/**
 * Author: @Rongronggg9
 *
 * There are at least three folders which are relevant with WeChat MP (Official Account Platform / Media Platform):
 * lib/v2/wechat
 * lib/v2/gov/npma
 * lib/v2/gzh360
 * lib/v2/pku/nsd/gd
 * lib/v2/sdu/cs
 * lib/v2/nua/utils
 *
 * If your new route is not in the above folders, please add it to the list.
 *
 * If your route needs to fetch MP articles from mp.weixin.qq.com, you SHOULD use `finishArticleItem`.
 * However, if your route need to determine some metadata by itself, you MAY use `fetchArticle`.
 * If you find more metadata on the webpage, consider modifying `fetchArticle` to include them.
 * NEVER fetch MP articles from mp.weixin.qq.com in your route in order to avoid cache key collision.
 * NO NEED TO use cache if you are using `finishArticleItem` or `fetchArticle`, they will handle cache for you.
 *
 * If your route fetches MP articles from other websites, you SHOULD use `fixArticleContent` to fix the content format.
 * If you find more fixes that should be applied, consider modifying `fixArticleContent` to include them.
 *
 * For more details of these functions, please refer to the jsDoc in the source code.
 */

const got = require('@/utils/got');
const cheerio = require('cheerio');
const { parseDate } = require('@/utils/parse-date');

const replaceTag = ($, oldTag, newTagName) => {
    oldTag = $(oldTag);
    const NewTag = $($(`<${newTagName} />`));
    const oldTagAttr = oldTag.attr();
    for (const key in oldTagAttr) {
        NewTag.attr(key, oldTagAttr[key]);
    }
    NewTag.append(oldTag.contents());
    oldTag.replaceWith(NewTag);
};

const detectOriginalArticleUrl = ($) => {
    // No article content get, try the original url
    // example: https://mp.weixin.qq.com/s/f6sKObaZZhADTYU2Jl5Bnw
    if (!$('#js_content').text()) {
        return $('#js_share_source').attr('data-url');
    }
    // Article content is too short, try the first link
    // example: https://mp.weixin.qq.com/s/9saVB4KaolRyJfpajzeFRg
    if ($('#js_content').text().length < 80) {
        return $('#js_content a').attr('href');
    }
    return null;
};

const detectSourceUrl = ($) => {
    const matchs = $.root()
        .html()
        .match(/msg_source_url = '(.+)';/);

    if (matchs) {
        return matchs[1];
    }
    return null;
};

/**
 * Articles from WeChat MP have weird formats, this function is used to fix them.
 *
 * Even though your content are not directly fetched from WeChat MP, you SHOULD still call this function.
 * Calling this function is safe in most situations.
 *
 * Example usage: item.description = fixArticleContent($('div#js_content.rich_media_content'));
 * @param {*} html - The html to be fixed, a string or a cheerio object.
 * @param {boolean} skipImg - Whether to skip fixing images.
 * @return {string} - The fixed html, a string.
 */
const fixArticleContent = (html, skipImg = false) => {
    html = html && html.html ? html.html() : html; // do not disturb the original tree
    if (!html) {
        return '';
    }
    const $ = cheerio.load(html, undefined, false);
    if (!skipImg) {
        // fix img lazy loading
        $('img[data-src]').each((_, img) => {
            img = $(img);
            const realSrc = img.attr('data-src');
            if (realSrc) {
                img.attr('src', realSrc);
                img.removeAttr('data-src');
            }
        });
    }
    // fix section
    $('section').each((_, section) => {
        section = $(section);
        const p_count = section.find('p').length;
        const div_count = section.find('div').length;
        const section_count = section.find('section').length;
        if (p_count + div_count + section_count === 0) {
            // make it a p
            replaceTag($, section, 'p');
        } else {
            // make it a div
            replaceTag($, section, 'div');
        }
    });

    // add breaks in code section
    $('code').each((_, code) => {
        $('<br>').insertAfter(code);
    });

    // clear line index tags in code section
    $('.code-snippet__line-index').remove();

    // fix single picture article
    // example: https://mp.weixin.qq.com/s/4p5YmYuASiQSYFiy7KqydQ
    $('script').each((_, script) => {
        script = $(script);
        const matchs = script.html().match(/document\.getElementById\('js_image_desc'\)\.innerHTML = "(.*)"\.replace/);

        if (matchs) {
            script.replaceWith(matchs[1].replace(/\r/g, '').replace(/\n/g, '<br>').replace(/\\x0d/g, '').replace(/\\x0a/g, '<br>'));
        }
    });

    // clean scripts
    $('script').remove();
    return $.html();
};

// Ref:
// https://soaked.in/2020/08/wechat-platform-url/
// Known params (permanent long link):
// __biz (essential), mid (essential), idx (essential), sn (essential), chksm, mpshare, scene, ascene, subscene, srcid,
// lang, sharer_sharetime, sharer_shareid, version, exportkey, pass_ticket, clicktime, enterid, devicetype, nettype,
// abtest_cookie, wx_header
// Known params (temporary link):
// src, timestamp, ver, signature, new (unessential)
const normalizeUrl = (url, bypassHostCheck = false) => {
    const oriUrl = url;
    const urlObj = new URL(url);
    if (!bypassHostCheck && urlObj.host !== 'mp.weixin.qq.com') {
        throw new Error('wechat-mp: URL host must be "mp.weixin.qq.com", but got ' + oriUrl);
    }
    urlObj.protocol = 'https:';
    urlObj.hash = ''; // remove hash
    if (urlObj.pathname.match(/^\/s\/.+/)) {
        // a short link, just remove all the params
        urlObj.search = '';
    } else if (urlObj.pathname.match(/^\/s$/)) {
        const biz = urlObj.searchParams.get('__biz');
        const mid = urlObj.searchParams.get('mid') || urlObj.searchParams.get('appmsgid');
        const idx = urlObj.searchParams.get('idx') || urlObj.searchParams.get('itemidx');
        const sn = urlObj.searchParams.get('sn') || urlObj.searchParams.get('sign');
        if (biz && mid && idx && sn) {
            // a permanent long link, remove all unessential params
            // no need to escape anything so no need to use `new URLSearchParams({...}).toString()`
            urlObj.search = `?__biz=${biz}&mid=${mid}&idx=${idx}&sn=${sn}`;
        } else {
            const src = urlObj.searchParams.get('src');
            const timestamp = urlObj.searchParams.get('timestamp');
            const ver = urlObj.searchParams.get('ver');
            const signature = urlObj.searchParams.get('signature');
            if (src && timestamp && ver && signature) {
                // a temporary link, remove all unessential params
                urlObj.search = `?src=${src}&timestamp=${timestamp}&ver=${ver}&signature=${signature}`;
            } else {
                // unknown link, just let it go
            }
        }
    } else {
        // IDK what it is, just let it go
    }
    return urlObj.href;
};

/**
 * Fetch article and its metadata from WeChat MP (mp.weixin.qq.com).
 *
 * If you use this function, no need to call `fixArticleContent`
 * @param {object} ctx - The context object.
 * @param {string} url - The url of the article.
 * @param {boolean} bypassHostCheck - Whether to bypass host check.
 * @return {Promise<object>} - An object containing the article and its metadata.
 */
const fetchArticle = async (ctx, url, bypassHostCheck = false) => {
    url = normalizeUrl(url, bypassHostCheck);
    return await ctx.cache.tryGet(url, async () => {
        const response = await got(url);
        const $ = cheerio.load(response.data);

        const title = ($('meta[property="og:title"]').attr('content') || '').replace(/\\r/g, '').replace(/\\n/g, ' ');
        const author = $('meta[name=author]').attr('content');
        let summary = $('meta[name=description]').attr('content');
        summary = summary !== title ? summary : '';
        let description = fixArticleContent($('#js_content'));
        // No article get or article is too short, try the original url
        const originalUrl = detectOriginalArticleUrl($);
        if (originalUrl) {
            // try to fetch the description from the original article
            const originalResponse = await got(normalizeUrl(originalUrl, bypassHostCheck));
            const original$ = cheerio.load(originalResponse.data);
            description += fixArticleContent(original$('#js_content'));
        }

        const sourceUrl = detectSourceUrl($);
        if (sourceUrl) {
            description += `<a href="${sourceUrl}">阅读原文</a>`;
        }

        let pubDate;
        const publish_time_script = $('script[nonce][type="text/javascript"]:contains("var ct")').first().html();
        const publish_time_match = publish_time_script && publish_time_script.match(/var ct *= *"?(\d{10})"?/);
        const publish_timestamp = publish_time_match && publish_time_match[1];
        if (publish_timestamp) {
            pubDate = parseDate(publish_timestamp * 1000);
        }

        let mpName = $('.profile_nickname').first().text();
        mpName = mpName && mpName.trim();
        return { title, author, description, summary, pubDate, mpName, link: url };
    });
};

/**
 * Fetch article and its metadata from WeChat MP (mp.weixin.qq.com), then fill the `item` object with the result.
 *
 * If you use this function, no need to call `fetchArticle` or `fixArticleContent`
 *
 * A new route SHOULD use this function instead of manually calling the above functions
 *
 * An existing route adopting this function SHOULD either:
 * - set `skipLink` to true (not recommended)
 * - set `item.guid` to `item.link` BEFORE calling this function
 * @param {object} ctx - The context object.
 * @param {object} item - The item object to be filled.
 * @param {boolean} setMpNameAsAuthor - If `true`, `author` will be the MP itself, otherwise the real author of the article.
 * @param {boolean} skipLink - Whether to skip overriding `item.link` with the normalized url.
 * @return {Promise<object>} - The incoming `item` object, with the article and its metadata filled in.
 */
const finishArticleItem = async (ctx, item, setMpNameAsAuthor = false, skipLink = false) => {
    const { title, author, description, summary, pubDate, mpName, link } = await fetchArticle(ctx, item.link);
    item.title = title || item.title;
    item.description = description || item.description;
    item.summary = summary || item.summary;
    item.pubDate = pubDate || item.pubDate;
    if (setMpNameAsAuthor) {
        // the Official Account itself. if your route return articles from different accounts, you may want to use this
        item.author = mpName || item.author;
    } else {
        // the real author of the article. if your route return articles from a certain account, use this
        item.author = author || item.author;
    }
    if (!skipLink) {
        item.link = link || item.link;
    }
    return item;
};

module.exports = {
    fixArticleContent,
    fetchArticle,
    finishArticleItem, // a new route SHOULD use this function instead of manually calling the above functions
    _internal: {
        normalizeUrl, // for internal use only, exported for testing
    },
};