feat(plugin): color bracket pairs and mark unmatched brackets red

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/plugin/src/brackets.js b/plugin/src/brackets.js
new file mode 100644
index 0000000..ad79ea5
--- /dev/null
+++ b/plugin/src/brackets.js
@@ -0,0 +1,25 @@
+'use strict';
+
+const { codeOnly } = require('./lexical');
+const pairs = { ')': '(', ']': '[' };
+
+function unmatchedBrackets(text) {
+	const code = codeOnly(text);
+	const stack = [];
+	const unmatched = [];
+	for (let offset = 0; offset < code.length; offset++) {
+		const char = code[offset];
+		if (char === '(' || char === '[') {
+			stack.push({ char, offset });
+		} else if (pairs[char]) {
+			const opening = stack.pop();
+			if (!opening || opening.char !== pairs[char]) {
+				if (opening) unmatched.push(opening.offset);
+				unmatched.push(offset);
+			}
+		}
+	}
+	return unmatched.concat(stack.map(opening => opening.offset)).sort((a, b) => a - b);
+}
+
+module.exports = { unmatchedBrackets };