const {KJUR, hextob64} = require('jsrsasign');

const HashMap = {
    SHA256withRSA: 'SHA256withRSA',
    SHA1withRSA: 'SHA1withRSA'
};

const PEM_BEGIN = '-----BEGIN PRIVATE KEY-----\n';
const PEM_END = '\n-----END PRIVATE KEY-----';

/**
 * rsa签名参考：https://www.jianshu.com/p/145eab95322c
 */
module.exports = {
    /**
     * 创建签名
     * @param params 请求参数
     * @param privateKey 私钥，PKCS8
     * @param signType 签名类型，RSA,RSA2
     * @returns 返回签名内容
     */
    createSign(params, privateKey, signType) {
        const content = this.getSignContent(params);
        return this.sign(content, privateKey, signType);
    },
    sign: function (content, privateKey, signType) {
        if (signType.toUpperCase() === 'RSA') {
            return this.rsaSign(content, privateKey, HashMap.SHA1withRSA);
        } else if (signType.toUpperCase() === 'RSA2') {
            return this.rsaSign(content, privateKey, HashMap.SHA256withRSA);
        } else {
            throw 'signType错误';
        }
    },
    /**
     * rsa签名
     * @param content 签名内容
     * @param privateKey 私钥
     * @param hash hash算法，SHA256withRSA，SHA1withRSA
     * @returns 返回签名字符串，base64
     */
    rsaSign: function (content, privateKey, hash) {
        privateKey = this._formatKey(privateKey);
        // 创建 Signature 对象
        const signature = new KJUR.crypto.Signature({
            alg: hash,
            //!这里指定 私钥 pem!
            prvkeypem: privateKey
        });
        signature.updateString(content);
        const signData = signature.sign();
        // 将内容转成base64
        return hextob64(signData);
    },
    _formatKey: function (key) {
        if (!key.startsWith(PEM_BEGIN)) {
            key = PEM_BEGIN + key;
        }
        if (!key.endsWith(PEM_END)) {
            key = key + PEM_END;
        }
        return key;
    },
    /**
     * 获取签名内容
     * @param params 请求参数
     * @returns {string}
     */
    getSignContent: function (params) {
        const paramNames = [];
        for (const key in params) {
            paramNames.push(key);
        }

        paramNames.sort();

        const paramNameValue = [];

        for (let i = 0, len = paramNames.length; i < len; i++) {
            const paramName = paramNames[i];
            const val = params[paramName];
            if (paramName && val) {
                paramNameValue.push(`${paramName}=${val}`);
            }
        }
        return paramNameValue.join('&');
    }
};