#include <kapi/devices.hpp>

#include <kstd/memory.hpp>

#include <catch2/catch_test_macros.hpp>

#include <cstddef>

namespace
{
  struct probe_device
  {
    constexpr auto static id = kapi::capabilities::facet_id{"probe"};

    virtual ~probe_device() = default;

    [[nodiscard]] auto virtual get_value() const noexcept -> int = 0;
  };

  struct const_device
  {
    constexpr auto static id = kapi::capabilities::facet_id{"flip"};

    virtual ~const_device() = default;

    [[nodiscard]] auto get_constant() const noexcept -> int
    {
      return 0;
    }
  };

  struct unimplemented_device
  {
    constexpr auto static id = kapi::capabilities::facet_id{"unimplemented"};

    virtual ~unimplemented_device() = default;
  };

  struct test_device final : kapi::devices::device, probe_device
  {
    explicit test_device(int value, const_device & const_device)
        : device{"probeable"}
        , m_value{value}
        , m_const_device{&const_device}
    {}

    [[nodiscard]] constexpr auto get_value() const noexcept -> int override
    {
      return m_value;
    }

    auto query_facet(kapi::capabilities::facet_id facet) -> void * override
    {
      if (facet == probe_device::id)
      {
        return static_cast<probe_device *>(this);
      }
      if (facet == const_device::id)
      {
        return m_const_device;
      }

      return kapi::devices::device::query_facet(facet);
    }

  private:
    int m_value;
    const_device * m_const_device;
  };

  struct counting_observer final : kapi::devices::facet_registry_observer
  {
    auto on_facet_published(kapi::capabilities::facet_id, kapi::devices::facet_registry::entry const &) -> void override
    {
      ++published;
    }

    auto on_facet_withdrawn(kapi::capabilities::facet_id, kapi::devices::device &) -> void override
    {
      ++withdrawn;
    }

    std::size_t published{};
    std::size_t withdrawn{};
  };

  struct evil_observer final : kapi::devices::facet_registry_observer
  {
    explicit evil_observer(kstd::shared_ptr<counting_observer> & victim)
        : m_victim{victim}
    {}

    auto on_facet_published(kapi::capabilities::facet_id, kapi::devices::facet_registry::entry const &) -> void override
    {
      m_victim.reset();
    }

    auto on_facet_withdrawn(kapi::capabilities::facet_id, kapi::devices::device &) -> void override
    {
      m_victim.reset();
    }

  private:
    kstd::shared_ptr<counting_observer> & m_victim;  // NOLINT
  };

}  // namespace

SCENARIO("Publishing and finding a device", "[kapi][devices][facet_registry]")
{
  GIVEN("An empty registry, a device, and a facet the device implements by inheritance")
  {
    auto registry = kapi::devices::facet_registry{};
    auto free_standing_facet = const_device{};
    auto device = kstd::make_shared<test_device>(128, free_standing_facet);

    THEN("Publishing an facet without a name fails")
    {
      REQUIRE_FALSE(registry.publish<probe_device>(device, ""));
    }

    WHEN("publishing the facet for the device")
    {
      CHECK(device->has_facet<probe_device>());
      CHECK(device->has_facet<const_device>());
      auto published = registry.publish(device, "probe0", device->facet<probe_device>());

      THEN("publishing is successful")
      {
        REQUIRE(published);
      }

      THEN("publishing the same device and facet with a different name fails")
      {
        REQUIRE_FALSE(registry.publish(device, "probe1", device->facet<probe_device>()));
      }

      THEN("publishing a second facet for the same device succeeds")
      {
        REQUIRE(registry.publish<const_device>(device, "probe0"));
      }

      THEN("publishing a free standing second facet for the same device succeeds")
      {
        REQUIRE(registry.publish(device, "probe0", &free_standing_facet));
      }

      AND_WHEN("getting all devices implementing that facet")
      {
        auto probeable_devices = registry.all(probe_device::id);

        THEN("there is exactly one such device")
        {
          REQUIRE(probeable_devices.size() == 1);
        }

        THEN("the name of the device is 'probe0'")
        {
          REQUIRE(probeable_devices[0].name() == "probe0");
        }

        THEN("the returned device pointer is valid")
        {
          REQUIRE(probeable_devices[0].device());
        }

        THEN("the returned implementation equals the result of device::as")
        {
          REQUIRE(probeable_devices[0].untyped_facet() == device->facet<probe_device>());
        }

        THEN("the facet provided function can be invoked")
        {
          auto implementation = probeable_devices[0].facet<probe_device>();
          REQUIRE(implementation->get_value() == device->get_value());
        }
      }

      THEN("resolve finds the published capability by name")
      {
        REQUIRE(registry.resolve<probe_device>("probe0"));
      }

      THEN("resolve finds a capability the device implements but never published")
      {
        REQUIRE(registry.resolve<const_device>("probe0"));
      }

      THEN("resolve for a capability the device implements nowhere at all does not find anything")
      {
        REQUIRE_FALSE(registry.resolve<unimplemented_device>("probe0"));
      }

      THEN("resolve for an unpublished device does not find a device")
      {
        REQUIRE_FALSE(registry.resolve<probe_device>("probe1"));
      }

      THEN("withdrawing an facet for a device removes it from the registry")
      {
        registry.withdraw(*device, probe_device::id);
        REQUIRE_FALSE(registry.resolve<probe_device>("probe0"));
      }
    }

    WHEN("the device is destroyed without withdrawing it")
    {
      CHECK(registry.publish(device, "probe0", device->facet<probe_device>()));
      device.reset();

      THEN("querying all does no longer report it")
      {
        REQUIRE(registry.all(probe_device::id).empty());
      }

      THEN("resolve() no longer finds it")
      {
        REQUIRE_FALSE(registry.resolve<probe_device>("probe0"));
      }
    }
  }

  GIVEN("no device has ever been published")
  {
    auto registry = kapi::devices::facet_registry{};

    THEN("all() returns an empty vector")
    {
      REQUIRE(registry.all(probe_device::id).empty());
    }
  }

  GIVEN("a null device")
  {
    auto registry = kapi::devices::facet_registry{};
    auto device = kstd::shared_ptr<kapi::devices::device>{};
    auto facet = const_device{};

    THEN("publishing the facet for the device fails")
    {
      REQUIRE_FALSE(registry.publish(device, "probe0", &facet));
    }
  }
}

SCENARIO("facet registry notifies subscribers", "[kapi][devices][facet_registry]")
{
  GIVEN("a device and a subscribed observer")
  {
    auto registry = kapi::devices::facet_registry{};
    auto free_standing_facet = const_device{};
    auto device = kstd::make_shared<test_device>(128, free_standing_facet);
    auto observer = kstd::make_shared<counting_observer>();

    registry.subscribe(observer);

    WHEN("an facet is published for the device")
    {
      CHECK(registry.publish(device, "probe0", device->facet<probe_device>()));

      THEN("the observer is notified exactly once")
      {
        REQUIRE(observer->published == 1);
        REQUIRE(observer->withdrawn == 0);
      }
    }

    WHEN("an facet is published and then withdrawn")
    {
      CHECK(registry.publish(device, "probe0", device->facet<probe_device>()));
      registry.withdraw(*device, probe_device::id);

      THEN("the observer is notified of both exactly one")
      {
        REQUIRE(observer->published == 1);
        REQUIRE(observer->withdrawn == 1);
      }
    }

    WHEN("the observer is destroyed before anything is published")
    {
      observer.reset();

      THEN("publishing afterward does not crash")
      {
        REQUIRE_NOTHROW(registry.publish(device, "probe0", device->facet<probe_device>()));
      }
    }

    WHEN("the observer unsubscribes before anything is published")
    {
      registry.unsubscribe(*observer);

      THEN("publishing afterward does not crash")
      {
        REQUIRE_NOTHROW(registry.publish(device, "probe0", device->facet<probe_device>()));
      }

      THEN("the subscriber is not notified")
      {
        REQUIRE_NOTHROW(registry.publish(device, "probe0", device->facet<probe_device>()));
        REQUIRE_NOTHROW(registry.withdraw(*device, probe_device::id));
        REQUIRE(observer->published == 0);
        REQUIRE(observer->withdrawn == 0);
      }
    }
  }

  GIVEN("two subscriber, the first destroying the second")
  {
    auto registry = kapi::devices::facet_registry{};
    auto free_standing_facet = const_device{};
    auto device = kstd::make_shared<test_device>(128, free_standing_facet);

    auto second = kstd::make_shared<counting_observer>();
    auto first = kstd::make_shared<evil_observer>(second);

    registry.subscribe(first);
    registry.subscribe(second);

    THEN("publishing an facet does not crash")
    {
      REQUIRE_NOTHROW(registry.publish(device, "probe0", device->facet<probe_device>()));
      REQUIRE(second == nullptr);
    }
  }
}