const date = require('./date');
const dayjs = require('dayjs');
const customParseFormat = require('dayjs/plugin/customParseFormat');
const logger = require('./logger');
const utc = require('dayjs/plugin/utc');
dayjs.extend(utc);
dayjs.extend(customParseFormat);

/**
 * Convert unconventional i8n to the one supported by dayjs https://bit.ly/2psVwIJ
 * @param {String} x i8n string
 */
const i8nconv = (x) => {
    const c = {
        'zh-hans': 'zh-cn',
        'zh-chs': 'zh-cn',
        'zh-sg': 'zh-cn',
        'zh-hant': 'zh-hk',
        'zh-cht': 'zh-hk',
        'zh-mo': 'zh-hk',
    };
    for (const prop in c) {
        if (RegExp(`^${prop}$`, 'i').test(x)) {
            x = c[prop];
            break;
        }
    }
    return x;
};

/**
 * A function to convert a string of time based on specified format
 * @param {string} [html]                    A string of time to convert.
 * @param {string} [customFormat=undefined]  Format to parse html by dayjs.
 * @param {string} [lang=en]                 Language (must be supported by dayjs).
 * @param {int}    [htmlOffset=0]            UTC offset of html. It will be neglected if html contains timezone indicated by strings like "+0800".
 */
const tStringParser = (html, customFormat = undefined, lang = 'en', htmlOffset = 0) => {
    lang = i8nconv(lang);

    // Remove weekdays and comma from the string
    // dayjs v1.8.16 is not able to parse weekdays
    // https://github.com/iamkun/dayjs/blob/dev/docs/en/Plugin.md#list-of-all-available-format-tokens
    // We don't remove weekdayMini since the month may contains weekdayMini, like "六" in "六月"
    let removeStr = [];
    if (lang !== 'en') {
        try {
            require(`dayjs/locale/${lang}`);
            if (/^zh/.test(lang)) {
                removeStr = removeStr.concat(['，']);
            }
            // Add locale
            dayjs.locale(lang);
        } catch (error) {
            logger.error(`Locale "${lang}" passed to dateParser is not supported by dayjs`);
            return date(html);
        }
    }
    Object.values(dayjs.Ls).forEach((k) => {
        ['weekdays', 'weekdaysShort'].forEach((x) => {
            if (k.hasOwnProperty(x)) {
                const a = k[x].map((z) => z);
                removeStr = removeStr.concat(...a);
            }
        });
    });
    removeStr = removeStr.concat([',', 'Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat']);
    let htmlP = html;
    removeStr.forEach((x) => {
        // Order matters
        htmlP = htmlP.replace(RegExp(x, 'gi'), '');
    });

    const d = dayjs.utc(htmlP, customFormat);
    // console.log(htmlP,d)
    if (d.isValid()) {
        if (/[+-](\d{2}:?\d{2})/.test(html)) {
            return d.toDate().toUTCString();
        } else {
            return d.add(htmlOffset, 'h').toDate().toUTCString();
        }
    } else {
        return date(html);
    }
};

tStringParser.i8nconv = i8nconv;

module.exports = tStringParser;