<?php

namespace utils;

class Jwt
{
	private $typ = 'JWT';

	#key用户生成secret
	private $key = 'jSCq5heSuhDiuhSsad441wq6541SDA5415W6QE564dsda';

	private $secret;

	#加密算法
	private $alg = 'HS256';

	#签发者-payload组成部分
	private $iss;

	#过期时间-payload组成部分
	private $exp;

	#签发时间-payload组成部分
	private $iat;

	#用户基础信息-payload组成部分
	private $user_info;

	#过期多久之前有效
	private $timeout = 7200;

	public function __construct($config)
	{
		$this->config = $config;
		$this->init();
	}

	private function init()
	{
		$this->iss = $this->config['iss'];
		$this->exp = $this->config['exp'];
		$this->iat = time();
	}

    /**
     * 获取token
     * @param array $user_info
     * @return string
     */
	public function getToken(array $user_info):string
	{
		//头信息
		$header = [
			'typ' => $this->typ,
			'alg' => $this->alg
		];
		$base64_header = base64_encode(json_encode($header));

		//有效载荷
		$payload = [
			'iss' => $this->iss,
			'exp' => $this->exp,
			'iat' => $this->iat,
			'user_info' => $user_info,
		];
		$base64_payload = base64_encode(json_encode($payload));

		//签名信息
		$this->secret = $this->getSecret($user_info);
		$signature = $base64_header . $base64_payload . $this->secret;
		$base64_signature = $this->enc($this->alg, $signature);

		$jwt_token = $base64_header . '.' . $base64_payload . '.' . $base64_signature;
		return $jwt_token;
	}

    /**
     * 校验token
     * @param $jwt_token
     * @return int
     */
	public function checkToken($jwt_token)
	{
		$arr = explode('.', $jwt_token);
		if (count($arr) < 3) {
			return -1;
		}

		$base64_header = $arr[0];
		$base64_payload = $arr[1];
		$base64_signature = $arr[2];

		$payload = json_decode(base64_decode($base64_payload), true);
		if (!is_array($payload) || !isset($payload['exp']) || !isset($payload['iat']) || !isset($payload['user_info'])) {
			return -2;
		}

		//生成签名，比较
		$this->secret = $this->getSecret($payload['user_info']);
		$tmp_signature = $base64_header . $base64_payload . $this->secret;
		$tmp_base64_signature = $this->enc($this->alg, $tmp_signature);

		if ($base64_signature !== $tmp_base64_signature) {
			return -3;
		}

		// 是否过期
		if ($payload['exp'] + $payload['iat'] - time() < 0) {
			// token过期了
			return -4;
		} else {
			// token没有过期
			if ($payload['exp'] + $payload['iat'] - time() - $this->timeout < 0) {
				return 201;
			}

			return 200;
		}
	}

    /**
     * 获取用户信息
     * @param $jwt_token
     * @return array|mixed
     */
	public function getUserInfo($jwt_token)
	{
		$arr = explode('.', $jwt_token);
		if (count($arr) < 3) {
			return [];
		}

		$base64_payload = $arr[1];

		$payload = json_decode(base64_decode($base64_payload), true);
		if (!is_array($payload) || !isset($payload['user_info'])) {
			return [];
		}

		return $payload['user_info'];
	}


    /**
     * 获取secret，保证每个用户的secret都不同
     * @param $user_info
     * @return string
     */
	private function getSecret($user_info)
	{
		return md5($this->key . json_encode($user_info));
	}

    /**
     * 加密
     * @param $enc_type
     * @param $content
     * @return string
     */
	private function enc($enc_type, $content)
	{
		if ($enc_type == 'HS256')
		{
			return hash('sha256', $content);
		}
	}

}