import {hasProperty, pushUnique} from '../lib/utils.js';
import {dateValue} from '../lib/date.js';
import {reFormatTokens, parseDate} from '../lib/date-format.js';
import {parseHTML} from '../lib/dom.js';
import defaultOptions from './defaultOptions.js';

const {
  language: defaultLang,
  format: defaultFormat,
  weekStart: defaultWeekStart,
} = defaultOptions;

// Reducer function to filter out invalid day-of-week from the input
function sanitizeDOW(dow, day) {
  return dow.length < 6 && day >= 0 && day < 7
    ? pushUnique(dow, day)
    : dow;
}

function calcEndOfWeek(startOfWeek) {
  return (startOfWeek + 6) % 7;
}

// validate input date. if invalid, fallback to the original value
function validateDate(value, format, locale, origValue) {
  const date = parseDate(value, format, locale);
  return date !== undefined ? date : origValue;
}

// Validate viewId. if invalid, fallback to the original value
function validateViewId(value, origValue, max = 3) {
  const viewId = parseInt(value, 10);
  return viewId >= 0 && viewId <= max ? viewId : origValue;
}

// Create Datepicker configuration to set
export default function processOptions(options, datepicker) {
  const inOpts = Object.assign({}, options);
  const config = {};
  const locales = datepicker.constructor.locales;
  let {
    format,
    language,
    locale,
    maxDate,
    maxView,
    minDate,
    pickLevel,
    startView,
    weekStart,
  } = datepicker.config || {};

  if (inOpts.language) {
    let lang;
    if (inOpts.language !== language) {
      if (locales[inOpts.language]) {
        lang = inOpts.language;
      } else {
        // Check if langauge + region tag can fallback to the one without
        // region (e.g. fr-CA → fr)
        lang = inOpts.language.split('-')[0];
        if (locales[lang] === undefined) {
          lang = false;
        }
      }
    }
    delete inOpts.language;
    if (lang) {
      language = config.language = lang;

      // update locale as well when updating language
      const origLocale = locale || locales[defaultLang];
      // use default language's properties for the fallback
      locale = Object.assign({
        format: defaultFormat,
        weekStart: defaultWeekStart
      }, locales[defaultLang]);
      if (language !== defaultLang) {
        Object.assign(locale, locales[language]);
      }
      config.locale = locale;
      // if format and/or weekStart are the same as old locale's defaults,
      // update them to new locale's defaults
      if (format === origLocale.format) {
        format = config.format = locale.format;
      }
      if (weekStart === origLocale.weekStart) {
        weekStart = config.weekStart = locale.weekStart;
        config.weekEnd = calcEndOfWeek(locale.weekStart);
      }
    }
  }

  if (inOpts.format) {
    const hasToDisplay = typeof inOpts.format.toDisplay === 'function';
    const hasToValue = typeof inOpts.format.toValue === 'function';
    const validFormatString = reFormatTokens.test(inOpts.format);
    if ((hasToDisplay && hasToValue) || validFormatString) {
      format = config.format = inOpts.format;
    }
    delete inOpts.format;
  }

  //*** dates ***//
  // while min and maxDate for "no limit" in the options are better to be null
  // (especially when updating), the ones in the config have to be undefined
  // because null is treated as 0 (= unix epoch) when comparing with time value
  let minDt = minDate;
  let maxDt = maxDate;
  if (inOpts.minDate !== undefined) {
    minDt = inOpts.minDate === null
      ? dateValue(0, 0, 1)  // set 0000-01-01 to prevent negative values for year
      : validateDate(inOpts.minDate, format, locale, minDt);
    delete inOpts.minDate;
  }
  if (inOpts.maxDate !== undefined) {
    maxDt = inOpts.maxDate === null
      ? undefined
      : validateDate(inOpts.maxDate, format, locale, maxDt);
    delete inOpts.maxDate;
  }
  if (maxDt < minDt) {
    minDate = config.minDate = maxDt;
    maxDate = config.maxDate = minDt;
  } else {
    if (minDate !== minDt) {
      minDate = config.minDate = minDt;
    }
    if (maxDate !== maxDt) {
      maxDate = config.maxDate = maxDt;
    }
  }

  if (inOpts.datesDisabled) {
    config.datesDisabled = inOpts.datesDisabled.reduce((dates, dt) => {
      const date = parseDate(dt, format, locale);
      return date !== undefined ? pushUnique(dates, date) : dates;
    }, []);
    delete inOpts.datesDisabled;
  }
  if (inOpts.defaultViewDate !== undefined) {
    const viewDate = parseDate(inOpts.defaultViewDate, format, locale);
    if (viewDate !== undefined) {
      config.defaultViewDate = viewDate;
    }
    delete inOpts.defaultViewDate;
  }

  //*** days of week ***//
  if (inOpts.weekStart !== undefined) {
    const wkStart = Number(inOpts.weekStart) % 7;
    if (!isNaN(wkStart)) {
      weekStart = config.weekStart = wkStart;
      config.weekEnd = calcEndOfWeek(wkStart);
    }
    delete inOpts.weekStart;
  }
  if (inOpts.daysOfWeekDisabled) {
    config.daysOfWeekDisabled = inOpts.daysOfWeekDisabled.reduce(sanitizeDOW, []);
    delete inOpts.daysOfWeekDisabled;
  }
  if (inOpts.daysOfWeekHighlighted) {
    config.daysOfWeekHighlighted = inOpts.daysOfWeekHighlighted.reduce(sanitizeDOW, []);
    delete inOpts.daysOfWeekHighlighted;
  }

  //*** multi date ***//
  if (inOpts.maxNumberOfDates !== undefined) {
    const maxNumberOfDates = parseInt(inOpts.maxNumberOfDates, 10);
    if (maxNumberOfDates >= 0) {
      config.maxNumberOfDates = maxNumberOfDates;
      config.multidate = maxNumberOfDates !== 1;
    }
    delete inOpts.maxNumberOfDates;
  }
  if (inOpts.dateDelimiter) {
    config.dateDelimiter = String(inOpts.dateDelimiter);
    delete inOpts.dateDelimiter;
  }

  //*** pick level & view ***//
  let newPickLevel = pickLevel;
  if (inOpts.pickLevel !== undefined) {
    newPickLevel = validateViewId(inOpts.pickLevel, 2);
    delete inOpts.pickLevel;
  }
  if (newPickLevel !== pickLevel) {
    pickLevel = config.pickLevel = newPickLevel;
  }

  let newMaxView = maxView;
  if (inOpts.maxView !== undefined) {
    newMaxView = validateViewId(inOpts.maxView, maxView);
    delete inOpts.maxView;
  }
  // ensure max view >= pick level
  newMaxView = pickLevel > newMaxView ? pickLevel : newMaxView;
  if (newMaxView !== maxView) {
    maxView = config.maxView = newMaxView;
  }

  let newStartView = startView;
  if (inOpts.startView !== undefined) {
    newStartView = validateViewId(inOpts.startView, newStartView);
    delete inOpts.startView;
  }
  // ensure pick level <= start view <= max view
  if (newStartView < pickLevel) {
    newStartView = pickLevel;
  } else if (newStartView > maxView) {
    newStartView = maxView;
  }
  if (newStartView !== startView) {
    config.startView = newStartView;
  }

  //*** template ***//
  if (inOpts.prevArrow) {
    const prevArrow = parseHTML(inOpts.prevArrow);
    if (prevArrow.childNodes.length > 0) {
      config.prevArrow = prevArrow.childNodes;
    }
    delete inOpts.prevArrow;
  }
  if (inOpts.nextArrow) {
    const nextArrow = parseHTML(inOpts.nextArrow);
    if (nextArrow.childNodes.length > 0) {
      config.nextArrow = nextArrow.childNodes;
    }
    delete inOpts.nextArrow;
  }

  //*** misc ***//
  if (inOpts.disableTouchKeyboard !== undefined) {
    config.disableTouchKeyboard = 'ontouchstart' in document && !!inOpts.disableTouchKeyboard;
    delete inOpts.disableTouchKeyboard;
  }
  if (inOpts.orientation) {
    const orientation = inOpts.orientation.toLowerCase().split(/\s+/g);
    config.orientation = {
      x: orientation.find(x => (x === 'left' || x === 'right')) || 'auto',
      y: orientation.find(y => (y === 'top' || y === 'bottom')) || 'auto',
    };
    delete inOpts.orientation;
  }
  if (inOpts.todayBtnMode !== undefined) {
    switch(inOpts.todayBtnMode) {
      case 0:
      case 1:
        config.todayBtnMode = inOpts.todayBtnMode;
    }
    delete inOpts.todayBtnMode;
  }

  //*** copy the rest ***//
  Object.keys(inOpts).forEach((key) => {
    if (inOpts[key] !== undefined && hasProperty(defaultOptions, key)) {
      config[key] = inOpts[key];
    }
  });

  return config;
}