/* Copyright 2019 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.
==============================================================================*/

#ifndef TENSORFLOW_LITE_DELEGATES_GPU_GL_COMPILER_VARIABLE_ACCESSOR_H_
#define TENSORFLOW_LITE_DELEGATES_GPU_GL_COMPILER_VARIABLE_ACCESSOR_H_

#include <string>
#include <unordered_map>
#include <set>
#include <vector>

#include "tensorflow/lite/delegates/gpu/gl/compiler/preprocessor.h"
#include "tensorflow/lite/delegates/gpu/gl/variable.h"

namespace tflite {
namespace gpu {
namespace gl {

// This rewrite handles access to variables. It may rewrite a variable with
// actual values if 'inline_values' is set to true.
//
// The following syntax is supported to access variables:
//  - simple variable: name
//  - variable with field: name.(x|y|z|w)
//  - variable with index: name[i]
//  - variable with index and field: name[i].(x|y|z|w)
//
// If 'inline_values' is set to true, non-variable-length variables will be
// inlined. For example, 'base.x' will be replaced with value of 'x' field from
// 'base'. Variable-length variables are declared as const and accessed via
// index. These declarations are returned by GetConstDeclarations.
//
// If 'inline_values' is set to false, all variables will be declared as
// uniforms. Uniform declarations are returned by GetUniformDeclarations.
class VariableAccessor : public InlineRewrite {
 public:
  explicit VariableAccessor(bool inline_values)
      : inline_values_(inline_values) {}

  RewriteStatus Rewrite(absl::string_view input, std::string* output) final;

  // Returns true if variable was successfully added.
  bool AddSharedVariable(Variable&& variable);

  // Returns true if variable was successfully added.
  bool AddUniformParameter(Variable&& variable);

  // Returns const variables that need to be inlined in the a shader's code.
  std::string GetConstDeclarations() const;

  // Returns shared varaible declarations that need to be inlined.
  std::string GetSharedVariableDeclarations() const;

  // Returns uniform parameter declarations that need to be inlined.
  std::string GetUniformParameterDeclarations() const;

  // Returns a collection of uniform parameters.
  std::vector<Variable> GetUniformParameters() const;

 private:
  const bool inline_values_;
  std::unordered_map<std::string, Variable> name_to_variable_;
  std::set<std::string> shared_variables_;
  std::set<std::string> uniform_parameters_;
};

// Implementation details below.

namespace variable_accessor_internal {

struct VariableReference {
  absl::string_view name;
  absl::string_view index;
  absl::string_view field;
};

// Parse the following regex manually
// name(\[index\])?(\.field)?
VariableReference Parse(absl::string_view input);

}  // namespace variable_accessor_internal
}  // namespace gl
}  // namespace gpu
}  // namespace tflite

#endif  // TENSORFLOW_LITE_DELEGATES_GPU_GL_COMPILER_VARIABLE_ACCESSOR_H_
