#include <kapi/devices/interface_registry.hpp>

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

#include <kstd/memory.hpp>
#include <kstd/result.hpp>
#include <kstd/string.hpp>
#include <kstd/system_error.hpp>
#include <kstd/vector.hpp>

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

namespace kapi::devices
{

  namespace
  {
    constinit auto static registry = std::optional<interface_registry>{};
  }

  auto interface_registry::init() -> void
  {
    if (registry.has_value())
    {
      system::panic("[kernel] Device interface registry has already been initialized.");
    }

    registry.emplace();
  }

  auto interface_registry::get() -> interface_registry &
  {
    if (!registry)
    {
      system::panic("[kernel] Device interface registry has not been initialized.");
    }

    return *registry;
  }

  auto interface_registry::do_publish(kstd::shared_ptr<device> device, kstd::string name, interface_id interface,
                                      void * implementation) -> kstd::result<void>
  {
    // TODO: lock registry

    erase_if(m_entries, [interface](auto e) { return e.interface() == interface && !e.device(); });

    if (!device || !implementation || name.empty())
    {
      return kstd::failure(make_error_code(kstd::errc::invalid_argument));
    }

    auto already_published = std::ranges::any_of(m_entries, [&](auto const & entry) {
      return entry.interface() == interface && entry.device().get() == device.get();
    });

    if (already_published)
    {
      return kstd::failure(make_error_code(kstd::errc::file_exists));
    }

    auto & published = m_entries.emplace_back(device, std::move(name), interface, implementation);

    do_notify_published(interface, published);

    return kstd::success();
  }

  auto interface_registry::do_notify_published(interface_id interface, entry const & published) -> void
  {
    std::ranges::for_each(m_observers, [&](auto observer) {
      if (auto locked_observer = observer.lock())
      {
        locked_observer->on_interface_published(interface, published);
      }
    });

    std::ranges::for_each(m_static_observers,
                          [&](auto observer) { observer->on_interface_published(interface, published); });
  }

  auto interface_registry::do_notify_withdrawn(interface_id interface, device const & device) -> void
  {
    std::ranges::for_each(m_observers, [&](auto observer) {
      if (auto locked_observer = observer.lock())
      {
        locked_observer->on_interface_withdrawn(interface, const_cast<devices::device &>(device));
      }
    });

    std::ranges::for_each(m_static_observers, [&](auto observer) {
      observer->on_interface_withdrawn(interface, const_cast<devices::device &>(device));
    });
  }

  auto interface_registry::withdraw(device const & device, interface_id interface) -> void
  {
    // TODO: lock registry

    auto did_remove = erase_if(m_entries, [&](auto e) {
                        auto locked_device = e.device();
                        return e.interface() == interface && locked_device && locked_device.get() == &device;
                      }) != 0;

    if (did_remove)
    {
      do_notify_withdrawn(interface, device);
    }
  }

  auto interface_registry::withdraw_all_for(device const & device) -> void
  {
    // TODO: lock registry

    auto withdrawn_interfaces = kstd::vector<interface_id>{};

    erase_if(m_entries, [&](auto e) {
      auto locked_device = e.device();
      auto do_erase = locked_device && locked_device.get() == &device;
      if (do_erase)
      {
        withdrawn_interfaces.push_back(e.interface());
      }
      return do_erase;
    });

    std::ranges::for_each(withdrawn_interfaces, [&](auto interface) { do_notify_withdrawn(interface, device); });
  }

  auto interface_registry::all(interface_id interface) const -> kstd::vector<entry>
  {
    // TODO: lock registry

    auto filtered = m_entries;
    erase_if(filtered, [&](auto e) {
      auto locked_device = e.device();
      return !(e.interface() == interface && locked_device);
    });
    return filtered;
  }

  auto interface_registry::resolve(interface_id interface, std::string_view name) -> void *
  {
    // TODO: lock registry

    auto found = std::ranges::find_if(m_entries, [&](auto e) { return e.name() == name && e.device(); });

    if (found == m_entries.cend())
    {
      return nullptr;
    }
    else if (auto device = found->device())
    {
      return resolve(interface, *device);
    }

    return nullptr;
  }

  auto interface_registry::resolve(interface_id interface, device & device) -> void *
  {
    // TODO: lock registry

    if (auto by_device = device.as(interface))
    {
      return by_device;
    }

    auto found = std::ranges::find_if(m_entries, [&](auto e) {
      auto locked_device = e.device();
      return e.interface() == interface && locked_device && locked_device.get() == &device;
    });

    if (found == m_entries.cend())
    {
      return nullptr;
    }

    return found->implementation();
  }

  auto interface_registry::subscribe(kstd::weak_ptr<interface_registry_observer> observer) -> void
  {
    // TODO: lock registry

    erase_if(m_observers, [](auto const & observer) { return observer.expired(); });
    m_observers.push_back(observer);
  }

  auto interface_registry::subscribe(interface_registry_observer & observer) -> void
  {
    // TODO: lock registry

    m_static_observers.push_back(&observer);
  }

  auto interface_registry::unsubscribe(interface_registry_observer & observer) -> void
  {
    // TODO: lock registry

    erase_if(m_observers, [&](auto const & subscribed) { return subscribed.lock().get() == &observer; });
    erase(m_static_observers, &observer);
  }

}  // namespace kapi::devices

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