timetable-app

useIndexAndDate.ts (1866B)

---

 import { addDays, isFuture, set } from 'date-fns';
 import { useCallback, useMemo, useState } from 'react';
 
 import { DATE_FORMAT } from 'common/constant';
 import formatDate from 'common/utils/formatDate';
 
 type BaseReturn = {
 	index: number;
 	date: Date | null;
 	dates: Date[];
 	setDate: (d: Date) => void;
 	setIndex: React.Dispatch<React.SetStateAction<number>>;
 };
 
 type Return = BaseReturn;
 
 const useIndexAndDate = (dateStrings: string[]): Return => {
 	const size = dateStrings.length;
 	const dates = useMemo(
 		() => dateStrings.map((v) => new Date(v)),
 		[dateStrings],
 	);
 
 	// 初期設定の日付: 16時以前なら当日; 16時以降なら翌日; その日の時間割がなければ最も近い未来の日付; 未来がなければ最も新しい日付
 	const [index, setIndex] = useState<number>(() => {
 		// 1. 16時以前なら当日、16時以降なら翌日
 		{
 			const todays16hour = set(new Date(), {
 				hours: 16,
 				minutes: 0,
 				seconds: 0,
 			});
 			const initialDate = isFuture(todays16hour)
 				? new Date() // 16時以前
 				: addDays(new Date(), 1); // 16時以降
 			const i = dateStrings.indexOf(formatDate(initialDate, DATE_FORMAT));
 			if (i !== -1) {
 				return i;
 			}
 		}
 
 		// 2. 最も近い未来の日付
 		{
 			const i = dateStrings.findIndex((v) => isFuture(new Date(v)));
 			if (i !== -1) {
 				return i;
 			}
 		}
 
 		// 3. 最も新しい（過去の）日付
 		return size - 1;
 	});
 
 	const dateString = dateStrings[index];
 	const date = useMemo(
 		() => (dateString ? new Date(dateString) : null),
 		[dateString],
 	);
 
 	const setDate = useCallback(
 		(d: Date) => {
 			const newIndex = dateStrings.indexOf(formatDate(d, DATE_FORMAT));
 			if (newIndex !== -1) {
 				setIndex(newIndex);
 			}
 		},
 		[dateStrings],
 	);
 
 	return {
 		index,
 		date,
 		dates,
 		setDate,
 		setIndex,
 	};
 };
 
 export default useIndexAndDate;