'use strict';

const path = require('path');
const cachePage = require('../../config/cache');

module.exports = () => {
    return (req, res, next) => {
        if (req.get('X-Requested-With') === 'XMLHttpRequest') {
            res.set('Cache-Control', 'no-cache');
        }

        function onRender() {
            let route = req.route ? req.route.path : '';
            let appPath = req.app.mountpath;
            let key = path.join(appPath, route.toString()); // route may be a regexp

            req.app.set('etag', false);

            // 如果存在cache配置，并且业务代码中没有设置
            if (cachePage[key] && res.get('Cache-Control') !== 'no-cache') {
                res.set({
                    'Cache-Control': 'max-age=' + cachePage[key]
                });
                res.removeHeader('Pragma');
                res.removeHeader('Expires');
            } else {
                res.set({
                    'Cache-Control': 'no-cache',
                    Pragma: 'no-cache',
                    Expires: new Date(1900, 0, 1, 0, 0, 0, 0)
                });
            }

        }

        res.on('render', onRender);
        next();
    };
};