/*

        David Rosas
        djr8@po.cwru.edu
        Reciation leader: Bill Coates

        Assignment #2
        Program #2b, P1: use named pipes to pass variables between programs

        Compiler : gcc
        Compiled from command line on Sun ultra5 (gulam.cwru.edu)
        gcc -o p1.out p1.c -Wall 
*/

/* Include files */
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <sys/stat.h>
#include <errno.h>


/*
program must do the following things:
	--read in values from the pipe (PP0) created in session p0.c
	--use printf/fprintf/snprintf with each format string 
	--provide a var of an appropriate type to output
	--output will be sent to PP1
*/
int main()
{
	int received; 	//holds number of bytes received from pipe
	const int BUFFERSIZE = 1024;	//buffersize to use with pipes
	char buffer[BUFFERSIZE];	//actual buffer for using with pipes
	char readpipe[] = "PP0";	//two different pipe names
	char writepipe[] = "PP1";
	int rpipedes, wpipedes;		//pipe descriptors for referring to them
	FILE *pipestream;		//for converting our pipe to a filestream
	struct stat pipestatus; 	//will receive pipe status information
        char reply[10]; 		//string used to get info from user
	int strnum;			//holds which string number im' on
	double mydbl = 1.23456;		//assignment says to make up some interesting values
	int myint = 101010;
	char mychar = 'a';
	char mystring[] = "i'm interesting... really!";

	//open up the pipe to read from it (should have been created earlier)
	if((rpipedes=open(readpipe,O_RDONLY)) == -1 ) 
	{
		perror("<P1> Error opening pipe for reading\n");
		exit(-1);
	}


	   //check to see if there's already a pipe there and if not, create one
        if(stat(writepipe  ,&pipestatus) == -1)
        {
                if(errno != ENOENT) //we got a pretty big error here
                {
                        perror("I can't stat the file and it appears to exist\n");
                        perror("Exiting... Fix this from the commandline\n");
                        exit(-1);
                }
                if(mknod(writepipe,S_IFIFO|0666,0) == -1) //okay, let's try to create the pipe, then
                {
                        perror("<P1> Error creating the pipe\n");
                        exit(-1);
                }
        }
        //maybe the pipe is already around in a different form
        else if(!S_ISFIFO(pipestatus.st_mode))
        {
                printf("There is a file with the name of the pipe but it is not\n");
                printf("a pipe. Should I remove the file and create the pipe (y/n)\n");
                scanf("%s",reply);
                if((strcmp(reply,"y") == 0)||(strcmp(reply,"Y")== 0))
                {
                        printf("<P1> Deleting the file and creating a pipe...\n\n");
                        if(unlink(writepipe) == -1)
                        {
                                perror("couldn't delete the file\n");
                                exit(-1);
                        }
                        if(mknod(writepipe,S_IFIFO|0666,0) == -1)
                        {
                                perror("error creating the pipe\n");
                                exit(-1);
                        }
                }
                else
                {
                        //user wanted to keep the file (whatever they say)
                        perror("<PO> OK, I'll leave the file. Exiting now...\n");
                        exit(1);
                }
        }
        else
        {
                printf("<P1> Pipe appears to be there-- i'm gonna use it.\n");
		           fflush( stdout );
        }

        // open the pipe
        if( ( wpipedes = open(writepipe, O_WRONLY) ) == -1 )
        {
                perror("error opening pipe for writing\n");
                exit(-1);
        }

	//create a stream to the pipe so we can use it like a file...
	if ((pipestream = fdopen(wpipedes, "w") ) == NULL )
	{
		perror("<P1> Unable to morph pipe into a stream.\n");
	}
	


	//start looping and looking at our pipe
	strnum = 0;		//don't forget to init which string i'm on
	for(;;) 
	{ // read some data
		if((received=read(rpipedes,buffer,BUFFERSIZE)) == -1) 
		{
			perror("<P1> Error reading from the pipe %s in P1\n\n");
			exit(1);
		}
		else if (received == 0)
			break;  //we've read all the data from the file, apparently
		
		//insert a newline after the last filled space
                buffer[received] = '\0';

		//let's print it out to our stream and get it with cat 
		//we'll look at which number we're on to decide what type
		//of value to pass it
		fprintf(pipestream,"<P1>");
		if (strnum < 6)
			fprintf(pipestream, buffer, mydbl);
		else if (strnum < 13)
			fprintf(pipestream, buffer, myint);
		else if (strnum < 15)
			fprintf(pipestream, buffer, mychar);
		else
			fprintf(pipestream, buffer, mystring);

		//insert a few blank lines for separation
		//so we can clearly see p0,p1...p0,p1... 
		fprintf(pipestream, "\n\n");
			
		//flush it through so it goes right now
		fflush( pipestream );

		//increment our string counter
		strnum++;
	} 

	fprintf(pipestream, "\n\n");	//make the file end with a few newlines
	
	//mommy always told me to clean up after myself
        close(rpipedes);		//we no longer need that pipe to read from	
	close(wpipedes);		//we no longer need that pipe to write to
	fclose(pipestream);		//we don't need to stream anymore either	

	//let's close up shop and go home
	return 0;
}