#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>
#include <string.h>
#include <signal.h>

void signalHandler(int);
void getTime(char*);
void addDot(char*);
int cFlag = 0, alarmFlag = 0, childFinishedFlag = 0;

int main() {
	char outputFileName[100], parentFileName[100], childFileName[100];
	int parentPID = getpid(), childPID, fd[2];
	char timeString[30];
	const int MAXLINE = 4096;
	char line[MAXLINE];

	//Set up signals
	signal(SIGINT, signalHandler);
	signal(SIGCHLD, signalHandler);
	signal(SIGALRM, signalHandler);
	
	//Populate timeString array with current time
	getTime(timeString);
	
	//Prompt user for output filename
	scanf("%100s", outputFileName);
	addDot(outputFileName);
	if(cFlag == 1) {
		strcpy(outputFileName, "Output.");
	}
	
	//Populate other filename strings
	strcpy(parentFileName, "ParentStatus.");
	strcat(parentFileName, timeString);
	strcpy(childFileName, "ChildStatus.");
	strcat(childFileName, timeString);
	
	//File pointers
	FILE *outputFile;
	FILE *parentLog;
	FILE *childLog;

	//Open outputfile
	if((outputFile = fopen(strcat(outputFileName,timeString), "w")) == NULL) {
		printf("Error opening output file.\n");
		return 1;
	}
	else {
		//Write output file info here
		fprintf(outputFile, "Opened: %s\n", timeString);
	}
	
	
	//Create pipe
	if (pipe(fd) < 0) {
		printf("Pipe Error, program closing");
		return 1;
	}
		
	//Fork returns the PID of the child process
	if ((childPID = fork()) < 0)	{
		printf("Fork Error");
		return 1;
	}	
	//Parent process
	else if (childPID > 0) {
		//Open parent log file
		if((parentLog = fopen(parentFileName,"w")) == NULL) {
			printf("Error opening output file.\n");
			return 1;
		}
		else {
			fprintf(parentLog, "Opened: %s\n", timeString);
			
			//Set standard output
			dup2(fd[1], STDOUT_FILENO);
			
			//Close the reading end of the pipe
			close(fd[0]);
			
			
			//Write output file info here
			fprintf(parentLog, "Parent Log\nPID: %i\n", parentPID);
			
			//Seed for random number
			srand((int)time(NULL));
			int num;
			
			//Wait for child to finish
			while(childFinishedFlag == 0) {
				//Generate new number
				num = (int)(5.0 * rand() / (RAND_MAX + 1.0));
				//Write to pipe
				write(STDOUT_FILENO, &num, 1);
			}
						
			//When child is finished, close parent log and output file
			getTime(timeString);
			fprintf(parentLog, "Parent finished at: %s", timeString);

		}
	}
	//Child process
	else {
		
		//Open child log file
		if((childLog = fopen(childFileName,"w")) == NULL) {
			printf("Error opening output file.\n");
			return 1;
		}	
		else {
			fprintf(childLog, "Opened: %s\n", timeString);
			
			//Set standard input
			dup2(fd[0], STDIN_FILENO);
			
			//Seed rand and set alarm
			srand((int)time(NULL));
			int randTime = 1 + (int)(10.0 * rand() / (RAND_MAX + 1.0));
			alarm(randTime);
			
			int n1, n2, num1, num2;
			while(alarmFlag == 0) {
				//Get 2 random numbers
				n1 = read(STDIN_FILENO, &num1, 1);
				n2 = read(STDIN_FILENO, &num2, 1);
				//DEBUG: printf("Number: %i, %i\n",num1, num2);
				
				//If the first number is greater than 2, multiply, otherwise divide
				if(num1 > 2) {
					int result = num1 * num2;
					fprintf(childLog, "%i * %i = %i\n", num1, num2, result);	
				}
				else {
					//int result = num1 / num2;
					//fprintf(childLog, "%i / %i = %i\n", num1, num2, result);
				}
				
			}
			
			//When alarm goes off close child log
			getTime(timeString);
			fprintf(childLog, "Child finished at: %s", timeString);
			fclose(childLog);
			
		}
	}
	
	
	fprintf(outputFile, "Output finished at: %s", timeString);	
	fclose(parentLog);
	fclose(outputFile);
	
	return 0;
}

/*
 * signalHandler(int) - Handles the signals generated by the program
 */ 
void signalHandler(int signo) {
	//Ctrl-C Handler
	if(signo == SIGINT) {
		cFlag = 1;
	}
	//Signal when child is finished
	if(signo == SIGCHLD) {
		childFinishedFlag = 1;
	}
	//Signal when alarm goes off in child program
	if(signo == SIGALRM) {
		alarmFlag = 1;
	}
}

/*
 * getTime(char*) - Gets the current time and populates the string
 * passed as a parameter.
 */
void getTime(char *timeString) {
	time_t clock;
	struct tm *theTime;
	time(&clock);
	
	theTime = localtime(&clock);
	strftime(timeString,29,"%T",theTime);
}

/*
 * addDot(char*) - A support function. Simply adds a dot to the filename.
 */
void addDot(char *string) {
	strcat(string, ".");
}