feat: calendar

src/components/Calendar/Calendar.stories.tsx

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+import React from "react";
+import { StoryObj } from "@storybook/react";
+
+import Calendar, { CalendarProps } from "./Calendar";
+import dayjs from "dayjs";
+
+export default {
+  title: "Components/Inputs/Calendar",
+  components: Calendar,
+};
+
+export const Default: StoryObj<CalendarProps> = {
+  render: () => {
+    const [date, setDate] = React.useState(dayjs());
+    return <Calendar date={date} onChange={setDate} />;
+  },
+};
+
+export const WithActions: StoryObj<CalendarProps> = {
+  render: () => {
+    const [date, setDate] = React.useState(dayjs());
+    const actions = [
+      {
+        text: "今日",
+        onClick: () => setDate(dayjs()),
+      },
+      {
+        text: "来週",
+        onClick: () => setDate(dayjs().add(1, "week")),
+      },
+      {
+        text: "来月",
+        onClick: () => setDate(dayjs().add(1, "month")),
+      },
+    ];
+    return <Calendar date={date} actions={actions} onChange={setDate} />;
+  },
+};

src/components/Calendar/Calendar.tsx

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+import dayjs, { Dayjs } from "dayjs";
+import { Card, ScrollArea, Typography } from "..";
+import React, { forwardRef, memo, useRef } from "react";
+import { Day } from "./internal/Day";
+import { weekList, HEIGHT } from "./constants";
+import {
+  Container,
+  CalendarContainer,
+  DatePickerContainer,
+  DayStyle,
+  CalendarMonth,
+} from "./styled";
+import { useScroll } from "./hooks/useScroll";
+import { Action, Actions } from "./internal/Actions";
+
+export type CalendarProps = {
+  date: Dayjs;
+  actions?: Action[];
+  onChange: (value: Dayjs) => void;
+};
+
+const Calendar = forwardRef<HTMLDivElement, CalendarProps>(function Calendar({
+  date,
+  actions,
+  onChange,
+}) {
+  const ref = useRef<HTMLDivElement>(null);
+  const { monthList } = useScroll(date, ref);
+
+  return (
+    <Card ref={ref} display="flex" style={{ width: "fit-content" }}>
+      <Actions actions={actions} />
+      <Container>
+        <ScrollArea
+          ref={ref}
+          minHeight={HEIGHT}
+          maxHeight={HEIGHT}
+          id="calendar"
+        >
+          <>
+            {monthList.map((m) => (
+              <DatePickerContainer
+                key={m.format("YYYY-MM")}
+                id={m.format("YYYY-MM")}
+                className={m.format("YYYY-MM")}
+              >
+                {/* 年月の表示 */}
+                <CalendarMonth>
+                  <Typography weight="bold" size="xl">
+                    {m.format("YYYY年MM月")}
+                  </Typography>
+                </CalendarMonth>
+
+                {/* カレンダーの表示 */}
+                <CalendarContainer>
+                  {/* 曜日の表示 */}
+                  {weekList["ja"].map((week) => (
+                    <DayStyle key={week}>{week}</DayStyle>
+                  ))}
+
+                  {/* 開始曜日まで空白をセット */}
+                  {Array.from(new Array(m.startOf("month").day()), (_, i) => (
+                    <DayStyle key={i} />
+                  ))}
+
+                  {/* 日付の表示 */}
+                  {Array.from(new Array(m.daysInMonth()), (_, i) => i + 1).map(
+                    (day) => (
+                      <Day
+                        key={day}
+                        value={dayjs(new Date(m.year(), m.month(), day))}
+                        // ややこしいけど、ここでのselectedは、選択中の日付かどうかを判定している
+                        // つまり、選択中の日付の場合はtrueになり、style で色を変える
+                        selected={
+                          date.format("YYYY-MM-DD") ===
+                          dayjs(new Date(m.year(), m.month(), day)).format(
+                            "YYYY-MM-DD",
+                          )
+                        }
+                        onClickDate={onChange}
+                      >
+                        {day}
+                      </Day>
+                    ),
+                  )}
+                </CalendarContainer>
+              </DatePickerContainer>
+            ))}
+          </>
+        </ScrollArea>
+      </Container>
+    </Card>
+  );
+});
+
+export default memo(Calendar);

src/components/Calendar/constants.ts

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+// for `<ScrollArea />`
+export const HEIGHT = "400px";
+
+export const weekList = {
+  en: ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"],
+  ja: ["日", "月", "火", "水", "木", "金", "土"],
+};
+
+export const monthList = {
+  en: [
+    "Jan",
+    "Feb",
+    "Mar",
+    "Apr",
+    "May",
+    "June",
+    "July",
+    "Aug",
+    "Sept",
+    "Oct",
+    "Nov",
+    "Dec",
+  ],
+  ja: [
+    "1月",
+    "2月",
+    "3月",
+    "4月",
+    "5月",
+    "6月",
+    "7月",
+    "8月",
+    "9月",
+    "10月",
+    "11月",
+    "12月",
+  ],
+};

src/components/Calendar/hooks/__tests__/useScroll.test.ts

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+import { renderHook, act } from "@testing-library/react";
+import dayjs, { Dayjs } from "dayjs";
+import { useScroll, getNextMonthList, getPrevMonthList } from "../useScroll";
+
+(global as any).IntersectionObserver = jest.fn().mockImplementation(() => ({
+  observe: () => jest.fn(),
+  unobserve: () => jest.fn(),
+  disconnect: () => jest.fn(),
+}));
+
+describe("useScroll hook", () => {
+  let date: Dayjs;
+  let ref: React.RefObject<HTMLDivElement>;
+
+  beforeEach(() => {
+    date = dayjs("2021-01-01");
+    ref = { current: document.createElement("div") };
+  });
+
+  test("loads next six months when reaching the bottom 10% of ScrollArea", () => {
+    const { result } = renderHook(() => useScroll(date, ref));
+
+    act(() => {
+      //   const targets = document.getElementsByClassName(date.format("YYYY-MM"));
+    });
+
+    const months = [...getPrevMonthList(date), ...getNextMonthList(date)].map(
+      (d) => d.format("YYYY-MM"),
+    );
+    expect(result.current.monthList.map((m) => m.format("YYYY-MM"))).toEqual(
+      expect.arrayContaining(months),
+    );
+  });
+
+  test("loads previous six months when reaching the top 10% of ScrollArea", () => {
+    const { result } = renderHook(() => useScroll(date, ref));
+
+    act(() => {
+      //   const targets = document.getElementsByClassName(date.format("YYYY-MM"));
+    });
+
+    const months = [...getPrevMonthList(date), ...getNextMonthList(date)].map(
+      (d) => d.format("YYYY-MM"),
+    );
+    expect(result.current.monthList.map((m) => m.format("YYYY-MM"))).toEqual(
+      expect.arrayContaining(months),
+    );
+  });
+});

src/components/Calendar/hooks/constants.ts

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+// MEMO: 3ヶ月でもいいかも？
+export const MONTH_SIZE = 4;

src/components/Calendar/hooks/useScroll.ts

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+import { Dayjs } from "dayjs";
+import { useEffect, useState } from "react";
+import { MONTH_SIZE } from "./constants";
+
+export const getNextMonthList = (date: Dayjs) =>
+  Array.from(new Array(MONTH_SIZE)).map((_, i) => date.add(i, "month"));
+
+export const getPrevMonthList = (date: Dayjs) =>
+  Array.from(new Array(MONTH_SIZE)).map((_, i) =>
+    date.subtract(MONTH_SIZE - i, "month"),
+  );
+
+/**
+ * @memo カレンダーを選択中の月にするときに、アニメーション等があるといいかもしれない
+ *
+ * @param date 選択中の日付
+ * @param ref カレンダーの親要素のref、IntersectionObserverのrootに使う
+ * @return monthList 表示する月のリスト
+ */
+export const useScroll = (
+  date: Dayjs,
+  ref: React.RefObject<HTMLDivElement>,
+) => {
+  // 読み込み済みの日付を保持する
+  const [loaded, setLoaded] = useState<{
+    prev: Dayjs;
+    next: Dayjs;
+  }>({
+    prev: date.subtract(MONTH_SIZE, "month"),
+    next: date.add(MONTH_SIZE, "month"),
+  });
+  // 表示する月のリスト
+  // この hooks の戻り値
+  const [monthList, setMonthList] = useState<Dayjs[]>([
+    ...getPrevMonthList(date),
+    ...getNextMonthList(date),
+  ]);
+
+  useEffect(() => {
+    // 全てのカレンダーに 2023-06 のような名前の className を振ってある
+    const targets = document.getElementsByClassName(date.format("YYYY-MM"));
+    for (const target of Array.from(targets)) {
+      target.scrollIntoView({ block: "center" });
+    }
+  }, [date]);
+
+  useEffect(() => {
+    setLoaded({
+      prev: date.subtract(MONTH_SIZE, "month"),
+      next: date.add(MONTH_SIZE, "month"),
+    });
+    setMonthList([...getPrevMonthList(date), ...getNextMonthList(date)]);
+  }, [date]);
+
+  // next を読み込む
+  useEffect(() => {
+    const observer = new IntersectionObserver(
+      (entries) => {
+        entries.forEach((entry) => {
+          if (entry.isIntersecting) {
+            // next、prev をそれぞれ MONTH_SIZE 分ずらす
+            const next = loaded.next.add(MONTH_SIZE, "month");
+            const prev = loaded.prev.add(MONTH_SIZE, "month");
+
+            // prev と next の月のリストを取得
+            const prevYearMonthList = getPrevMonthList(loaded.next);
+            const nextYearMonthList = getNextMonthList(loaded.next);
+
+            setLoaded({ next, prev });
+            setMonthList([...prevYearMonthList, ...nextYearMonthList]);
+          }
+        });
+      },
+      {
+        root: ref.current,
+        threshold: 0.1,
+      },
+    );
+
+    const targets = document.getElementsByClassName(
+      loaded.next.subtract(1, "month").format("YYYY-MM"),
+    );
+
+    for (const target of Array.from(targets)) {
+      observer.observe(target);
+    }
+
+    return () => {
+      for (const target of Array.from(targets)) {
+        observer.unobserve(target);
+      }
+    };
+  }, [loaded, ref]);
+
+  // prev を読み込む
+  useEffect(() => {
+    const observer = new IntersectionObserver(
+      (entries) => {
+        entries.forEach((entry) => {
+          if (entry.isIntersecting) {
+            // next、prev をそれぞれ MONTH_SIZE 分ずらす
+            const next = loaded.next.subtract(MONTH_SIZE, "month");
+            const prev = loaded.prev.subtract(MONTH_SIZE, "month");
+
+            // prev と next の月のリストを取得
+            const prevYearMonthList = getPrevMonthList(loaded.prev);
+            const nextYearMonthList = getNextMonthList(loaded.prev);
+
+            setLoaded({ next, prev });
+            setMonthList([...prevYearMonthList, ...nextYearMonthList]);
+          }
+        });
+      },
+      {
+        root: ref.current,
+        threshold: 0.1,
+      },
+    );
+
+    const targets = document.getElementsByClassName(
+      loaded.prev.add(1, "month").format("YYYY-MM"),
+    );
+
+    for (const target of Array.from(targets)) {
+      observer.observe(target);
+    }
+
+    return () => {
+      for (const target of Array.from(targets)) {
+        observer.unobserve(target);
+      }
+    };
+  }, [loaded, ref]);
+
+  return { monthList };
+};

src/components/Calendar/index.ts

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+export { Calendar } from "./Calendar";