#!/usr/bin/env node

'use strict';

var CryptoJS = require("crypto-js");
var FileSystem = require("fs");
const Yargs = require('yargs');

const SCRIPT_URL = 'https://cdnjs.cloudflare.com/ajax/libs/crypto-js/3.1.9-1/crypto-js.min.js';
const SCRIPT_TAG = '<script src="' + SCRIPT_URL + '" integrity="sha384-lp4k1VRKPU9eBnPePjnJ9M2RF3i7PC30gXs70+elCVfgwLwx1tv5+ctxdtwxqZa7" crossorigin="anonymous"></script>';

const namedArgs = Yargs
      .usage('Usage: staticrypt <input> <password> [options]')
      .demandCommand(2)
      .option('e', {
          alias: 'embed',
          type: 'boolean',
          describe: 'Whether or not to embed crypto-js in the page (or use an external CDN)',
          default: false
      })
      .option('o', {
          alias: 'output',
          type: 'string',
          describe: 'File name / path for generated encrypted file',
          default: null
      })
      .option('t', {
          alias: 'title',
          type: 'string',
          describe: "Title for output HTML page",
          default: 'Protected Page'
      })
      .option('i', {
          alias: 'instructions',
          type: 'string',
          describe: 'Special instructions to display to the user.',
          default: ''
      })
      .argv;

if(namedArgs._.length !== 2){
    Yargs.showHelp();
    process.exit(1);
}

const input = namedArgs._[0].toString();
const password = namedArgs._[1].toString();

try{
    var contents = FileSystem.readFileSync(input, 'utf8');
}catch(e){
    console.log("Failure: input file does not exist!");
    process.exit(1);
}

// encrypt input
var encrypted = CryptoJS.AES.encrypt(contents, password);
var hmac = CryptoJS.HmacSHA256(encrypted.toString(), CryptoJS.SHA256(password).toString()).toString();
var encryptedMessage = hmac + encrypted;

// create crypto-js tag (embedded or not)
var cryptoTag = SCRIPT_TAG;
if (namedArgs.embed) {
    try {
        var embedContents = FileSystem.readFileSync('crypto-js.min.js', 'utf8');
    } catch(e) {
        console.log("Failure: embed file does not exist!");
        process.exit(1);
    }
    cryptoTag = '<script>' + embedContents + '</script>';
}


var data = {
    title: namedArgs.title,
    instructions: namedArgs.instructions,
    encrypted: encryptedMessage,
    crypto_tag: cryptoTag,
    embed: namedArgs.embed,
    outputFilePath: namedArgs.output !== null ? namedArgs.output : input.replace(/\.html$/, '') + "_encrypted.html"
};

genFile(data);


/**
 * Fill the template with provided data and writes it to output file.
 *
 * @param data
 */
function genFile(data){
    try{
        var templateContents = FileSystem.readFileSync(__dirname + '/password_template.html', 'utf8');
    }catch(e){
        console.log("Failure: could not read template!");
        process.exit(1);
    }

    var renderedTemplate = render(templateContents, data);

    try{
        FileSystem.writeFileSync(data.outputFilePath, renderedTemplate);
    }catch(e){
        console.log("Failure: could not generate output file!");
        process.exit(1);
    }
}

/**
 * Replace the placeholder tags (between '{tag}') in 'tpl' string with provided data.
 *
 * @param tpl
 * @param data
 * @returns string
 */
function render(tpl, data){
    return tpl.replace(/{(.*?)}/g, function (_, key) {
        return data && data[key] || '';
    });
}