package com.cyksj.common.util.corp;

import cn.hutool.core.codec.Base64;
import com.cyksj.common.exception.AesException;
import lombok.AllArgsConstructor;
import lombok.Data;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.util.Random;

/**
 * <pre>
 * 对公众平台发送给公众账号的消息加解密示例代码.
 * Copyright (c) 1998-2014 Tencent Inc.
 * 针对org.apache.commons.codec.binary.Base64，
 * 需要导入架包commons-codec-1.9（或commons-codec-1.8等其他版本）
 * 官方下载地址：http://commons.apache.org/proper/commons-codec/download_codec.cgi
 * </pre>
 *
 * @author Tencent
 */
public class WxCryptUtil {

	private static final Charset CHARSET = StandardCharsets.UTF_8;

	private static final ThreadLocal<DocumentBuilder> BUILDER_LOCAL = ThreadLocal.withInitial(() -> {
		try {
			final DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
			factory.setExpandEntityReferences(false);
			factory.setFeature("http://apache.org/xml/features/disallow-doctype-decl", true);
			return factory.newDocumentBuilder();
		} catch (ParserConfigurationException exc) {
			throw new IllegalArgumentException(exc);
		}
	});

	protected byte[] aesKey;
	protected String token;
	protected String appidOrCorpid;

	public WxCryptUtil() {
	}

	/**
	 * 构造函数.
	 *
	 * @param token          公众平台上，开发者设置的token
	 * @param encodingAesKey 公众平台上，开发者设置的EncodingAESKey
	 * @param appidOrCorpid  公众平台appid/corpid
	 */
	public WxCryptUtil(String token, String encodingAesKey, String appidOrCorpid) {
		this.token = token;
		this.appidOrCorpid = appidOrCorpid;
		this.aesKey = Base64.decode(encodingAesKey);
	}


	/**
	 * 将一个数字转换成生成4个字节的网络字节序bytes数组.
	 */
	private static byte[] number2BytesInNetworkOrder(int number) {
		byte[] orderBytes = new byte[4];
		orderBytes[3] = (byte) (number & 0xFF);
		orderBytes[2] = (byte) (number >> 8 & 0xFF);
		orderBytes[1] = (byte) (number >> 16 & 0xFF);
		orderBytes[0] = (byte) (number >> 24 & 0xFF);
		return orderBytes;
	}

	/**
	 * 4个字节的网络字节序bytes数组还原成一个数字.
	 */
	private static int bytesNetworkOrder2Number(byte[] bytesInNetworkOrder) {
		int sourceNumber = 0;
		for (int i = 0; i < 4; i++) {
			sourceNumber <<= 8;
			sourceNumber |= bytesInNetworkOrder[i] & 0xff;
		}
		return sourceNumber;
	}

	/**
	 * 随机生成16位字符串.
	 */
	private static String genRandomStr() {
		String base = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
		Random random = new Random();
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < 16; i++) {
			int number = random.nextInt(base.length());
			sb.append(base.charAt(number));
		}
		return sb.toString();
	}

	/**
	 * 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
	 */
	private static String generateXml(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);
	}

	/**
	 * 将公众平台回复用户的消息加密打包.
	 * <ol>
	 * <li>对要发送的消息进行AES-CBC加密</li>
	 * <li>生成安全签名</li>
	 * <li>将消息密文和安全签名打包成xml格式</li>
	 * </ol>
	 *
	 * @param plainText 公众平台待回复用户的消息，xml格式的字符串
	 * @return 加密后的可以直接回复用户的密文，包括msg_signature, timestamp, nonce, encrypt的xml格式的字符串
	 */
	public String encrypt(String plainText) throws AesException {
		// 加密
		String encryptedXml = encrypt(genRandomStr(), plainText);

		// 生成安全签名
		String timeStamp = Long.toString(System.currentTimeMillis() / 1000L);
		String nonce = genRandomStr();

		String signature = SHA1.getSHA1(this.token, timeStamp, nonce, encryptedXml);
		return generateXml(encryptedXml, signature, timeStamp, nonce);
	}

	/**
	 * 将公众平台回复用户的消息加密打包.
	 * <ol>
	 * <li>对要发送的消息进行AES-CBC加密</li>
	 * <li>生成安全签名</li>
	 * <li>将消息密文和安全签名打包成xml格式</li>
	 * </ol>
	 *
	 * @param plainText 公众平台待回复用户的消息，xml格式的字符串
	 * @return 加密消息所需的值对象
	 */
	public EncryptContext encryptContext(String plainText) throws AesException {
		// 加密
		String encryptedXml = encrypt(genRandomStr(), plainText);

		// 生成安全签名
		String timeStamp = Long.toString(System.currentTimeMillis() / 1000L);
		String nonce = genRandomStr();

		String signature = SHA1.getSHA1(this.token, timeStamp, nonce, encryptedXml);
		return new EncryptContext(encryptedXml, signature, timeStamp, nonce);
	}

	/**
	 * 对明文进行加密.
	 *
	 * @param plainText 需要加密的明文
	 * @return 加密后base64编码的字符串
	 */
	public String encrypt(String randomStr, String plainText) {
		ByteGroup byteCollector = new ByteGroup();
		byte[] randomStringBytes = randomStr.getBytes(CHARSET);
		byte[] plainTextBytes = plainText.getBytes(CHARSET);
		byte[] bytesOfSizeInNetworkOrder = number2BytesInNetworkOrder(plainTextBytes.length);
		byte[] appIdBytes = this.appidOrCorpid.getBytes(CHARSET);

		// randomStr + networkBytesOrder + text + appid
		byteCollector.addBytes(randomStringBytes);
		byteCollector.addBytes(bytesOfSizeInNetworkOrder);
		byteCollector.addBytes(plainTextBytes);
		byteCollector.addBytes(appIdBytes);

		// ... + pad: 使用自定义的填充方式对明文进行补位填充
		byte[] padBytes = PKCS7Encoder.encode(byteCollector.size());
		byteCollector.addBytes(padBytes);

		// 获得最终的字节流, 未加密
		byte[] unencrypted = byteCollector.toBytes();

		try {
			// 设置加密模式为AES的CBC模式
			Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
			SecretKeySpec keySpec = new SecretKeySpec(this.aesKey, "AES");
			IvParameterSpec iv = new IvParameterSpec(this.aesKey, 0, 16);
			cipher.init(Cipher.ENCRYPT_MODE, keySpec, iv);

			// 加密
			byte[] encrypted = cipher.doFinal(unencrypted);

			// 使用BASE64对加密后的字符串进行编码
			return Base64.encode(encrypted);
		} catch (Exception e) {
			throw new RuntimeException(e);
		}

	}

	@Data
	@AllArgsConstructor
	public static class EncryptContext {
		private String encrypt;
		private String signature;
		private String timeStamp;
		private String nonce;
	}
}
