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/**
* Number of days in a regular month.
*
* Month order:
*
* spring 1 Thawing 2 Greening 3 Blossomtide
* summer 4 Highsun 5 Amberhaze 6 Harvestmark
* autumn 7 Firstfall 8 Stormturn 9 Ashfall
* winter 10 Rainfall 11 Hollowdark 12 Rimefrost
* festival 13 Year's End Festival (5 days)
*
* The year begins with Thawing and closes with the festival, which sits
* between Rimefrost and the next year's Thawing.
*/
export const DAYS_PER_MONTH = 30
/** Twelve named months — all except the festival. */
export const REGULAR_MONTH_COUNT = 12
/** Days in the Year's End Festival — the thirteenth "month". */
export const FESTIVAL_DAYS = 5
/** Month index for the festival. */
export const FESTIVAL_MONTH = 13
/** Total month slots in the calendar cycle (12 regular + festival). */
export const MONTHS_PER_YEAR = REGULAR_MONTH_COUNT + 1
/** Days in a year: 12 × 30 + 5 = 365. */
export const DAYS_PER_YEAR = REGULAR_MONTH_COUNT * DAYS_PER_MONTH + FESTIVAL_DAYS
/** Seven-day weeks. */
export const DAYS_PER_WEEK = 7
/** Month names in calendar order. Index 0 is Thawing; index 12 is the festival. */
export const MONTH_NAMES = [
'Thawing',
'Greening',
'Blossomtide',
'Highsun',
'Amberhaze',
'Harvestmark',
'Firstfall',
'Stormturn',
'Ashfall',
'Rainfall',
'Hollowdark',
'Rimefrost',
"Year's End Festival"
] as const
/** The named-month type derived from `MONTH_NAMES`. */
export type MonthName = (typeof MONTH_NAMES)[number]
/** Four regular seasons plus a distinct `festival` tag for the year-end. */
export type Season = 'spring' | 'summer' | 'autumn' | 'winter' | 'festival'
const SEASON_BY_MONTH: readonly Season[] = [
'spring',
'spring',
'spring',
'summer',
'summer',
'summer',
'autumn',
'autumn',
'autumn',
'winter',
'winter',
'winter',
'festival'
]
function validateMonth(monthIndex: number): void {
if (!Number.isInteger(monthIndex) || monthIndex < 1 || monthIndex > MONTHS_PER_YEAR) {
throw new Error(`Invalid month index: ${monthIndex}`)
}
}
/**
* Return the named month for a 1-based month index. Throws on invalid input.
* @param monthIndex 1 (Thawing) through 13 (Year's End Festival).
*/
export function monthName(monthIndex: number): MonthName {
validateMonth(monthIndex)
return MONTH_NAMES[monthIndex - 1] as MonthName
}
/**
* Return the season label for a 1-based month index. The festival has its
* own tag ('festival') rather than reusing one of the four seasons.
*/
export function monthSeason(monthIndex: number): Season {
validateMonth(monthIndex)
return SEASON_BY_MONTH[monthIndex - 1] as Season
}
/**
* Days in the given month. 30 for regular months, 5 for the festival.
*/
export function daysInMonth(monthIndex: number): number {
validateMonth(monthIndex)
return monthIndex === FESTIVAL_MONTH ? FESTIVAL_DAYS : DAYS_PER_MONTH
}
/** True when the supplied month index is the festival slot. */
export function isFestival(monthIndex: number): boolean {
return monthIndex === FESTIVAL_MONTH
}
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