package iot.lidee.common.utils.wechat;

/**
 * 对企业微信发送给企业后台的消息加解密示例代码.
 *
 * @copyright Copyright (c) 1998-2014 Tencent Inc.
 */

// ------------------------------------------------------------------------

import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import java.io.StringReader;

/**
 * XMLParse class
 *
 * 提供提取消息格式中的密文及生成回复消息格式的接口.
 */
class XMLParse {

    /**
     * 提取出xml数据包中的加密消息
     * @param xmltext 待提取的xml字符串
     * @return 提取出的加密消息字符串
     * @throws AesException
     */
    public static Object[] extract(String xmltext) throws AesException     {
        Object[] result = new Object[3];
        try {
            DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

            String FEATURE = null;
            // This is the PRIMARY defense. If DTDs (doctypes) are disallowed, almost all XML entity attacks are prevented
            // Xerces 2 only - http://xerces.apache.org/xerces2-j/features.html#disallow-doctype-decl
            FEATURE = "http://apache.org/xml/features/disallow-doctype-decl";
            dbf.setFeature(FEATURE, true);

            // If you can't completely disable DTDs, then at least do the following:
            // Xerces 1 - http://xerces.apache.org/xerces-j/features.html#external-general-entities
            // Xerces 2 - http://xerces.apache.org/xerces2-j/features.html#external-general-entities
            // JDK7+ - http://xml.org/sax/features/external-general-entities
            FEATURE = "http://xml.org/sax/features/external-general-entities";
            dbf.setFeature(FEATURE, false);

            // Xerces 1 - http://xerces.apache.org/xerces-j/features.html#external-parameter-entities
            // Xerces 2 - http://xerces.apache.org/xerces2-j/features.html#external-parameter-entities
            // JDK7+ - http://xml.org/sax/features/external-parameter-entities
            FEATURE = "http://xml.org/sax/features/external-parameter-entities";
            dbf.setFeature(FEATURE, false);

            // Disable external DTDs as well
            FEATURE = "http://apache.org/xml/features/nonvalidating/load-external-dtd";
            dbf.setFeature(FEATURE, false);

            // and these as well, per Timothy Morgan's 2014 paper: "XML Schema, DTD, and Entity Attacks"
            dbf.setXIncludeAware(false);
            dbf.setExpandEntityReferences(false);

            // And, per Timothy Morgan: "If for some reason support for inline DOCTYPEs are a requirement, then
            // ensure the entity settings are disabled (as shown above) and beware that SSRF attacks
            // (http://cwe.mitre.org/data/definitions/918.html) and denial
            // of service attacks (such as billion laughs or decompression bombs via "jar:") are a risk."

            // remaining parser logic
            DocumentBuilder db = dbf.newDocumentBuilder();
            StringReader sr = new StringReader(xmltext);
            InputSource is = new InputSource(sr);
            Document document = db.parse(is);

            Element root = document.getDocumentElement();
            NodeList nodelist1 = root.getElementsByTagName("Encrypt");
            result[0] = 0;
            result[1] = nodelist1.item(0).getTextContent();
            return result;
        } catch (Exception e) {
            e.printStackTrace();
            throw new AesException(AesException.ParseXmlError);
        }
    }

    /**
     * 生成xml消息
     * @param encrypt 加密后的消息密文
     * @param signature 安全签名
     * @param timestamp 时间戳
     * @param nonce 随机字符串
     * @return 生成的xml字符串
     */
    public static String generate(String encrypt, String signature, String timestamp, String nonce) {

        String format = "<xml>\n" + "<Encrypt><![CDATA[%1$s]]></Encrypt>\n"
                + "<MsgSignature><![CDATA[%2$s]]></MsgSignature>\n"
                + "<TimeStamp>%3$s</TimeStamp>\n" + "<Nonce><![CDATA[%4$s]]></Nonce>\n" + "</xml>";
        return String.format(format, encrypt, signature, timestamp, nonce);

    }
}
