export function buildTraversal(path, value) {
  const traversal = {
    type: 'traversal',
    steps: path.map((key) => {
      return {
        type: 'key',
        key: key,
      };
    }),
  };
  if ('undefined' !== typeof value) {
    traversal.value = buildValue(value);
  }
  return traversal;
}

export function buildInvoke (path, args = []) {
  const traversal = buildTraversal(path);
  traversal.steps.push({
    type: 'invoke',
    args: args.map((arg) => {
      return buildValue(arg);
    }),
  });
  return traversal;
}

export function buildValue(value) {
  if (
    'object' === typeof value
    && (
      'traversal' === value.type
      || 'condition' === value.type
    )
  ) {
    return value;
  }
  return {
    type: 'literal',
    value,
  };
}

export function buildCondition(operator, operands) {
  return {
    type: 'condition',
    operator,
    operands: operands.map((operand) => {
      return buildValue(operand);
    }),
  };
}