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import { List, walk } from 'css-tree';
import {
unsafeToSkipNode,
isEqualSelectors,
compareDeclarations,
addSelectors
} from './utils.js';
function calcSelectorLength(list) {
return list.reduce((res, data) => res + data.id.length + 1, 0) - 1;
}
function calcDeclarationsLength(tokens) {
let length = 0;
for (const token of tokens) {
length += token.length;
}
return (
length + // declarations
tokens.length - 1 // delimeters
);
}
function processRule(node, item, list) {
const avoidRulesMerge = this.block !== null ? this.block.avoidRulesMerge : false;
const selectors = node.prelude.children;
const block = node.block;
const disallowDownMarkers = Object.create(null);
let allowMergeUp = true;
let allowMergeDown = true;
list.prevUntil(item.prev, function(prev, prevItem) {
const prevBlock = prev.block;
const prevType = prev.type;
if (prevType !== 'Rule') {
const unsafe = unsafeToSkipNode.call(selectors, prev);
if (!unsafe && prevType === 'Atrule' && prevBlock) {
walk(prevBlock, {
visit: 'Rule',
enter(node) {
node.prelude.children.forEach((data) => {
disallowDownMarkers[data.compareMarker] = true;
});
}
});
}
return unsafe;
}
if (node.pseudoSignature !== prev.pseudoSignature) {
return true;
}
const prevSelectors = prev.prelude.children;
allowMergeDown = !prevSelectors.some((selector) =>
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 && isEqualSelectors(prevSelectors, selectors)) {
prevBlock.children.appendList(block.children);
list.remove(item);
return true;
}
// try to join by properties
const diff = compareDeclarations(block.children, prevBlock.children);
// console.log(diff.eq, diff.ne1, diff.ne2);
if (diff.eq.length) {
if (!diff.ne1.length && !diff.ne2.length) {
// equal blocks
if (allowMergeDown) {
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
const selectorLength = calcSelectorLength(selectors);
const blockLength = calcDeclarationsLength(diff.eq); // declarations length
if (allowMergeUp && selectorLength < blockLength) {
addSelectors(prevSelectors, selectors);
block.children.fromArray(diff.ne1);
}
} else if (!diff.ne1.length && diff.ne2.length) {
// node is subset of prevBlock
const selectorLength = calcSelectorLength(prevSelectors);
const blockLength = calcDeclarationsLength(diff.eq); // declarations length
if (allowMergeDown && selectorLength < blockLength) {
addSelectors(selectors, prevSelectors);
prevBlock.children.fromArray(diff.ne2);
}
} else {
// diff.ne1.length && diff.ne2.length
// extract equal block
const newSelector = {
type: 'SelectorList',
loc: null,
children: addSelectors(prevSelectors.copy(), selectors)
};
const newBlockLength = calcSelectorLength(newSelector.children) + 2; // selectors length + curly braces length
const blockLength = calcDeclarationsLength(diff.eq); // declarations length
// create new ruleset if declarations length greater than
// ruleset description overhead
if (blockLength >= newBlockLength) {
const newItem = list.createItem({
type: 'Rule',
loc: null,
prelude: newSelector,
block: {
type: 'Block',
loc: null,
children: new List().fromArray(diff.eq)
},
pseudoSignature: node.pseudoSignature
});
block.children.fromArray(diff.ne1);
prevBlock.children.fromArray(diff.ne2overrided);
if (allowMergeUp) {
list.insert(newItem, prevItem);
} else {
list.insert(newItem, item);
}
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((prevSelector) =>
selectors.some((selector) =>
selector.compareMarker === prevSelector.compareMarker
)
);
}
prevSelectors.forEach((data) => {
disallowDownMarkers[data.compareMarker] = true;
});
});
}
export default function restructRule(ast) {
walk(ast, {
visit: 'Rule',
reverse: true,
enter: processRule
});
};
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