bracket-matcher.js

function getLeftMarkIndex (codeStr, idx) {
	var leftCS = codeStr.slice(0, idx);
	var leftMarkIdx;
	var rOpenMark = /[\[\{\(]/;
	var rCloseMark = /[\]\}\)]/;
	var matchMarks = /([\[\{\(]|[\]\}\)])/;
	var matchMap = {']': '[', '}': ']', ')': '('};
	var unpairedCount = 0;

	for (var i = leftCS.length - 1; i >= 0; i--) {
		var c = leftCS[i];
		var match = c.match(matchMarks);
		var leftChar = leftCS[i-1];
		if (!match) {
			continue;
		}
		if (leftChar === '\\') {
			continue;
		}
		if ( match[0].match(rCloseMark) ) {
			unpairedCount++;
			continue;
		} else if (match[0].match(rOpenMark)) {
			unpairedCount--;
			if (unpairedCount < 0) {
				leftMarkIdx = i;
				break;
			}
		}
	}

	return leftMarkIdx;
}

function getCloseMarkIndex (codeStr, leftMarkIndex) {
	var matchMap = {'[': ']', '{': '}'};
	var openMark = codeStr[leftMarkIndex];
	var closeMark = matchMap[openMark];
	var rightCS = codeStr.slice(leftMarkIndex+1);
	var rOpenMark = /[\[|{]/;
	var rCloseMark = /[\]|}]/;
	var rightMarkIdx, lastMatch;
	var unpairedCount = 0;
	for (var i = 0; i < rightCS.length; i++) {
		var c = rightCS[i];
		var leftChar = rightCS[i-1];
		if (leftChar === '\\') {
			continue;
		}
		if ( c === openMark ) {
			unpairedCount++;
			continue;
		} else if ( c === closeMark ) {
			unpairedCount--;

			if ( unpairedCount < 0 ) {
					rightMarkIdx = i;
					lastMatch = c;
					break;
			}
		}
	}

	return rightMarkIdx ? (leftMarkIndex + rightMarkIdx + 1) : null;
}

function getBlockRange (codeStr, cursorPos) {
	var l = getLeftMarkIndex(str, i);
	var r = getCloseMarkIndex(str, l);
	if (l && r) {
		return {
			start: l,
			end: r
		};
	}
	return null;
}