//
// 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_ERROR_HPP
#define SERVERTECHCHAT_SERVER_INCLUDE_ERROR_HPP

#include <boost/assert/source_location.hpp>
#include <boost/system/error_category.hpp>
#include <boost/system/error_code.hpp>
#include <boost/system/result.hpp>

#include <string>
#include <string_view>
#include <utility>

// Error management infrastructure. Uses Boost.System error codes and categories.
// This is consistent with Asio, Beast and Redis.

namespace chat {

// Type alias to reduce verbosity.
using error_code = boost::system::error_code;

// Type alias to reduce verbosity.
template <class T>
using result = boost::system::result<T>;

// An error code with a diagnostics message
struct error_with_message
{
 error_code ec;
 std::string msg;
};

// Required by the Boost.System infrastructure.
// Throws an exception from an error_with_message.
[[noreturn]] void throw_exception_from_error(const error_with_message& e, const boost::source_location&);

// Like result, but the error state includes an error message
template <class T>
using result_with_message = boost::system::result<T, error_with_message>;

// Error code enum for errors originated within our application
enum class errc
{
 redis_parse_error = 1, // Data retrieved from Redis didn't match the format we expected
 redis_command_failed, // A Redis command failed execution (e.g. we provided the wrong number of args)
 websocket_parse_error, // Data received from the client didn't match the format we expected
 username_exists, // couldn't create user, duplicate username
 email_exists, // couldn't create user, duplicate username
 not_found, // couldn't retrieve a certain resource, it doesn't exist
 invalid_password_hash, // we found a password hash that was malformed
 already_exists, // an entity can't be created because it already exists
 requires_auth, // the requested resource requires authentication, but credentials haven't been provided
 // or are invalid
 invalid_base64, // attempt to decode an invalid base64 string
 uncaught_exception, // an API handler threw an unexpected exception
 invalid_content_type, // an endpoint received an unsupported Content-Type
};

// The error category for errc
const boost::system::error_category& get_chat_category() noexcept;

// Allows constructing error_code from errc
inline error_code make_error_code(errc v) noexcept
{
 return error_code(static_cast<int>(v), get_chat_category());
}

// Logs ec to stderr
void log_error(error_code ec, std::string_view what, std::string_view diagnostics = "");
inline void log_error(const error_with_message& err, std::string_view what)
{
 log_error(err.ec, what, err.msg);
}

} // namespace chat

// Allows constructing error_code from errc
namespace boost {
namespace system {

template <>
struct is_error_code_enum<chat::errc>
{
 static constexpr bool value = true;
};
} // namespace system
} // namespace boost

// Returns an error_code with source-code location information on it
#define CHAT_RETURN_ERROR(e) \
 { \
 static constexpr auto loc = BOOST_CURRENT_LOCATION; \
 return ::chat::error_code(::chat::error_code(e), &loc); \
 }

// Returns an error_with_message with source-code location information on the error_code
#define CHAT_RETURN_ERROR_WITH_MESSAGE(e, msg) \
 { \
 static constexpr auto loc = BOOST_CURRENT_LOCATION; \
 return ::chat::error_with_message{::chat::error_code(::chat::error_code(e), &loc), msg}; \
 }

#endif