| var walk = require('css-tree').walk; | 
| var utils = require('./utils'); | 
|   | 
| function processRule(node, item, list) { | 
|     var selectors = node.prelude.children; | 
|     var declarations = node.block.children; | 
|   | 
|     list.prevUntil(item.prev, function(prev) { | 
|         // skip non-ruleset node if safe | 
|         if (prev.type !== 'Rule') { | 
|             return utils.unsafeToSkipNode.call(selectors, prev); | 
|         } | 
|   | 
|         var prevSelectors = prev.prelude.children; | 
|         var prevDeclarations = prev.block.children; | 
|   | 
|         // try to join rulesets with equal pseudo signature | 
|         if (node.pseudoSignature === prev.pseudoSignature) { | 
|             // try to join by selectors | 
|             if (utils.isEqualSelectors(prevSelectors, selectors)) { | 
|                 prevDeclarations.appendList(declarations); | 
|                 list.remove(item); | 
|                 return true; | 
|             } | 
|   | 
|             // try to join by declarations | 
|             if (utils.isEqualDeclarations(declarations, prevDeclarations)) { | 
|                 utils.addSelectors(prevSelectors, selectors); | 
|                 list.remove(item); | 
|                 return true; | 
|             } | 
|         } | 
|   | 
|         // go to prev ruleset if has no selector similarities | 
|         return utils.hasSimilarSelectors(selectors, prevSelectors); | 
|     }); | 
| } | 
|   | 
| // NOTE: direction should be left to right, since rulesets merge to left | 
| // ruleset. When direction right to left unmerged rulesets may prevent lookup | 
| // TODO: remove initial merge | 
| module.exports = function initialMergeRule(ast) { | 
|     walk(ast, { | 
|         visit: 'Rule', | 
|         enter: processRule | 
|     }); | 
| }; |