// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <utility>

#include "base/functional/bind.h"
#include "base/functional/callback.h"
#include "mojo/public/cpp/system/data_pipe_utils.h"
#include "mojo/public/cpp/system/wait.h"

namespace mojo {
namespace {

bool BlockingCopyHelper(
    ScopedDataPipeConsumerHandle source,
    base::RepeatingCallback<size_t(const void*, uint32_t)> write_bytes) {
  for (;;) {
    const void* buffer;
    uint32_t num_bytes;
    MojoResult result =
        source->BeginReadData(&buffer, &num_bytes, MOJO_READ_DATA_FLAG_NONE);
    if (result == MOJO_RESULT_OK) {
      size_t bytes_written = write_bytes.Run(buffer, num_bytes);
      result = source->EndReadData(num_bytes);
      if (bytes_written < num_bytes || result != MOJO_RESULT_OK)
        return false;
    } else if (result == MOJO_RESULT_SHOULD_WAIT) {
      result = Wait(source.get(), MOJO_HANDLE_SIGNAL_READABLE);
      if (result != MOJO_RESULT_OK) {
        // If the producer handle was closed, then treat as EOF.
        return result == MOJO_RESULT_FAILED_PRECONDITION;
      }
    } else if (result == MOJO_RESULT_FAILED_PRECONDITION) {
      // If the producer handle was closed, then treat as EOF.
      return true;
    } else {
      // Some other error occurred.
      break;
    }
  }

  return false;
}

size_t CopyToStringHelper(std::string* result,
                          const void* buffer,
                          uint32_t num_bytes) {
  result->append(static_cast<const char*>(buffer), num_bytes);
  return num_bytes;
}

}  // namespace

// TODO(hansmuller): Add a max_size parameter.
bool BlockingCopyToString(ScopedDataPipeConsumerHandle source,
                          std::string* result) {
  CHECK(result);
  result->clear();
  return BlockingCopyHelper(std::move(source),
                            base::BindRepeating(&CopyToStringHelper, result));
}

bool MOJO_CPP_SYSTEM_EXPORT
BlockingCopyFromString(const std::string& source,
                       const ScopedDataPipeProducerHandle& destination) {
  auto it = source.begin();
  for (;;) {
    void* buffer = nullptr;
    uint32_t buffer_num_bytes = static_cast<uint32_t>(source.end() - it);
    MojoResult result = destination->BeginWriteData(&buffer, &buffer_num_bytes,
                                                    MOJO_WRITE_DATA_FLAG_NONE);
    if (result == MOJO_RESULT_OK) {
      char* char_buffer = static_cast<char*>(buffer);
      uint32_t byte_index = 0;
      while (it != source.end() && byte_index < buffer_num_bytes) {
        char_buffer[byte_index++] = *it++;
      }
      destination->EndWriteData(byte_index);
      if (it == source.end())
        return true;
    } else if (result == MOJO_RESULT_SHOULD_WAIT) {
      result = Wait(destination.get(), MOJO_HANDLE_SIGNAL_WRITABLE);
      if (result != MOJO_RESULT_OK) {
        // If the consumer handle was closed, then treat as EOF.
        return result == MOJO_RESULT_FAILED_PRECONDITION;
      }
    } else {
      // If the consumer handle was closed, then treat as EOF.
      return result == MOJO_RESULT_FAILED_PRECONDITION;
    }
  }
}

}  // namespace mojo