export default function(node, {evaluate, scope}) {
  const {operator, left} = node;
  const right = evaluate(node.right, {scope});
  if (!('MemberExpression' === left.type)) {
    const assign = (value) => {
      switch (operator) {
        case '='   : return scope.set(left.name, value);
        case '+='  : return scope.set(left.name, scope.get(left.name) +  value);
        case '-='  : return scope.set(left.name, scope.get(left.name) -  value);
        case '*='  : return scope.set(left.name, scope.get(left.name) *  value);
        case '/='  : return scope.set(left.name, scope.get(left.name) /  value);
        case '%='  : return scope.set(left.name, scope.get(left.name) %  value);
        case '**=' : return scope.set(left.name, scope.get(left.name) ** value);
        case '<<=' : return scope.set(left.name, scope.get(left.name) <<  value);
        case '>>=' : return scope.set(left.name, scope.get(left.name) >>  value);
        case '>>>=': return scope.set(left.name, scope.get(left.name) >>> value);
        case '|='  : return scope.set(left.name, scope.get(left.name) |   value);
        case '^='  : return scope.set(left.name, scope.get(left.name) ^   value);
        case '&='  : return scope.set(left.name, scope.get(left.name) &   value);
        case '||=' : return scope.set(left.name, scope.get(left.name) || value);
        case '&&=' : return scope.set(left.name, scope.get(left.name) && value);
        case '??=' : {
          const l = scope.get(left.name);
          return scope.set(left.name, (l === null || l === undefined) ? value : l);
        }
        /* v8 ignore next 2 */
        default:
          throw new Error(`operator not implemented: ${node.operator}`);
      }
    };
    if (right.async) {
      return {
        async: true,
        value: Promise.resolve(right.value).then(assign),
      };
    }
    return {value: assign(right.value)};
  }
  const {
    computed,
    object,
    property,
  } = left;
  const memberAssign = (O, P, value) => {
    switch (operator) {
      case '='   : return O[P] =   value;
      case '+='  : return O[P] +=  value;
      case '-='  : return O[P] -=  value;
      case '*='  : return O[P] *=  value;
      case '/='  : return O[P] /=  value;
      case '%='  : return O[P] %=  value;
      case '**=' : return O[P] **= value;
      case '<<=' : return O[P] <<=  value;
      case '>>=' : return O[P] >>=  value;
      case '>>>=': return O[P] >>>= value;
      case '|='  : return O[P] |=   value;
      case '^='  : return O[P] ^=   value;
      case '&='  : return O[P] &=   value;
      case '||=' : return O[P] ||= value;
      case '&&=' : return O[P] &&= value;
      case '??=' : return O[P] = (O[P] === null || O[P] === undefined) ? value : O[P];
      /* v8 ignore next 2 */
      default:
        throw new Error(`operator not implemented: ${node.operator}`);
    }
  };
  const makeAsync = (O, P, value) => (
    Promise.all([O, P, value]).then(([O, P, value]) => memberAssign(O, P, value))
  );
  const O = evaluate(object, {scope});
  const P = computed
    ? evaluate(property, {scope})
    // Otherwise, identifier
    : {value: property.name};
  if (right.async || O.async || P.async) {
    return {
      async: true,
      value: makeAsync(O.value, P.value, right.value),
    };
  }
  return {value: memberAssign(O.value, P.value, right.value)};
}