Custom Grunt script for couting CSS imports count, and seperating files before hitting IE limit of 31 imports

gistfile1.js

/*

    Processing CSS @imports file, and counting how much @imports it includes.
    
    If import count reaches the limit of 31 files (in IE8-9) and more, script will create additional CSS files:
    
    input.css:
        @import 1;
        ...
        @import 36;
        
    output.css:
        @import 1;
        ...
        @import 30;
        @import output2.css;
        
    output2.css:
        @import 31;
        ...
        @import 36;
        
    Script is based on PostCSS https://github.com/ai/postcss and cuts down other CSS rules during the processing.
    
    Maybe this script will be moved to seperate Grunt plugin in future.

*/

var path = require('path'),
    postcss = require('postcss');

var generateImportFiles = function() {
    var cssBundlesDir = grunt.config.get('cssBundlesDir'),
        outputDir = grunt.config.get('outputDir');

    grunt.file.recurse(cssBundlesDir, function (abspath, rootdir, subdir, filename) {
        var subDirectory = subdir ? subdir + '/' : '';

        var processFile = postcss(function (css) {
            var importsCount = 0,
                importsLimit = 31,
                filesCount = 1,
                generatedCSSFiles = {
                    file1: []
                };

            css.eachAtRule(function (atRule) {
                if (atRule.name = 'import') {
                    importsCount++
                }
            });

            // Counting how many additional files we need
            var addFilesCount = Math.floor(importsCount / importsLimit),
                firstFileImportLimit = importsLimit - addFilesCount,
                iteration = 0;

            // Creating object with seperated CSS files
            css.eachAtRule(function (atRule) {
                if (atRule.name = 'import') {
                    if (filesCount === 1 ? iteration < firstFileImportLimit : iteration < importsLimit) {
                        generatedCSSFiles['file' + filesCount].push(atRule);
                    } else {
                        iteration = 0;
                        filesCount++;
                        generatedCSSFiles['file' + filesCount] = [];
                        generatedCSSFiles['file' + filesCount].push(atRule);
                    }
                }

                iteration++;
            });

            // Creating and writing processed CSS
            for (var i = 0; i < filesCount; i++) {
                var newCSS = postcss.root(),
                    fileNum = i + 1,
                    resultWriteFileName= i === 0 ? filename : filename.split('.css')[0] + fileNum + '.css';

                generatedCSSFiles['file'+fileNum].map(function (item) {
                    newCSS.append(item);
                });

                // First file
                if (i === 0) {

                    // Adding links to created files with @imports
                    for (var ii = 0; ii < addFilesCount; ii++) {
                        var nextFileNum = ii + 2;

                        newCSS.append(postcss.atRule({
                            before: '\n',
                            semicolon: true,
                            name: 'import',
                            params: '"'+filename.split('.css')[0] + nextFileNum + '.css'+'"'
                        }));
                    }
                }

                grunt.file.write(path.normalize(outputDir + '/'+ subDirectory + '/' + resultWriteFileName), newCSS.toResult());
            }

        });

        if (path.extname(filename) === '.css') {
            processFile.process(grunt.file.read(abspath));
        }
    });
};

Useful snippet for getting Grunt config from this kind of functions https://gist.github.com/operatino/d8ec45b39c27ade30757