fix: fix type error in datetime module

frontend/src/utils/datetime.ts

@@ -1,3 +1,5 @@
+import { lcm, format } from "./utils";
+import { universalGetDayOfWeek } from "./i18n";
 
 // YYC MARK:
 // This file is synchronized with "dt.py".
@@ -30,16 +32,366 @@ const PRECOMPILED_LOOP_STOP_RULES = {
 
 // region: Core Functions
 
-export function resolveLoopRules4UI(strl: string) {
+/** Year loop: [type=0, isStrict, yearSpan] */
+type YearLoopRule = [0, boolean, number];
+/** Month loop: [type=1, isStrict, mode, monthSpan] */
+type MonthLoopRule = [1, boolean, 'A' | 'B' | 'C' | 'D', number];
+/** Week loop: [type=2, 7 weekday booleans, weekSpan] */
+type WeekLoopRule = [2, boolean, boolean, boolean, boolean, boolean, boolean, boolean, number];
+/** Day loop: [type=3, daySpan] */
+type DayLoopRule = [3, number];
 
+type LoopRule = YearLoopRule | MonthLoopRule | WeekLoopRule | DayLoopRule;
+
+/** Infinity stop: [type=0] */
+type InfinityStopRule = [0];
+/** Datetime stop: [type=1, timestamp] */
+type DatetimeStopRule = [1, number];
+/** Times stop: [type=2, times] */
+type TimesStopRule = [2, number];
+
+type LoopStopRule = InfinityStopRule | DatetimeStopRule | TimesStopRule;
+
+/**
+ * Parses a raw loop rule string (e.g. "YS2-F") into structured rule arrays
+ * for UI display purposes.
+ * @param strl - The loop rule string in format "loopRule-stopRule".
+ * @returns A tuple of [LoopRule, LoopStopRule] on success, or undefined
+ *          when the string is empty, malformed, or contains no valid rule.
+ */
+export function resolveLoopRules4UI(strl: string): [LoopRule, LoopStopRule] | undefined {
+  if (strl == '') return undefined;
+
+  let sp = strl.split('-');
+  if (sp.length != 2) return undefined;
+  let loopRules: LoopRule | undefined = undefined;
+  let loopStopRules: LoopStopRule | undefined = undefined;
+
+  let match: RegExpExecArray | null;
+  if ((match = PRECOMPILED_LOOP_RULES.year.exec(sp[0]!)) !== null) {
+    loopRules = [0, match[1]! == 'S', parseInt(match[2]!)];
+  } else if ((match = PRECOMPILED_LOOP_RULES.month.exec(sp[0]!)) !== null) {
+    loopRules = [1, match[1]! == 'S', match[2]! as 'A' | 'B' | 'C' | 'D', parseInt(match[3]!)];
+  } else if ((match = PRECOMPILED_LOOP_RULES.week.exec(sp[0]!)) !== null) {
+    const w = match[1]!;
+    loopRules = [2, w[0] == 'T', w[1] == 'T', w[2] == 'T', w[3] == 'T', w[4] == 'T', w[5] == 'T', w[6] == 'T', parseInt(match[2]!)] as WeekLoopRule;
+  } else if ((match = PRECOMPILED_LOOP_RULES.day.exec(sp[0]!)) !== null) {
+    loopRules = [3, parseInt(match[1]!)];
+  } else return undefined;
+
+  if ((match = PRECOMPILED_LOOP_STOP_RULES.infinity.exec(sp[1]!)) !== null) {
+    loopStopRules = [0];
+  } else if ((match = PRECOMPILED_LOOP_STOP_RULES.datetime.exec(sp[1]!)) !== null) {
+    loopStopRules = [1, parseInt(match[1]!)];
+  } else if ((match = PRECOMPILED_LOOP_STOP_RULES.times.exec(sp[1]!)) !== null) {
+    loopStopRules = [2, parseInt(match[1]!)];
+  } else return undefined;
+
+  return [loopRules, loopStopRules];
 }
 
-export function resolveLoopRules2Event(loopRules: string, loopDateTimeStart: number, loopDateTimeEnd: number, eventDateTimeStart: number, eventDateTimeEnd: number, timezoneOffset: number, clampStartDateTime: number) {
+/** A pair of [start, end] timestamps (in minutes) representing a single event occurrence. */
+type TimeRange = [number, number];
 
+/**
+ * Resolves a loop rule string into concrete event date ranges by expanding
+ * the loop pattern across the detection window.
+ * @remark loopDateTimeStart's value does not correspond with the database;
+ *         it is calculated by the program and should point to the closet
+ *         potential event start datetime.
+ * @remark loopDateTimeEnd is performed like loopDateTimeStart and
+ *         it indicates the possible time point of the tail of legal event.
+ * @remark clampStartDateTime is the real clamp datetime of event start
+ *         datetime.
+ * @remark loopDateTimeStart is the start datetime for detection.
+ * @remark In this section, all times should be analysed with
+ *         `Date((time + timezoneOffset) * 60000)` and use `.getUTC...()`
+ *         functions.
+ * @param loopRules - The loop rule string (e.g. "YS2-F").
+ * @param loopDateTimeStart - Start of the detection window (minutes).
+ * @param loopDateTimeEnd - End of the detection window (minutes).
+ * @param eventDateTimeStart - Original event start datetime (minutes).
+ * @param eventDateTimeEnd - Original event end datetime (minutes).
+ * @param timezoneOffset - Timezone offset in minutes.
+ * @param clampStartDateTime - Earliest allowed start datetime (minutes).
+ * @returns An array of [start, end] timestamp pairs representing every
+ *          occurrence within the window, or undefined if the rule is invalid.
+ */
+export function resolveLoopRules2Event(
+  fullLoopRules: string,
+  loopDateTimeStart: number,
+  loopDateTimeEnd: number,
+  eventDateTimeStart: number,
+  eventDateTimeEnd: number,
+  timezoneOffset: number,
+  clampStartDateTime: number): TimeRange[] | undefined {
+  if (fullLoopRules == '') return [
+    [Math.max(eventDateTimeStart, clampStartDateTime),
+    Math.max(loopDateTimeEnd, eventDateTimeEnd)]
+  ];
+
+  let sp = fullLoopRules.split('-');
+  if (sp.length != 2) return undefined;
+  let loopRules = sp[0]!;  // we don't need consider stop flag
+  let result: TimeRange[] = new Array();
+
+  // compute offset and duration
+  let eventDateTime = new Date((eventDateTimeStart + timezoneOffset) * 60000);
+  eventDateTime.setUTCHours(0, 0, 0, 0);
+  let eventOffset = eventDateTimeStart - (Math.floor(eventDateTime.getTime() / 60000) - timezoneOffset);
+  let eventDuration = eventDateTimeEnd - eventDateTimeStart;
+
+  let detectDateTime = new Date(loopDateTimeStart * 60000);
+  detectDateTime.setUTCHours(0, 0, 0, 0);
+  let originalYear = eventDateTime.getUTCFullYear();
+  let originalMonth = eventDateTime.getUTCMonth() + 1;
+  let originalDay = eventDateTime.getUTCDate();
+
+  // compute event
+  let match: RegExpExecArray | null;
+  if ((match = PRECOMPILED_LOOP_RULES.year.exec(loopRules)) !== null) {
+    let isStrict = match[1]! == 'S';
+    let loopSpan = parseInt(match[2]!);
+
+    let yearCount = detectDateTime.getFullYear() - originalYear;
+    let isSpecial = (originalMonth == 2 && originalDay == 29);
+    let realLoopSpan = (isSpecial && isStrict) ? lcm(4, loopSpan) : loopSpan;
+
+    //let fullSpanCount = Math.floor(yearCount / realLoopSpan);
+    let remainYear = yearCount % realLoopSpan;
+    //detectDateTime.setUTCFullYear(fullSpanCount + detectDateTime.getUTCFullYear(), 1, 1);
+    if (remainYear != 0)
+      detectDateTime.setUTCFullYear(realLoopSpan - remainYear + detectDateTime.getUTCFullYear(), 1 - 1, 1);
+
+    let skipFlag = false;
+    while (Math.floor(detectDateTime.getTime() / 60000) + eventOffset - timezoneOffset <= loopDateTimeEnd) {
+      skipFlag = false;
+      if (isSpecial) {
+        // is special day, 29 Feb
+        // try set it in 29 Feb
+        if (isStrict) {
+          if (isLeapYear(detectDateTime.getUTCFullYear())) detectDateTime.setUTCMonth(2 - 1, 29);
+          else skipFlag = true;  // order skip
+        } else {
+          if (isLeapYear(detectDateTime.getUTCFullYear())) detectDateTime.setUTCMonth(2 - 1, 29);
+          else detectDateTime.setUTCMonth(2 - 1, 28);
+        }
+      } else detectDateTime.setUTCMonth(originalMonth - 1, originalDay);
+
+      if (!skipFlag) {
+        result.push(
+          [Math.floor(detectDateTime.getTime() / 60000) + eventOffset - timezoneOffset,
+          Math.floor(detectDateTime.getTime() / 60000) + eventOffset + eventDuration - timezoneOffset]
+        );
+      }
+
+      detectDateTime.setUTCFullYear(realLoopSpan + detectDateTime.getUTCFullYear());
+    }
+
+  } else if ((match = PRECOMPILED_LOOP_RULES.month.exec(loopRules)) !== null) {
+    let isStrict = match[1]! == 'S';
+    let loopMethod = match[2]!;
+    let loopSpan = parseInt(match[3]!);
+
+    let monthsCountValue = monthsCount(detectDateTime.getUTCFullYear(), detectDateTime.getUTCMonth() + 1) -
+      monthsCount(originalYear, originalMonth);
+
+    //let fullSpanCount = Math.floor(monthsCountValue / loopSpan);
+    let remainMonth = monthsCountValue % loopSpan;
+    //detectDateTime.setUTCMonth(fullSpanCount * loopSpan + detectDateTime.getUTCMonth(), 1);
+    detectDateTime.setUTCDate(1);
+    if (remainMonth != 0)
+      detectDateTime.setUTCMonth(loopSpan - remainMonth + detectDateTime.getUTCMonth(), 1);
+
+    while (Math.floor(detectDateTime.getTime() / 60000) + eventOffset - timezoneOffset <= loopDateTimeEnd) {
+      let data = getRemanagedDayInMonth(originalYear, originalMonth, originalDay, detectDateTime.getUTCFullYear(), detectDateTime.getUTCMonth() + 1, isStrict);
+      let predictedDay: number | undefined = undefined;
+      switch (loopMethod) {
+        case 'A':
+          if (typeof (data[0]) !== 'undefined') predictedDay = data[0];
+          break;
+        case 'B':
+          if (typeof (data[1]) !== 'undefined') predictedDay = data[1];
+          break;
+        case 'C':
+          if (typeof (data[2]) !== 'undefined') predictedDay = data[2];
+          break;
+        case 'D':
+          if (typeof (data[3]) !== 'undefined') predictedDay = data[3];
+          break;
+      }
+      if (typeof (predictedDay) !== 'undefined') {
+        detectDateTime.setUTCDate(predictedDay);
+        result.push(
+          [Math.floor(detectDateTime.getTime() / 60000) + eventOffset - timezoneOffset,
+          Math.floor(detectDateTime.getTime() / 60000) + eventOffset + eventDuration - timezoneOffset]
+        );
+      }
+
+      detectDateTime.setUTCMonth(loopSpan + detectDateTime.getUTCMonth(), 1);
+    }
+
+
+  } else if ((match = PRECOMPILED_LOOP_RULES.week.exec(loopRules)) !== null) {
+    let loopSpan = parseInt(match[2]!);
+    let weekOption: boolean[] = [];
+    let weekEventCount = 0
+    for (let i = 0; i < 7; i++) {
+      weekOption.push(match[1]![i] == 'T');
+      if (match[1]![i] == 'T') weekEventCount++;
+    }
+
+    let originalWeek = dayOfWeek(originalYear, originalMonth, originalDay);
+
+    // try insert original event
+    if (!weekOption[originalWeek]) {
+      result.push(
+        [eventDateTimeStart, eventDateTimeEnd]
+      );
+    }
+
+    let daysCountValue = daysCount(detectDateTime.getUTCFullYear(), detectDateTime.getUTCMonth() + 1, detectDateTime.getDate()) -
+      daysCount(originalYear, originalMonth, originalDay);
+    //let fullSpanCount = Math.floor(daysCountValue / (7 * loopSpan));
+    let remainFullSpanCount = Math.floor((daysCountValue % (7 * loopSpan)) / 7);
+    let remainDays = (daysCountValue % (7 * loopSpan)) % 7;
+
+    //detectDateTime.setUTCDate((7 * loopSpan * fullSpanCount) + detectDateTime.getUTCDate());
+    if (remainFullSpanCount != 0) {
+      detectDateTime.setUTCDate((loopSpan - remainFullSpanCount) * 7 + detectDateTime.getUTCDate());
+    }
+    let weekCounter = remainDays;
+
+    while (Math.floor(detectDateTime.getTime() / 60000) + eventOffset - timezoneOffset <= loopDateTimeEnd) {
+      if (weekOption[(weekCounter + originalWeek) % 7])
+        result.push(
+          [Math.floor(detectDateTime.getTime() / 60000) + eventOffset - timezoneOffset,
+          Math.floor(detectDateTime.getTime() / 60000) + eventOffset + eventDuration - timezoneOffset]
+        );
+
+      weekCounter = (weekCounter + 1) % 7;
+      detectDateTime.setUTCDate(detectDateTime.getUTCDate() + 1);
+      if (weekCounter == 0)
+        detectDateTime.setUTCDate(detectDateTime.getUTCDate() + (loopSpan - 1) * 7);
+    }
+
+  } else if ((match = PRECOMPILED_LOOP_RULES.day.exec(loopRules)) !== null) {
+    let loopSpan = parseInt(match[1]!);
+
+    let daysCountValue = daysCount(detectDateTime.getUTCFullYear(), detectDateTime.getUTCMonth() + 1, detectDateTime.getUTCDate()) -
+      daysCount(originalYear, originalMonth, originalDay);
+    //let fullSpanCount = Math.floor(daysCountValue / loopSpan);
+    let remainDays = daysCountValue % loopSpan;
+    //detectDateTime.setUTCDate(fullSpanCount * loopSpan + detectDateTime.getUTCDate());
+    if (remainDays != 0)
+      detectDateTime.setUTCDate(loopSpan - remainDays + detectDateTime.getUTCDate());
+
+    while (Math.floor(detectDateTime.getTime() / 60000) + eventOffset - timezoneOffset <= loopDateTimeEnd) {
+      result.push(
+        [Math.floor(detectDateTime.getTime() / 60000) + eventOffset - timezoneOffset,
+        Math.floor(detectDateTime.getTime() / 60000) + eventOffset + eventDuration - timezoneOffset]
+      );
+      detectDateTime.setUTCDate(detectDateTime.getUTCDate() + loopSpan);
+    }
+  } else return undefined;
+
+  // clamp item
+  let realResult: TimeRange[] = new Array();
+  for (let i of result) {
+    let start = i[0];
+    let end = i[1];
+    if (end > clampStartDateTime && start <= loopDateTimeEnd)
+      realResult.push([Math.max(start, clampStartDateTime), Math.min(end, loopDateTimeEnd)]);
+  }
+  return realResult;
 }
 
-export function resolveLoopRules4Text(strl: string, startDateTime: number, timezoneOffset: number) {
+/**
+ * Resolves a loop rule string into a human-readable i18n-localised text
+ * description suitable for display in the UI.
+ * @param strl - The loop rule string in format "loopRule-stopRule".
+ * @param startDateTime - Reference start datetime (minutes) for computing
+ *                        contextual fields (e.g. day-in-month info).
+ * @param timezoneOffset - Timezone offset in minutes.
+ * @returns A concatenated human-readable string, or an empty string when
+ *          the input is empty or cannot be parsed.
+ */
+export function resolveLoopRules4Text(strl: string, startDateTime: number, timezoneOffset: number): string {
+  if (strl == '') return "";
 
+  let sp = strl.split('-');
+  if (sp.length != 2) return "";
+  let loopRules: string;
+  let loopStopRules: string;
+  let datetimeInstance = new Date((startDateTime + timezoneOffset) * 60000)
+
+  let match: RegExpExecArray | null;
+  if ((match = PRECOMPILED_LOOP_RULES.year.exec(sp[0]!)) !== null) {
+    if (match[1]! == 'S')
+      loopRules = "严格模式。";
+    else
+      loopRules = "宽松模式。";
+    loopRules += format("每{0}年于{1}循环一次。",
+      parseInt(match[2]!), datetimeInstance.toLocaleDateString(undefined, { timeZone: "UTC" })
+    );
+  } else if ((match = PRECOMPILED_LOOP_RULES.month.exec(sp[0]!)) !== null) {
+    if (match[1]! == 'S')
+      loopRules = "严格模式。";
+    else
+      loopRules = "宽松模式。";
+
+    let dayInMonth = getDayInMonth(
+      datetimeInstance.getUTCFullYear(),
+      datetimeInstance.getUTCMonth() + 1,
+      datetimeInstance.getUTCDate());
+    switch (match[2]!) {
+      case 'A':
+        loopRules = format("每{0}月的第{1}日循环一次。",
+          parseInt(match[3]!), dayInMonth[0]
+        );
+        break;
+      case 'B':
+        loopRules = format("每{0}月的倒数第{1}日循环一次。",
+          parseInt(match[3]!), dayInMonth[1]
+        );
+        break;
+      case 'C':
+        loopRules = format("每{0}月的第{1}个星期{2}循环一次。",
+          parseInt(match[3]!), dayInMonth[2], dayInMonth[3]
+        );
+        break;
+      case 'D':
+        loopRules = format("每{0}月的倒数第{1}个星期{2}循环一次。",
+          parseInt(match[3]!), dayInMonth[4], dayInMonth[5]
+        );
+        break;
+    }
+  } else if ((match = PRECOMPILED_LOOP_RULES.week.exec(sp[0]!)) !== null) {
+    let weekOfDayCache = [];
+    for (let i = 0; i < 7; i++) {
+      if (match[1]![i] == 'T')
+        weekOfDayCache.push(universalGetDayOfWeek(i));
+    }
+
+    loopRules = format("每{0}周的{1}循环一次。",
+      parseInt(match[2]!), weekOfDayCache.join(', ')
+    );
+  } else if ((match = PRECOMPILED_LOOP_RULES.day.exec(sp[0]!)) !== null) {
+    loopRules = format("每{0}天循环一次。", parseInt(match[1]!));
+  } else return "";
+
+
+  if ((match = PRECOMPILED_LOOP_STOP_RULES.infinity.exec(sp[1]!)) !== null) {
+    loopStopRules = "永远循环。";
+  } else if ((match = PRECOMPILED_LOOP_STOP_RULES.datetime.exec(sp[1]!)) !== null) {
+    loopStopRules = format("到{0}停止循环。",
+      new Date(parseInt(match[1]!)).toLocaleDateString()
+    );
+  } else if ((match = PRECOMPILED_LOOP_STOP_RULES.times.exec(sp[1]!)) !== null) {
+    loopStopRules = format("循环{0}次。", parseInt(match[1]!));
+  } else return "";
+
+  return (loopRules + loopStopRules);
 }
 
 // endregion
@@ -77,11 +429,11 @@ function daysCount(year: number, month: number, day: number): number {
 }
 
 function monthsCount(year: number, month: number): number {
-    return (year - 1) * 12 + (month - 1);
+  return (year - 1) * 12 + (month - 1);
 }
 
 function dayOfWeek(year: number, month: number, day: number): number {
-    return daysCount(year, month, day) % 7;
+  return daysCount(year, month, day) % 7;
 }
 
 type DayInMonthInfo = [
@@ -100,17 +452,17 @@ type DayInMonthInfo = [
 ];
 
 function getDayInMonth(year: number, month: number, day: number): DayInMonthInfo {
-    let days = MONTH_DAY_COUNT[month - 1]! + ((month == 2 && isLeapYear(year)) ? 1 : 0);
+  let days = MONTH_DAY_COUNT[month - 1]! + ((month == 2 && isLeapYear(year)) ? 1 : 0);
-    let firstDayOfWeek = dayOfWeek(year, month, 1);
+  let firstDayOfWeek = dayOfWeek(year, month, 1);
-    let bilateralDayOfWeek = (firstDayOfWeek + day - 1) % 7;
+  let bilateralDayOfWeek = (firstDayOfWeek + day - 1) % 7;
 
-    let dayForwards = day;
+  let dayForwards = day;
-    let dayBackwards = days - day + 1;
+  let dayBackwards = days - day + 1;
 
-    let weeksForward = Math.floor((dayForwards - 1) / 7) + 1;
+  let weeksForward = Math.floor((dayForwards - 1) / 7) + 1;
-    let weeksBackwards = Math.floor((dayBackwards - 1) / 7) + 1;
+  let weeksBackwards = Math.floor((dayBackwards - 1) / 7) + 1;
 
-    return [dayForwards, dayBackwards, weeksForward, bilateralDayOfWeek, weeksBackwards, bilateralDayOfWeek];
+  return [dayForwards, dayBackwards, weeksForward, bilateralDayOfWeek, weeksBackwards, bilateralDayOfWeek];
 }
 
 // YYC MARK:
@@ -119,13 +471,13 @@ function getDayInMonth(year: number, month: number, day: number): DayInMonthInfo
 
 type RemanagedDayInMonth = [
   /** Count forward by days (Day N)  */
-  forwardByDayCount: number,
+  forwardByDayCount: number | undefined,
   /** Count backward by days (Nth day from the end) */
-  backwardByDayCount: number,
+  backwardByDayCount: number | undefined,
   /** Count forward by weeks (Week N, Youbi X) */
-  forwardByWeekCount: number,
+  forwardByWeekCount: number | undefined,
   /** Count backward by weeks (Nth week from the end, Youbi X) */
-  backwardByWeekCount: number,
+  backwardByWeekCount: number | undefined,
 ];
 
 /**
@@ -140,37 +492,37 @@ type RemanagedDayInMonth = [
  * @param isStrict 
  * @returns 
  */
-function getRemanagedDayInMonth(oldYear: number, oldMonth: number, oldDay: number, newYear: number, newMonth: number, isStrict: boolean) {
+function getRemanagedDayInMonth(oldYear: number, oldMonth: number, oldDay: number, newYear: number, newMonth: number, isStrict: boolean): RemanagedDayInMonth {
-    let ddata = getDayInMonth(oldYear, oldMonth, oldDay);
+  let ddata = getDayInMonth(oldYear, oldMonth, oldDay);
-    let mdata = getMonthWeekStatistics(newYear, newMonth);
+  let mdata = getMonthWeekStatistics(newYear, newMonth);
-    let days = MONTH_DAY_COUNT[newMonth - 1]! + ((newMonth == 2 && isLeapYear(newYear)) ? 1 : 0);
+  let days = MONTH_DAY_COUNT[newMonth - 1]! + ((newMonth == 2 && isLeapYear(newYear)) ? 1 : 0);
-    let firstDayOfWeek = dayOfWeek(newYear, newMonth, 1);
+  let firstDayOfWeek = dayOfWeek(newYear, newMonth, 1);
-    //let lastDayOfWeek = (firstDayOfWeek + days - 1) % 7;
+  //let lastDayOfWeek = (firstDayOfWeek + days - 1) % 7;
 
-    let methodA = undefined;
+  let methodA = undefined;
-    let methodB = undefined;
+  let methodB = undefined;
-    if (isStrict) {
+  if (isStrict) {
-        methodA = ddata[0] > days ? undefined : ddata[0];
+    methodA = ddata[0] > days ? undefined : ddata[0];
-        methodB = ddata[1] > days ? undefined : (days - ddata[1] + 1);
+    methodB = ddata[1] > days ? undefined : (days - ddata[1] + 1);
-    } else {
+  } else {
-        methodA = Math.min(ddata[0], days);
+    methodA = Math.min(ddata[0], days);
-        methodB = days - Math.min(ddata[1], days) + 1;
+    methodB = days - Math.min(ddata[1], days) + 1;
-    }
+  }
 
-    let methodC = undefined;
+  let methodC = undefined;
-    if (ddata[2] <= mdata[ddata[3]]! || !isStrict) {
+  if (ddata[2] <= mdata[ddata[3]]! || !isStrict) {
-        let targetWeek = Math.min(ddata[2], mdata[ddata[3]]!);
+    let targetWeek = Math.min(ddata[2], mdata[ddata[3]]!);
-        methodC = 1 + (targetWeek - 1) * 7 + ((ddata[3] + 7 - firstDayOfWeek) % 7);
+    methodC = 1 + (targetWeek - 1) * 7 + ((ddata[3] + 7 - firstDayOfWeek) % 7);
-    }
+  }
 
-    let methodD = undefined;
+  let methodD = undefined;
-    if (ddata[4] <= mdata[ddata[5]]! || !isStrict) {
+  if (ddata[4] <= mdata[ddata[5]]! || !isStrict) {
-        // convert to type c and calc
+    // convert to type c and calc
-        let targetWeek = mdata[ddata[5]]! - Math.min(ddata[4], mdata[ddata[5]]!) + 1;
+    let targetWeek = mdata[ddata[5]]! - Math.min(ddata[4], mdata[ddata[5]]!) + 1;
-        methodD = 1 + (targetWeek - 1) * 7 + ((ddata[5] + 7 - firstDayOfWeek) % 7);
+    methodD = 1 + (targetWeek - 1) * 7 + ((ddata[5] + 7 - firstDayOfWeek) % 7);
-    }
+  }
 
-    return [methodA, methodB, methodC, methodD];
+  return [methodA, methodB, methodC, methodD];
 }
 
 type MonthWeekStatistics = [
@@ -191,27 +543,27 @@ type MonthWeekStatistics = [
 ];
 
 function getMonthWeekStatistics(year: number, month: number): MonthWeekStatistics {
-    let days = MONTH_DAY_COUNT[month - 1]! + ((month == 2 && isLeapYear(year)) ? 1 : 0);
+  let days = MONTH_DAY_COUNT[month - 1]! + ((month == 2 && isLeapYear(year)) ? 1 : 0);
-    let firstDayOfWeek = dayOfWeek(year, month, 1);
+  let firstDayOfWeek = dayOfWeek(year, month, 1);
 
-    let result: MonthWeekStatistics = [4, 4, 4, 4, 4, 4, 4];
+  let result: MonthWeekStatistics = [4, 4, 4, 4, 4, 4, 4];
-    let remain = days % 7;
+  let remain = days % 7;
-    let week = firstDayOfWeek;
+  let week = firstDayOfWeek;
-    while (remain > 0) {
+  while (remain > 0) {
-        result[week % 7]! += 1;
+    result[week % 7]! += 1;
-        week++;
+    week++;
-        remain--;
+    remain--;
-    }
+  }
 
-    return result;
+  return result;
 }
 
 function isLeapYear(year: number): boolean {
-    let isLeap = false;
+  let isLeap = false;
-    if (year % 4 == 0) isLeap = true;
+  if (year % 4 == 0) isLeap = true;
-    if (year % 100 == 0) isLeap = false;
+  if (year % 100 == 0) isLeap = false;
-    if (year % 400 == 0) isLeap = true;
+  if (year % 400 == 0) isLeap = true;
-    return isLeap;
+  return isLeap;
 }
 
 // endregion

frontend/src/utils/i18n.ts

@@ -2,3 +2,65 @@ export enum Language {
     English,
     SimplifiedChinese,
 }
+
+/**
+ * 
+ * @param month Zero-based month.
+ * @returns 
+ */
+export function universalGetMonth(month: number): string {
+    switch (month) {
+        case 0:
+            return "January";
+        case 1:
+            return "February";
+        case 2:
+            return "March";
+        case 3:
+            return "April";
+        case 4:
+            return "May";
+        case 5:
+            return "June";
+        case 6:
+            return "July";
+        case 7:
+            return "August";
+        case 8:
+            return "September";
+        case 9:
+            return "October";
+        case 10:
+            return "November";
+        case 11:
+            return "December";
+        default:
+            return ""
+    }
+}
+
+/**
+ * 
+ * @param dayOfWeek Zero-based day of week
+ * @returns 
+ */
+export function universalGetDayOfWeek(dayOfWeek: number): string {
+    switch (dayOfWeek) {
+        case 0:
+            return "Monday";
+        case 1:
+            return "Tuesday";
+        case 2:
+            return "Wednesday";
+        case 3:
+            return "Thursday";
+        case 4:
+            return "Friday";
+        case 5:
+            return "Saturday";
+        case 6:
+            return "Sunday";
+        default:
+            return "";
+    }
+}

frontend/src/utils/utils.ts

@@ -10,6 +10,24 @@ export function lcm(a: number, b: number): number {
   return a / gcd(a, b) * b;
 }
 
+/**
+ * 将字符串中的 `{n}` 占位符替换为对应的参数值
+ * @param str 目标字符串，若为 `null`/`undefined`/空字符串则返回原值或空串（根据需求）
+ * @param args 用于替换的值列表
+ * @returns 格式化后的字符串
+ */
+export function format(str: string, ...args: any[]): string {
+  // 若 str 为假值（null/undefined/''），直接返回空字符串
+  if (!str) return '';
+
+  return str.replace(/\{(\d+)\}/g, (match, index) => {
+    const idx = parseInt(index, 10);
+    const value = args[idx];
+    // 若参数存在且不为 null/undefined，则转为字符串，否则保留占位符
+    return value != null ? String(value) : match;
+  });
+}
+
 /**
  * Get Monday-first the day of week from given date instead of Sunday-first.
  * @param date The date for getting weekday.