Convert ebooks using calibri CLI

convert-books.js

#!/usr/bin/env node

/*
 * Converts e-books using calibri convert-ebook binary to files well readable on ipad/any tablet
 *
 * Libs required can be installed by running `yarn add glob async yargs`
 *
 * Requires node >= 10 I guess.
 */

const glob = require('glob');
const async = require('async');
const yargs = require('yargs');

const util = require('util');
const exec = util.promisify(require('child_process').exec);
const fs = require('fs');
const path = require('path');
const os = require('os');

const argv = require('yargs')
  .version(false)
  .usage('$0', 'Converts e-books from --source-dir to the same dir in --outputformat')
  .alias('h', 'host')
  .string('source-dir')
  .describe('source-dir', 'Source directory to process')
  .string('out-dir')
  .describe('out-dir', 'The destination directory')
  .string('output-format')
  .default('pdf')
  .describe('output-format', 'The output format to get')
  .number('j')
  .default('j', String(os.cpus().length))
  .describe('j', 'Number of parallel jobs')
  .help()
  .epilog('BTW I hate the yargs docs.')
  .argv;

const sourceDir = argv['source-dir'];
const outDir = argv['out-dir'];
const outputExtension = argv['output-format'].toLowerCase();
const nJobs = argv.j;

console.log(`Running with ${nJobs} jobs...`);

function getFilenameWithoutExtension(filename) {
  return filename.split('.').slice(0, -1).join('.');
}

async function getAllFilesInDirectory(dir) {
  var getDirectories = function (src, callback) {
    glob(src + '/**/*', callback);
  };

  return new Promise(resolve => {
    getDirectories(dir, function (err, res) {
      if (err) {
        console.log('Error', err);
      } else {
        resolve(res);
      }
    });
  });
}

async function doOne(tuple, resolve) {
  const infile = tuple[0], outfile = tuple[1];
  exec(`ebook-convert "${infile}" "${outfile}" --input-profile=kindle --output-profile=ipad`)
    .then(() => {
      console.log(`Finished ${infile} => ${outfile}`);
    }).catch(() => {
      console.error(`Failed to convert ${infile} => ${outfile}`);
    })
    .finally(resolve);
}

(async () => {
  const jobs = [];
  const allFiles = await getAllFilesInDirectory(sourceDir);
  if (! fs.existsSync(outDir)) {
    fs.mkdirSync(outDir, {recursive: true});
  }

  for (const idx in allFiles) {
    const filename = allFiles[idx];
    const filenameWithoutExtension = getFilenameWithoutExtension(filename);
    const outDirClean = path.relative(sourceDir, filename);
    const outputFilename = `${getFilenameWithoutExtension(outDirClean)}.${outputExtension}`;

    if (fs.lstatSync(filename).isDirectory()) {
      console.log(`${filename} is a directory, skipping`);
      continue;
    }

    if (fs.existsSync(outputFilename)) {
      console.log(`${outputFilename} Already exists, skipping...`);
      continue;
    }

    if (path.extname(filename).toLowerCase() === `.${outputExtension}`) {
      console.log(`The input and output files have the same format! ${outputFilename}`);
      continue;
    }

    jobs.push([filename, path.join(outDir, outputFilename)]);
  }

  console.log(`Processing ${jobs.length} files...`);

  const ret = await async.mapLimit(jobs, nJobs, async (one) => {
    return new Promise(resolve => {
      doOne(one, resolve);
    });
  }, (err) => {
    console.error(err);
  });
})();