/**
 * This will create a recursive object from list of tokens - tokens between parenthesis are grouped in a single array
 */
function parens(tokens) {
    if (tokens.length === 0) {
        throw new Error("Empty expression.");
    }

    while (true) {
        const leftIdx = tokens.findIndex(token => token === '(');

        if (leftIdx === -1) {
            return tokens;
        }

        let rightIdx;
        let parensLevel = 0

        for (rightIdx = leftIdx; rightIdx < tokens.length; rightIdx++) {
            if (tokens[rightIdx] === ')') {
                parensLevel--;

                if (parensLevel === 0) {
                    break;
                }
            } else if (tokens[rightIdx] === '(') {
                parensLevel++;
            }
        }

        if (rightIdx >= tokens.length) {
            throw new Error("Did not find matching right parenthesis.");
        }

        tokens = [
            ...tokens.slice(0, leftIdx),
            parens(tokens.slice(leftIdx + 1, rightIdx)),
            ...tokens.slice(rightIdx + 1)
        ];
    }
}

module.exports = parens;