index.js

'use strict';

const isLogicalCombination = require('../../utils/isLogicalCombination');
const isStandardSyntaxRule = require('../../utils/isStandardSyntaxRule');
const parseSelector = require('../../utils/parseSelector');
const report = require('../../utils/report');
const resolvedNestedSelector = require('postcss-resolve-nested-selector');
const ruleMessages = require('../../utils/ruleMessages');
const validateOptions = require('../../utils/validateOptions');

const ruleName = 'selector-max-id';

const messages = ruleMessages(ruleName, {
	expected: (selector, max) =>
		`Expected "${selector}" to have no more than ${max} ID ${max === 1 ? 'selector' : 'selectors'}`,
});

function rule(max) {
	return (root, result) => {
		const validOptions = validateOptions(result, ruleName, {
			actual: max,
			possible: [
				function(max) {
					return typeof max === 'number' && max >= 0;
				},
			],
		});

		if (!validOptions) {
			return;
		}

		function checkSelector(selectorNode, ruleNode) {
			const count = selectorNode.reduce((total, childNode) => {
				// Only traverse inside actual selectors and logical combinations
				if (childNode.type === 'selector' || isLogicalCombination(childNode)) {
					checkSelector(childNode, ruleNode);
				}

				return (total += childNode.type === 'id' ? 1 : 0);
			}, 0);

			if (selectorNode.type !== 'root' && selectorNode.type !== 'pseudo' && count > max) {
				report({
					ruleName,
					result,
					node: ruleNode,
					message: messages.expected(selectorNode, max),
					word: selectorNode,
				});
			}
		}

		root.walkRules((ruleNode) => {
			if (!isStandardSyntaxRule(ruleNode)) {
				return;
			}

			ruleNode.selectors.forEach((selector) => {
				resolvedNestedSelector(selector, ruleNode).forEach((resolvedSelector) => {
					parseSelector(resolvedSelector, result, ruleNode, (container) =>
						checkSelector(container, ruleNode),
					);
				});
			});
		});
	};
}

rule.ruleName = ruleName;
rule.messages = messages;
module.exports = rule;