/* -*- Mode: C++; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
 *   Copyright 2024. 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/scan_result_item.hxx>

#include <future>
#include <iterator>
#include <memory>
#include <system_error>
#include <utility>

namespace couchbase
{
#ifndef COUCHBASE_CXX_CLIENT_DOXYGEN
class internal_scan_result;
#endif

/**
 * The signature for the handler of the @ref scan_result#next() operation
 *
 * @since 1.0.0
 * @volatile
 */
using scan_item_handler = std::function<void(std::error_code, std::optional<scan_result_item>)>;

class scan_result
{
  public:
    /**
     * Constructs an empty scan result.
     *
     * @since 1.0.0
     * @internal
     */
    scan_result() = default;

    /**
     * Constructs a scan result from an internal scan result.
     *
     * @param internal the internal scan result
     *
     * @since 1.0.0
     * @internal
     */
    explicit scan_result(std::shared_ptr<internal_scan_result> internal);

    /**
     * Fetches the next scan result item.
     *
     * @param handler callable that implements @ref scan_handler
     *
     * @since 1.0.0
     * @volatile
     */
    void next(scan_item_handler&& handler) const;

    /**
     * Fetches the next scan result item.
     *
     * @return future object that carries the result of the operation
     *
     * @since 1.0.0
     * @volatile
     */
    auto next() const -> std::future<std::pair<std::error_code, std::optional<scan_result_item>>>;

    /**
     * Cancels the scan.
     *
     * @since 1.0.0
     * @volatile
     */
    void cancel();

    /**
     * An iterator that can be used to iterate through all the {@link scan_result_item}s.
     *
     * @since 1.0.0
     * @volatile
     */
    class iterator
    {
      public:
        auto operator==(const iterator& other) const -> bool;
        auto operator!=(const iterator& other) const -> bool;
        auto operator*() -> std::pair<std::error_code, scan_result_item>;
        auto operator++() -> iterator&;

        explicit iterator(std::shared_ptr<internal_scan_result> internal);
        explicit iterator(std::pair<std::error_code, scan_result_item> item);

        using difference_type = std::ptrdiff_t;
        using value_type = scan_result_item;
        using pointer = const scan_result_item*;
        using reference = const scan_result_item&;
        using iterator_category = std::input_iterator_tag;

      private:
        void fetch_item();

        std::shared_ptr<internal_scan_result> internal_{};
        std::pair<std::error_code, scan_result_item> item_{};
    };

    /**
     * Returns an iterator to the beginning.
     *
     * @return iterator to the beginning
     *
     * @since 1.0.0
     * @volatile
     */
    auto begin() -> iterator;

    /**
     * Returns an iterator to the end.
     *
     * @return iterator to the end
     *
     * @since 1.0.0
     * @volatile
     */
    auto end() -> iterator;

  private:
    std::shared_ptr<internal_scan_result> internal_{};
};
} // namespace couchbase
