#include <kapi/devices/device_registry.hpp>

#include <kapi/devices/device.hpp>
#include <kapi/system.hpp>

#include <kstd/memory.hpp>
#include <kstd/mutex.hpp>
#include <kstd/print.hpp>
#include <kstd/string.hpp>
#include <kstd/vector.hpp>

#include <optional>
#include <string_view>
#include <utility>

namespace kapi::devices
{

  namespace
  {
    auto constinit instance = std::optional<device_registry>{};
  }

  auto device_registry::init() -> void
  {
    if (instance)
    {
      system::panic("[OS:DEV] Device registry has already been initialized");
    }

    instance.emplace();
  }

  auto device_registry::get() -> device_registry &
  {
    if (!instance)
    {
      system::panic("[OS:DEV] Device registry has not been initialized");
    }

    return *instance;
  }

  auto device_registry::add(kstd::shared_ptr<device> device) -> bool
  {
    if (!device)
    {
      return false;
    }

    kstd::println("[OS:DEV] Registering device {}", device->name());

    auto added = false;
    {
      auto guard = kstd::lock_guard{m_lock};

      auto found = m_devices.find(device->name());
      if (found != m_devices.end())
      {
        if (!found->second.expired())
        {
          added = false;
        }

        found->second = device;
        added = true;
      }
      else
      {
        added = m_devices.emplace(device->name(), device).second;
      }
    }

    if (!added)
    {
      return false;
    }

    auto observers = kstd::vector<kstd::weak_ptr<device_registry_observer>>{};
    {
      auto guard = kstd::lock_guard{m_lock};
      observers = m_observers;
    }

    for (auto const & observer : observers)
    {
      if (auto locked_observer = observer.lock())
      {
        locked_observer->on_device_added(device);
      }
    }

    {
      auto guard = kstd::lock_guard{m_lock};
      erase_if(m_observers, [](auto const & observer) { return observer.expired(); });
    }

    return true;
  }

  auto device_registry::remove(device & device) -> bool
  {
    {
      auto guard = kstd::lock_guard{m_lock};

      auto found = m_devices.find(device.name());
      if (found == m_devices.end())
      {
        return false;
      }

      auto locked = found->second.lock();
      if (!locked || locked.get() != &device)
      {
        return false;
      }

      found->second = kstd::weak_ptr<struct device>{};
    }

    kstd::println("[OS:DEV] Unregistering device {}", device.name());

    auto observers = kstd::vector<kstd::weak_ptr<device_registry_observer>>{};
    {
      auto guard = kstd::lock_guard{m_lock};
      observers = m_observers;
    }

    for (auto const & observer : observers)
    {
      if (auto locked_observer = observer.lock())
      {
        locked_observer->on_device_removed(device);
      }
    }

    {
      auto guard = kstd::lock_guard{m_lock};
      erase_if(m_observers, [](auto const & observer) { return observer.expired(); });
    }

    return true;
  }

  auto device_registry::find(std::string_view name) const -> kstd::shared_ptr<device>
  {
    auto guard = kstd::lock_guard{m_lock};

    auto found = m_devices.find(kstd::string{name});
    if (found == m_devices.end())
    {
      return nullptr;
    }

    return found->second.lock();
  }

  auto device_registry::all() const -> kstd::vector<kstd::shared_ptr<device>>
  {
    auto guard = kstd::lock_guard{m_lock};

    auto result = kstd::vector<kstd::shared_ptr<device>>{};

    for (auto const & [name, weak_device] : m_devices)
    {
      if (auto device = weak_device.lock())
      {
        result.push_back(std::move(device));
      }
    }

    return result;
  }

  auto device_registry::subscribe(kstd::weak_ptr<device_registry_observer> observer) -> void
  {
    auto guard = kstd::lock_guard{m_lock};

    erase_if(m_observers, [](auto const & observer) { return observer.expired(); });
    m_observers.push_back(observer);
  }
}  // namespace kapi::devices

namespace kapi::test_support::devices
{
  auto deinit_device_registry() -> void
  {
    kapi::devices::instance.reset();
  }
}  // namespace kapi::test_support::devices