#include "../../interface/sycldevice.hpp"
#include <csetjmp> // for MPI sycl device awareness
#include <csignal> // SIGSEGV
#include <vector>
#include <CL/sycl.hpp>

#if PetscDefined(USE_LOG)
PETSC_INTERN PetscErrorCode PetscLogInitialize(void);
#else
#define PetscLogInitialize() 0
#endif

namespace Petsc {

namespace Device {

namespace SYCL {

// definition for static
std::array<Device::DeviceInternal *, PETSC_DEVICE_MAX_DEVICES> Device::devices_array_ = {};
Device::DeviceInternal                                       **Device::devices_       = &Device::devices_array_[1];
int                                                            Device::defaultDevice_ = PETSC_SYCL_DEVICE_NONE;
bool                                                           Device::initialized_   = false;

static std::jmp_buf MPISyclAwareJumpBuffer;
static bool         MPISyclAwareJumpBufferSet;

// internal "impls" class for SyclDevice. Each instance represents a single sycl device
class PETSC_NODISCARD Device::DeviceInternal {
  const int          id_; // -1 for the host device; 0 and up for gpu devices
  bool               devInitialized_;
  const sycl::device syclDevice_;

public:
  // default constructor
  DeviceInternal(int id) noexcept : id_(id), devInitialized_(false), syclDevice_(chooseSYCLDevice_(id)) { }
  int  id() const { return id_; }
  bool initialized() const { return devInitialized_; }

  PETSC_NODISCARD PetscErrorCode initialize() noexcept {
    PetscFunctionBegin;
    if (devInitialized_) PetscFunctionReturn(0);
    if (syclDevice_.is_gpu() && use_gpu_aware_mpi) {
      if (!isMPISyclAware_()) {
        (*PetscErrorPrintf)("PETSc is configured with sycl support, but your MPI is not aware of sycl GPU devices. For better performance, please use a sycl GPU-aware MPI.\n");
        (*PetscErrorPrintf)("If you do not care, add option -use_gpu_aware_mpi 0. To not see the message again, add the option to your .petscrc, OR add it to the env var PETSC_OPTIONS.\n");
        PETSCABORT(PETSC_COMM_SELF, PETSC_ERR_LIB);
      }
    }
    devInitialized_ = true;
    PetscFunctionReturn(0);
  }

  PETSC_NODISCARD PetscErrorCode view(PetscViewer viewer) const noexcept {
    MPI_Comm    comm;
    PetscMPIInt rank;
    PetscBool   iascii;

    PetscFunctionBegin;
    PetscCheck(devInitialized_, PETSC_COMM_SELF, PETSC_ERR_COR, "Device %d being viewed before it was initialized or configured", id_);
    PetscCall(PetscObjectTypeCompare(reinterpret_cast<PetscObject>(viewer), PETSCVIEWERASCII, &iascii));
    PetscCall(PetscObjectGetComm(reinterpret_cast<PetscObject>(viewer), &comm));
    if (iascii) {
      PetscViewer sviewer;

      PetscCallMPI(MPI_Comm_rank(comm, &rank));
      PetscCall(PetscViewerGetSubViewer(viewer, PETSC_COMM_SELF, &sviewer));
      PetscCall(PetscViewerASCIIPrintf(sviewer, "[%d] device: %s\n", rank, syclDevice_.get_info<sycl::info::device::name>().c_str()));
      PetscCall(PetscViewerASCIIPushTab(sviewer));
      PetscCall(PetscViewerASCIIPrintf(sviewer, "-> Device vendor: %s\n", syclDevice_.get_info<sycl::info::device::vendor>().c_str()));
      PetscCall(PetscViewerASCIIPopTab(sviewer));
      PetscCall(PetscViewerFlush(sviewer));
      PetscCall(PetscViewerRestoreSubViewer(viewer, PETSC_COMM_SELF, &sviewer));
      PetscCall(PetscViewerFlush(viewer));
    }
    PetscFunctionReturn(0);
  }

  PETSC_NODISCARD PetscErrorCode getattribute(PetscDeviceAttribute attr, void *value) const noexcept {
    PetscFunctionBegin;
    PetscCheck(initialized(), PETSC_COMM_SELF, PETSC_ERR_COR, "Device %d not initialized", id());
    switch (attr) {
    case PETSC_DEVICE_ATTR_SIZE_T_SHARED_MEM_PER_BLOCK: *static_cast<std::size_t *>(value) = syclDevice_.get_info<sycl::info::device::local_mem_size>();
    case PETSC_DEVICE_ATTR_MAX: break;
    }
    PetscFunctionReturn(0);
  }

private:
  static sycl::device chooseSYCLDevice_(int id) {
    if (id == PETSC_SYCL_DEVICE_HOST) {
      return sycl::device(sycl::host_selector());
    } else {
      return sycl::device::get_devices(sycl::info::device_type::gpu)[id];
    }
  }

  // Is the underlying MPI aware of sycl (GPU) devices?
  bool isMPISyclAware_() noexcept {
    const int  bufSize           = 2;
    const int  hbuf[bufSize]     = {1, 0};
    int       *dbuf              = nullptr;
    bool       awareness         = false;
    const auto SyclSignalHandler = [](int signal, void *ptr) -> PetscErrorCode {
      if ((signal == SIGSEGV) && MPISyclAwareJumpBufferSet) std::longjmp(MPISyclAwareJumpBuffer, 1);
      return PetscSignalHandlerDefault(signal, ptr);
    };

    PetscFunctionBegin;
    auto Q = sycl::queue(syclDevice_);
    dbuf   = sycl::malloc_device<int>(bufSize, Q);
    Q.memcpy(dbuf, hbuf, sizeof(int) * bufSize).wait();
    PetscCallAbort(PETSC_COMM_SELF, PetscPushSignalHandler(SyclSignalHandler, nullptr));
    MPISyclAwareJumpBufferSet = true;
    if (setjmp(MPISyclAwareJumpBuffer)) {
      // if a segv was triggered in the MPI_Allreduce below, it is very likely due to MPI not being GPU-aware
      awareness = false;
      PetscStackPop;
    } else if (!MPI_Allreduce(dbuf, dbuf + 1, 1, MPI_INT, MPI_SUM, PETSC_COMM_SELF)) awareness = true;
    MPISyclAwareJumpBufferSet = false;
    PetscCallAbort(PETSC_COMM_SELF, PetscPopSignalHandler());
    sycl::free(dbuf, Q);
    PetscFunctionReturn(awareness);
  }
};

PetscErrorCode Device::initialize(MPI_Comm comm, PetscInt *defaultDeviceId, PetscDeviceInitType *defaultInitType) noexcept {
  PetscInt  initType = *defaultInitType, id = *defaultDeviceId;
  PetscBool view = PETSC_FALSE, flg;
  PetscInt  ngpus;

  PetscFunctionBegin;
  if (initialized_) PetscFunctionReturn(0);
  initialized_ = true;
  PetscCall(PetscRegisterFinalize(finalize_));

  PetscOptionsBegin(comm, nullptr, "PetscDevice SYCL Options", "Sys");
  PetscCall(PetscOptionsEList("-device_enable_sycl", "How (or whether) to initialize a device", "SyclDevice::initialize()", PetscDeviceInitTypes, 3, PetscDeviceInitTypes[initType], &initType, nullptr));
  PetscCall(PetscOptionsRangeInt("-device_select_sycl", "Which sycl device to use? Pass -2 for host, PETSC_DECIDE (-1) to let PETSc decide, 0 and up for GPUs", "PetscDeviceCreate", id, &id, nullptr, -2, std::numeric_limits<decltype(ngpus)>::max()));
  PetscCall(PetscOptionsBool("-device_view_sycl", "Display device information and assignments (forces eager initialization)", nullptr, view, &view, &flg));
  PetscOptionsEnd();

  // post-process the options and lay the groundwork for initialization if needs be
  std::vector<sycl::device> gpu_devices = sycl::device::get_devices(sycl::info::device_type::gpu);
  ngpus                                 = static_cast<PetscInt>(gpu_devices.size());
  PetscCheck(ngpus || id < 0, comm, PETSC_ERR_USER_INPUT, "You specified a sycl gpu device with -device_select_sycl %d but there is no GPU", (int)id);
  PetscCheck(ngpus <= 0 || id < ngpus, comm, PETSC_ERR_USER_INPUT, "You specified a sycl gpu device with -device_select_sycl %d but there are only %d GPU", (int)id, (int)ngpus);

  if (initType == PETSC_DEVICE_INIT_NONE) id = PETSC_SYCL_DEVICE_NONE; /* user wants to disable all sycl devices */
  else {
    PetscCall(PetscDeviceCheckDeviceCount_Internal(ngpus));
    if (id == PETSC_DECIDE) { /* petsc will choose a GPU device if any, otherwise a CPU device */
      if (ngpus) {
        PetscMPIInt rank;
        PetscCallMPI(MPI_Comm_rank(comm, &rank));
        id = rank % ngpus;
      } else id = PETSC_SYCL_DEVICE_HOST;
    }
    view = static_cast<decltype(view)>(view && flg);
    if (view) initType = PETSC_DEVICE_INIT_EAGER;
  }

  if (id == -2) id = PETSC_SYCL_DEVICE_HOST; // user passed in '-device_select_sycl -2'. We transform it into canonical form

  defaultDevice_ = static_cast<decltype(defaultDevice_)>(id);
  PetscCheck(initType != PETSC_DEVICE_INIT_EAGER || id != PETSC_SYCL_DEVICE_NONE, comm, PETSC_ERR_USER_INPUT, "Cannot eagerly initialize sycl devices as you disabled them by -device_enable_sycl none");

  if (initType == PETSC_DEVICE_INIT_EAGER) {
    devices_[defaultDevice_] = new DeviceInternal(defaultDevice_);
    PetscCall(devices_[defaultDevice_]->initialize());
    if (view) {
      PetscViewer viewer;
      PetscCall(PetscLogInitialize());
      PetscCall(PetscViewerASCIIGetStdout(comm, &viewer));
      PetscCall(devices_[defaultDevice_]->view(viewer));
    }
  }

  // record the results of the initialization
  *defaultInitType = static_cast<PetscDeviceInitType>(initType);
  *defaultDeviceId = id;
  PetscFunctionReturn(0);
}

PetscErrorCode Device::finalize_() noexcept {
  PetscFunctionBegin;
  if (!initialized_) PetscFunctionReturn(0);
  for (auto &&devPtr : devices_array_) delete devPtr;
  defaultDevice_ = PETSC_SYCL_DEVICE_NONE; // disabled by default
  initialized_   = false;
  PetscFunctionReturn(0);
}

PetscErrorCode Device::getDevice(PetscDevice device, PetscInt id) const noexcept {
  PetscFunctionBegin;
  PetscCheck(defaultDevice_ != PETSC_SYCL_DEVICE_NONE, PETSC_COMM_SELF, PETSC_ERR_ARG_WRONGSTATE, "Trying to retrieve a SYCL PetscDevice when it has been disabled");
  if (id == PETSC_DECIDE) id = defaultDevice_;
  PetscCheck(!(id < PETSC_SYCL_DEVICE_HOST) && !(id - PETSC_SYCL_DEVICE_HOST >= PETSC_DEVICE_MAX_DEVICES), PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Only supports %zu number of devices but trying to get device with id %" PetscInt_FMT,
             devices_array_.size(), id);
  if (devices_[id]) {
    PetscCheck(id == devices_[id]->id(), PETSC_COMM_SELF, PETSC_ERR_PLIB, "Entry %" PetscInt_FMT " contains device with mismatching id %" PetscInt_FMT, id, devices_[id]->id());
  } else devices_[id] = new DeviceInternal(id);
  PetscCall(devices_[id]->initialize());
  device->deviceId           = devices_[id]->id(); // technically id = devices_[id]->id_ here
  device->ops->createcontext = create_;
  device->ops->configure     = this->configureDevice;
  device->ops->view          = this->viewDevice;
  device->ops->getattribute  = this->getAttribute;
  PetscFunctionReturn(0);
}

PetscErrorCode Device::configureDevice(PetscDevice device) noexcept {
  PetscFunctionBegin;
  // Nothing for now
  PetscFunctionReturn(0);
}

PetscErrorCode Device::viewDevice(PetscDevice device, PetscViewer viewer) noexcept {
  PetscFunctionBegin;
  PetscCall(devices_[device->deviceId]->view(viewer));
  PetscFunctionReturn(0);
}

PetscErrorCode Device::getAttribute(PetscDevice device, PetscDeviceAttribute attr, void *value) noexcept {
  PetscFunctionBegin;
  PetscCall(devices_[device->deviceId]->getattribute(attr, value));
  PetscFunctionReturn(0);
}

} // namespace SYCL

} // namespace Device

} // namespace Petsc