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const isPlainObject = require('lodash.isplainobject')
const parser = require('postcss-selector-parser')
const parseSelector = parser()
module.exports = {
isUsableColor(color, values) {
return isPlainObject(values) && color !== 'gray' && values[600]
},
/**
* @param {string} selector
*/
commonTrailingPseudos(selector) {
let ast = parseSelector.astSync(selector)
/** @type {import('postcss-selector-parser').Pseudo[][]} */
let matrix = []
// Put the pseudo elements in reverse order in a sparse, column-major 2D array
for (let [i, sel] of ast.nodes.entries()) {
for (const [j, child] of [...sel.nodes].reverse().entries()) {
// We only care about pseudo elements
if (child.type !== 'pseudo' || !child.value.startsWith('::')) {
break
}
matrix[j] = matrix[j] || []
matrix[j][i] = child
}
}
let trailingPseudos = parser.selector()
// At this point the pseudo elements are in a column-major 2D array
// This means each row contains one "column" of pseudo elements from each selector
// We can compare all the pseudo elements in a row to see if they are the same
for (const pseudos of matrix) {
// It's a sparse 2D array so there are going to be holes in the rows
// We skip those
if (!pseudos) {
continue
}
let values = new Set([...pseudos.map((p) => p.value)])
// The pseudo elements are not the same
if (values.size > 1) {
break
}
pseudos.forEach((pseudo) => pseudo.remove())
trailingPseudos.prepend(pseudos[0])
}
if (trailingPseudos.nodes.length) {
return [trailingPseudos.toString(), ast.toString()]
}
return [null, selector]
},
}
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