import {
  startOfWeek,
  startOfMonth,
  endOfWeek,
  endOfMonth,
  isBefore,
  addDays,
  isSameDay,
  isWithinInterval,
  isSameMonth,
  addMonths,
  parseISO,
  isValid,
  min,
  max,
} from 'date-fns';
import { DateRange } from './types';

export const identity = <T>(x: T) => x;

export const chunks = <T>(array: ReadonlyArray<T>, size: number): T[][] => (
  Array.from(
    { length: Math.ceil(array.length / size) },
    (_v, i) => array.slice(i * size, i * size + size),
  )
);

// Date
export const getDaysInMonth = (date: Date, locale?: Locale) => {
  const startWeek = startOfWeek(startOfMonth(date), {locale});
  const endWeek = endOfWeek(endOfMonth(date), {locale});
  const days = [];
  for (let curr = startWeek; isBefore(curr, endWeek);) {
    days.push(curr);
    curr = addDays(curr, 1);
  }
  return days;
};

export const isStartOfRange = ({ startDate }: DateRange, day: Date) => (
  (startDate && isSameDay(day, startDate)) as boolean
);

export const isEndOfRange = ({ endDate }: DateRange, day: Date) => (
  (endDate && isSameDay(day, endDate)) as boolean
);

export const inDateRange = ({ startDate, endDate }: DateRange, day: Date) => (
  startDate
  && endDate
  && (isWithinInterval(day, { start: startDate, end: endDate })
  || isSameDay(day, startDate)
  || isSameDay(day, endDate))
) as boolean;

export const isRangeSameDay = ({ startDate, endDate }: DateRange) => {
  if (startDate && endDate) {
    return isSameDay(startDate, endDate);
  }
  return false;
};

type Falsy = false | null | undefined | 0 | '';

export const parseOptionalDate = (date: Date | string | Falsy, defaultValue: Date) => {
  if (date) {
    const parsed = date instanceof Date ? date : parseISO(date);
    if (isValid(parsed)) return parsed;
  }
  return defaultValue;
};

export const getValidatedMonths = (range: DateRange, minDate: Date, maxDate: Date) => {
  const { startDate, endDate } = range;
  if (startDate && endDate) {
    const newStart = max([startDate, minDate]);
    const newEnd = min([endDate, maxDate]);

    return [newStart, isSameMonth(newStart, newEnd) ? addMonths(newStart, 1) : newEnd];
  }
  return [startDate, endDate];
};