/* Copyright 2017 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 THIRD_PARTY_STATUSOR_STATUS_MACROS_H_
#define THIRD_PARTY_STATUSOR_STATUS_MACROS_H_

#include <memory>
#include <ostream>  // NOLINT
#include <sstream>
#include <string>
#include <utility>
#include <vector>

#include "third_party/statusor/statusor.h"

namespace statusor {
namespace status_macros {

using cobalt::util::Status;

// Stream object used to collect error messages in MAKE_ERROR macros
// or append error messages with APPEND_ERROR.  It accepts any
// arguments with operator<< to build an error string, and then has an
// implicit cast operator to Status, which converts the
// logged string to a Status object and returns it, after logging the
// error.  At least one call to operator<< is required; a compile time
// error will be generated if none are given. Errors will only be
// logged by default for certain status codes, as defined in
// IsLoggedByDefault. This class will give ERROR errors if you don't
// retrieve a Status exactly once before destruction.
//
// The class converts into an intermediate wrapper object
// MakeErrorStreamWithOutput to check that the error stream gets at least one
// item of input.
class MakeErrorStream {
 public:
  // Wrapper around MakeErrorStream that only allows for output. This
  // is created as output of the first operator<< call on
  // MakeErrorStream. The bare MakeErrorStream does not have a
  // Status operator. The net effect of that is that you
  // have to call operator<< at least once or else you'll get a
  // compile time error.
  class MakeErrorStreamWithOutput {
   public:
    explicit MakeErrorStreamWithOutput(MakeErrorStream* error_stream)
        : wrapped_error_stream_(error_stream) {}

    template <typename T>
    MakeErrorStreamWithOutput& operator<<(const T& value) {
      *wrapped_error_stream_ << value;
      return *this;
    }

    // Implicit cast operators to Status and StatusOr.
    // Exactly one of these must be called exactly once before destruction.
    operator Status() { return wrapped_error_stream_->GetStatus(); }
    template <typename T>
    operator StatusOr<T>() {
      return wrapped_error_stream_->GetStatus();
    }

   private:
    MakeErrorStream* wrapped_error_stream_;
  };

  // When starting from an existing error status, this determines whether we'll
  // append or prepend to that status's error message.
  enum PriorMessageHandling { kAppendToPriorMessage, kPrependToPriorMessage };

  // Make an error with the given code.
  template <typename ERROR_CODE_TYPE>
  MakeErrorStream(const char* file, int line, ERROR_CODE_TYPE code)
      : impl_(new Impl(file, line, code, this, true)) {}

  template <typename T>
  MakeErrorStreamWithOutput& operator<<(const T& value) {
    CheckNotDone();
    impl_->stream_ << value;
    return impl_->make_error_stream_with_output_wrapper_;
  }

  // When this message is logged (see with_logging()), include the stack trace.
  MakeErrorStream& with_log_stack_trace() {
    impl_->should_log_stack_trace_ = true;
    return *this;
  }

  // Adds RET_CHECK failure text to error message.
  MakeErrorStreamWithOutput& add_ret_check_failure(const char* condition) {
    return *this << "RET_CHECK failure (" << impl_->file_ << ":" << impl_->line_
                 << ") " << condition << " ";
  }

 private:
  class Impl {
   public:
    Impl(const char* file, int line, cobalt::util::StatusCode code,
         MakeErrorStream* error_stream, bool is_logged_by_default = true);
    Impl(const Status& status, PriorMessageHandling prior_message_handling,
         const char* file, int line, MakeErrorStream* error_stream);

    ~Impl();

    // This must be called exactly once before destruction.
    Status GetStatus();

    void CheckNotDone() const;

   private:
    const char* file_;
    int line_;
    cobalt::util::StatusCode code_;

    PriorMessageHandling prior_message_handling_ = kAppendToPriorMessage;
    std::string prior_message_;
    bool is_done_;  // true after Status object has been returned
    std::ostringstream stream_;
    bool should_log_;
    int log_severity_;
    bool should_log_stack_trace_;

    // Wrapper around the MakeErrorStream object that has a
    // Status conversion. The first << operator called on
    // MakeErrorStream will return this object, and only this object
    // can implicitly convert to Status. The net effect of
    // this is that you'll get a compile time error if you call
    // MAKE_ERROR etc. without adding any output.
    MakeErrorStreamWithOutput make_error_stream_with_output_wrapper_;

    friend class MakeErrorStream;
  };

  void CheckNotDone() const;

  // Returns the status. Used by MakeErrorStreamWithOutput.
  Status GetStatus() const { return impl_->GetStatus(); }

  // Store the actual data on the heap to reduce stack frame sizes.
  std::unique_ptr<Impl> impl_;
};

// Provides a conversion to bool so that it can be used inside an if statement
// that declares a variable.
class StatusAdaptorForMacros {
 public:
  explicit StatusAdaptorForMacros(Status status) : status_(std::move(status)) {}

  StatusAdaptorForMacros(const StatusAdaptorForMacros&) = delete;
  StatusAdaptorForMacros& operator=(const StatusAdaptorForMacros&) = delete;

  explicit operator bool() const { return status_.ok(); }

  Status&& Consume() { return std::move(status_); }

 private:
  Status status_;
};

}  // namespace status_macros
}  // namespace statusor

#define CB_RET_CHECK(condition)                                            \
  while (!(condition))                                                     \
  return util::status_macros::MakeErrorStream(__FILE__, __LINE__,          \
                                              tensorflow::error::INTERNAL) \
      .with_log_stack_trace()                                              \
      .add_ret_check_failure(#condition)

#define CB_ASSERT_OK_AND_ASSIGN(lhs, rexpr)                             \
  CB_ASSERT_OK_AND_ASSIGN_IMPL(                                         \
      CB_STATUS_MACROS_CONCAT_NAME(_status_or_value, __COUNTER__), lhs, \
      rexpr);

#define CB_ASSERT_OK_AND_ASSIGN_IMPL(statusor, lhs, rexpr)  \
  auto statusor = (rexpr);                                  \
  ASSERT_TRUE(statusor.status().ok()) << statusor.status(); \
  lhs = std::move(statusor.ValueOrDie())

#define CB_STATUS_MACROS_CONCAT_NAME(x, y) CB_STATUS_MACROS_CONCAT_IMPL(x, y)
#define CB_STATUS_MACROS_CONCAT_IMPL(x, y) x##y

#define CB_ASSIGN_OR_RETURN(lhs, rexpr) \
  CB_ASSIGN_OR_RETURN_IMPL(             \
      CB_STATUS_MACROS_CONCAT_NAME(_status_or_value, __COUNTER__), lhs, rexpr)

#define CB_ASSIGN_OR_RETURN_IMPL(statusor, lhs, rexpr) \
  auto statusor = (rexpr);                             \
  if (!statusor.ok()) {                                \
    return statusor.status();                          \
  }                                                    \
  lhs = std::move(statusor.ValueOrDie())

#endif  // THIRD_PARTY_STATUSOR_STATUS_MACROS_H_