const jwt = require('jsonwebtoken');
module.exports = MagicLink;

/**
 * @typedef { import('jsonwebtoken').Secret } Secret
 * @typedef { import('nodemailer').Transporter } MailTransporter
 * @typedef { import('nodemailer').SentMessageInfo } SentMessageInfo
 * @typedef { string } JSONWebToken
 * @typedef { string } URL
 */

/**
 * defaultGetText
 *
 * @param {URL} url - The url which will trigger sign in flow
 * @param {string} type - The type of email to send e.g. signin, signup
 * @param {string} email - The recipient of the email to send
 * @returns {string} text - The text content of an email to send
 */
function defaultGetText(url, type, email) {
    let msg = 'sign in';
    if (type === 'signup') {
        msg = 'confirm your email address';
    }
    return `Click here to ${msg} ${url}. This msg was sent to ${email}`;
}

/**
 * defaultGetHTML
 *
 * @param {URL} url - The url which will trigger sign in flow
 * @param {string} type - The type of email to send e.g. signin, signup
 * @param {string} email - The recipient of the email to send
 * @returns {string} HTML - The HTML content of an email to send
 */
function defaultGetHTML(url, type, email) {
    let msg = 'sign in';
    if (type === 'signup') {
        msg = 'confirm your email address';
    }
    return `<a href="${url}">Click here to ${msg}</a> This msg was sent to ${email}`;
}

/**
 * defaultGetSubject
 *
 * @param {string} type - The type of email to send e.g. signin, signup
 * @returns {string} subject - The subject of an email to send
 */
function defaultGetSubject(type) {
    if (type === 'signup') {
        return `Signup!`;
    }
    return `Signin!`;
}

/**
 * MagicLink
 * @constructor
 *
 * @param {object} options
 * @param {MailTransporter} options.transporter
 * @param {Secret} options.secret
 * @param {(token: JSONWebToken, type: string) => URL} options.getSigninURL
 * @param {typeof defaultGetText} [options.getText]
 * @param {typeof defaultGetHTML} [options.getHTML]
 * @param {typeof defaultGetSubject} [options.getSubject]
 */
function MagicLink(options) {
    if (!options || !options.transporter || !options.secret || !options.getSigninURL) {
        throw new Error('Missing options. Expects {transporter, secret, getSigninURL}');
    }
    this.transporter = options.transporter;
    this.secret = options.secret;
    this.getSigninURL = options.getSigninURL;
    this.getText = options.getText || defaultGetText;
    this.getHTML = options.getHTML || defaultGetHTML;
    this.getSubject = options.getSubject || defaultGetSubject;
}

/**
 * sendMagicLink
 *
 * @param {object} options
 * @param {string} options.email - The email to send magic link to
 * @param {object} options.subject - The subject to associate with the magic link (user id, or email)
 * @param {string=} [options.type='signin'] - The type to be passed to the url and content generator functions
 * @returns {Promise<{token: JSONWebToken, info: SentMessageInfo}>}
 */
MagicLink.prototype.sendMagicLink = async function sendMagicLink(options) {
    const token = jwt.sign({}, this.secret, {
        algorithm: 'HS256',
        subject: options.subject,
        expiresIn: '10m'
    });

    const type = options.type || 'signin';

    const url = this.getSigninURL(token, type);

    const info = await this.transporter.sendMail({
        to: options.email,
        subject: this.getSubject(type),
        text: this.getText(url, type, options.email),
        html: this.getHTML(url, type, options.email)
    });

    return {token, info};
};

/**
 * getUserFromToken
 *
 * @param {JSONWebToken} token - The token to decode
 * @returns {object} user - The user object associated with the magic link
 */
MagicLink.prototype.getUserFromToken = function getUserFromToken(token) {
    /** @type {object} */
    const claims = jwt.verify(token, this.secret, {
        algorithms: ['HS256'],
        maxAge: '10m'
    });
    return claims.sub;
};