@date-io/date-fns

import DateFnsUtils from "@date-io/date-fns";

import { default as DateFnsUtils } from "@date-io/date-fns";

const DateFnsUtils = require("@date-io/date-fns").default;

import DateFnsUtils from "@date-io/date-fns";
import { enUS } from "date-fns/locale/en-US";

// Create adapter instance
const dateFns = new DateFnsUtils({
  locale: enUS,
  formats: {
    fullDate: "PPP" // Override default formats if needed
  }
});

// Create and manipulate dates
const today = dateFns.date(); // Current date
const specificDate = dateFns.date("2024-01-15T10:30:00Z");

// Format dates
const formatted = dateFns.format(today, "fullDate"); // "January 15, 2024"
const customFormat = dateFns.formatByString(today, "yyyy-MM-dd");

// Date arithmetic
const nextWeek = dateFns.addWeeks(today, 1);
const daysDiff = dateFns.getDiff(nextWeek, today, "days"); // 7

// Validation and comparison
const isValid = dateFns.isValid(specificDate); // true
const isSame = dateFns.isSameDay(today, specificDate);

/**
 * DateFnsUtils adapter class implementing IUtils interface
 */
class DateFnsUtils implements IUtils<Date, Locale> {
  constructor(options?: {
    formats?: Partial<DateIOFormats>;
    locale?: Locale;
    instance?: any;
  });
  
  /** Name of the underlying library */
  lib: string; // "date-fns"
  
  /** Current locale configuration */
  locale?: Locale;
  
  /** Format strings for various date/time representations */
  formats: DateIOFormats;
}

type Locale = typeof import("date-fns/locale/en-US").default;

/**
 * Creates a date object with generic type support
 * @param value - Optional date value (string, number, Date, or undefined)
 * @returns Date object, null if input was null, current date if undefined
 */
date<
  TArg extends unknown = undefined,
  TRes extends unknown = TArg extends null
    ? null
    : TArg extends undefined
    ? Date
    : Date | null
>(value?: TArg): TRes;

/**
 * Convert date to JavaScript Date object (identity function for native dates)
 * @param value - Date to convert
 * @returns JavaScript Date object
 */
toJsDate(value: Date): Date;

/**
 * Parse ISO date string
 * @param isoString - ISO 8601 date string
 * @returns Parsed date object
 */
parseISO(isoString: string): Date;

/**
 * Convert date to ISO string
 * @param value - Date to convert
 * @returns ISO 8601 formatted string
 */
toISO(value: Date): string;

/**
 * Parse date string with custom format
 * @param value - Date string to parse
 * @param formatString - Format pattern (date-fns format)
 * @returns Parsed date or null if invalid
 */
parse(value: string, formatString: string): Date | null;

/**
 * Check if date is valid
 * @param value - Value to validate
 * @returns True if valid date
 */
isValid(value: any): boolean;

/**
 * Check if date is null
 * @param date - Date to check
 * @returns True if date is null
 */
isNull(date: Date): boolean;

/**
 * Compare dates for equality
 * @param date - First date
 * @param comparing - Second date
 * @returns True if dates are equal
 */
isEqual(date: any, comparing: any): boolean;

/**
 * Check if dates are on the same day
 * @param value - First date
 * @param comparing - Second date
 * @returns True if same day
 */
isSameDay(value: Date, comparing: Date): boolean;

/**
 * Check if dates are in the same month
 * @param value - First date
 * @param comparing - Second date
 * @returns True if same month
 */
isSameMonth(value: Date, comparing: Date): boolean;

/**
 * Check if dates are in the same year
 * @param value - First date
 * @param comparing - Second date
 * @returns True if same year
 */
isSameYear(value: Date, comparing: Date): boolean;

/**
 * Check if dates are in the same hour
 * @param value - First date
 * @param comparing - Second date
 * @returns True if same hour
 */
isSameHour(value: Date, comparing: Date): boolean;

/**
 * Check if first date is after second date
 * @param value - First date
 * @param comparing - Second date
 * @returns True if first date is after second
 */
isAfter(value: Date, comparing: Date): boolean;

/**
 * Check if first date is before second date
 * @param value - First date
 * @param comparing - Second date
 * @returns True if first date is before second
 */
isBefore(value: Date, comparing: Date): boolean;

/**
 * Check if date is after the end of another day
 * @param date - Date to check
 * @param value - Reference date
 * @returns True if date is after end of reference day
 */
isAfterDay(date: Date, value: Date): boolean;

/**
 * Check if date is before the start of another day
 * @param date - Date to check
 * @param value - Reference date
 * @returns True if date is before start of reference day
 */
isBeforeDay(date: Date, value: Date): boolean;

/**
 * Check if date is after the end of another year
 * @param date - Date to check
 * @param value - Reference date
 * @returns True if date is after end of reference year
 */
isAfterYear(date: Date, value: Date): boolean;

/**
 * Check if date is before the start of another year
 * @param date - Date to check
 * @param value - Reference date
 * @returns True if date is before start of reference year
 */
isBeforeYear(date: Date, value: Date): boolean;

/**
 * Check if date is after the start of another month
 * @param value - Date to check
 * @param comparing - Reference date
 * @returns True if date is after start of reference month
 */
isAfterMonth(value: Date, comparing: Date): boolean;

/**
 * Check if date is before the start of another month
 * @param value - Date to check
 * @param comparing - Reference date
 * @returns True if date is before start of reference month
 */
isBeforeMonth(value: Date, comparing: Date): boolean;

/**
 * Check if date is within a range (inclusive)
 * @param date - Date to check
 * @param range - Array containing start and end dates
 * @returns True if date is within range
 */
isWithinRange(date: Date, range: [Date, Date]): boolean;

/**
 * Get start of day (00:00:00.000)
 * @param value - Input date
 * @returns Date at start of day
 */
startOfDay(value: Date): Date;

/**
 * Get end of day (23:59:59.999)
 * @param value - Input date
 * @returns Date at end of day
 */
endOfDay(value: Date): Date;

/**
 * Get start of week (locale-aware)
 * @param value - Input date
 * @returns Date at start of week
 */
startOfWeek(value: Date): Date;

/**
 * Get end of week (locale-aware)
 * @param value - Input date
 * @returns Date at end of week
 */
endOfWeek(value: Date): Date;

/**
 * Get start of month
 * @param value - Input date
 * @returns Date at start of month
 */
startOfMonth(value: Date): Date;

/**
 * Get end of month
 * @param value - Input date
 * @returns Date at end of month
 */
endOfMonth(value: Date): Date;

/**
 * Get start of year
 * @param value - Input date
 * @returns Date at start of year
 */
startOfYear(value: Date): Date;

/**
 * Get end of year
 * @param value - Input date
 * @returns Date at end of year
 */
endOfYear(value: Date): Date;

/**
 * Add seconds to a date
 * @param value - Input date
 * @param count - Number of seconds to add
 * @returns New date with seconds added
 */
addSeconds(value: Date, count: number): Date;

/**
 * Add minutes to a date
 * @param value - Input date
 * @param count - Number of minutes to add
 * @returns New date with minutes added
 */
addMinutes(value: Date, count: number): Date;

/**
 * Add hours to a date
 * @param value - Input date
 * @param count - Number of hours to add
 * @returns New date with hours added
 */
addHours(value: Date, count: number): Date;

/**
 * Add days to a date
 * @param value - Input date
 * @param count - Number of days to add
 * @returns New date with days added
 */
addDays(value: Date, count: number): Date;

/**
 * Add weeks to a date
 * @param value - Input date
 * @param count - Number of weeks to add
 * @returns New date with weeks added
 */
addWeeks(value: Date, count: number): Date;

/**
 * Add months to a date
 * @param value - Input date
 * @param count - Number of months to add
 * @returns New date with months added
 */
addMonths(value: Date, count: number): Date;

/**
 * Add years to a date
 * @param value - Input date
 * @param count - Number of years to add
 * @returns New date with years added
 */
addYears(value: Date, count: number): Date;

/**
 * Calculate difference between dates in specified unit
 * @param value - First date
 * @param comparing - Second date or string
 * @param unit - Unit of measurement (optional, defaults to milliseconds)
 * @returns Difference in specified unit
 */
getDiff(value: Date, comparing: Date | string, unit?: Unit): number;

/**
 * Get hours from date (0-23)
 * @param value - Input date
 * @returns Hours value
 */
getHours(value: Date): number;

/**
 * Set hours on date
 * @param value - Input date
 * @param count - Hours value (0-23)
 * @returns New date with hours set
 */
setHours(value: Date, count: number): Date;

/**
 * Get minutes from date (0-59)
 * @param date - Input date
 * @returns Minutes value
 */
getMinutes(date: Date): number;

/**
 * Set minutes on date
 * @param value - Input date
 * @param count - Minutes value (0-59)
 * @returns New date with minutes set
 */
setMinutes(value: Date, count: number): Date;

/**
 * Get seconds from date (0-59)
 * @param value - Input date
 * @returns Seconds value
 */
getSeconds(value: Date): number;

/**
 * Set seconds on date
 * @param value - Input date
 * @param count - Seconds value (0-59)
 * @returns New date with seconds set
 */
setSeconds(value: Date, count: number): Date;

/**
 * Get day of month from date (1-31)
 * @param date - Input date
 * @returns Day of month value
 */
getDate(date: Date): number;

/**
 * Set day of month on date
 * @param date - Input date
 * @param count - Day value (1-31)
 * @returns New date with day set
 */
setDate(date: Date, count: number): Date;

/**
 * Get week number from date
 * @param date - Input date
 * @returns Week number
 */
getWeek(date: Date): number;

/**
 * Get month from date (0-11)
 * @param date - Input date
 * @returns Month value (0-11)
 */
getMonth(date: Date): number;

/**
 * Get number of days in month
 * @param date - Input date
 * @returns Number of days in the month
 */
getDaysInMonth(date: Date): number;

/**
 * Set month on date
 * @param date - Input date
 * @param count - Month value (0-11)
 * @returns New date with month set
 */
setMonth(date: Date, count: number): Date;

/**
 * Get full year from date
 * @param value - Input date
 * @returns Full year value
 */
getYear(value: Date): number;

/**
 * Set year on date
 * @param value - Input date
 * @param count - Year value
 * @returns New date with year set
 */
setYear(value: Date, count: number): Date;

/**
 * Format date using predefined format key
 * @param date - Date to format
 * @param formatKey - Key from DateIOFormats
 * @returns Formatted date string
 */
format(date: Date, formatKey: keyof DateIOFormats): string;

/**
 * Format date using custom format string
 * @param date - Date to format
 * @param formatString - Custom format pattern (date-fns format)
 * @returns Formatted date string
 */
formatByString(date: Date, formatString: string): string;

/**
 * Format number (identity function)
 * @param numberToFormat - Number string to format
 * @returns Formatted number string
 */
formatNumber(numberToFormat: string): string;

/**
 * Get AM/PM text for meridiem
 * @param ampm - "am" or "pm"
 * @returns "AM" or "PM"
 */
getMeridiemText(ampm: "am" | "pm"): string;

/**
 * Get current locale code
 * @returns Locale code string (e.g., "en-US")
 */
getCurrentLocaleCode(): string;

/**
 * Check if current locale uses 12-hour clock
 * @returns True if 12-hour format is used
 */
is12HourCycleInCurrentLocale(): boolean;

/**
 * Get human-readable format help text
 * @param format - Format string
 * @returns Helper text for the format
 */
getFormatHelperText(format: string): string;

/**
 * Get next month from date
 * @param date - Input date
 * @returns Date in next month
 */
getNextMonth(date: Date): Date;

/**
 * Get previous month from date
 * @param date - Input date
 * @returns Date in previous month
 */
getPreviousMonth(date: Date): Date;

/**
 * Get array of 12 months starting from year start
 * @param date - Reference date
 * @returns Array of 12 date objects representing months
 */
getMonthArray(date: Date): Date[];

/**
 * Get localized weekday names (abbreviated)
 * @returns Array of abbreviated weekday names
 */
getWeekdays(): string[];

/**
 * Get calendar month as 2D array of weeks
 * @param date - Reference date
 * @returns 2D array where each sub-array represents a week
 */
getWeekArray(date: Date): Date[][];

/**
 * Get array of years in range
 * @param start - Start date
 * @param end - End date
 * @returns Array of date objects representing years
 */
getYearRange(start: Date, end: Date): Date[];

/**
 * Combine date and time components
 * @param date - Date component
 * @param time - Time component
 * @returns New date with combined date and time
 */
mergeDateAndTime(date: Date, time: Date): Date;

/**
 * Format strings for various date/time representations
 */
interface DateIOFormats {
  /** Localized full date @example "Jan 1, 2019" */
  fullDate: string;
  /** Partially localized full date with weekday @example "Tuesday, January 1, 2019" */
  fullDateWithWeekday: string;
  /** Date format with month and day @example "1 January" */
  normalDate: string;
  /** Date format with weekday, month and day @example "Wed, Jan 1" */
  normalDateWithWeekday: string;
  /** Shorter day format @example "Jan 1" */
  shortDate: string;
  /** Year format @example "2019" */
  year: string;
  /** Month format @example "January" */
  month: string;
  /** Short month format @example "Jan" */
  monthShort: string;
  /** Month with year format @example "January 2018" */
  monthAndYear: string;
  /** Month with date format @example "January 1" */
  monthAndDate: string;
  /** Weekday format @example "Wednesday" */
  weekday: string;
  /** Short weekday format @example "Wed" */
  weekdayShort: string;
  /** Day format @example "1" */
  dayOfMonth: string;
  /** Hours format 12h @example "11" */
  hours12h: string;
  /** Hours format 24h @example "23" */
  hours24h: string;
  /** Minutes format @example "44" */
  minutes: string;
  /** Seconds format @example "00" */
  seconds: string;
  /** Full time localized format @example "11:44 PM" for US, "23:44" for Europe */
  fullTime: string;
  /** Full time 12h format @example "11:44 PM" */
  fullTime12h: string;
  /** Full time 24h format @example "23:44" */
  fullTime24h: string;
  /** Date & time with localized time @example "Jan 1, 2018 11:44 PM" */
  fullDateTime: string;
  /** Date & time 12h format @example "Jan 1, 2018 11:44 PM" */
  fullDateTime12h: string;
  /** Date & time 24h format @example "Jan 1, 2018 23:44" */
  fullDateTime24h: string;
  /** Keyboard input friendly date @example "02/13/2020" */
  keyboardDate: string;
  /** Keyboard input friendly date/time @example "02/13/2020 23:44" */
  keyboardDateTime: string;
  /** Keyboard input friendly date/time 12h @example "02/13/2020 11:44 PM" */
  keyboardDateTime12h: string;
  /** Keyboard input friendly date/time 24h @example "02/13/2020 23:44" */
  keyboardDateTime24h: string;
}

/**
 * Time unit for difference calculations
 */
type Unit = 
  | "years" 
  | "quarters" 
  | "months" 
  | "weeks" 
  | "days" 
  | "hours" 
  | "minutes" 
  | "seconds" 
  | "milliseconds";

/**
 * IUtils interface from @date-io/core
 */
interface IUtils<TDate, TLocale> {
  formats: DateIOFormats;
  locale?: TLocale;
  lib: string;
  // ... all methods listed above
}