/* Copyright 2015 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 "tensorflow/python/framework/python_op_gen.h"

#include <stdio.h>
#include <sstream>
#include <unordered_map>
#include "tensorflow/core/framework/attr_value.pb.h"
#include "tensorflow/core/framework/op.h"
#include "tensorflow/core/framework/op_def.pb_text.h"
#include "tensorflow/core/framework/op_def.pb.h"
#include "tensorflow/core/framework/op_def_util.h"
#include "tensorflow/core/framework/op_gen_lib.h"
#include "tensorflow/core/framework/tensor.pb_text.h"
#include "tensorflow/core/framework/tensor.pb.h"
#include "tensorflow/core/framework/tensor_shape.pb.h"
#include "tensorflow/core/framework/types.h"
#include "tensorflow/core/framework/types.pb.h"
#include "tensorflow/core/lib/gtl/map_util.h"
#include "tensorflow/core/lib/gtl/stl_util.h"
#include "tensorflow/core/lib/strings/str_util.h"
#include "tensorflow/core/lib/strings/strcat.h"
#include "tensorflow/core/lib/strings/stringprintf.h"
#include "tensorflow/core/platform/logging.h"
#include "tensorflow/core/platform/macros.h"
#include "tensorflow/core/platform/types.h"
#include "tensorflow/python/framework/python_op_gen_internal.h"

namespace tensorflow {
namespace python_op_gen_internal {

const int kRightMargin = 78;

bool IsPythonReserved(const string& s) {
  static const std::set<string>* const kPythonReserved = new std::set<string>(
      {// Keywords in Python, from:
       //   import keyword
       //   print keyword.kwlist
       "and", "as", "assert", "break", "class", "continue", "def", "del",
       "elif", "else", "except", "exec", "finally", "for", "from", "global",
       "if", "import", "in", "is", "lambda", "not", "or", "pass", "print",
       "raise", "return", "try", "while", "with", "yield",
       // Built-in functions and types in Python, from:
       //   [x for x in dir(__builtins__) if not x[0].islower()]
       "ArithmeticError", "AssertionError", "AttributeError", "BaseException",
       "BufferError", "BytesWarning", "DeprecationWarning", "EOFError",
       "Ellipsis", "EnvironmentError", "Exception", "False",
       "FloatingPointError", "FutureWarning", "GeneratorExit", "IOError",
       "ImportError", "ImportWarning", "IndentationError", "IndexError",
       "KeyError", "KeyboardInterrupt", "LookupError", "MemoryError",
       "NameError", "None", "NotImplemented", "NotImplementedError", "OSError",
       "OverflowError", "PendingDeprecationWarning", "ReferenceError",
       "RuntimeError", "RuntimeWarning", "StandardError", "StopIteration",
       "SyntaxError", "SyntaxWarning", "SystemError", "SystemExit", "TabError",
       "True", "TypeError", "UnboundLocalError", "UnicodeDecodeError",
       "UnicodeEncodeError", "UnicodeError", "UnicodeTranslateError",
       "UnicodeWarning", "UserWarning", "ValueError", "Warning",
       "ZeroDivisionError", "__debug__", "__doc__", "__import__", "__name__",
       "__package__"});

  return kPythonReserved->count(s) > 0;
}

string AvoidPythonReserved(const string& s) {
  if (IsPythonReserved(s)) return strings::StrCat(s, "_");
  return s;
}

// Indent the first line by "initial" spaces and all following lines
// by "rest" spaces.
string Indent(int initial, int rest, StringPiece in) {
  // TODO(josh11b): Also word-wrapping?
  string copy(in.data(), in.size());
  str_util::StripTrailingWhitespace(&copy);
  std::vector<string> v = str_util::Split(copy, '\n');

  string result;
  bool first = true;
  for (const string& line : v) {
    if (first) {
      result = strings::StrCat(Spaces(initial), line, "\n");
      first = false;
    } else {
      if (line.empty()) {
        strings::StrAppend(&result, "\n");
      } else {
        strings::StrAppend(&result, Spaces(rest), line, "\n");
      }
    }
  }
  return result;
}

// Adds append to *dest, with a space if the first line will be <= width,
// or a newline otherwise.
void AppendWithinWidth(string* dest, StringPiece append, int width) {
  auto first_line = append.find('\n');
  if (first_line == string::npos) first_line = append.size();
  if (dest->size() + first_line + 1 /* space */ > static_cast<size_t>(width)) {
    strings::StrAppend(dest, "\n", append);
  } else {
    strings::StrAppend(dest, " ", append);
  }
}

// Like DataTypeString() but uses the Python names for the
// float types.
string PythonDataTypeString(DataType dtype) {
  switch (dtype) {
    case DT_FLOAT:
      return "float32";
    case DT_DOUBLE:
      return "float64";
    default:
      return DataTypeString(dtype);
  }
}

string TypeString(DataType dtype, bool ref) {
  if (ref) {
    return strings::StrCat("mutable `", PythonDataTypeString(dtype), "`");
  } else {
    return strings::StrCat("`", PythonDataTypeString(dtype), "`");
  }
}

string TypeListString(const AttrValue& value) {
  string ret;
  for (int t : value.list().type()) {
    if (!ret.empty()) strings::StrAppend(&ret, ", ");
    DataType dtype = static_cast<DataType>(t);
    if (IsRefType(dtype)) {
      strings::StrAppend(&ret, PythonDataTypeString(RemoveRefType(dtype)),
                         " mutable");
    } else {
      strings::StrAppend(&ret, "`", PythonDataTypeString(dtype), "`");
    }
  }
  return ret;
}

string SingleTensorName(DataType dtype, bool is_ref) {
  const string type_str = TypeString(dtype, is_ref);
  return strings::StrCat("A `Tensor` of type ", type_str, ".");
}

const char kUnknownTensorType[] = {"A `Tensor`."};

string ArgTypeName(const OpDef& op_def, const OpDef::ArgDef& arg,
                   const std::unordered_map<string, string>& inferred_attrs,
                   bool is_output) {
  if (!arg.number_attr().empty()) {
    // N Tensors with the same type
    const string* original_arg =
        gtl::FindOrNull(inferred_attrs, arg.number_attr());
    string prefix;
    if (original_arg == nullptr) {
      prefix = strings::StrCat("A list of `", arg.number_attr(), "`");
    } else if (*original_arg == arg.name()) {
      const OpDef::AttrDef* attr = FindAttr(arg.number_attr(), op_def);
      if (attr->has_minimum() && attr->minimum() > 0) {
        prefix = strings::StrCat("A list of at least ", attr->minimum());
      } else {
        prefix = "A list of";
      }
    } else {
      prefix = strings::StrCat("A list with the same length as `",
                               AvoidPythonReserved(*original_arg), "` of");
    }

    if (arg.type() != DT_INVALID) {
      return strings::StrCat(prefix, " `Tensor` objects with type ",
                             TypeString(arg.type(), arg.is_ref()), ".");
    } else {
      original_arg = gtl::FindOrNull(inferred_attrs, arg.type_attr());
      if (arg.is_ref()) {
        strings::StrAppend(&prefix, " mutable");
      }
      if (original_arg == nullptr) {
        return strings::StrCat(prefix, " `Tensor` objects with type `",
                               arg.type_attr(), "`.");
      } else if (*original_arg == arg.name()) {
        const OpDef::AttrDef* attr = FindAttr(arg.type_attr(), op_def);
        if (attr->has_allowed_values()) {
          return strings::StrCat(prefix,
                                 " `Tensor` objects with the same type in: ",
                                 TypeListString(attr->allowed_values()), ".");
        } else {
          return strings::StrCat(prefix,
                                 " `Tensor` objects with the same type.");
        }
      } else {
        return strings::StrCat(prefix,
                               " `Tensor` objects with the same type as `",
                               AvoidPythonReserved(*original_arg), "`.");
      }
    }
  } else if (!arg.type_attr().empty() || !arg.type_list_attr().empty()) {
    const bool is_list = !arg.type_list_attr().empty();
    const string attr_name = is_list ? arg.type_list_attr() : arg.type_attr();
    const OpDef::AttrDef* attr = FindAttr(attr_name, op_def);
    const string mutable_str = arg.is_ref() ? "mutable " : "";
    const string prefix =
        is_list ? strings::StrCat("A list of ", mutable_str, "`Tensor` objects")
                : strings::StrCat("A ", mutable_str, "`Tensor`");
    const string* original_arg = gtl::FindOrNull(inferred_attrs, attr_name);
    if (original_arg == nullptr) {
      return strings::StrCat(prefix, " of type `", attr_name, "`.");
    } else if (*original_arg == arg.name()) {
      if (attr->has_allowed_values()) {
        if (is_list) {
          return strings::StrCat(prefix, " with types from: ",
                                 TypeListString(attr->allowed_values()), ".");
        } else {
          return strings::StrCat(
              prefix, is_output ? ". Has one of the following types: "
                                : ". Must be one of the following types: ",
              TypeListString(attr->allowed_values()), ".");
        }
      } else {
        return strings::StrCat(prefix, ".");
      }
    } else {
      return strings::StrCat(prefix,
                             is_output ? ". Has the same type as `"
                                       : ". Must have the same type as `",
                             AvoidPythonReserved(*original_arg), "`.");
    }
  } else {
    return SingleTensorName(arg.type(), arg.is_ref());
  }
}

string GetReturns(const OpDef& op_def,
                  const std::vector<string>& output_type_string) {
  string result;
  DCHECK_EQ(op_def.output_arg_size(), output_type_string.size());
  const int num_outs = op_def.output_arg_size();
  strings::StrAppend(&result, "\n  Returns:\n");
  if (num_outs == 0) {
    strings::StrAppend(&result, "    The created Operation.\n");
  } else {
    if (num_outs == 1) {
      StringPiece description = op_def.output_arg(0).description();
      if (ConsumeEquals(&description)) {  // Skip the generated type info.
        strings::StrAppend(&result, Indent(4, 4, description));
      } else {
        // Special case of one output, don't use the name of the output unless
        // there is no description.
        string desc = output_type_string.empty() ? kUnknownTensorType
                                                 : output_type_string[0];
        if (desc == kUnknownTensorType) {
          // Special case where we don't understand how the output tensor type
          // depends on the input tensor types, just use the output arg
          // description if we can.
          if (!description.empty()) {
            desc = op_def.output_arg(0).description();
          } else if (!op_def.output_arg(0).name().empty()) {
            desc = strings::StrCat(" The ", op_def.output_arg(0).name(),
                                   " `Tensor`.");
          }
        } else if (!description.empty()) {
          AppendWithinWidth(&desc, description, kRightMargin - 4 /* indent */);
        }
        strings::StrAppend(&result, Indent(4, 4, desc));
      }
    } else {
      std::vector<string> out_names(num_outs);
      for (int i = 0; i < num_outs; ++i) {
        if (!op_def.output_arg(i).name().empty()) {
          out_names[i] = op_def.output_arg(i).name();
        } else {
          out_names[i] = strings::StrCat("output", i);
        }
      }
      strings::StrAppend(&result, "    A tuple of `Tensor` objects (",
                         str_util::Join(out_names, ", "), ").\n\n");
      for (int i = 0; i < num_outs; ++i) {
        string desc = strings::StrCat(out_names[i], ": ");
        StringPiece description = op_def.output_arg(i).description();
        if (ConsumeEquals(&description)) {  // Skip the generated type info.
          strings::StrAppend(&desc, description);
        } else {
          const string type = static_cast<size_t>(i) < output_type_string.size()
                                  ? output_type_string[i]
                                  : kUnknownTensorType;
          if (!description.empty()) {
            if (type == kUnknownTensorType) {
              // Special case where we don't understand how the output tensor
              // type depends on the input tensor types, so we just use the
              // output arg description.
              strings::StrAppend(&desc, description);
            } else {
              strings::StrAppend(&desc, type, " ", description);
            }
          } else {
            strings::StrAppend(&desc, type);
          }
        }
        strings::StrAppend(&result, Indent(4, 6, desc));
      }
    }
  }
  return result;
}

string StringToPython(const string& str) {
  return strings::StrCat("\"", str_util::CEscape(str), "\"");
}

string DataTypeToPython(DataType dtype, const string& dtype_module) {
  return strings::StrCat(dtype_module, PythonDataTypeString(dtype));
}

string ShapeToPython(const TensorShapeProto& shape) {
  string python = "[";
  for (const auto& dim : shape.dim()) {
    if (python.size() > 1) strings::StrAppend(&python, ", ");
    if (!dim.name().empty()) {
      strings::StrAppend(&python, "(", StringToPython(dim.name()), ", ",
                         dim.size(), ")");
    } else {
      strings::StrAppend(&python, dim.size());
    }
  }
  strings::StrAppend(&python, "]");
  return python;
}

string TensorToPython(const TensorProto& proto) {
  return ProtoShortDebugString(proto);
}

string AttrListToPython(const AttrValue& value,
                        const string& dtype_module = "tf.") {
  string ret;
  if (value.list().s_size() > 0) {
    for (int i = 0; i < value.list().s_size(); ++i) {
      if (i > 0) strings::StrAppend(&ret, ", ");
      strings::StrAppend(&ret, StringToPython(value.list().s(i)));
    }
  } else if (value.list().i_size() > 0) {
    for (int i = 0; i < value.list().i_size(); ++i) {
      if (i > 0) strings::StrAppend(&ret, ", ");
      strings::StrAppend(&ret, value.list().i(i));
    }
  } else if (value.list().f_size() > 0) {
    for (int i = 0; i < value.list().f_size(); ++i) {
      if (i > 0) strings::StrAppend(&ret, ", ");
      strings::StrAppend(&ret, value.list().f(i));
    }
  } else if (value.list().b_size() > 0) {
    for (int i = 0; i < value.list().b_size(); ++i) {
      if (i > 0) strings::StrAppend(&ret, ", ");
      strings::StrAppend(&ret, value.list().b(i) ? "True" : "False");
    }
  } else if (value.list().type_size() > 0) {
    for (int i = 0; i < value.list().type_size(); ++i) {
      if (i > 0) strings::StrAppend(&ret, ", ");
      strings::StrAppend(&ret,
                         DataTypeToPython(value.list().type(i), dtype_module));
    }
  } else if (value.list().shape_size() > 0) {
    for (int i = 0; i < value.list().shape_size(); ++i) {
      if (i > 0) strings::StrAppend(&ret, ", ");
      strings::StrAppend(&ret, ShapeToPython(value.list().shape(i)));
    }
  } else if (value.list().tensor_size() > 0) {
    for (int i = 0; i < value.list().tensor_size(); ++i) {
      if (i > 0) strings::StrAppend(&ret, ", ");
      strings::StrAppend(&ret, TensorToPython(value.list().tensor(i)));
    }
  } else if (value.list().func_size() > 0) {
    for (int i = 0; i < value.list().func_size(); ++i) {
      if (i > 0) strings::StrAppend(&ret, ", ");
      strings::StrAppend(&ret, StringToPython(value.list().func(i).name()));
    }
  }
  return ret;
}

string AttrValueToPython(const string& type, const AttrValue& value,
                         const string& dtype_module) {
  if (type == "string") {
    return StringToPython(value.s());
  } else if (type == "int") {
    return strings::StrCat(value.i());
  } else if (type == "float") {
    return strings::StrCat(value.f());
  } else if (type == "bool") {
    return value.b() ? "True" : "False";
  } else if (type == "type") {
    return DataTypeToPython(value.type(), dtype_module);
  } else if (type == "shape") {
    return ShapeToPython(value.shape());
  } else if (type == "tensor") {
    return TensorToPython(value.tensor());
  } else if (type == "func") {
    return StringToPython(value.func().name());
  } else if (StringPiece(type).starts_with("list(")) {
    return strings::StrCat("[", AttrListToPython(value, dtype_module), "]");
  } else {
    return "?";
  }
}

void GenerateLowerCaseOpName(const string& str, string* result) {
  const char joiner = '_';
  const int last_index = str.size() - 1;
  for (int i = 0; i <= last_index; ++i) {
    const char c = str[i];
    // Emit a joiner only if a previous-lower-to-now-upper or a
    // now-upper-to-next-lower transition happens.
    if (isupper(c) && (i > 0)) {
      if (islower(str[i - 1]) || ((i < last_index) && islower(str[i + 1]))) {
        result->push_back(joiner);
      }
    }
    result->push_back(tolower(c));
  }
}

static void AddDelimiter(string* append_to, const string& delim) {
  if (!append_to->empty()) strings::StrAppend(append_to, delim);
}

GenPythonOp::GenPythonOp(const OpDef& op_def, const string& function_name)
    : op_def_(op_def),
      function_name_(function_name),
      num_outs_(op_def.output_arg_size()) {}

GenPythonOp::~GenPythonOp() {}

string GenPythonOp::Code() {
  // This has all the input args followed by those attrs that don't have
  // defaults.
  std::vector<string> args_no_default;
  // The parameters with defaults (these have to be listed after those without).
  // No input args are included, just attrs.
  std::vector<string> args_with_defaults;
  for (int i = 0; i < op_def_.input_arg_size(); ++i) {
    const auto& arg(op_def_.input_arg(i));
    args_no_default.push_back(arg.name());
    if (!arg.type_attr().empty()) {
      gtl::InsertIfNotPresent(&inferred_attrs_, arg.type_attr(), arg.name());
    } else if (!arg.type_list_attr().empty()) {
      gtl::InsertIfNotPresent(&inferred_attrs_, arg.type_list_attr(),
                              arg.name());
    }
    if (!arg.number_attr().empty()) {
      gtl::InsertIfNotPresent(&inferred_attrs_, arg.number_attr(), arg.name());
    }
  }
  for (int i = 0; i < op_def_.attr_size(); ++i) {
    const auto& attr(op_def_.attr(i));
    // Do not add inferred attrs to the Python function signature.
    if (inferred_attrs_.find(attr.name()) == inferred_attrs_.end()) {
      if (attr.has_default_value()) {
        args_with_defaults.push_back(attr.name());
      } else {
        args_no_default.push_back(attr.name());
      }
    }
  }

  // Save the list of attr parameters (attrs that won't be inferred),
  // those with defaults go at the end.
  // Get the attrs in the order we want by taking the attrs without defaults
  // from the end of args_no_default, and adding args_no_default.
  attrs_.reserve(args_no_default.size() - op_def_.input_arg_size() +
                 args_with_defaults.size());
  attrs_.insert(attrs_.end(),
                args_no_default.begin() + op_def_.input_arg_size(),
                args_no_default.end());
  attrs_.insert(attrs_.end(), args_with_defaults.begin(),
                args_with_defaults.end());

  param_names_.reserve(args_no_default.size() + args_with_defaults.size());
  string parameters;
  for (const string& name : args_no_default) {
    AddDelimiter(&parameters, ", ");
    const string param = AvoidPythonReserved(name);
    strings::StrAppend(&parameters, param);
    param_names_.push_back(param);
  }
  for (const string& name : args_with_defaults) {
    AddDelimiter(&parameters, ", ");
    const string param = AvoidPythonReserved(name);
    strings::StrAppend(&parameters, param, "=None");
    param_names_.push_back(param);
  }
  AddDelimiter(&parameters, ", ");
  strings::StrAppend(&parameters, "name=None");

  AddDefLine(parameters);
  AddDocStringDescription();
  AddDocStringArgs();
  AddDocStringInputs();
  AddDocStringAttrs();
  AddDocStringNameArg();
  AddOutputGlobals();
  AddDocStringOutputs();
  strings::StrAppend(&result_, "  \"\"\"\n");
  AddBody("  ");
  strings::StrAppend(&result_, "\n\n");

  return prelude_ + result_;
}

void GenPythonOp::AddDefLine(const string& parameters) {
  const string def_prefix = strings::StrCat("def ", function_name_, "(");
  strings::StrAppend(
      &result_, WordWrap(def_prefix, parameters + "):", kRightMargin), "\n");
}

void GenPythonOp::AddDocStringDescription() {
  string comment;
  if (op_def_.summary().empty()) {
    comment = "TODO: add doc.\n";
  } else {
    comment = strings::StrCat(op_def_.summary(), "\n");
    if (!op_def_.description().empty()) {
      strings::StrAppend(&comment, "\n", Indent(2, 2, op_def_.description()));
    }
  }
  strings::StrAppend(&result_, "  r\"\"\"", comment, "\n");
}

void GenPythonOp::AddDocStringArgs() {
  strings::StrAppend(&result_, "  Args:\n");
}

void GenPythonOp::AddDocStringInputs() {
  for (int i = 0; i < op_def_.input_arg_size(); ++i) {
    const auto& arg(op_def_.input_arg(i));
    StringPiece description = op_def_.input_arg(i).description();
    string desc;
    if (ConsumeEquals(&description)) {  // Skip the generated type info.
      desc = strings::StrCat(param_names_[i], ": ");
    } else {
      desc = strings::StrCat(param_names_[i], ": ",
                             ArgTypeName(op_def_, arg, inferred_attrs_, false));
    }
    if (!description.empty()) {
      AppendWithinWidth(&desc, description, kRightMargin - 4 /* indent */);
    }
    strings::StrAppend(&result_, Indent(4, 6, desc));
  }
}

void GenPythonOp::AddDocStringAttrs() {
  for (const string& name : attrs_) {
    const auto& attr = *FindAttr(name, op_def_);
    string desc = strings::StrCat(AvoidPythonReserved(name), ": ");

    static const char* const kAttrTypeName[][2] = {
        {"string", "`string`"},
        {"list(string)", "list of `strings`"},
        {"int", "`int`"},
        {"list(int)", "list of `ints`"},
        {"float", "`float`"},
        {"list(float)", "list of `floats`"},
        {"bool", "`bool`"},
        {"list(bool)", "list of `bools`"},
        {"type", "`tf.DType`"},
        {"list(type)", "list of `tf.DTypes`"},
        {"shape", "`tf.TensorShape` or list of `ints`"},
        {"list(shape)",
         "list of shapes (each a `tf.TensorShape` or list of `ints`)"},
        {"tensor", "`tf.TensorProto`"},
        {"list(tensor)", "list of `tf.TensorProto` objects"},
        {"func", "function decorated with @Defun"},
        {"list(func)", "list of functions decorated with @Defun"},
    };
    for (size_t i = 0; i < TF_ARRAYSIZE(kAttrTypeName); ++i) {
      if (attr.type() == kAttrTypeName[i][0]) {
        string s;
        if (attr.has_default_value()) {
          s = strings::StrCat("optional ", kAttrTypeName[i][1]);
        } else {
          s = kAttrTypeName[i][1];
        }
        if (s[0] == 'o' || (s[0] == '`' && (s[1] == 'i' || s[1] == 'o'))) {
          strings::StrAppend(&desc, "An ", s);
        } else {
          strings::StrAppend(&desc, "A ", s);
        }
        break;
      }
    }

    if (attr.has_allowed_values()) {
      strings::StrAppend(&desc, " from: `",
                         AttrListToPython(attr.allowed_values()), "`");
    }

    if (attr.has_minimum()) {
      if (attr.type() == "int") {
        strings::StrAppend(&desc, " that is `>= ", attr.minimum(), "`");
      } else if (attr.minimum() > 0) {
        strings::StrAppend(&desc, " that has length `>= ", attr.minimum(), "`");
      }
    }

    strings::StrAppend(&desc, ".");

    if (attr.has_default_value()) {
      strings::StrAppend(&desc, " Defaults to `",
                         AttrValueToPython(attr.type(), attr.default_value()),
                         "`.");
    }

    if (!attr.description().empty()) {
      AppendWithinWidth(&desc, attr.description(),
                        kRightMargin - 4 /* indent */);
    }
    strings::StrAppend(&result_, Indent(4, 6, desc));
  }
}

void GenPythonOp::AddDocStringNameArg() {
  strings::StrAppend(&result_,
                     "    name: A name for the operation (optional).\n");
}

void GenPythonOp::AddOutputGlobals() {
  // Prepare a NamedTuple type to hold the outputs, if there are multiple
  if (num_outs_ > 1) {
    // Prepare the list of output names
    std::vector<string> out_names(num_outs_);
    for (int i = 0; i < num_outs_; ++i) {
      if (!op_def_.output_arg(i).name().empty()) {
        out_names[i] = op_def_.output_arg(i).name();
      } else {
        out_names[i] = strings::StrCat("output", i);
      }
    }
    string out_names_list =
        strings::StrCat("[\"", str_util::Join(out_names, "\", \""), "\"]");

    // Provide the output names as a Python list
    string lower_op_name_outputs =
        strings::StrCat("_", function_name_, "_outputs");
    const string outputs_prefix = strings::StrCat(lower_op_name_outputs, " = ");
    strings::StrAppend(&prelude_, "\n",
                       WordWrap(outputs_prefix, out_names_list, kRightMargin),
                       "\n");

    strings::StrAppend(&prelude_, "_", op_def_.name(),
                       "Output = _collections.namedtuple(\n");
    const string tuple_type_prefix = "    ";
    const string tuple_type_suffix = strings::StrCat(
        "\"", op_def_.name(), "\", ", lower_op_name_outputs, ")");
    strings::StrAppend(
        &prelude_, WordWrap(tuple_type_prefix, tuple_type_suffix, kRightMargin),
        "\n\n");
  }
  strings::StrAppend(&prelude_, "\n");
}

void GenPythonOp::AddDocStringOutputs() {
  std::vector<string> output_type_string;
  output_type_string.reserve(num_outs_);
  for (int i = 0; i < num_outs_; ++i) {
    output_type_string.push_back(
        ArgTypeName(op_def_, op_def_.output_arg(i), inferred_attrs_, true));
  }
  strings::StrAppend(&result_, GetReturns(op_def_, output_type_string));
}

void GenPythonOp::AddBody(const string& prefix) {
  string return_prefix =
      strings::StrCat(prefix, "result = _op_def_lib.apply_op(");
  string return_args = strings::StrCat("\"", op_def_.name(), "\", ");
  for (size_t i = 0; i < param_names_.size(); ++i) {
    strings::StrAppend(&return_args, param_names_[i], "=", param_names_[i],
                       ", ");
  }
  strings::StrAppend(&return_args, "name=name)");

  strings::StrAppend(&result_,
                     // Wrap the arguments, and indent to the (.
                     WordWrap(return_prefix, return_args, kRightMargin), "\n");

  if (num_outs_ <= 1) {
    strings::StrAppend(&result_, prefix, "return result\n");
  } else {
    strings::StrAppend(&result_, prefix, "return _", op_def_.name(),
                       "Output._make(result)\n");
  }
}

}  // namespace python_op_gen_internal

string GetPythonOp(const OpDef& op_def, const string& function_name) {
  return python_op_gen_internal::GenPythonOp(op_def, function_name).Code();
}

string GetPythonOps(const OpList& ops, const std::vector<string>& hidden_ops,
                    bool require_shapes) {
  string result;
  // Header
  // TODO(josh11b): Mention the library for which wrappers are being generated.
  strings::StrAppend(&result, R"("""Python wrappers around TensorFlow ops.

This file is MACHINE GENERATED! Do not edit.
"""

import collections as _collections

from tensorflow.core.framework import op_def_pb2 as _op_def_pb2

# Needed to trigger the call to _set_call_cpp_shape_fn.
from tensorflow.python.framework import common_shapes as _common_shapes

from tensorflow.python.framework import op_def_registry as _op_def_registry
from tensorflow.python.framework import ops as _ops
from tensorflow.python.framework import op_def_library as _op_def_library
)");

  // We'll make a copy of ops that filters out descriptions.
  OpList cleaned_ops;
  auto out = cleaned_ops.mutable_op();
  out->Reserve(ops.op_size());
  for (const auto& op_def : ops.op()) {
    bool is_hidden = false;
    for (const string& hidden : hidden_ops) {
      if (op_def.name() == hidden) {
        is_hidden = true;
        break;
      }
    }

    string function_name;
    python_op_gen_internal::GenerateLowerCaseOpName(op_def.name(),
                                                    &function_name);
    if (is_hidden) function_name = strings::StrCat("_", function_name);

    // When users create custom python wrappers, they may link in the
    // default op registry by accident, and because they can't
    // enumerate all 'hidden' symbols, this guard is to prevent
    // instantiating a python reserved word in their wrapper.
    if (python_op_gen_internal::IsPythonReserved(function_name)) {
      continue;
    }

    strings::StrAppend(&result, GetPythonOp(op_def, function_name));

    if (!require_shapes) {
      strings::StrAppend(&result, "_ops.RegisterShape(\"", op_def.name(),
                         "\")(None)\n");
    }

    auto added = out->Add();
    *added = op_def;
    RemoveNonDeprecationDescriptionsFromOpDef(added);
  }

  result.append(R"(def _InitOpDefLibrary(op_list_proto_bytes):
  op_list = _op_def_pb2.OpList()
  op_list.ParseFromString(op_list_proto_bytes)
  _op_def_registry.register_op_list(op_list)
  op_def_lib = _op_def_library.OpDefLibrary()
  op_def_lib.add_op_list(op_list)
  return op_def_lib


)");

  result.append("# ");
  auto ops_text = ProtoDebugString(cleaned_ops);
  str_util::StripTrailingWhitespace(&ops_text);
  result.append(str_util::StringReplace(ops_text, "\n", "\n# ", true));
  result.append("\n");
  strings::Appendf(&result, "_op_def_lib = _InitOpDefLibrary(b\"%s\")\n",
                   str_util::CEscape(cleaned_ops.SerializeAsString()).c_str());
  return result;
}

void PrintPythonOps(const OpList& ops, const std::vector<string>& hidden_ops,
                    bool require_shapes) {
  printf("%s", GetPythonOps(ops, hidden_ops, require_shapes).c_str());
}

string GetPythonWrappers(const char* op_list_buf, size_t op_list_len) {
  string op_list_str(op_list_buf, op_list_len);
  OpList ops;
  ops.ParseFromString(op_list_str);
  return GetPythonOps(ops, {}, false);
}

}  // namespace tensorflow
