query_stream_result.hxx

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/* -*- Mode: C++; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
 *   Copyright 2026. Couchbase, Inc.
 *
 *   Licensed under the Apache License, Version 2.0 (the "License");
 *   you may not use this file except in compliance with the License.
 *   You may obtain a copy of the License at
 *
 *       http://www.apache.org/licenses/LICENSE-2.0
 *
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *   limitations under the License.
 */
 
#pragma once
 
#include <couchbase/codec/encoded_value.hxx>
#include <couchbase/error.hxx>
#include <couchbase/query_meta_data.hxx>
#include <couchbase/query_row.hxx>
 
#include <functional>
#include <future>
#include <memory>
#include <optional>
#include <utility>
 
namespace couchbase
{
#ifndef COUCHBASE_CXX_CLIENT_DOXYGEN
class internal_query_stream_result;
#endif

using query_row_handler = std::function<void(error, std::optional<query_row>)>;

class query_stream_result
{
public:
  query_stream_result() = default;

  explicit query_stream_result(std::shared_ptr<internal_query_stream_result> internal);

  void next(query_row_handler&& handler) const;

  [[nodiscard]] auto next() const -> std::future<std::pair<error, std::optional<query_row>>>;

  [[nodiscard]] auto signature() const -> std::optional<codec::binary>;

  [[nodiscard]] auto meta_data() const -> std::future<std::pair<error, query_meta_data>>;

  void cancel() const;

  struct end_sentinel {
  };

  class iterator
  {
  public:
    auto operator*() const -> std::pair<error, query_row>;
    auto operator++() -> iterator&;

    explicit iterator(std::shared_ptr<internal_query_stream_result> internal);

    friend auto operator==(const iterator& it, end_sentinel /* end */) -> bool
    {
      return it.terminal_;
    }
    friend auto operator==(end_sentinel end, const iterator& it) -> bool
    {
      return it == end;
    }
    friend auto operator!=(const iterator& it, end_sentinel end) -> bool
    {
      return !(it == end);
    }
    friend auto operator!=(end_sentinel end, const iterator& it) -> bool
    {
      return !(it == end);
    }
 
    // Intentionally no std::iterator_traits typedefs (notably no iterator_category). This is a
    // deliberately minimal single-pass iterator for range-based for and `while (it !=
    // result.end())` loops only (see the class doc); it omits post-increment and operator->.
    // Declaring an input_iterator_tag while omitting those would falsely advertise
    // LegacyInputIterator / std::input_iterator conformance and could break generic code that
    // trusts iterator_traits. Range-based for needs none of these typedefs.
 
  private:
    void fetch_item();
 
    std::shared_ptr<internal_query_stream_result> internal_{};
    std::pair<error, query_row> item_{};
    bool terminal_{ false };
    // Set when fetch_item() lands on a terminal error: the error element is delivered once (the
    // iterator is not yet equal to end()), and the next increment advances to true end.
    bool error_pending_{ false };
  };

  [[nodiscard]] auto begin() const -> iterator;

  [[nodiscard]] auto end() const -> end_sentinel;
 
private:
  std::shared_ptr<internal_query_stream_result> internal_{};
};
} // namespace couchbase