// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <iostream>

#include "base/logging.h"
#include "mojo/public/cpp/bindings/lib/array_serialization.h"
#include "mojo/public/cpp/bindings/lib/string_serialization.h"
#include "services/flog/flog_reader_impl.h"

namespace mojo {
namespace flog {

// static
std::shared_ptr<FlogReaderImpl> FlogReaderImpl::Create(
    InterfaceRequest<FlogReader> request,
    uint32_t log_id,
    const std::string& label,
    std::shared_ptr<FlogDirectory> directory,
    FlogServiceImpl* owner) {
  return std::shared_ptr<FlogReaderImpl>(
      new FlogReaderImpl(request.Pass(), log_id, label, directory, owner));
}

FlogReaderImpl::FlogReaderImpl(InterfaceRequest<FlogReader> request,
                               uint32_t log_id,
                               const std::string& label,
                               std::shared_ptr<FlogDirectory> directory,
                               FlogServiceImpl* owner)
    : FlogServiceImpl::Product<FlogReader>(this, request.Pass(), owner),
      log_id_(log_id),
      file_(directory->GetFile(log_id, label, false)) {
  FillReadBuffer(true);
  stub_.set_sink(this);
}

FlogReaderImpl::~FlogReaderImpl() {}

void FlogReaderImpl::GetEntries(uint32_t start_index,
                                uint32_t max_count,
                                const GetEntriesCallback& callback) {
  if (fault_) {
    std::cerr << "FlogReaderImpl::GetEntries: fault_" << std::endl;
    callback.Run(Array<FlogEntryPtr>::New(0));
    return;
  }

  if (current_entry_index_ > start_index) {
    std::cerr << "FlogReaderImpl::GetEntries: resetting" << std::endl;
    current_entry_index_ = 0;
    FillReadBuffer(true);
  }

  while (current_entry_index_ < start_index) {
    std::cerr << "FlogReaderImpl::GetEntries: discard" << std::endl;
    if (!DiscardEntry()) {
      callback.Run(Array<FlogEntryPtr>::New(0));
      return;
    }
  }

  DCHECK(current_entry_index_ == start_index);

  Array<FlogEntryPtr> entries = Array<FlogEntryPtr>::New(max_count);

  for (uint32_t i = 0; i < max_count; i++) {
    FlogEntryPtr entry = GetEntry();
    if (!entry) {
      if (fault_) {
        callback.Run(Array<FlogEntryPtr>::New(0));
        return;
      }

      // Reached end-of-file.
      entries.resize(i);
      callback.Run(entries.Pass());
      return;
    }

    entries[i] = entry.Pass();
  }

  callback.Run(entries.Pass());
}

bool FlogReaderImpl::DiscardEntry() {
  uint32_t message_size;
  size_t bytes_read = ReadData(sizeof(message_size), &message_size);
  if (bytes_read < sizeof(message_size)) {
    if (bytes_read != 0) {
      std::cerr << "FlogReaderImpl::DiscardEntry: FAULT: bytes_read < "
                   "sizeof(message_size)"
                << std::endl;
    }
    fault_ = bytes_read != 0;
    return false;
  }

  if (message_size == 0) {
    std::cerr << "FlogReaderImpl::DiscardEntry: FAULT: message_size == 0"
              << std::endl;
    fault_ = true;
    return false;
  }

  bytes_read = ReadData(message_size, nullptr);
  if (bytes_read < message_size) {
    std::cerr
        << "FlogReaderImpl::DiscardEntry: FAULT: bytes_read < message_size"
        << std::endl;
    fault_ = true;
    return false;
  }

  ++current_entry_index_;

  return true;
}

FlogEntryPtr FlogReaderImpl::GetEntry() {
  uint32_t message_size;
  size_t bytes_read = ReadData(sizeof(message_size), &message_size);
  if (bytes_read < sizeof(message_size)) {
    if (bytes_read != 0) {
      std::cerr << "FlogReaderImpl::GetEntry: FAULT: bytes_read < "
                   "sizeof(message_size)"
                << std::endl;
    }
    fault_ = bytes_read != 0;
    return nullptr;
  }

  if (message_size == 0) {
    std::cerr << "FlogReaderImpl::GetEntry: FAULT: message_size == 0"
              << std::endl;
    fault_ = true;
    return nullptr;
  }

  std::unique_ptr<Message> message = std::unique_ptr<Message>(new Message());
  message->AllocUninitializedData(message_size);

  bytes_read = ReadData(message_size, message->mutable_data());
  if (bytes_read < message_size) {
    std::cerr << "FlogReaderImpl::GetEntry: FAULT: bytes_read < message_size"
              << std::endl;
    fault_ = true;
    return nullptr;
  }

  ++current_entry_index_;

  // Use the stub to deserialize into entry_.
  stub_.Accept(message.get());
  DCHECK(entry_);
  return entry_.Pass();
}

size_t FlogReaderImpl::ReadData(size_t data_size, void* data) {
  DCHECK(data_size != 0);

  while (read_buffer_bytes_remaining() == 0) {
    if (read_buffer_.size() < kReadBufferSize) {
      // read_buffer_ is exhausted and short (because we reached end of file).
      return 0;
    }

    FillReadBuffer(false);
  }

  // Copy up to data_size bytes from the buffer.
  uint32_t initial_data_size = read_buffer_bytes_remaining();
  if (initial_data_size > data_size) {
    initial_data_size = data_size;
  }

  if (data != nullptr) {
    memcpy(data, read_buffer_.data() + read_buffer_bytes_used_,
           initial_data_size);
  }

  read_buffer_bytes_used_ += initial_data_size;

  if (initial_data_size == data_size || read_buffer_.size() < kReadBufferSize) {
    // Either read_buffer_ contained all the required data, or read_buffer_ is
    // short, indicating we've hit end-of-file.
    return initial_data_size;
  }

  DCHECK(read_buffer_bytes_remaining() == 0);

  // Read the remainder.
  return ReadData(data_size - initial_data_size,
                  reinterpret_cast<uint8_t*>(data) + initial_data_size) +
         initial_data_size;
}

void FlogReaderImpl::FillReadBuffer(bool restart) {
  file_->Read(kReadBufferSize, 0,
              restart ? files::Whence::FROM_START : files::Whence::FROM_CURRENT,
              [this](files::Error error, Array<uint8_t> bytes_read) {
                if (error != files::Error::OK) {
                  std::cerr << "FlogReaderImpl::FillReadBuffer: FAULT: error "
                            << error << std::endl;
                  fault_ = true;
                  read_buffer_.clear();
                  return;
                }

                bytes_read.Swap(&read_buffer_);
              });
  file_.WaitForIncomingResponse();
  read_buffer_bytes_used_ = 0;
}

FlogEntryPtr FlogReaderImpl::CreateEntry(int64_t time_us, uint32_t channel_id) {
  FlogEntryPtr entry = FlogEntry::New();
  entry->time_us = time_us;
  entry->log_id = log_id_;
  entry->channel_id = channel_id;
  entry->details = FlogEntryDetails::New();
  return entry;
}

void FlogReaderImpl::LogMojoLoggerMessage(int64_t time_us,
                                          int32_t log_level,
                                          const String& message,
                                          const String& source_file,
                                          uint32_t source_line) {
  entry_ = CreateEntry(time_us, 0);
  FlogMojoLoggerMessageEntryDetailsPtr details =
      FlogMojoLoggerMessageEntryDetails::New();
  details->log_level = log_level;
  details->message = message;
  details->source_file = source_file;
  details->source_line = source_line;
  entry_->details->set_mojo_logger_message(details.Pass());
}

void FlogReaderImpl::LogChannelCreation(int64_t time_us,
                                        uint32_t channel_id,
                                        const String& type_name) {
  entry_ = CreateEntry(time_us, channel_id);
  FlogChannelCreationEntryDetailsPtr details =
      FlogChannelCreationEntryDetails::New();
  details->type_name = type_name;
  entry_->details->set_channel_creation(details.Pass());
}

void FlogReaderImpl::LogChannelMessage(int64_t time_us,
                                       uint32_t channel_id,
                                       mojo::Array<uint8_t> data) {
  entry_ = CreateEntry(time_us, channel_id);
  FlogChannelMessageEntryDetailsPtr details =
      FlogChannelMessageEntryDetails::New();
  details->data = data.Pass();
  entry_->details->set_channel_message(details.Pass());
}

void FlogReaderImpl::LogChannelDeletion(int64_t time_us, uint32_t channel_id) {
  entry_ = CreateEntry(time_us, channel_id);
  FlogChannelDeletionEntryDetailsPtr details =
      FlogChannelDeletionEntryDetails::New();
  entry_->details->set_channel_deletion(details.Pass());
}

}  // namespace flog
}  // namespace mojo