Uikit scss transform

gulpfile.js

var pkg         = require('./package.json'),
    fs          = require('fs'),
    path        = require('path'),
    glob        = require('glob'),
    mkdirp      = require('mkdirp'),
    gulp        = require('gulp'),
    gutil       = require('gulp-util'),
    concat      = require('gulp-concat'),
    ignore      = require('gulp-ignore'),
    rename      = require('gulp-rename'),
    rimraf      = require('gulp-rimraf'),
    replace     = require('gulp-replace'),
    header      = require('gulp-header'),
    less        = require('gulp-less'),
    minifycss   = require('gulp-minify-css'),
    uglify      = require('gulp-uglify'),
    watch       = require('gulp-watch'),
    tap         = require('gulp-tap'),
    zip         = require('gulp-zip'),
    runSequence = require('run-sequence'),
    browserSync = require('browser-sync'),
    sass        = require('gulp-sass')
    Promise     = require('promise');

gulp.task('styles', function () {
  return gulp.src('./src/scss/uikit.scss')
    .pipe(sass())
    .pipe(gulp.dest('./dist/css/'))
})

gulp.task('sass-copy', function() {

    return gulp.src('./src/less/**/*.less').pipe(rename(function (path) {
        path.extname = ".scss";
    })).pipe(gulp.dest('./src/scss'));
});

gulp.task('sass-convert', ['sass-copy'], function() {

    return gulp.src('./src/scss/**/*.scss')
           .pipe(replace(/\/less\//g, '/scss/'))                              // change less/ dir to scss/ on imports
           .pipe(replace(/\.less/g, '.scss'))                                 // change .less extensions to .scss on imports
           .pipe(replace(/@/g, '$'))                                          // convert variables
           .pipe(replace(/\\\$/g, '@'))                                       // convert variables
           .pipe(replace(/ e\(/g, ' unquote('))                               // convert escape function
           .pipe(replace(/\.([\w\-]*)\s*\((.*)\)\s*\{/g, '@mixin $1($2){'))   // hook -> mixins
           .pipe(replace(/\.svg-fill/g, '@svg-fill'))   // hook -> mixins
           .pipe(replace(/when \(/g, '@if ('))   // hook -> mixins
           .pipe(replace(/@mixin ([\w\-]*)\s*\((.*)\)\s*\{\s*\}/g, '// @mixin $1($2){}'))   // comment empty mixins
           .pipe(replace(/\.(hook[a-zA-Z\-\d]+);/g, '@include $1();'))        // hook calls
           .pipe(replace(/\$(import|media|font-face|page|-ms-viewport|keyframes|-webkit-keyframes)/g, '@$1')) // replace valid '@' statements
           .pipe(replace(/(\$[\w\-]*)\s*:(.*);\n/g, '$1: $2 !default;\n'))    // make variables optional
           .pipe(replace(/\$\{/g, '#{$'))                                     // string literals: from: /~"(.*)"/g, to: '#{"$1"}'
           .pipe(replace(/~('[^']+')/g, 'unquote($1)'))                       // string literals: for real
           .pipe(gulp.dest('./src/scss'));
});

gulp.task('sass', ['sass-convert'], function(done) {

    glob('./src/scss/**/*.scss', function (err, files) {

        if (err) return;

        var re     = /\/\/ @mixin ([\w\-]*)\s*\((.*)\)\s*\{\s*\}/g,
            mixins = [],
            promises = [],
            cache = {};

        files.forEach(function(file) {

            promises.push(new Promise(function(resolve, reject){


                fs.readFile(file, {encoding: 'utf-8'},function read(err, content) {

                    if (err) throw err;

                    var matches, tmp;

                    while(matches = re.exec(content)) {

                        tmp = matches[0].replace(/\/\/\s*/, '');

                        if (!cache[tmp]) {
                            mixins.push(String(tmp));
                            cache[tmp] = true;
                        }
                    }

                    resolve();
                });

            }));
        });

        Promise.all(promises).then(function(){
            fs.writeFile('./src/scss/uikit-mixins.scss', mixins.join('\n'), function (err) {
              if (err) throw err;
              done();
            });
        });
    });
});