//hw2.c
//Date: 6/8/2003
//Description: Simulation of a Snakes and Ladders game

#include<iostream>
#include<stdlib.h>
#include<signal.h>
#include<sys/types.h>
#include<sys/wait.h>
#include<unistd.h>

int playerA = 0;
int playerB = 0;
int result;

int roll();
void game(int& player);

main(void){

	cout << "TWO-PLAYER SNAKES AND LADDERS GAME.\n" << endl;

	int parentPid, childPid, status;
	void sigChldHandler (int sig);
	struct sigaction act;

	sigfillset(&(act.sa_mask));
	act.sa_flags = 0;
	act.sa_handler = sigChldHandler;

	void sigHandler(int sig);
	struct sigaction players;
	sigfillset(&(players.sa_mask));
	players.sa_flags = 0;
	players.sa_handler = sigHandler;

	parentPid = getpid();

	cout << "Player A is at square 0." << endl;
	cout << "Player B is at square 0." << endl << endl;

	if((childPid = fork()) == 0) {		//child process
	sigaction(SIGUSR1, &players, NULL);
	srand(getpid());
	int oldB;

	while(1){
		pause();			//wait for SIGUSR1 from parent
		result = roll();
		playerB += result;
		oldB = playerB;
		cout << "Player B rolls a " << result << ", lands on square ";
		cout << playerB << "." << endl;
		game(playerB);

		if(playerB > oldB)
			cout << "Player B climbs up a ladder to square " << playerB << "!" << endl;
		if(playerB < oldB)
			cout << "Player B slides down a snake to square " << playerB << "!" << endl;

		cout << endl;

		if(playerB < 100) {		//Player B hasn't yet won
		sleep(1);
		kill(parentPid, SIGUSR2);
			}

		else{
			cout << "PLAYER B WINS!!!" << endl;
			exit(0);
			}
		}
	}

	else {					//parent process
	sigaction(SIGUSR2, &players, NULL);
	sigaction(SIGCHLD, &act, NULL);
	srand(getpid());
	int oldA;
	while(1){
		result = roll();
		playerA += result;
		oldA = playerA;
		cout << "Player A rolls a " << result << ", lands on square ";
		cout << playerA << "." << endl;
		game(playerA);

		if(playerA > oldA)
			cout << "Player A climbs up a ladder to square " << playerA << "!" << endl;
		if(playerA < oldA)
			cout << "Player A slides down a snake to square " << playerA << "!" << endl;

		cout << endl;

		if(playerA < 100) {		//Player A hasn't yet won
		sleep(1);
		kill(childPid, SIGUSR1);	//send SIGUSR1 to child
		pause();			//wait for SIGUSR2 from child
			}

		else {				//Player A wins
		cout << "PLAYER A WINS!!!" << endl;
		kill(childPid, SIGTERM);
		wait(&status);
			}

		}
	}
}

int roll(){
	int d1 = rand() % 6 + 1;
	return d1;
}

void game(int& player){

	switch(player){
	case 1: player += 37; break;
	case 4: player += 10; break;
	case 9: player += 22; break;
	case 16: player += -10; break;
	case 17: player += 6; break;
	case 21: player += 21; break;
	case 28: player += 56; break;
	case 38: player += 8; break;
	case 47: player += -21; break;
	case 49: player += -38; break;
	case 51: player += 16; break;
	case 56: player += -3; break;
	case 62: player += -43; break;
	case 64: player += -4; break;
	case 71: player += 20; break;
	case 73: player += 19; break;
	case 80: player += 20; break;
	case 87: player += -63; break;
	case 93:
	case 95:
	case 98: player += -20; break;

	default: break;
	}
}

void sigChldHandler(int sig){
	int childPid, status;
	childPid = wait(&status);
	exit(0);
}

void sigHandler(int sig){
	return;
}