/* Copyright 2015 Google Inc. 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.
==============================================================================*/

// The utility to read checkpoints for google brain tensor ops and v3
// checkpoints for dist_belief.
//

#ifndef TENSORFLOW_UTIL_TENSOR_SLICE_READER_H_
#define TENSORFLOW_UTIL_TENSOR_SLICE_READER_H_

#include <unordered_map>

#include <vector>
#include "tensorflow/core/framework/tensor.h"
#include "tensorflow/core/framework/tensor_shape.h"
#include "tensorflow/core/framework/tensor_slice.h"
#include "tensorflow/core/framework/types.pb.h"
#include "tensorflow/core/lib/core/status.h"
#include "tensorflow/core/lib/core/stringpiece.h"
#include "tensorflow/core/lib/gtl/map_util.h"
#include "tensorflow/core/platform/logging.h"
#include "tensorflow/core/platform/macros.h"
#include "tensorflow/core/platform/mutex.h"
#include "tensorflow/core/platform/protobuf.h"
#include "tensorflow/core/platform/types.h"
#include "tensorflow/core/util/saved_tensor_slice.pb.h"
#include "tensorflow/core/util/saved_tensor_slice_util.h"
#include "tensorflow/core/util/tensor_slice_set.h"
#include "tensorflow/core/util/tensor_slice_util.h"

namespace tensorflow {

namespace checkpoint {

// The reader reads in all the meta data about all the tensor slices. Then it
// will try to read the relevant data on-demand to produce the data for the
// slices needed.
// NOTE(yangke): another way to do this is to first load a list of the tensor
// slices needed and then just selectively read some of the meta data. That
// might optimize the loading but makes the logic a bit more complicated. We
// might want to revisit that.
// TODO(yangke): consider moving to TensorProto.
class TensorSliceReader {
 public:
  // Abstract interface for reading data out of a tensor slice checkpoint file
  class Table {
   public:
    virtual ~Table();
    virtual bool Get(const string& key, string* value) = 0;
  };
  typedef std::function<Status(const string&, Table**)> OpenTableFunction;

  static const int kLoadAllShards = -1;
  TensorSliceReader(const string& filepattern);
  TensorSliceReader(const string& filepattern, OpenTableFunction open_function);
  TensorSliceReader(const string& filepattern, OpenTableFunction open_function,
                    int preferred_shard);
  virtual ~TensorSliceReader();

  // Get the filename this reader is attached to.
  const string& filepattern() const { return filepattern_; }

  // Get the number of files matched.
  int num_files() const { return sss_.size(); }

  // Get the status of the reader.
  const Status status() const { return status_; }

  // Checks if the reader contains any slice of a tensor. In case the reader
  // does contain the tensor, if "shape" is not nullptr, fill "shape" with the
  // shape of the tensor; if "type" is not nullptr, fill "type" with the type
  // of the tensor.
  bool HasTensor(const string& name, TensorShape* shape, DataType* type) const;

  // Checks if the reader contains all the data about a tensor slice, and if
  // yes, copies the data of the slice to "data". The caller needs to make sure
  // that "data" points to a buffer that holds enough data.
  // This is a slow function since it needs to read sstables.
  template <typename T>
  bool CopySliceData(const string& name, const TensorSlice& slice,
                     T* data) const;

  // Get the tensors.
  const std::unordered_map<string, TensorSliceSet*>& Tensors() const {
    return tensors_;
  }

  // Returns value for one tensor. Only single slice checkpoints are supported
  // at the moment.
  Status GetTensor(const string& name,
                   std::unique_ptr<tensorflow::Tensor>* out_tensor) const;

  typedef std::unordered_map<string, TensorShape> VarToShapeMap;
  // Returns a map from tensor name to shape.
  VarToShapeMap GetVariableToShapeMap() const;

  // Returns a string containing names and shapes of all the tensors.
  const string DebugString() const;

 private:
  friend class TensorSliceWriteTestHelper;

  void LoadShard(int shard) const;
  void LoadAllShards() const;
  void RegisterTensorSlice(const string& name, const TensorShape& shape,
                           DataType type, const string& tag,
                           const TensorSlice& slice) const;

  const TensorSliceSet* FindTensorSlice(
      const string& name, const TensorSlice& slice,
      std::vector<std::pair<TensorSlice, string>>* details) const;

  const string filepattern_;
  const OpenTableFunction open_function_;
  std::vector<string> fnames_;
  std::unordered_map<string, int> fname_to_index_;

  // Guards the attributes below.
  mutable mutex mu_;
  mutable bool all_shards_loaded_ = false;
  mutable std::vector<std::unique_ptr<Table>> sss_;
  mutable std::unordered_map<string, TensorSliceSet*> tensors_;
  mutable Status status_;

  TF_DISALLOW_COPY_AND_ASSIGN(TensorSliceReader);
};

Status OpenTableTensorSliceReader(const string& fname,
                                  TensorSliceReader::Table** table);

template <typename T>
bool TensorSliceReader::CopySliceData(const string& name,
                                      const TensorSlice& slice, T* data) const {
  std::vector<std::pair<TensorSlice, string>> details;
  const TensorSliceSet* tss;
  {
    mutex_lock l(mu_);
    tss = FindTensorSlice(name, slice, &details);
    if (!tss && !all_shards_loaded_) {
      VLOG(1) << "Did not find slice in preferred shard, loading all shards."
              << name << ": " << slice.DebugString();
      LoadAllShards();
      tss = FindTensorSlice(name, slice, &details);
    }
    if (!tss) {
      // No such tensor
      return false;
    }
  }
  // We have the data -- copy it over.
  string value;
  for (const auto& x : details) {
    const TensorSlice& slice_s = x.first;
    const string& fname = x.second;
    int idx = gtl::FindWithDefault(fname_to_index_, fname, -1);
    CHECK_GE(idx, 0) << "Failed to find the index for filename " << fname;
    // We read a record in the corresponding sstable
    const string key = EncodeTensorNameSlice(name, slice_s);
    CHECK(sss_[idx]->Get(key, &value))
        << "Failed to seek to the record for tensor " << name << ", slice "
        << slice_s.DebugString() << ": computed key = " << key;
    SavedTensorSlices sts;
    CHECK(ParseProtoUnlimited(&sts, value))
        << "Failed to parse the record for tensor " << name << ", slice "
        << slice_s.DebugString() << ": computed key = " << key;
    CopyDataFromTensorSliceToTensorSlice(
        tss->shape(), slice_s, slice,
        checkpoint::TensorProtoData<T>(sts.data().data()), data);
  }
  return true;
}

}  // namespace checkpoint

}  // namespace tensorflow

#endif  // TENSORFLOW_UTIL_TENSOR_SLICE_READER_H_
