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

/////////////////////////////////////////////////////
// Decrements the Environment Variable HIPPO,
// Checks the return values, and prints the output
/////////////////////////////////////////////////////
void DecrementHIPPO(char* name, int decr)
{
	char cmvar[50];
	char* pmvar = cmvar;
	pmvar  = getenv("HIPPO");
	if(pmvar == NULL)
		perror("Failed to get evironment variable");
	int tmpHippo=atoi(pmvar);
	tmpHippo -= decr;
	char mvar[50];
	sprintf(mvar, "%d", tmpHippo);
	if(setenv("HIPPO", mvar, 1) != 0)
		perror("Failed to set environment variable");
	printf("%s:\tHIPPO=%d\n", name, tmpHippo);
	fflush(0);
}

////////////////////////////////////////////////////
// Displays the hostname, userid, and other misc
// system information relative to the session
///////////////////////////////////////////////////
void ShowSystemInfo()
{
	char hostname[255];
	// Display the hostname
	if(gethostname(hostname, 255) != 0)
		perror("Failed to get the hostname.");
	else
		printf("Hostname: %s\n", hostname);

	// Display the userid
	char userid[255];
	cuserid(userid);
	if(userid[0] == '\0')
		perror("Failed to get the userid.");
	else
		printf("UserID: %s\n", userid);

	// Display the current time
	time_t currentTime;
	if(!time(&currentTime))
		perror("Failed to get systemtime.");
	else
		// Note: ctime() adds a linefeed at the end of the string
		printf("Time: %s", ctime(&currentTime));

	// Display the working directory
	char currentDir[255];
	if(!getcwd(currentDir, 255))
		perror("Failed to get working directory.");
	else
		printf("WorkingDir: %s\n", currentDir);
}

main()
{
	////////////////////////////////////////////////////////
	//	Parent Process Setup
	///////////////////////////////////////////////////////

	// Getpid() never fails, so we don't need to check it.
	pid_t pid1 = getpid();
	printf("\nParent Process Info:\n");
	printf("ProcessID: %d\n", pid1);
	
	ShowSystemInfo();

	if(putenv("HIPPO=11") != 0)
		perror("Failed to initialize environment variable.");
	
	/////////////////////////////////////////////////////
	// Create the child processes
	/////////////////////////////////////////////////////
	int pid, status1, status2;
	// Create the first process (parent skips this if)
	if((pid=fork()) == 0)
	{		
		int pidC1 = getpid();
		int ppidC1 = getppid();
		printf("C1 started.  ID: %d, ParentID: %d\n", pidC1, ppidC1);
		fflush(0);
		sleep(1);
		//HIPPO=11
		DecrementHIPPO("C1", 2);
		//HIPPO=9
		sleep(4);	
		DecrementHIPPO("C1", 3);
		//HIPPO=6
		sleep(7);	
		DecrementHIPPO("C1", 3);
		//HIPPO=3

		sleep(10);
		// Change the working directory of C1
		char currentDirOld[255];
		if(!getcwd(currentDirOld, 255))
			perror("Failed to get old C1 working directory.");
		
		if(chdir("..") != 0)
			perror("C1 Failed to change directory.");
		
		char currentDirNew[255];
		if(!getcwd(currentDirNew, 255))
			perror("Failed to get new C1 working directory.");
		else
		{
			printf("Current (C1) working directory changed from:\n%s to %s \n", currentDirOld, currentDirNew);
		}

		printf("Listing contents of the new C1 working directory:\n");
		fflush(0);
		execl("/bin/ls", "-l", (char *) 0); 
		exit(1);
	}
	// Create the second process (parent skips this if)
	else if((pid=fork()) == 0)
	{		
		int pidC2 = getpid();
        int ppidC2 = getppid();
        printf("C2 started.  ID: %d, ParentID: %d\n", pidC2, ppidC2);
        fflush(0);
		sleep(2);
		//HIPPO=11
		DecrementHIPPO("C2", 3);
		//HIPPO=8
		sleep(5);
		DecrementHIPPO("C2", 3);
		//HIPPO=5
		sleep(8);
		DecrementHIPPO("C2", 3);
		//HIPPO=2

		sleep(11);
		// Display the working directory
		char currentDir[255];
		if(!getcwd(currentDir, 255))
			perror("Failed to get working directory.");
		else
			printf("C2 WorkingDir: %s\n", currentDir);

		DecrementHIPPO("C2", -1);
		printf("\n");
		fflush(0);
        exit(2);
		
	}

	//////////////////////////////////////////////
	// Only the parent process executes this code
	//////////////////////////////////////////////
	//HIPPO=11
	DecrementHIPPO("P1", 1);
	//HIPPO=10
	sleep(3);
	DecrementHIPPO("P1", 3);	
	//HIPPO=7
	sleep(6);
	DecrementHIPPO("P1", 3);
	//HIPPO=4
	sleep(9);
	DecrementHIPPO("P1", 3);
	//HIPPO=1

	wait(&status1);
	wait(&status2);

	printf("Both children have exited.\nFinal Value: ");
	fflush(0);
	DecrementHIPPO("P1", -1);

}