/* Copyright 2020 The TensorFlow Authors. All Rights Reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
==============================================================================*/

#include <dirent.h>
#include <dlfcn.h>
#include <fcntl.h>
#include <link.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include <cstdlib>
#include <cstring>
#include <filesystem>
#include <string>
#include <utility>
#include <vector>

#include "absl/status/status.h"
#include "absl/status/statusor.h"
#include "absl/strings/str_cat.h"
#include "xla/stream_executor/tpu/libtftpu.h"
#include "xla/stream_executor/tpu/tpu_api.h"
#include "xla/stream_executor/tpu/tpu_api_dlsym_set_fn.h"
#include "xla/stream_executor/tpu/tpu_executor_c_api.h"
#include "xla/stream_executor/tpu/tpu_initialize_util.h"
#include "xla/stream_executor/tpu/tpu_platform.h"
#include "tsl/platform/errors.h"
#include "tsl/platform/logging.h"  // IWYU pragma: keep

#if !defined(PLATFORM_GOOGLE)
#include "xla/stream_executor/tpu/tpu_library_init_fns.inc"

namespace tensorflow {
namespace tpu {
namespace {

absl::Status InitializeTpuLibrary(void* library_handle) {
  absl::Status s = InitializeTpuStructFns(library_handle);

  // TODO(b/296588097): remove the initialization below after StreamExecutor is
  // fully deprecated in Cloud TPU. Only InitializeTpuStructFns is required in
  // TFRT based PJRT client.

  // Retrieve arguments from environment if applicable
  std::pair<std::vector<std::string>, std::vector<const char*>> args =
      GetLibTpuInitArguments();

  // TPU platform registration must only be performed after the library is
  // loaded. We do not want to register a TPU platform in XLA without the
  // supporting library providing the necessary APIs.
  if (s.ok()) {
    void (*initialize_fn)(bool init_library, int num_args, const char** args);
    initialize_fn = reinterpret_cast<decltype(initialize_fn)>(
        dlsym(library_handle, "TfTpu_Initialize"));
    (*initialize_fn)(/*init_library=*/true, args.second.size(),
                     args.second.data());

    RegisterTpuPlatform();
  }

  return s;
}

// Gets the path of current module. It is usually tensorflow_framework.so.
const char* GetCurrentModulePath() {
  Dl_info DlInfo;
  struct link_map* linkmap = nullptr;
  if (!dladdr1((void*)GetCurrentModulePath, &DlInfo,
               reinterpret_cast<void**>(&linkmap), RTLD_DL_LINKMAP)) {
    return nullptr;
  }
  return linkmap->l_name;
}

absl::Status FindAndLoadTpuLibrary() {
  // Reopen tensorflow_framework.so as RTLD_GLOBAL. So that libtpu can link to
  // Tensorflow C API.
  // TODO(b/299313561): Remove this dependency.
  const char* so_name = GetCurrentModulePath();
  if (so_name != nullptr) {
    LOG(INFO) << "Opening library: " << so_name;
    void* tf_lib = dlopen(so_name, RTLD_NOW | RTLD_GLOBAL);
    if (tf_lib == nullptr) {
      LOG(WARNING) << "Failed to open library " << dlerror()
                   << ". This may be expected if Tensorflow API is not used";
    }
  }

  // Check if libtpu pip package is installed along with tf whl. In that case,
  // libtpu should be in the path `python3.x/site_packages/libtpu/libtpu.so`.
  std::filesystem::path whl_libtpu_path =
      std::filesystem::path(so_name).parent_path() / "libtpu/libtpu.so";

  const char* env_value = getenv("TPU_LIBRARY_PATH");
  const char* libtpu_path = nullptr;
  if (env_value && strlen(env_value) > 0) {
    libtpu_path = env_value;
  } else if (std::filesystem::exists(whl_libtpu_path)) {
    // whl_libtpu_path must outlive libtpu_path.
    libtpu_path = whl_libtpu_path.c_str();
  } else {
    libtpu_path = "libtpu.so";
  }

  LOG(INFO) << "Libtpu path is: " << libtpu_path;
  void* library = dlopen(libtpu_path, RTLD_LAZY);
  if (library == nullptr) {
    return absl::InternalError(
        absl::StrCat("Failed to open libtpu ", dlerror()));
  }

  // We can open the shared library which means we are in a TPU environment.
  // Try to acquire exclusive access.
  TF_RETURN_IF_ERROR(TryAcquireTpuLock());
  TF_RETURN_IF_ERROR(InitializeTpuLibrary(library));
  return absl::OkStatus();
}

bool FindAndInitializeTpuLibrary() {
  absl::Status status = FindAndLoadTpuLibrary();
  if (!status.ok()) {
    LOG(INFO) << "FindAndLoadTpuLibrary failed with " << status
              << ". This is expected if TPU is not used.";
    return false;
  }
  return true;
}

static bool tpu_library_finder = FindAndInitializeTpuLibrary();

}  // namespace
}  // namespace tpu
}  // namespace tensorflow
#endif
