//Calendar implementation for the HTWK Leipzig timetable. Evaluation and display of the individual dates in iCal format.
//Copyright (C) 2024 HTWKalender support@htwkalender.de

//This program is free software: you can redistribute it and/or modify
//it under the terms of the GNU Affero General Public License as published by
//the Free Software Foundation, either version 3 of the License, or
//(at your option) any later version.

//This program is distributed in the hope that it will be useful,
//but WITHOUT ANY WARRANTY; without even the implied warranty of
//MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//GNU Affero General Public License for more details.

//You should have received a copy of the GNU Affero General Public License
//along with this program.  If not, see <https://www.gnu.org/licenses/>.

import { BSON } from "bson";
import { RoomOccupancyList } from "@/model/roomOccupancyList.ts";
import { Duration, NormalizedInterval, add, addDays, addMinutes, addMonths, clamp, differenceInMinutes, eachDayOfInterval, endOfDay, interval, isAfter, isBefore, isEqual, max, min, startOfDay, subDays } from "date-fns";
import { formatYearMonthDay } from "@/helpers/dates";

const END_OF_SUMMER_SEMESTER = "0930";
const END_OF_WINTER_SEMESTER = "0331";

/** 
 * check if date is in winter semester before summer semester
 * @param date - The date to check
 * @returns boolean - true if date is in winter semester
 */
export function isBeforeSummer(date: Date): boolean {
  const formattedDate = formatYearMonthDay(date).slice(4);
  return formattedDate <= END_OF_WINTER_SEMESTER;
}

/** 
 * check if date is in winter semester after summer semester
 * @param date - The date to check
 * @returns boolean - true if date is in winter semester
 */
export function isAfterSummer(date: Date): boolean {
  const formattedDate = formatYearMonthDay(date).slice(4);
  return formattedDate > END_OF_SUMMER_SEMESTER;
}

/**
 * Gets the start date of the current semester
 * @param date - The date to check
 * @returns Date - The start date of the current semester
 */
export function getSemesterStart(date: Date): Date {
  if (isBeforeSummer(date)) {
    return new Date(date.getFullYear()-1, 9, 1);
  } else if (isAfterSummer(date)) {
    return new Date(date.getFullYear(), 9, 1);
  } else {
    return new Date(date.getFullYear(), 3, 1);
  }
}

/**
 *  Fetches the room occupancy for a given date range.
 * @param from_date the start date of the date range
 * @param to_date  the end date of the date range
 * @returns RoomOccupancyList - the room occupancy list
 */

export async function fetchRoomOccupancy(
  from_date?: string,
  to_date?: string
): Promise<RoomOccupancyList> {
  if (from_date == undefined) {
    let new_from_date = getSemesterStart(new Date());
    from_date = new_from_date.toISOString();
  }
  if (to_date == undefined) {
    let new_to_date = getSemesterStart(addMonths(new Date(), 6));
    to_date = new_to_date.toISOString();
  }

  var roomOccupancyList: RoomOccupancyList = new RoomOccupancyList(
    new Date(),
    0,
    0,
    [],
  );

  await fetch("/api/schedule/rooms?from=" + from_date + "&to=" + to_date)
    .then((response) => {
      return response.arrayBuffer();
    })
    .then((roomsResponse: ArrayBuffer | null) => {
      if (roomsResponse == null) {
        return null;
      }
      const data = new Uint8Array(roomsResponse);
      roomOccupancyList = RoomOccupancyList.fromJSON(BSON.deserialize(data));
      return roomOccupancyList;
    });

  return roomOccupancyList;
}