From 790f39e95bcc25cc433ba278a6f7ff37d1b5930b Mon Sep 17 00:00:00 2001
From: miteruzo <miteruzo@naver.com>
Date: Sat, 14 Mar 2026 18:32:19 +0900
Subject: [PATCH] =?UTF-8?q?=E6=97=A5=E3=81=A5=E3=81=91=E4=B8=8D=E8=A9=B3?=
 =?UTF-8?q?=E3=81=AE=E8=A1=A8=E7=A4=BA=E4=BF=AE=E6=AD=A3?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 frontend/src/lib/utils.ts | 65 +++++++++++++++++++++++++++++++++------
 1 file changed, 56 insertions(+), 9 deletions(-)

diff --git a/frontend/src/lib/utils.ts b/frontend/src/lib/utils.ts
index 95caded..0207b5f 100644
--- a/frontend/src/lib/utils.ts
+++ b/frontend/src/lib/utils.ts
@@ -10,17 +10,64 @@ export const toDate = (d: string | Date): Date => typeof d === 'string' ? new Da
 export const cn = (...inputs: ClassValue[]) => twMerge (clsx (...inputs))
 
 
-export const dateString = (d: string | Date): string =>
-    toDate (d).toLocaleString ('ja-JP-u-ca-japanese')
+export const dateString = (
+    d:        string | Date,
+    unknown:  'month' | 'day' | 'hour' | 'minute' | 'second' | null = null,
+): string =>
+    toDate (d).toLocaleString (
+	'ja-JP-u-ca-japanese',
+	{ era: 'long',
+	  year: 'numeric',
+	  month: (unknown === 'month' ? undefined : 'long'),
+	  day: unknown != null && ['month', 'day'].includes (unknown) ? undefined : 'numeric',
+	  weekday: unknown != null && ['month', 'day'].includes (unknown) ? undefined : 'short',
+	  hour: unknown == null || ['second', 'minute'].includes (unknown) ? 'numeric' : undefined,
+	  minute: unknown == null || unknown === 'second' ? 'numeric' : undefined,
+	  second: unknown == null ? 'numeric' : undefined })
 
 
-// TODO: 表示形式きしょすぎるので何とかする
 export const originalCreatedAtString = (
     f:  string | Date | null,
     b:  string | Date | null,
-): string =>
-    ([f ? `${ dateString (f) } 以降` : '',
-      b ? `${ dateString (b) } より前` : '']
-     .filter (Boolean)
-     .join (' '))
-    || '不明'
+): string => {
+  const from = f ? toDate (f) : null
+  const before = b ? toDate (b) : null
+
+  if (from && before)
+    {
+      const diff = before.getTime () - from.getTime ()
+
+      if (diff <= 60_000 /* 1 分 */)
+	return dateString (from, 'second')
+
+      if (from.getMinutes () === 0 && before.getMinutes () === 0)
+	{
+	  if (Math.abs (diff - 3_600_000 /* 1 時間 */) < 60_000)
+	    return dateString (from, 'minute') + ' (分不詳)'
+
+	  if (from.getHours () === 0 && before.getHours () === 0)
+	    {
+	      if (Math.abs (diff - 86_400_000) < 60_000)
+		return dateString (from, 'hour') + ' (時刻不詳)'
+
+	      if (from.getDate () === 1 && before.getDate () === 1)
+		{
+		  if (2_419_200_000 /* 28 日 */ <= diff && diff < 2_764_800_000 /* 32 日 */)
+		    return dateString (from, 'day') + ' (日不詳)'
+
+		  if (from.getMonth () === 0 && before.getMonth () === 0
+		      && (31_536_000_000 /* 365 日 */ <= diff
+			  && diff < 31_708_800_000 /* 367 日 */))
+		    return dateString (from, 'month') + ' (月日不詳)'
+		}
+	    }
+	}
+    }
+
+  const rtn = ([from ? `${ dateString (from, 'second') }` : '',
+		'～',
+		before ? `${ dateString (new Date (before.getTime () - 60_000), 'second') }` : '']
+	       .filter (Boolean)
+	       .join (' '))
+  return rtn === '～' ? '年月日不詳' : rtn
+}