/// @copyright 2020 ECCI, Universidad de Costa Rica. All rights reserved
/// This code is released under the GNU Public License version 3
/// @author Jeisson Hidalgo-Céspedes <jeisson.hidalgo@ucr.ac.cr>

#ifndef CONSUMER_HPP
#define CONSUMER_HPP

#include "Queue.hpp"
#include "Thread.hpp"

/**
 * @brief A template that generates abstract base classes for Consumers
 * Consumers are execution threads. They extract elements from a queue
 * These elements were pushed to the queue by a producer or dispatcher thread.
 * @remark For this software, the consumer is the owner of its queue
 */
template <typename DataType>
class Consumer : public Thread {
  DISABLE_COPY(Consumer);

 protected:
  /// This thread will consume from its queue
  Queue<DataType> queue;

  /// This data will be used to represent that the Consumer must stop the
  /// consumption, and finish its work. It is used for cleaning purposes.
  const DataType stopCondition;

 public:
  /// Constructor
  /// @see stopCondition
  explicit Consumer(const DataType& stopCondition = DataType())
    : stopCondition(stopCondition) {
  }

  /// Destructor
  virtual ~Consumer() {
  }

  /// Get access to the queue where this thread will consume
  inline Queue<DataType>* getQueue() {
    return &this->queue;
  }

  /// Consumes from its queue, util the stop condition is popped
  /// For each data consumed, the @a consume method will be called
  virtual void consumeForever() {
    while ( true ) {
      // Get the next data to consume, or block while queue is empty
      DataType data = this->queue.pop();
      // If data is the stop condition, stop the loop
      if ( data == this->stopCondition ) {
        break;
      }
      // Process this data
      this->consume(data);
    }
  }

  /// Override this method to process any data extracted from the queue
  virtual void consume(const DataType& data) = 0;
};

#endif  // CONSUMER_HPP