// Copyright 2019 Google LLC
//
// 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 DARWINN_PORT_DEFAULT_STATUS_MACROS_H_
#define DARWINN_PORT_DEFAULT_STATUS_MACROS_H_

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

#include "port/default/error_codes.h"
#include "port/default/logging.h"
#include "port/default/macros.h"
#include "port/default/status.h"
#include "port/default/statusor.h"

namespace platforms {
namespace darwinn {
namespace status_macros {

// 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 DFATAL 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_;

    DISALLOW_COPY_AND_ASSIGN(MakeErrorStreamWithOutput);
  };

  // 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, error::Code 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_;
    error::Code 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;
    DISALLOW_COPY_AND_ASSIGN(Impl);
  };

  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_;

  DISALLOW_COPY_AND_ASSIGN(MakeErrorStream);
};

// 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 PREDICT_TRUE(status_.ok()); }

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

 private:
  Status status_;
};

}  // namespace status_macros
}  // namespace darwinn
}  // namespace platforms

#define RET_CHECK(condition)                                            \
  while (PREDICT_FALSE(!(condition)))                                   \
  return ::platforms::darwinn::status_macros::MakeErrorStream(          \
             __FILE__, __LINE__, ::platforms::darwinn::error::INTERNAL) \
      .with_log_stack_trace()                                           \
      .add_ret_check_failure(#condition)

#define ASSIGN_OR_ASSERT_OK(lhs, rexpr) \
  ASSIGN_OR_ASSERT_OK_IMPL(             \
      STATUS_MACROS_CONCAT_NAME(_status_or_value, __COUNTER__), lhs, rexpr);

#define ASSIGN_OR_ASSERT_OK_IMPL(statusor, lhs, rexpr)      \
  auto statusor = (rexpr);                                  \
  ASSERT_TRUE(statusor.status().ok()) << statusor.status(); \
  lhs = statusor.ConsumeValueOrDie()

#define STATUS_MACROS_CONCAT_NAME(x, y) STATUS_MACROS_CONCAT_IMPL(x, y)
#define STATUS_MACROS_CONCAT_IMPL(x, y) x##y

#if defined(_WIN32)
#define ASSIGN_OR_RETURN(_1, _2, ...) ASSIGN_OR_RETURN_IMPL_2(_1, _2)
#else
#define ASSIGN_OR_RETURN(...)                                          \
  STATUS_MACRO_GET_VARIADIC_IMPL(__VA_ARGS__, ASSIGN_OR_RETURN_IMPL_3, \
                                 ASSIGN_OR_RETURN_IMPL_2)              \
  (__VA_ARGS__)

#define STATUS_MACRO_GET_VARIADIC_IMPL(_1, _2, _3, NAME, ...) NAME
#endif

#define ASSIGN_OR_RETURN_IMPL_2(lhs, rexpr) ASSIGN_OR_RETURN_IMPL_3(lhs, rexpr)

#define ASSIGN_OR_RETURN_IMPL_3(lhs, rexpr) \
  ASSIGN_OR_RETURN_IMPL(                    \
      STATUS_MACROS_CONCAT_NAME(_status_or_value, __COUNTER__), lhs, rexpr)

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

// For propagating errors when calling a function.
#define RETURN_IF_ERROR(expr)                            \
  do {                                                   \
    const ::platforms::darwinn::Status _status = (expr); \
    if (PREDICT_FALSE(!_status.ok())) return _status;    \
  } while (0)

#define RETURN_WITH_CONTEXT_IF_ERROR(expr, ...)                     \
  do {                                                              \
    ::platforms::darwinn::Status _status = (expr);                  \
    if (PREDICT_FALSE(!_status.ok())) {                             \
      ::platforms::darwinn::AppendToMessage(&_status, __VA_ARGS__); \
      return _status;                                               \
    }                                                               \
  } while (0)

#endif  // DARWINN_PORT_DEFAULT_STATUS_MACROS_H_