#include "kapi/devices.hpp"

#include "kapi/system.hpp"

#include "kernel/devices/root_bus.hpp"

#include <kstd/flat_map>
#include <kstd/memory>
#include <kstd/print>

#include <atomic>
#include <cstddef>
#include <optional>
#include <string_view>
#include <utility>

namespace kapi::devices
{
  namespace
  {
    auto constinit next_major_number = std::atomic_size_t{1};
    auto constinit root_bus = std::optional<kernel::devices::root_bus>{};
    auto constinit device_tree = kstd::flat_map<std::pair<std::size_t, std::size_t>, kstd::observer_ptr<device>>{};
  }  // namespace

  auto init() -> void
  {
    auto static is_initialized = std::atomic_flag{};
    if (is_initialized.test_and_set())
    {
      return;
    }

    auto & bus = root_bus.emplace();
    register_device(bus);
    bus.init();
  }

  auto get_root_bus() -> bus &
  {
    if (!root_bus.has_value())
    {
      kapi::system::panic("[OS:DEV] Root bus not initialized!");
    }
    return *root_bus;
  }

  auto allocate_major_number() -> std::size_t
  {
    return next_major_number++;
  }

  auto register_device(device & device) -> bool
  {
    kstd::println("[OS:DEV] Registering device {}@{}:{}", device.name(), device.major(), device.minor());
    return device_tree.emplace(std::pair{device.major(), device.minor()}, &device).second;
  }

  auto unregister_device(device &) -> bool
  {
    kstd::println("[OS:DEV] TODO: implement device deregistration");
    return false;
  }

  auto find_device(std::size_t major, std::size_t minor) -> kstd::observer_ptr<device>
  {
    if (device_tree.contains(std::pair{major, minor}))
    {
      return device_tree.at(std::pair{major, minor});
    }
    return nullptr;
  }

  auto find_device(std::string_view name) -> kstd::observer_ptr<device>
  {
    for (auto const & [key, value] : device_tree)
    {
      if (value->name() == name)
      {
        return value;
      }
    }
    return nullptr;
  }

}  // namespace kapi::devices