import {
    startOfWeek,
    startOfMonth,
    endOfWeek,
    endOfMonth,
    isBefore,
    addDays,
    isSameDay,
    isSameMonth,
    addMonths,
    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),
    )
);

export const isWithinRange = (date: Date, startDate: Date, endDate: Date) => {
    if (date && startDate && endDate) {
        return startDate.getTime() <= date.getTime() && date.getTime() <= endDate.getTime()
    }
    return false;
}

export const getDaysInMonth = (date: Date) => {
    const startWeek = startOfWeek(startOfMonth(date));
    const endWeek = endOfWeek(endOfMonth(date));
    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
    && (isWithinRange(day, startDate, 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) {
        try {
            const parsed = new Date(date);
            if (isValid(parsed)) return parsed;
        }
        catch { }
    }
    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];
};