export default function(node, {evaluate, scope}) {
  const binary = (left, right) => {
    switch (node.operator) {
      case '+'  : return left +   right;
      case '-'  : return left -   right;
      case '/'  : return left /   right;
      case '%'  : return left %   right;
      case '*'  : return left *   right;
      case '>'  : return left >   right;
      case '<'  : return left <   right;
      case 'in' : return left in  right;
      case '>=' : return left >=  right;
      case '<=' : return left <=  right;
      case '**' : return left **  right;
      case '===': return left === right;
      case '!==': return left !== right;
      case '^'  : return left ^   right;
      case '&'  : return left &   right;
      case '|'  : return left |   right;
      case '>>' : return left >>  right;
      case '<<' : return left <<  right;
      case '>>>': return left >>> right;
      case '==' : return left ==  right;
      case '!=' : return left !=  right;
      case '||' : return left || right;
      case '&&' : return left && right;
      case '??' : return (left === null || left === undefined) ? right : left;
      case 'instanceof': return left instanceof right;
      /* v8 ignore next 2 */
      default:
        throw new Error(`operator not implemented: ${node.operator}`);
    }
  };
  const left = evaluate(node.left, {scope});
  const right = evaluate(node.right, {scope});
  if (left.async || right.async) {
    return {
      async: true,
      value: Promise
        .all([left.value, right.value])
        .then(([left, right]) => binary(left, right)),
    };
  }
  return {
    async: false,
    value: binary(left.value, right.value),
  };
}