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import { walk } from 'css-tree';
import { unsafeToSkipNode, isEqualDeclarations} from './utils.js';
/*
At this step all rules has single simple selector. We try to join by equal
declaration blocks to first rule, e.g.
.a { color: red }
b { ... }
.b { color: red }
->
.a, .b { color: red }
b { ... }
*/
function processRule(node, item, list) {
const selectors = node.prelude.children;
const declarations = node.block.children;
const nodeCompareMarker = selectors.first.compareMarker;
const skippedCompareMarkers = {};
list.nextUntil(item.next, function(next, nextItem) {
// skip non-ruleset node if safe
if (next.type !== 'Rule') {
return unsafeToSkipNode.call(selectors, next);
}
if (node.pseudoSignature !== next.pseudoSignature) {
return true;
}
const nextFirstSelector = next.prelude.children.head;
const nextDeclarations = next.block.children;
const nextCompareMarker = nextFirstSelector.data.compareMarker;
// if next ruleset has same marked as one of skipped then stop joining
if (nextCompareMarker in skippedCompareMarkers) {
return true;
}
// try to join by selectors
if (selectors.head === selectors.tail) {
if (selectors.first.id === nextFirstSelector.data.id) {
declarations.appendList(nextDeclarations);
list.remove(nextItem);
return;
}
}
// try to join by properties
if (isEqualDeclarations(declarations, nextDeclarations)) {
const nextStr = nextFirstSelector.data.id;
selectors.some((data, item) => {
const curStr = data.id;
if (nextStr < curStr) {
selectors.insert(nextFirstSelector, item);
return true;
}
if (!item.next) {
selectors.insert(nextFirstSelector);
return true;
}
});
list.remove(nextItem);
return;
}
// go to next ruleset if current one can be skipped (has no equal specificity nor element selector)
if (nextCompareMarker === nodeCompareMarker) {
return true;
}
skippedCompareMarkers[nextCompareMarker] = true;
});
}
export default function mergeRule(ast) {
walk(ast, {
visit: 'Rule',
enter: processRule
});
};
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