//
// custom_tracking.hpp
// ~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2024 Christopher M. Kohlhoff (chris at kohlhoff 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 CUSTOM_TRACKING_HPP
#define CUSTOM_TRACKING_HPP

#include <cinttypes>
#include <cstdint>
#include <cstdio>

# define BOOST_ASIO_INHERIT_TRACKED_HANDLER \
  : public ::custom_tracking::tracked_handler

# define BOOST_ASIO_ALSO_INHERIT_TRACKED_HANDLER \
  , public ::custom_tracking::tracked_handler

# define BOOST_ASIO_HANDLER_TRACKING_INIT \
  ::custom_tracking::init()

# define BOOST_ASIO_HANDLER_LOCATION(args) \
  ::custom_tracking::location args

# define BOOST_ASIO_HANDLER_CREATION(args) \
  ::custom_tracking::creation args

# define BOOST_ASIO_HANDLER_COMPLETION(args) \
  ::custom_tracking::completion tracked_completion args

# define BOOST_ASIO_HANDLER_INVOCATION_BEGIN(args) \
  tracked_completion.invocation_begin args

# define BOOST_ASIO_HANDLER_INVOCATION_END \
  tracked_completion.invocation_end()

# define BOOST_ASIO_HANDLER_OPERATION(args) \
  ::custom_tracking::operation args

# define BOOST_ASIO_HANDLER_REACTOR_REGISTRATION(args) \
  ::custom_tracking::reactor_registration args

# define BOOST_ASIO_HANDLER_REACTOR_DEREGISTRATION(args) \
  ::custom_tracking::reactor_deregistration args

# define BOOST_ASIO_HANDLER_REACTOR_READ_EVENT 1
# define BOOST_ASIO_HANDLER_REACTOR_WRITE_EVENT 2
# define BOOST_ASIO_HANDLER_REACTOR_ERROR_EVENT 4

# define BOOST_ASIO_HANDLER_REACTOR_EVENTS(args) \
  ::custom_tracking::reactor_events args

# define BOOST_ASIO_HANDLER_REACTOR_OPERATION(args) \
  ::custom_tracking::reactor_operation args

struct custom_tracking
{
  // Base class for objects containing tracked handlers.
  struct tracked_handler
  {
    std::uintmax_t handler_id_ = 0; // To uniquely identify a handler.
    std::uintmax_t tree_id_ = 0; // To identify related handlers.
    const char* object_type_; // The object type associated with the handler.
    std::uintmax_t native_handle_; // Native handle, if any.
  };

  // Initialise the tracking system.
  static void init()
  {
  }

  // Record a source location.
  static void location(const char* file_name,
      int line, const char* function_name)
  {
    std::printf("At location %s:%d in %s\n", file_name, line, function_name);
  }

  // Record the creation of a tracked handler.
  static void creation(boost::asio::execution_context& /*ctx*/,
      tracked_handler& h, const char* object_type, void* /*object*/,
      std::uintmax_t native_handle, const char* op_name)
  {
    // Generate a unique id for the new handler.
    static std::atomic<std::uintmax_t> next_handler_id{1};
    h.handler_id_ = next_handler_id++;

    // Copy the tree identifier forward from the current handler.
    if (*current_completion())
      h.tree_id_ = (*current_completion())->handler_.tree_id_;

    // Store various attributes of the operation to use in later output.
    h.object_type_ = object_type;
    h.native_handle_ = native_handle;

    std::printf(
        "Starting operation %s.%s for native_handle = %" PRIuMAX
        ", handler = %" PRIuMAX ", tree = %" PRIuMAX "\n",
        object_type, op_name, h.native_handle_, h.handler_id_, h.tree_id_);
  }

  struct completion
  {
    explicit completion(const tracked_handler& h)
      : handler_(h),
        next_(*current_completion())
    {
      *current_completion() = this;
    }

    completion(const completion&) = delete;
    completion& operator=(const completion&) = delete;

    // Destructor records only when an exception is thrown from the handler, or
    // if the memory is being freed without the handler having been invoked.
    ~completion()
    {
      *current_completion() = next_;
    }

    // Records that handler is to be invoked with the specified arguments.
    template <class... Args>
    void invocation_begin(Args&&... /*args*/)
    {
      std::printf("Entering handler %" PRIuMAX " in tree %" PRIuMAX "\n",
          handler_.handler_id_, handler_.tree_id_);
    }

    // Record that handler invocation has ended.
    void invocation_end()
    {
      std::printf("Leaving handler %" PRIuMAX " in tree %" PRIuMAX "\n",
          handler_.handler_id_, handler_.tree_id_);
    }

    tracked_handler handler_;

    // Completions may nest. Here we stash a pointer to the outer completion.
    completion* next_;
  };

  static completion** current_completion()
  {
    static BOOST_ASIO_THREAD_KEYWORD completion* current = nullptr;
    return &current;
  }

  // Record an operation that is not directly associated with a handler.
  static void operation(boost::asio::execution_context& /*ctx*/,
      const char* /*object_type*/, void* /*object*/,
      std::uintmax_t /*native_handle*/, const char* /*op_name*/)
  {
  }

  // Record that a descriptor has been registered with the reactor.
  static void reactor_registration(boost::asio::execution_context& context,
      uintmax_t native_handle, uintmax_t registration)
  {
    std::printf("Adding to reactor native_handle = %" PRIuMAX
        ", registration = %" PRIuMAX "\n", native_handle, registration);
  }

  // Record that a descriptor has been deregistered from the reactor.
  static void reactor_deregistration(boost::asio::execution_context& context,
      uintmax_t native_handle, uintmax_t registration)
  {
    std::printf("Removing from reactor native_handle = %" PRIuMAX
        ", registration = %" PRIuMAX "\n", native_handle, registration);
  }

  // Record reactor-based readiness events associated with a descriptor.
  static void reactor_events(boost::asio::execution_context& context,
      uintmax_t registration, unsigned events)
  {
    std::printf(
        "Reactor readiness for registration = %" PRIuMAX ", events =%s%s%s\n",
        registration,
        (events & BOOST_ASIO_HANDLER_REACTOR_READ_EVENT) ? " read" : "",
        (events & BOOST_ASIO_HANDLER_REACTOR_WRITE_EVENT) ? " write" : "",
        (events & BOOST_ASIO_HANDLER_REACTOR_ERROR_EVENT) ? " error" : "");
  }

  // Record a reactor-based operation that is associated with a handler.
  static void reactor_operation(const tracked_handler& h,
      const char* op_name, const boost::system::error_code& ec)
  {
    std::printf(
        "Performed operation %s.%s for native_handle = %" PRIuMAX
        ", ec = %s:%d\n", h.object_type_, op_name, h.native_handle_,
        ec.category().name(), ec.value());
  }

  // Record a reactor-based operation that is associated with a handler.
  static void reactor_operation(const tracked_handler& h,
      const char* op_name, const boost::system::error_code& ec,
      std::size_t bytes_transferred)
  {
    std::printf(
        "Performed operation %s.%s for native_handle = %" PRIuMAX
        ", ec = %s:%d, n = %" PRIuMAX "\n", h.object_type_, op_name,
        h.native_handle_, ec.category().name(), ec.value(),
        static_cast<uintmax_t>(bytes_transferred));
  }
};

#endif // CUSTOM_TRACKING_HPP
