karmen/node_modules/csso/lib/compressor/restructure/8-restructRuleset.js

var List = require('../../utils/list.js');
var utils = require('./utils.js');
var walkRulesRight = require('../../utils/walk.js').rulesRight;

function calcSelectorLength(list) {
    var length = 0;

    list.each(function(data) {
        length += data.id.length + 1;
    });

    return length - 1;
}

function calcDeclarationsLength(tokens) {
    var length = 0;

    for (var i = 0; i < tokens.length; i++) {
        length += tokens[i].length;
    }

    return (
        length +          // declarations
        tokens.length - 1 // delimeters
    );
}

function processRuleset(node, item, list) {
    var avoidRulesMerge = this.stylesheet.avoidRulesMerge;
    var selectors = node.selector.selectors;
    var block = node.block;
    var disallowDownMarkers = Object.create(null);
    var allowMergeUp = true;
    var allowMergeDown = true;

    list.prevUntil(item.prev, function(prev, prevItem) {
        // skip non-ruleset node if safe
        if (prev.type !== 'Ruleset') {
            return utils.unsafeToSkipNode.call(selectors, prev);
        }

        var prevSelectors = prev.selector.selectors;
        var prevBlock = prev.block;

        if (node.pseudoSignature !== prev.pseudoSignature) {
            return true;
        }

        allowMergeDown = !prevSelectors.some(function(selector) {
            return selector.compareMarker in disallowDownMarkers;
        });

        // try prev ruleset if simpleselectors has no equal specifity and element selector
        if (!allowMergeDown && !allowMergeUp) {
            return true;
        }

        // try to join by selectors
        if (allowMergeUp && utils.isEqualLists(prevSelectors, selectors)) {
            prevBlock.declarations.appendList(block.declarations);
            list.remove(item);
            return true;
        }

        // try to join by properties
        var diff = utils.compareDeclarations(block.declarations, prevBlock.declarations);

        // console.log(diff.eq, diff.ne1, diff.ne2);

        if (diff.eq.length) {
            if (!diff.ne1.length && !diff.ne2.length) {
                // equal blocks
                if (allowMergeDown) {
                    utils.addSelectors(selectors, prevSelectors);
                    list.remove(prevItem);
                }

                return true;
            } else if (!avoidRulesMerge) { /* probably we don't need to prevent those merges for @keyframes
                                              TODO: need to be checked */

                if (diff.ne1.length && !diff.ne2.length) {
                    // prevBlock is subset block
                    var selectorLength = calcSelectorLength(selectors);
                    var blockLength = calcDeclarationsLength(diff.eq); // declarations length

                    if (allowMergeUp && selectorLength < blockLength) {
                        utils.addSelectors(prevSelectors, selectors);
                        block.declarations = new List(diff.ne1);
                    }
                } else if (!diff.ne1.length && diff.ne2.length) {
                    // node is subset of prevBlock
                    var selectorLength = calcSelectorLength(prevSelectors);
                    var blockLength = calcDeclarationsLength(diff.eq); // declarations length

                    if (allowMergeDown && selectorLength < blockLength) {
                        utils.addSelectors(selectors, prevSelectors);
                        prevBlock.declarations = new List(diff.ne2);
                    }
                } else {
                    // diff.ne1.length && diff.ne2.length
                    // extract equal block
                    var newSelector = {
                        type: 'Selector',
                        info: {},
                        selectors: utils.addSelectors(prevSelectors.copy(), selectors)
                    };
                    var newBlockLength = calcSelectorLength(newSelector.selectors) + 2; // selectors length + curly braces length
                    var blockLength = calcDeclarationsLength(diff.eq); // declarations length

                    // create new ruleset if declarations length greater than
                    // ruleset description overhead
                    if (allowMergeDown && blockLength >= newBlockLength) {
                        var newRuleset = {
                            type: 'Ruleset',
                            info: {},
                            pseudoSignature: node.pseudoSignature,
                            selector: newSelector,
                            block: {
                                type: 'Block',
                                info: {},
                                declarations: new List(diff.eq)
                            }
                        };

                        block.declarations = new List(diff.ne1);
                        prevBlock.declarations = new List(diff.ne2.concat(diff.ne2overrided));
                        list.insert(list.createItem(newRuleset), prevItem);
                        return true;
                    }
                }
            }
        }

        if (allowMergeUp) {
            // TODO: disallow up merge only if any property interception only (i.e. diff.ne2overrided.length > 0);
            // await property families to find property interception correctly
            allowMergeUp = !prevSelectors.some(function(prevSelector) {
                return selectors.some(function(selector) {
                    return selector.compareMarker === prevSelector.compareMarker;
                });
            });
        }

        prevSelectors.each(function(data) {
            disallowDownMarkers[data.compareMarker] = true;
        });
    });
};

module.exports = function restructRuleset(ast) {
    walkRulesRight(ast, function(node, item, list) {
        if (node.type === 'Ruleset') {
            processRuleset.call(this, node, item, list);
        }
    });
};