const _ = require('lodash');

/**
 * 处理用于筛选的 URL ， 拼接 URL 参数
 * @param originParam 当前 URL 中的参数
 * @param newParam 要拼接的 参数
 * @returns {string}
 */
const handleFilterUrl = (baseUrl, originParam, newParam, delParam) => {
    let dest = '?';
    let tempOriginParam = {};

    delParam = delParam || {};

    tempOriginParam = Object.assign(tempOriginParam, originParam, newParam);
    delete tempOriginParam.uid;

    _.forEach(tempOriginParam, (value, key) => {
        if (!delParam[key] && value) {
            // NOTE: 这里会对 query 进行编码，因为 query 有可以能是中文
            if (key === 'query') {
                value = encodeURIComponent(value);
            }
            dest += `${key}=${value}&`;
        }
    });

    return (baseUrl || '') + _.trim(dest, '&');
};

module.exports = (total, params = {}, baseUrl = '') => {
    const curPage = _.parseInt(params.page || 1);
    const pageSize = _.parseInt(params.limit) || 10;
    const totalPage = _.ceil(total / pageSize);
    const tip = {
        start: (curPage - 1) * pageSize + 1,
        end: curPage * pageSize > total ? total : curPage * pageSize,
        total
    };
    let prePage, nextPage;
    const pageUrl = handleFilterUrl(baseUrl, params, {page: '${page}'});

    if (curPage > 1) {
        prePage = {
            url: pageUrl.replace('${page}', curPage - 1)
        };
    }
    if (curPage < totalPage) {
        nextPage = {
            url: pageUrl.replace('${page}', curPage + 1)
        };
    }
    let pages = [];
    let pagesNums = totalPage > 5 ? 5 : totalPage;
    let offsetPage = curPage + _.round(0 - pagesNums / 2); // 遍历页码左侧数字

    if (offsetPage <= 0) {
        offsetPage = 1;
    } else if (offsetPage + pagesNums > totalPage) {
        offsetPage = totalPage - pagesNums + 1;
    }
    const preLimit = offsetPage - 1; // 页码1和遍历页码左侧的距离
    const nextLimit = totalPage - (offsetPage - 1 + pagesNums); // 总页码和遍历页码右侧的距离

    if (preLimit === 1) { // 如果左侧间距为1则显示这个页码
        pagesNums++;
        offsetPage--;
    }
    if (nextLimit === 1) { // 如果右侧间距为1则显示这个页码
        pagesNums++;
    }

    if (preLimit >= 2) {
        pages = _.concat(pages, {
            num: 1,
            url: pageUrl.replace('${page}', 1),
        }, {
            num: '...'
        });
    }
    if (offsetPage <= 0) {
        offsetPage = 1;
    } else if (offsetPage + pagesNums > totalPage) {
        offsetPage = totalPage - pagesNums + 1;
    }

    for (let i = 0; i < pagesNums; i++) {
        pages.push({
            num: offsetPage,
            url: pageUrl.replace('${page}', offsetPage),
            cur: curPage === offsetPage
        });
        offsetPage++;
    }

    if (nextLimit >= 2) {
        pages = _.concat(pages, {
            num: '...'
        }, {
            num: totalPage,
            url: pageUrl.replace('${page}', totalPage),
        });
    }
    return {tip, prePage, nextPage, pages};
};