merge removeUnusedStyles plugin with minifyStyles

plugins/minifyStyles.js

@@ -1,45 +1,147 @@
 'use strict';
 
-exports.type = 'perItem';
+exports.type = 'full';
 
 exports.active = true;
 
-exports.params = {
-    svgo: {}
-};
+exports.description = 'minifies styles and removes unused styles based on usage data';
 
-exports.description = 'minifies existing styles in svg';
+exports.params = {
+    // ... CSSO options goes here
+    svgo: {},
+
+    // additional 
+    usage: {
+        ids: true,
+        classes: true,
+        tags: true
+    }
+};
 
 var csso = require('csso');
 
 /**
- * Minifies styles (<style> element + style attribute) using svgo
- *
- * @param {Object} item current iteration item
- * @return {Boolean} if false, item will be filtered out
+ * Minifies styles (<style> element + style attribute) using CSSO
  *
  * @author strarsis <strarsis@gmail.com>
  */
-exports.fn = function(item, svgoOptions) {
+exports.fn = function(ast, options) {
+    options = options || {};
 
-    if(item.elem) {
-        if(item.isElem('style') && !item.isEmpty()) {
-            var styleCss = item.content[0].text || item.content[0].cdata || [],
-                DATA = styleCss.indexOf('>') >= 0 || styleCss.indexOf('<') >= 0 ? 'cdata' : 'text';
-            if(styleCss.length > 0) {
-                var styleCssMinified = csso.minify(styleCss, svgoOptions);
-                item.content[0][DATA] = styleCssMinified.css;
-            }
-      }
+    var minifyOptionsForStylesheet = cloneObject(options);
+    var minifyOptionsForAttribute = cloneObject(options);
+    var elems = findStyleElems(ast);
 
-      if(item.hasAttr('style')) {
-          var itemCss = item.attr('style').value;
-          if(itemCss.length > 0) {
-              var itemCssMinified = csso.minifyBlock(itemCss, svgoOptions);
-              item.attr('style').value = itemCssMinified.css;
-          }
-      }
+    minifyOptionsForStylesheet.usage = collectUsageData(ast, options);
+    minifyOptionsForAttribute.usage = null;
+
+    elems.forEach(function(elem) {
+        if (elem.isElem('style')) {
+            // <style> element
+            var styleCss = elem.content[0].text || elem.content[0].cdata || [];
+            var DATA = styleCss.indexOf('>') >= 0 || styleCss.indexOf('<') >= 0 ? 'cdata' : 'text';
+
+            elem.content[0][DATA] = csso.minify(styleCss, minifyOptionsForStylesheet).css;
+        } else {
+            // style attribute
+            var elemStyle = elem.attr('style').value;
+
+            elem.attr('style').value = csso.minifyBlock(elemStyle, minifyOptionsForAttribute).css;
+        }
+    });
+
+    return ast;
+};
+
+function cloneObject(obj) {
+    var result = {};
+
+    for (var key in obj) {
+        result[key] = obj[key];
     }
 
-    return item;
-};
+    return result;
+}
+
+function findStyleElems(ast) {
+
+    function walk(items, styles) {
+        for (var i = 0; i < items.content.length; i++) {
+            var item = items.content[i];
+
+            // go deeper
+            if (item.content) {
+                walk(item, styles);
+            }
+
+            if (item.isElem('style') && !item.isEmpty()) {
+                styles.push(item);
+            } else if (item.isElem() && item.hasAttr('style')) {
+                styles.push(item);
+            }
+        }
+
+        return styles;
+    }
+
+    return walk(ast, []);
+}
+
+function shouldFilter(options, name) {
+    if ('usage' in options === false) {
+        return true;
+    }
+
+    if (options.usage && name in options.usage === false) {
+        return true;
+    }
+
+    return Boolean(options.usage && options.usage[name]);
+}
+
+function collectUsageData(ast, options) {
+
+    function walk(items, usageData) {
+        for (var i = 0; i < items.content.length; i++) {
+            var item = items.content[i];
+
+            // go deeper
+            if (item.content) {
+                walk(item, usageData);
+            }
+
+            if (item.isElem()) {
+                usageData.tags[item.elem] = true;
+
+                if (item.hasAttr('id')) {
+                    usageData.ids[item.attr('id').value] = true;
+                }
+
+                if (item.hasAttr('class')) {
+                    item.attr('class').value.replace(/^\s+|\s+$/g, '').split(/\s+/).forEach(function(className) {
+                        usageData.classes[className] = true;
+                    });
+                }
+            }
+        }
+
+        return usageData;
+    }
+
+    var hasData = false;
+    var usageData = walk(ast, {
+        ids: Object.create(null),
+        classes: Object.create(null),
+        tags: Object.create(null)
+    });
+
+    for (var key in usageData) {
+        usageData[key] = shouldFilter(options, key) && Object.keys(usageData[key]);
+
+        if (usageData[key]) {
+            hasData = true;
+        }
+    }
+
+    return hasData ? usageData : null;
+}