//
// Copyright (c) 2023 Ruben Perez Hidalgo (rubenperez038 at gmail dot com)
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//

#ifndef SERVERTECHCHAT_SERVER_INCLUDE_SERVICES_REDIS_CLIENT_HPP
#define SERVERTECHCHAT_SERVER_INCLUDE_SERVICES_REDIS_CLIENT_HPP

#include <boost/asio/any_io_executor.hpp>
#include <boost/asio/spawn.hpp>
#include <boost/core/span.hpp>

#include <chrono>
#include <memory>
#include <optional>
#include <string>
#include <string_view>
#include <vector>

#include "business_types.hpp"
#include "error.hpp"

// A high-level, specialized Redis client. It implements the operations
// required by our server, abstracting away the actual Redis commands.

namespace chat {

// Using an interface to reduce build times and improve testability
class redis_client
{
public:
 virtual ~redis_client() {}

 // Starts the Redis runner task, in detached mode. This must be called once
 // to allow other operations to make progress and keep the reconnection loop
 // running
 virtual void start_run() = 0;

 // Cancels the Redis runner task. To be called at shutdown
 virtual void cancel() = 0;

 // The maximum number of messages for a room that get retrieved in a single go
 static constexpr std::size_t message_batch_size = 100;

 // Used as input parameter to get_room_history
 struct room_histoy_request
 {
 // The ID of the room we want to lookup
 std::string_view room_id;

 // The last message we have fo this room; leave empty for "from the latest"
 std::optional<std::string_view> last_message_id;
 };

 // Retrieves a batch of room history for several rooms
 virtual result_with_message<std::vector<message_batch>> get_room_history(
 boost::span<const room_histoy_request> reqs,
 boost::asio::yield_context yield
 ) = 0;

 // Inserts a batch of messages into a certain room's history.
 // Returns the IDs of the inserted messages
 virtual result_with_message<std::vector<std::string>> store_messages(
 std::string_view room_id,
 boost::span<const message> messages,
 boost::asio::yield_context yield
 ) = 0;

 // Sets a certain key to a value, with the given time to live.
 // If the key already exists, the operation fails with already_exists
 virtual error_with_message set_nonexisting_key(
 std::string_view key,
 std::string_view value,
 std::chrono::seconds ttl,
 boost::asio::yield_context yield
 ) = 0;

 // Gets the specified key, as an int64_t.
 // Returns not_found if the key does not exist
 virtual result_with_message<std::int64_t> get_int_key(
 std::string_view key,
 boost::asio::yield_context yield
 ) = 0;
};

// Creates a concrete implementation of redis_client
std::unique_ptr<redis_client> create_redis_client(boost::asio::any_io_executor ex);

} // namespace chat

#endif