import { addWeeks } from "date-fns";
import * as R from "remeda";
import { AVAILABILITY } from "../availability-constants";
import type { ScheduleWeekView } from "../availability-types";
import * as Availability from "./Availability";
import * as ScheduleWeek from "./ScheduleWeek";
import * as VisibleSchedules from "./VisibleSchedules.server";

/**
 * Reportable weeks keyed by user id, free time only (commitments subtracted). Users who reported
 * neither week, and those not sharing their schedule with the viewer, are left out; the friends
 * page sorts and shows its calendar icon by the missing key.
 */
export async function findByUserIds({
	userIds,
	timezone,
	viewerId,
}: {
	userIds: Array<number>;
	timezone: string;
	viewerId: number;
}): Promise<Map<number, Array<ScheduleWeekView>>> {
	const now = new Date();

	const ranges = R.range(0, AVAILABILITY.WEEK_HORIZON).map((weekOffset) =>
		Availability.weekRange(addWeeks(now, weekOffset), timezone),
	);
	const horizon = {
		startsAt: ranges[0].startsAt,
		endsAt: ranges[ranges.length - 1].endsAt,
	};

	const { reportedWeeks, busyByUserId } = await VisibleSchedules.findByUserIds({
		userIds,
		viewerId,
		...horizon,
	});

	const weeks = ranges.map((range, index) => ({
		range,
		week: index === 0 ? ("current" as const) : ("next" as const),
		weekNumber: ScheduleWeek.weekNumber(range, timezone),
		days: ScheduleWeek.days(range, timezone),
	}));

	return new Map(
		userIds.flatMap((userId) => {
			const busy = busyByUserId.get(userId) ?? [];

			const views = weeks.map((week): ScheduleWeekView => {
				const row = ScheduleWeek.memberRow({
					userId,
					days: week.days,
					timezone,
					reportedWeeks,
					range: week.range,
					busy,
				});

				return {
					week: week.week,
					weekNumber: week.weekNumber,
					reported: row.reported,
					days: week.days.map((day, dayIndex) => ({
						noonAt: day.noonAt,
						ranges: row.days[dayIndex].ranges,
					})),
				};
			});

			return views.some((view) => view.reported) ? [[userId, views]] : [];
		}),
	);
}