--- /dev/null
+"use strict";
+
+const atRuleParamIndex = require("../../utils/atRuleParamIndex");
+const findMediaOperator = require("../findMediaOperator");
+const report = require("../../utils/report");
+const ruleMessages = require("../../utils/ruleMessages");
+const validateOptions = require("../../utils/validateOptions");
+const whitespaceChecker = require("../../utils/whitespaceChecker");
+
+const ruleName = "media-feature-range-operator-space-before";
+
+const messages = ruleMessages(ruleName, {
+ expectedBefore: () => "Expected single space before range operator",
+ rejectedBefore: () => "Unexpected whitespace before range operator"
+});
+
+const rule = function(expectation) {
+ const checker = whitespaceChecker("space", expectation, messages);
+ return (root, result) => {
+ const validOptions = validateOptions(result, ruleName, {
+ actual: expectation,
+ possible: ["always", "never"]
+ });
+ if (!validOptions) {
+ return;
+ }
+
+ root.walkAtRules(/^media$/i, atRule => {
+ findMediaOperator(atRule, checkBeforeOperator);
+ });
+
+ function checkBeforeOperator(match, params, node) {
+ // The extra `+ 1` is because the match itself contains
+ // the character before the operator
+ checker.before({
+ source: params,
+ index: match.index + 1,
+ err: m => {
+ report({
+ message: m,
+ node,
+ index: match.index + atRuleParamIndex(node),
+ result,
+ ruleName
+ });
+ }
+ });
+ }
+ };
+};
+
+rule.ruleName = ruleName;
+rule.messages = messages;
+module.exports = rule;