gulpfile.js

const gulp = require('gulp');
const zip = require('gulp-zip');
const imagemin = require('gulp-imagemin');
const run = require('gulp-run');
const change = require('gulp-change');
const rename = require('gulp-rename');
const del = require('del');
const { series } = gulp;

let dark = false;

function setDark() {
  //returns promise so gulp won't complain
  return new Promise(function(resolve, reject) {
    dark = true;
    resolve();
  });
}
function setLight() {
  //returns promise so gulp won't complain
  return new Promise(function(resolve, reject) {
    dark = false;
    resolve();
  });
}

function cleanWorkspace(cb) {
  if (dark) {
    return del('guideDark.pdf');
  } else {
    return del('guideLight.pdf');
  }
}

function optimizeImages(cb) {
  //using gulp-imagemin to compress images, will not compress image that already has been
  return gulp
    .src('src/res/images/*')
    .pipe(imagemin())
    .pipe(gulp.dest('src/res/images'));
}

function backup(cb) {
  return gulp.src('src/guide.tex').pipe(gulp.dest('backup'));
}

function loadBackup(cb) {
  return gulp.src('backup/guide.tex').pipe(gulp.dest('src'));
}

function packagePdf(cb) {
  //creates the final output file including both the pdf file and the LICENSE file
  if (dark) {
    return gulp
      .src('LICENSE')
      .pipe(rename('LICENSE.txt'))
      .pipe(gulp.src('guideDark.pdf'))
      .pipe(zip('guideDarkPdf.zip'))
      .pipe(gulp.dest('dist'));
  } else {
    return gulp
      .src('LICENSE')
      .pipe(rename('LICENSE.txt'))
      .pipe(gulp.src('guideLight.pdf'))
      .pipe(zip('guideLightPdf.zip'))
      .pipe(gulp.dest('dist'));
  }
}

function packageImages(cb) {
  return gulp
    .src('src/res/images/*')
    .pipe(zip('guideImages.zip'))
    .pipe(gulp.dest('dist'));
}

function replaceStr(content) {
  let str = dark ? '%$DARK:' : '%$LIGHT:';
  str = str.replace(/([.*+?^=!:${}()|\[\]\/\\])/g, '\\$1');
  return content.replace(new RegExp(str, 'g'), '');
}

function makeDarkTex(cb) {
  //creates the guideDark.tex file using the guide.tex file and uncommenting all DARK marked lines
  return gulp
    .src('src/guide.tex')
    .pipe(change(replaceStr))
    .pipe(rename('guideDark.tex'))
    .pipe(gulp.dest('src/'));
}

function makeLightTex(cb) {
  //creates the guideLight.tex file using the guide.tex file and uncommenting all LIGHT marked lines
  return gulp
    .src('src/guide.tex')
    .pipe(change(replaceStr))
    .pipe(rename('guideLight.tex'))
    .pipe(gulp.dest('src/'));
}

function buildGuide(cb) {
  //using gulp-run and xelatex from your PATH, creates pdf file from either Light or Dark tex file
  if (dark) {
    return run(
      'xelatex -interaction=nonstopmode -file-line-error -aux-directory=src -include-directory=src/res/sections/ src/guideDark.tex'
    ).exec();
  } else {
    return run(
      'xelatex -interaction=nonstopmode -file-line-error -aux-directory=src -include-directory=src/res/sections/ src/guideLight.tex'
    ).exec();
  }
}

//all commands available using gulp <command>, requires gulp cli
exports.buildDark = series(
  setDark,
  backup,
  optimizeImages,
  makeDarkTex,
  buildGuide,
  loadBackup,
  packagePdf,
  cleanWorkspace
);
exports.buildLight = series(
  setLight,
  backup,
  optimizeImages,
  makeLightTex,
  buildGuide,
  loadBackup,
  packagePdf,
  cleanWorkspace
);
exports.testLight = series(
  setLight,
  backup,
  makeLightTex,
  buildGuide,
  loadBackup
);
exports.packageImages = series(optimizeImages, packageImages);