eml2png/index.js

Paint the EML to a single PNG image.

'use strict';

const fs = require('fs');
const stream = require('stream');
const wkhtmltox = require('wkhtmltox');
const simpleParser = require('mailparser').simpleParser;
const MailParser = require('mailparser2-mit').MailParser;

function eml2png(opts) {
    const self = this;

    self.converter = new wkhtmltox(opts || {
        interval: 10,
        maxWorkers: 0
    });
    self.converter.wkhtmltoimage = process.env.WKHTMLTOIMAGE || 'wkhtmltoimage';

    function isFile(path) {
        try {
            return fs.lstatSync(path).isFile();
        } catch (e) {
            return false;
        }
    };

    /**
     * Get HTML text from EML file.
     *
     * @param {string} input
     * @returns {Promise}
     */
    self.getHtmlStrFromFile = async (input) => {
        const emlContent = isFile(input) ? fs.createReadStream(input) : input;
        const parse = await simpleParser(emlContent);
        const html = parse.html;
        const textAsHtml = parse.textAsHtml;
        const text = parse.text;
        if (html === false && !textAsHtml && !text) {
            const fallbackContent = await new Promise((resolve, reject) => {
                const mailparser = new MailParser({
                    defaultCharset: 'utf8'
                });
                mailparser.on('end', (mailObject) => {
                    resolve(mailObject.html || mailObject.text);
                });
                if (isFile(input)) {
                    fs.createReadStream(input).pipe(mailparser);
                } else {
                    mailparser.write(input);
                    mailparser.end();
                }
            });
            return fallbackContent || undefined;
        }
        return html == false ? (textAsHtml || text) : html;
    };

    /**
     * Convert a EML file or string to PNG file.
     *
     * @param {string} input
     * @param {*} [options={}]
     * @param {string} outputPath
     * @returns {Promise}
     */
    self.png = async (input, options = {}, outputPath) => {
        const htmlContent = await self.getHtmlStrFromFile(input);
        if (!htmlContent) {
            return undefined;
        }
        const emlHtml = new stream.PassThrough();
        emlHtml.write(htmlContent);
        emlHtml.end();
        options = options || {};
        options.format = 'png';
        const pngStream = self.converter.image(emlHtml, options);
        if (outputPath) {
            const isDone = await new Promise((resolve, reject) => {
                pngStream.pipe(fs.createWriteStream(outputPath)).on('finish', () => {
                    resolve(true);
                }).on('error', () => {
                    resolve(false);
                });
            });
            return isDone ? outputPath : undefined;
        }
        return pngStream;
    };

    return self;
}

module.exports = eml2png;