import { addFormatToken } from '../format/format';
import { Locale } from '../locale/locale.class';
import { getDay } from '../utils/date-getters';
import { addRegexToken, match1to2 } from '../parse/regex';
import { addUnitAlias } from './aliases';
import { addUnitPriority } from './priorities';
import { addWeekParseToken } from '../parse/token';
import { getParsingFlags } from '../create/parsing-flags';
import { isNumber, isString, toInt } from '../utils/type-checks';
import { DateFormatterOptions, WeekParsing } from '../types';
import { DateParsingConfig } from '../create/parsing.types';
import { add } from '../moment/add-subtract';
import { getLocale } from '../locale/locales';


export function initDayOfWeek() {
// FORMATTING

  addFormatToken('d', null, 'do',
    function(date: Date, opts: DateFormatterOptions): string {
      return getDay(date, opts.isUTC)
        .toString(10);
    }
  );

  addFormatToken('dd', null, null,
    function(date: Date, opts: DateFormatterOptions): string {
      return opts.locale.weekdaysMin(date, opts.format, opts.isUTC);
    }
  );

  addFormatToken('ddd', null, null,
    function(date: Date, opts: DateFormatterOptions): string {
      return opts.locale.weekdaysShort(date, opts.format, opts.isUTC);
    }
  );

  addFormatToken('dddd', null, null,
    function(date: Date, opts: DateFormatterOptions): string {
      return opts.locale.weekdays(date, opts.format, opts.isUTC);
    }
  );

  addFormatToken('e', null, null,
    function(date: Date, opts: DateFormatterOptions): string {
      return getLocaleDayOfWeek(date, opts.locale, opts.isUTC)
        .toString(10);
      // return getDay(date, opts.isUTC).toString(10);
    }
  );
  addFormatToken('E', null, null,
    function(date: Date, opts: DateFormatterOptions): string {
      return getISODayOfWeek(date, opts.isUTC)
        .toString(10);
    }
  );

// ALIASES

  addUnitAlias('day', 'd');
  addUnitAlias('weekday', 'e');
  addUnitAlias('isoWeekday', 'E');

// PRIORITY
  addUnitPriority('day', 11);
  addUnitPriority('weekday', 11);
  addUnitPriority('isoWeekday', 11);

// PARSING

  addRegexToken('d', match1to2);
  addRegexToken('e', match1to2);
  addRegexToken('E', match1to2);

  addRegexToken('dd', function(isStrict: boolean, locale: Locale): RegExp {
    return locale.weekdaysMinRegex(isStrict);
  });

  addRegexToken('ddd', function(isStrict: boolean, locale: Locale): RegExp {
    return locale.weekdaysShortRegex(isStrict);
  });
  addRegexToken('dddd', function(isStrict: boolean, locale: Locale): RegExp {
    return locale.weekdaysRegex(isStrict);
  });

  addWeekParseToken(
    ['dd', 'ddd', 'dddd'],
    function(input: string, week: WeekParsing, config: DateParsingConfig, token) {
      const weekday = config._locale.weekdaysParse(input, token, config._strict);
      // if we didn't get a weekday name, mark the date as invalid
      if (weekday != null) {
        week.d = weekday;
      } else {
        getParsingFlags(config).invalidWeekday = !!input;
      }

      return config;
    }
  );

  addWeekParseToken(
    ['d', 'e', 'E'],
    function(input: string, week: WeekParsing, config: DateParsingConfig, token: string): DateParsingConfig {
      week[token] = toInt(input);

      return config;
    }
  );
}

// HELPERS

export function parseWeekday(input: string | number, locale: Locale): number {
  if (!isString(input)) {
    return input;
  }

  const _num = parseInt(input, 10);
  if (!isNaN(_num)) {
    return _num;
  }

  const _weekDay = locale.weekdaysParse(input);
  if (isNumber(_weekDay)) {
    return _weekDay;
  }

  return null;
}

export function parseIsoWeekday(input: string | number, locale: Locale = getLocale()): number {
  if (isString(input)) {
    return locale.weekdaysParse(input) % 7 || 7;
  }

  return isNumber(input) && isNaN(input) ? null : input;
}

// MOMENTS

export function getSetDayOfWeek(date: Date, input: number, opts: { isUTC?: boolean; locale: Locale }): Date | number {
  if (!input) {
    return getDayOfWeek(date, opts.isUTC);
  }

  return setDayOfWeek(date, input, opts.locale, opts.isUTC);
}

export function setDayOfWeek(date: Date, input: number, locale = getLocale(), isUTC?: boolean): Date {
  const day = getDay(date, isUTC);
  const _input = parseWeekday(input, locale);

  return add(date, _input - day, 'day');
}

export function getDayOfWeek(date: Date, isUTC?: boolean): number {
  return getDay(date, isUTC);
}

/********************************************/

// todo: utc
// getSetLocaleDayOfWeek
export function getLocaleDayOfWeek(date: Date, locale = getLocale(), isUTC?: boolean): number {
  return (getDay(date, isUTC) + 7 - locale.firstDayOfWeek()) % 7;
}

export function setLocaleDayOfWeek(date: Date, input: number, opts: { locale?: Locale; isUTC?: boolean } = {}): Date {
  const weekday = getLocaleDayOfWeek(date, opts.locale, opts.isUTC);

  return add(date, input - weekday, 'day');
}


// getSetISODayOfWeek
export function getISODayOfWeek(date: Date, isUTC?: boolean): number {
  return getDay(date, isUTC) || 7;
}

export function setISODayOfWeek(date: Date, input: number | string, opts: { locale?: Locale } = {}): Date {
  // behaves the same as moment#day except
  // as a getter, returns 7 instead of 0 (1-7 range instead of 0-6)
  // as a setter, sunday should belong to the previous week.

  const weekday = parseIsoWeekday(input, opts.locale);

  return setDayOfWeek(date, getDayOfWeek(date) % 7 ? weekday : weekday - 7);
}