44 lines
1.1 KiB
JavaScript
44 lines
1.1 KiB
JavaScript
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'use strict';
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/**
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* Create a collection of Maps that serve to contextualize a given node.
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* This is useful to ensure that you only compare nodes that share a certain
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* context.
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*
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* All nodes are initially contextualized by their input source.
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* From there, you can contextualize them however you want.
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*
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* For a usage example, see `selector-no-descending-specificity`.
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*/
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module.exports = function nodeContextLookup() {
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const contextMap = new Map();
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return {
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/**
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* @param {import('postcss').Node} node
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* @param {any[]} subContexts
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* @returns {Map<any, any>}
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*/
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getContext(node, ...subContexts) {
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if (!node.source) throw new Error('The node source must be present');
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const nodeSource = node.source.input.from;
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const baseContext = creativeGetMap(contextMap, nodeSource);
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return subContexts.reduce((result, context) => creativeGetMap(result, context), baseContext);
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},
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};
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};
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/**
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* @param {Map<any, any>} someMap
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* @param {any} someThing
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*/
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function creativeGetMap(someMap, someThing) {
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if (!someMap.has(someThing)) {
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someMap.set(someThing, new Map());
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}
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return someMap.get(someThing);
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}
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