/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */

/*!
 * \file tvm/runtime/memory/memory_manager.h
 * \brief Abstract device memory management API
 */
#ifndef TVM_RUNTIME_MEMORY_MEMORY_MANAGER_H_
#define TVM_RUNTIME_MEMORY_MEMORY_MANAGER_H_

#include <tvm/runtime/base.h>
#include <tvm/runtime/tensor.h>

#include <functional>
#include <memory>
#include <mutex>
#include <string>
#include <unordered_map>
#include <vector>

namespace tvm {
namespace runtime {
namespace memory {

enum AllocatorType {
  kNaive = 1,
  kPooled,
};

struct Buffer {
  /*! \brief The pointer to the allocated block of memory. */
  void* data{nullptr};
  /*! \brief The size of the block. */
  size_t size{0};
  /*! \brief The context of the allocated buffers. */
  Device device;
  /*! \brief The allocator that created this buffer. */
  AllocatorType alloc_type;
};

class TVM_RUNTIME_DLL Allocator {
 public:
  explicit Allocator(AllocatorType type) : type_(type) {}
  virtual ~Allocator() = default;
  /*! \brief Allocate an empty Tensor using from the allocator.
   *  \param shape The shape of the Tensor.
   *  \param dtype The datatype of the Tensor.
   *  \param dev The device where the array is allocated.
   *  \param mem_scope The device memory scope hint.
   *  \return The empty Tensor.
   */
  Tensor Empty(ffi::Shape shape, DLDataType dtype, Device dev,
               ffi::Optional<ffi::String> mem_scope = std::nullopt);
  /*! \brief Return the allocator type. */
  inline AllocatorType type() const { return type_; }
  /*! \brief Allocate a buffer given a size, alignment and type.
   *  \param dev The device where the array is allocated.
   *  \param nbytes The size of the buffer.
   *  \param alignment The alignment of the buffer.
   *  \param type_hint A type hint to the allocator.
   *  \return A sized allocation in the form of a buffer.
   */
  virtual Buffer Alloc(Device dev, size_t nbytes, size_t alignment, DLDataType type_hint) = 0;
  /*! \brief Allocate a buffer given a shape and type.
   *  \param dev The device where the array is allocated.
   *  \param shape The shape of the tensor.
   *  \param type_hint A type hint to the allocator.
   *  \param mem_scope A memory scope of the buffer.
   *  \return A sized allocation in the form of a buffer.
   */
  virtual Buffer Alloc(Device dev, ffi::Shape shape, DLDataType type_hint,
                       const std::string& mem_scope = "");

  /*! \brief Create a view for the buffer given a shape, type and scope.
   *  \param buffer The existing buffer upon which we need to create a view.
   *  \param shape The shape of the view.
   *  \param type_hint A type hint to the view.
   *  \param mem_scope A memory scope of the view.
   *  \return A device pointer to the created view.
   */
  virtual void* CreateView(const Buffer& buffer, ffi::Shape shape, DLDataType type_hint,
                           const std::string& mem_scope = "global") {
    return buffer.data;
  }

  /*! \brief Release the view .
   *  \param dev is the device where this view is created
   *  \param data The view pointer to be freed.
   */
  virtual void FreeView(Device dev, void* data) {}

  /*! \brief Free a buffer allocated by the allocator.
   *  \param buffer The buffer to free.
   */
  virtual void Free(const Buffer& buffer) = 0;
  /*! \brief Clear the allocated memory. */
  virtual void Clear();
  /*! \brief The amount of memory currently allocated.
   *  \return The amount of memory currently allocated.
   */
  virtual size_t UsedMemory() const = 0;

 protected:
  /*! \brief Check if the given memory scope is allowed to allocate by the allocator. */
  virtual bool AllowMemoryScope(const std::string& mem_scope) const;

 private:
  AllocatorType type_;
};

class MemoryManager {
 public:
  TVM_RUNTIME_DLL static MemoryManager* Global();
  /*!
   * \brief Get or create an allocator given the context and allocator type.
   * \param dev The TVM device
   * \param type The allocator type
   * \return The memory allocator.
   */
  TVM_RUNTIME_DLL static Allocator* GetOrCreateAllocator(Device dev, AllocatorType type);
  /*!
   * \brief Get an allocator given the context.
   * \param dev The TVM device
   * \param type The allocator type
   * \return The memory allocator.
   */
  TVM_RUNTIME_DLL static Allocator* GetAllocator(Device dev, AllocatorType type);
  /*! \brief Clear the allocators. */
  static void Clear();

 private:
  MemoryManager() {}

 protected:
  std::mutex mu_;
  std::unordered_map<Device, std::unordered_map<AllocatorType, std::unique_ptr<Allocator>>>
      allocators_;
};

/*! \brief An object representing a storage allocation. */
class StorageObj : public ffi::Object {
 public:
  /*! \brief The index into the VM function table. */
  Buffer buffer;
  /*! \brief The allocator where the storage buffer is allocated from. */
  Allocator* allocator = nullptr;

  /*! \brief Allocate an Tensor from a given piece of storage. */
  TVM_RUNTIME_DLL Tensor AllocTensor(int64_t offset, ffi::Shape shape, DLDataType dtype);

  /*! \brief Allocate an Tensor with memory scope from a given piece of storage. */
  TVM_RUNTIME_DLL Tensor AllocTensorScoped(int64_t offset, ffi::Shape shape, DLDataType dtype,
                                           ffi::String scope = "global");

  ~StorageObj() {
    if (allocator) {
      allocator->Free(buffer);
    }
  }

  static constexpr const bool _type_mutable = true;
  TVM_FFI_DECLARE_OBJECT_INFO_FINAL("vm.Storage", StorageObj, ffi::Object);
};

/*! \brief reference to storage. */
class Storage : public ffi::ObjectRef {
 public:
  TVM_RUNTIME_DLL explicit Storage(Buffer buffer, Allocator* allocator);

  TVM_FFI_DEFINE_OBJECT_REF_METHODS_NULLABLE(Storage, ffi::ObjectRef, StorageObj);
};

}  // namespace memory

using memory::Allocator;
using memory::AllocatorType;
using memory::MemoryManager;
using memory::StorageObj;

}  // namespace runtime
}  // namespace tvm

#endif  // TVM_RUNTIME_MEMORY_MEMORY_MANAGER_H_