('should say 今日 when updated today', () => {
+    vi.setSystemTime('2010-05-02T15:00:00')
+    expect(getDisplayDate(createdDateISO, updatedDateISO)).toBe('今日 14:28')
+  })
+  it('should say 昨日 when updated yesterday', () => {
+    vi.setSystemTime('2010-05-03T15:00:00')
+    expect(getDisplayDate(createdDateISO, updatedDateISO)).toBe('昨日 14:28')
+  })
+  it('should get MM/DD when updated in the same year', () => {
+    vi.setSystemTime('2010-07-07T15:00:00')
+    expect(getDisplayDate(createdDateISO, updatedDateISO)).toBe('05/02 14:28')
+  })
+  it('should get YYYY/MM/DD when updated before last year', () => {
+    vi.setSystemTime('2015-10-10T15:00:00')
+    expect(getDisplayDate(createdDateISO, updatedDateISO)).toBe(
+      '2010/05/02 14:28'
+    )
   })
 })