grunt-cache-bust-lazy-loading/tasks/lib/processCssFile.js

Bust static assets from the cache using content hashing. It also supports lazy loading for divs and images when using class lazy.

'use strict';

var css = require('css');
var flatten = require('flatten');

module.exports = function(opts) {
    var utils = require('./utils')(opts);

    return function(data) {
        var paths = [];
        var cssObj = css.parse(data);

        var filterDeclarations = function(declaration) {
            var hasBackgroundUrl = (/background/).test(declaration.property) && (/url/).test(declaration.value);
            var hasContentUrl = (/content/).test(declaration.property) && (/url/).test(declaration.value);
            var hasSrcUrl = (/src/).test(declaration.property) && (/url/).test(declaration.value);
            var dataImage = (/data\:image\//).test(declaration.value);

            // Check if it has a background property, and if so, check that it contains a URL
            return (hasBackgroundUrl || hasContentUrl || hasSrcUrl) && !dataImage;
        };

        var extractDeclaration = function(declaration) {
            return declaration.value.split(',')
                .map(function(val) {
                    var matches = val.match(/url\(["']?(.*?)['"]?\)/);

                    if (matches) {
                        return matches[1];
                    }
                });
        };

        // Loop through each stylesheet rules
        cssObj.stylesheet.rules.forEach(function(rule) {
            var mediaQueryDeclarations = rule.type !== 'media' ? [] : rule.rules.reduce(function(acc, rule) {
                return acc.concat(rule.declarations);
            }, []);

            var declarations = (rule.declarations || []).concat(mediaQueryDeclarations);

            // Loop through all declarations
            if (declarations && declarations.length > 0) {
                var foundDeclarations = declarations
                    .filter(filterDeclarations)
                    .map(extractDeclaration);

                paths = paths.concat(foundDeclarations);
            }
        });

        return flatten(paths);
    };
};