stylelint/lib/utils/nodeContextLookup.js

'use strict';

/**
 * Create a collection of Maps that serve to contextualize a given node.
 * This is useful to ensure that you only compare nodes that share a certain
 * context.
 *
 * All nodes are initially contextualized by their input source.
 * From there, you can contextualize them however you want.
 *
 * For a usage example, see `selector-no-descending-specificity`.
 */
module.exports = function () {
	const contextMap = new Map();

	return {
		/**
		 * @param {import('postcss').Node} node
		 */
		getContext(node, /** @type {any[]} */ ...subContexts) {
			// TODO TYPES node.source possible undefined
			const nodeSource = /** @type {import('postcss').NodeSource} */ (node.source).input.from;
			const baseContext = creativeGetMap(contextMap, nodeSource);

			return subContexts.reduce((result, context) => {
				return creativeGetMap(result, context);
			}, baseContext);
		},
	};
};

/**
 * TODO TYPES
 * @param {Map<any, any>} someMap
 * @param {any} someThing
 */
function creativeGetMap(someMap, someThing) {
	if (!someMap.has(someThing)) {
		someMap.set(someThing, new Map());
	}

	return someMap.get(someThing);
}