/**
  * @RDE_HEADER@
  * AvsCommandQueue
  * $Id$
  * $HeadURL$
  * $Author$
  * Created by Christian Fröbel, NLSE, 2018-02-23
  */

#include "avs_command_queue.h"
#include "icommand.h"
#include <LtsUtilsCore/connection.h>


namespace AudioVideoManagement
{

AvsCommandQueue::AvsCommandQueue(std::chrono::milliseconds timeout)
  : m_logger(getLogger("AvsCommandQueue"))
{
  if (timeout.count())
  {
    m_timer.setSingleShot(true);
    m_timer.setInterval(timeout.count());
    connect(&m_timer, &QTimer::timeout, this, &AvsCommandQueue::timeout); // signal -> signal
  }
}

AvsCommandQueue::~AvsCommandQueue()
{
  flush();
}

void AvsCommandQueue::queue(std::unique_ptr<ICommand> cmd, std::unique_ptr<LtsUtils::IConnection> connection)
{
  Q_ASSERT(cmd);

  bool   noPendingCommand = m_queue.empty();
  m_queue.push_back(CommandWithConn{std::move(cmd), std::move(connection)});
  DEBUG_LOG(m_logger) << "queueing command, queue size: " << m_queue.size();
  tryReduce();
  if (noPendingCommand)
    nextCommand();
}

void AvsCommandQueue::done()
{
  Q_ASSERT(!m_queue.empty());
  m_timer.stop();
  m_queue.pop_front();
  DEBUG_LOG(m_logger) << "command finished, queue size: " << m_queue.size();
  if (m_queue.empty())
    emit queueEmpty();
  else
    nextCommand();
}

ICommand *AvsCommandQueue::currentCommand() const
{
  Q_ASSERT(!m_queue.empty());
  return m_queue.front().cmd.get();
}

bool AvsCommandQueue::currentHasConnection() const
{
  Q_ASSERT(!m_queue.empty());
  return m_queue.front().connection != nullptr;
}

LtsUtils::IConnection *AvsCommandQueue::currentConnection() const
{
  Q_ASSERT(!m_queue.empty());
  Q_ASSERT(m_queue.front().connection);
  return m_queue.front().connection.get();
}

void AvsCommandQueue::flush()
{
  if (m_queue.empty())
    return;

  DEBUG_LOG(m_logger) << "flushing " << m_queue.size() << " commands";
  m_timer.stop();
  m_queue.clear();
  emit queueEmpty();
}

void AvsCommandQueue::alive()
{
  Q_ASSERT(!m_queue.empty());
  m_timer.start();
}

void AvsCommandQueue::nextCommand()
{
  Q_ASSERT(!m_queue.empty());

  DEBUG_LOG(m_logger) << "sending next command";
  ICommand   *cmd = currentCommand();
  m_timer.start();
  cmd->send();
}

/**
 * Given the last queued command in the queue this method
 * tries to find commands queued earlier where the effect
 * of the earlier command will be nullified by the new command.
 * If such a command is found, it will be dropped.
 * For example when there was a SetVolume(x) followed by
 * a SetVolume(y), we can simply drop the first one.
 */
void AvsCommandQueue::tryReduce()
{
  if (m_queue.size() <= 2)
    return;

  const CommandWithConn   &lastCommand = m_queue.back();

  // Do not check against the first command as it is beeing executed right now.
  for (size_t i = 1; i < m_queue.size() - 1; ++i)
  {
    const CommandWithConn   &current = m_queue[i];

    if (!lastCommand.cmd->nullifies(current.cmd.get()))
      continue;

    DEBUG_LOG(m_logger) << "dropping command due to override";
    m_queue.erase(m_queue.begin() + i);
    return;
  }
}

} // namespace AudioVideoManagement