import moment from 'moment-timezone';
import {
  addMinutes,
  addHours,
  addDays,
  addMonths,
  subHours,
  subDays,
  startOfHour,
  startOfDay,
  startOfWeek,
  startOfMonth,
  startOfYear,
  endOfHour,
  endOfDay,
  endOfWeek,
  endOfMonth,
  endOfYear,
  differenceInHours,
  differenceInCalendarDays,
  differenceInMonths,
} from 'date-fns';

export function getTimezone() {
  return moment.tz.guess();
}

export function getLocalTime(t) {
  return addMinutes(new Date(t), new Date().getTimezoneOffset());
}

export function getDateRange(value) {
  const now = new Date();

  const { num, unit } = value.match(/^(?<num>[0-9]+)(?<unit>hour|day|week|month|year)$/).groups;

  if (+num === 1) {
    switch (unit) {
      case 'day':
        return {
          startDate: startOfDay(now),
          endDate: endOfDay(now),
          unit: 'hour',
          value,
        };
      case 'week':
        return {
          startDate: startOfWeek(now),
          endDate: endOfWeek(now),
          unit: 'day',
          value,
        };
      case 'month':
        return {
          startDate: startOfMonth(now),
          endDate: endOfMonth(now),
          unit: 'day',
          value,
        };
      case 'year':
        return {
          startDate: startOfYear(now),
          endDate: endOfYear(now),
          unit: 'month',
          value,
        };
    }
  }

  switch (unit) {
    case 'day':
      return {
        startDate: subDays(startOfDay(now), num - 1),
        endDate: endOfDay(now),
        unit,
        value,
      };
    case 'hour':
      return {
        startDate: subHours(startOfHour(now), num - 1),
        endDate: endOfHour(now),
        unit,
        value,
      };
  }
}

const dateFuncs = {
  hour: [differenceInHours, addHours, startOfHour],
  day: [differenceInCalendarDays, addDays, startOfDay],
  month: [differenceInMonths, addMonths, startOfMonth],
};

export function getDateArray(data, startDate, endDate, unit) {
  const arr = [];
  const [diff, add, normalize] = dateFuncs[unit];
  const n = diff(endDate, startDate) + 1;

  function findData(t) {
    const x = data.find(e => {
      return getLocalTime(new Date(e.t)).getTime() === normalize(new Date(t)).getTime();
    });

    return x?.y || 0;
  }

  for (let i = 0; i < n; i++) {
    const t = add(startDate, i);
    const y = findData(t);

    arr.push({ ...data[i], t, y });
  }

  return arr;
}

export function getDateLength(startDate, endDate, unit) {
  const [diff] = dateFuncs[unit];
  return diff(endDate, startDate) + 1;
}