import axios from './axios.js';
import * as cheerio from 'cheerio';

/**
 * A generic function to scrape paginated data from the target ASP.NET website.
 * @param {string} startUrl - The initial URL to begin scraping.
 * @param {Function} extractDataFromHtml - The page-specific function to extract data from Cheerio object.
 * @returns {Promise<Array<Object>>} - An array of all scraped data records.
 */
export async function scrapePaginatedData(startUrl, extractDataFromHtml) {
    let allData = [];
    const origin = new URL(startUrl).origin;

    console.log(`开始抓取第一页数据: ${startUrl}`);
    let response = await axios.get(startUrl);
    let $ = cheerio.load(response.data);
    
    let firstPageData = await extractDataFromHtml($, origin);
    allData = allData.concat(firstPageData);
    console.log(`第一页抓取完成，获得 ${firstPageData.length} 条数据。`);

    // Get total pages for pagination
    const totalPagesSpan = $('#PageNavigator1_LblPageCount');
    const totalPages = totalPagesSpan.length ? parseInt(totalPagesSpan.text(), 10) : 1;
    console.log(`共发现 ${totalPages} 页。`);

    if (totalPages <= 1) {
        console.log('\n抓取全站数据完毕！');
        return allData;
    }

    // Collect form data for POST requests
    const formValues = {};
    $('input[name^="txt"], select').each((idx, el) => {
        const name = $(el).attr('name');
        if (name) {
            formValues[name] = $(el).val() || '';
        }
    });

    // Scrape remaining pages
    for (let i = 2; i <= totalPages; i++) {
        console.log(`正在抓取第 ${i} 页...`);

        const viewState = $('#__VIEWSTATE').val();
        const viewStateGenerator = $('#__VIEWSTATEGENERATOR').val();
        const eventValidation = $('#__EVENTVALIDATION').val();

        if (!viewState) {
            console.log('无法找到 __VIEWSTATE，终止抓取。');
            break;
        }

        const postData = new URLSearchParams();
        postData.append('__EVENTTARGET', 'PageNavigator1$LnkBtnNext');
        postData.append('__EVENTARGUMENT', '');
        postData.append('__VIEWSTATE', viewState);
        postData.append('__VIEWSTATEGENERATOR', viewStateGenerator);
        if (eventValidation) {
            postData.append('__EVENTVALIDATION', eventValidation);
        }
        
        for (const name in formValues) {
            postData.append(name, formValues[name]);
        }
        postData.append('PageNavigator1$txtNewPageIndex', (i - 1).toString());

        response = await axios.post(startUrl, postData, {
            headers: {
                'Content-Type': 'application/x-www-form-urlencoded',
                'Referer': startUrl,
            }
        });

        $ = cheerio.load(response.data);
        const nextPageData = await extractDataFromHtml($, origin);
        console.log(`第 ${i} 页抓取完成，获得 ${nextPageData.length} 条数据。`);

        if (nextPageData.length === 0) {
            console.log(`第 ${i} 页没有数据，抓取结束。`);
            break;
        }
        allData = allData.concat(nextPageData);
    }
    
    console.log(`\n抓取全站数据完毕！共 ${allData.length} 条原始记录。`);
    return allData;
}

/**
 * Re-indexes the "序号" field of each record in an array sequentially, starting from 1.
 * @param {Array<Object>} dataArray - The array of data to re-index.
 * @returns {Array<Object>} - The re-indexed data array.
 */
export function reIndex(dataArray) {
    if (!dataArray || dataArray.length === 0) return [];
    
    for (let i = 0; i < dataArray.length; i++) {
        dataArray[i]['序号'] = (i + 1).toString();
    }
    console.log('序号字段已重新编号。');
    return dataArray;
}