// exception4.cpp			By: Aiman Hanna -  ©1993-2006 Aiman Hanna

// This program gives more information about exception handling.
// In specific, this program illustrates what happens when you have an
// unhandled exception. In fact, the program crashes as a result of unhandled 
// exception. The next program, exception5.cpp will show one of the possible
// solutions to avoid such problems.  



#include "exception4.h"

ProducerConsumer::ProducerConsumer()
{
	for (int i = 0; i < 10; i++)
		buff[i] = -1;

}




bool ProducerConsumer::isEmpty()
{

	if (buff[0] == -1)
		return true;

	return false;
}




bool ProducerConsumer::isFull()
{

	if (buff[9] != -1)
		return true;

	return false;
}




void ProducerConsumer::produceItem( int item )
{
	if (isFull())
		throw ProduceOnFull();		// Not "throw ProduceOnFull;"

	if ( item == -1 )
		throw ProduceInvalidValue();

	int i = 0;
	while (buff[i++] != -1);
		buff[i - 1] = item;
	
}



void ProducerConsumer::consumeItem( )
{
	if (isEmpty())
		throw ConsumeOnEmpty();		

	int i = 0, item = -1;
	while ( (i < 10) && (buff[i] != -1) ) 
		i++;
	
	item = buff[i-1];
	buff[i-1] = -1;
	

}



void ProducerConsumer::setItem(int item)
{
	produceItem( item );
}




void ProducerConsumer::displayBuffContents()
{
	cout << "\nThe buffer contents at this point are: " << endl;
	for (int i= 0; i < 10; i++)
		cout << buff[i] << "  ";
	cout << endl << endl;

}




void Excp::showExcpMessage()
{

	cerr << "An exception has occurred" << endl;
	
}




void ProducerConsumerExcp::showExcpMessage()
{
	cerr << "A producer-consumer exception has occurred" << endl;

}



void ConsumeOnEmpty::showExcpMessage()
{
	cerr << "An exception has occurred: Trying to consume from an empty buffer" << endl;
}




void ProduceOnFull::showExcpMessage()
{
	cerr << "An exception has occurred: Trying to produce to a full buffer" << endl;
}




void ProduceInvalidValue::showExcpMessage()
{
	cerr << "An exception has occurred: Trying to produce an invalid value" << endl;
}



int main()
{
	
	ProducerConsumer pc1;
	

	try{
		pc1.consumeItem( );
	}
	catch (ConsumeOnEmpty coe)
	{
		coe.showExcpMessage();
	}

	// Try to produce more items than the buffer can hold
	// Notice what happens when the exception is thrown
	try
	{
		for (int i = 0; i < 13; i++)
		{
			if ( i == 9 )
				pc1.produceItem (-1);	// Attempt to produce an invalid value
			pc1.produceItem(i * 5);		// i*5 is just a value 
		}
	}
	catch (ProduceOnFull pof)
	{	
		pof.showExcpMessage();
	}


	pc1.displayBuffContents();

	// try to consume more items than what the buffer has
	try
	{
		for (int i = 0; i < 13; i++)
		{
			pc1.consumeItem();	

			if ((i == 7) || (i ==8) || (i == 9))		// display the contents just before the 
				pc1.displayBuffContents();				// exception should occur
					
		}
	}
	catch (ConsumeOnEmpty coe)
	{	
		coe.showExcpMessage();
	}
	

	return 0;
}


// The result of running the program
/*
An exception has occurred: Trying to consume from an empty buffer

// The program terminates abnormally (crashes) at this moment
*/