Lucas WintherandClaude Opus 5.5
664cdbe0db
Check-in goals and weekly tasks both need a period longer than a day. Working in game-day keys rather than instants means a week rolls exactly where the game's own day does, per region, with no second clock. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
72 lines
2.7 KiB
TypeScript
72 lines
2.7 KiB
TypeScript
import { z } from "zod";
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import { DAY } from "./time.ts";
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/**
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* Periods longer than a day — a week, a month — in day-key space.
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*
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* Every key here is a `YYYY-MM-DD` game-day that `dayKey` already cut on a
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* game's own reset clock for the reader's region. Working on keys rather than
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* instants means a period inherits every per-game, per-region reset rule for
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* free: the week rolls when the game's day rolls, and nowhere else. `streakOf`
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* and `catchUpDays` walk keys for the same reason.
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*
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* Pure, and takes "today" as an argument, so it is tested at fixed instants.
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*/
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/** ISO weekday: Monday is 1, Sunday is 7. */
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export const WeekdaySchema = z.number().int().min(1).max(7);
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export const PeriodSchema = z.union([
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z.object({ unit: z.literal("week"), startsOn: WeekdaySchema }),
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/** Day of month; 31 means "the last day" in a shorter month. */
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z.object({ unit: z.literal("month"), startsOn: z.number().int().min(1).max(31) }),
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]);
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export type Period = z.infer<typeof PeriodSchema>;
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const msOf = (key: string) => Date.parse(`${key}T00:00:00Z`);
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const keyOf = (ms: number) => new Date(ms).toISOString().slice(0, 10);
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/** A key is a date, not an instant, so its weekday is its UTC weekday. */
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export function isoWeekday(key: string): number {
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const d = new Date(msOf(key)).getUTCDay();
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return d === 0 ? 7 : d;
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}
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export function addDays(key: string, n: number): string {
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return keyOf(msOf(key) + n * DAY);
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}
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/** The month's start key, with `startsOn` clamped to the month's last day. */
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function monthStart(year: number, month0: number, startsOn: number): string {
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// Date.UTC normalises an out-of-range month, so month0 may be -1 or 12.
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const first = new Date(Date.UTC(year, month0, 1));
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const y = first.getUTCFullYear();
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const m = first.getUTCMonth();
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const last = new Date(Date.UTC(y, m + 1, 0)).getUTCDate();
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return keyOf(Date.UTC(y, m, Math.min(startsOn, last)));
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}
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/** The period containing `today`: its first key, and every key in it, oldest first. */
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export function periodOf(
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period: Period,
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today: string,
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): { start: string; days: string[] } {
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let start: string;
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let next: string;
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if (period.unit === "week") {
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start = addDays(today, -((isoWeekday(today) - period.startsOn + 7) % 7));
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next = addDays(start, 7);
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} else {
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const t = new Date(msOf(today));
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const y = t.getUTCFullYear();
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const m = t.getUTCMonth();
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const here = monthStart(y, m, period.startsOn);
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const startMonth = today >= here ? m : m - 1;
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start = monthStart(y, startMonth, period.startsOn);
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next = monthStart(y, startMonth + 1, period.startsOn);
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}
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const days: string[] = [];
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for (let k = start; k < next; k = addDays(k, 1)) days.push(k);
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return { start, days };
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}
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