/**
	Programmed By :	m1o2
*/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <sys/types.h>

#define WaitForEnter { fprintf(stderr,"\n\n Press the 'Enter' key to continue..."); fflush(stdout); fflush(stdin); getchar(); putchar('\n'); }
#define SystemError( msg ) { fprintf(stderr,"\n\n Error: "); fflush(stderr); perror(msg); exit( 1 ); }
#define Plumber( stream ) { if( pipe(stream) == FAIL ) SystemError( "Cannot open pipes." ); } 
#define Close( stream ) { if( close(stream) == FAIL ) SystemError( "Cannot close stream." ); }
#define dup3( stream ) { if( dup( stream ) == FAIL ) SystemError( "Cannot duplicate stream." ); }

typedef enum { FAIL = -1, CHILD,EMPTY = 0, SUCCESS } RESULT;
typedef enum { INPUT, OUTPUT } STREAM_INDEX;
typedef enum { False, True } Bool;
typedef int _stream;
typedef char* _string,_path;
typedef const char _letter;


/* the child process execution code(callin the sort function) */
void child( _stream in, _stream out, _string column );

/*  reading numbers from the file, multiply the number with the 'column' column, and send it throw pipe. */
int numbersWriter( _string path,  _stream out , size_t column, size_t mul );

/* reading Integers from files using row function and system calls */
Bool getInt( _stream in, int* var );



int main(int length, char *params[]){
	

	_stream pipeStream1[2], pipeStream2[2];
	int mul,number,counter;
	

	
	if( length < 4 || ( (((*params[2])-'0') < 1) || (((*params[2])-'0') > 3) ) )
		SystemError( "Not Enough Parameters Or Illegal Parameters." );

	
	/* opening two pipes. */
	Plumber( pipeStream1 );
	Plumber( pipeStream2 );


	if( fork() == CHILD ){  /* child process - calling the sort function */
		Close( pipeStream2[OUTPUT] );
		Close( pipeStream1[INPUT] );

		child( pipeStream2[INPUT], pipeStream1[OUTPUT], params[2] );

	}
	else{ /* father process */
		Close( pipeStream2[INPUT] );
		Close( pipeStream1[OUTPUT] );

		sscanf(params[3],"%d",&mul);

		/* multipying the currect column and sending the result to the sort process with a pipe */
		numbersWriter( params[1], pipeStream2[OUTPUT],((*params[2])-'0'),mul);

		Close( pipeStream2[OUTPUT] );
		Close( INPUT );

		dup3( pipeStream1[INPUT] );

	
		/* printing the result , which we got from the pipe of the sort process */
		printf("\n\n Factored, Sorted File : \n");
		fflush(stdout);
		for( counter = 1; getInt( INPUT,&number) == True; ++counter ){
			printf("%3d\t",number);
			fflush(stdout);
			if( (counter%3) == 0 )
				putchar('\n');
		}
	}

	
	wait();
	
WaitForEnter;
return 0;
}

/* reading the next Integer from a stream using row functions and system calls */
Bool getInt( _stream in, int* var ){

	char input;
	ssize_t got = 0;
	Bool result = False, negative = False,toContinue = True;

	(*var) = 0;
	
	

	while( toContinue && read(in, &input, 1) > EMPTY ){

		if( ((input >= '0' && input <='9') || input == '-' ) ){
			result = True;
			if( input == '-' )
				negative = True;
			else
				(*var) = (((*var) * 10)+(input-'0'));
		}
		else if( result )
			toContinue = False;
	}

	if( negative )
		(*var) = 0 - (*var);

	return result;

}

/* multiplying the currect column and sending the result to sort */
int numbersWriter( _string path, _stream out , size_t column, size_t mul ){

	_stream input_file;
	size_t index = 1,counter = 0;
	int result;
	Bool flag = True;
	int written;
	char s_result[17];
	


	if( ( input_file = open( path, O_RDONLY, 0644 ) ) == FAIL )
		SystemError( "Cannot open file." );

	while( getInt( input_file, &result ) ){
			
			++counter;
				
			if ( index == column )
				result *= mul;

			sprintf(s_result,"%3d        ",result);
			
			if( write( out, s_result, strlen(s_result) ) < strlen(s_result) )
				SystemError( "Cannot write to a stream." );
			
			if( ++index > 3 ){
				index = 1;
				strcpy(s_result,"\r\n");
			}
			else
				strcpy(s_result," ");

			if( write( out, s_result, strlen(s_result) ) < strlen(s_result) )
				SystemError( "Cannot write to a stream." );
	}

	fsync( out );
	Close( input_file );
	
	return counter;
}

/* calling the sort function using execlp */
void child( _stream in, _stream out, _string column ){
	

	Close( INPUT )
	dup3( in );
	

	Close( OUTPUT );
	dup3( out );
	
	if( execlp( "sort","sort","-n","-k",column,NULL) == FAIL )
		SystemError ("Cannot execute /usr/bin/sort" );

}