// Fig. 17.16: SynchronizedBuffer.h 
// SynchronizedBuffer using two binary_semaphores to  
// maintain synchronized access to a shared mutable int.
#pragma once
#include <fmt/format.h> 
#include <iostream>
#include <semaphore>
#include <string>

using namespace std::string_literals;

class SynchronizedBuffer {
public:
   // place value into m_buffer
   void put(int value) {
      // acquire m_produce semaphore to be able to write to m_buffer
      m_produce.acquire(); // blocks if it's not the producer's turn 

      m_buffer = value; // write to m_buffer
      m_occupied = true;

      std::cout << fmt::format("{:<40}{}\t\t{}\n",
         "Producer writes "s + std::to_string(value),
         m_buffer, m_occupied);

      m_consume.release(); // allow consumer to read
   }

   // return value from m_buffer
   int get() {
      int value; // will store the value returned by get

      // acquire m_consume semaphore to be able to read from m_buffer
      m_consume.acquire(); // blocks if it's not the consumer's turn

      value = m_buffer; // read from m_buffer
      m_occupied = false;

      std::cout << fmt::format("{:<40}{}\t\t{}\n",
         "Consumer reads "s + std::to_string(m_buffer),
         m_buffer, m_occupied);

      m_produce.release(); // allow producer to write
      return value;
   }
private:
   std::binary_semaphore m_produce{1}; // producer can produce
   std::binary_semaphore m_consume{0}; // consumer can't consume
   bool m_occupied{false};
   int m_buffer{-1}; // shared by producer and consumer threads
};



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