/******************************************************************
 * Created: Josep Valls 20080211
 * Simple shell for CMPS105/Winter2008
 * Practice the use of standard IO and signals 
 * Features: reads whole line, multiple arguments
 * Wishlist: command history, multiple commands using ;, pipes
 ******************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <assert.h>

const MAXJOBS = 20;
const ICSIZE = 255;

typedef struct{
	pid_t pid;
	int status;
	char commandline[255];
} s_jobs;

static void sig_int(int);

int main(int argc, char *argv[])
{
	char buf[ICSIZE],bufbak[ICSIZE];
	pid_t pid;
	int status;
	
	char *args[ICSIZE];
	char *u, *b;
	int argsc=0;
	
	s_jobs jobs[MAXJOBS];
	int jobsc=0;
	int i=0;
	int jobsr=0;

	//add the signal listener
	if(signal(SIGINT,sig_int)==SIG_ERR) printf("Error in the signal catching mechanics\n");
	if(signal(SIGUSR1,sig_int)==SIG_ERR) printf("Error in the signal catching mechanics\n");
	//test by kill -USR1 pid

	//main loop
	do{
		printf("\nCommand: ");
		if(fgets(buf,sizeof(buf),stdin)==NULL){
			continue;
		}
		//shell commands filter
		if(strcmp(buf,"exit\n")==0) continue;
		if(strcmp(buf,"jobs\n")==0) {
			printf("job\tpid\tstatus\tcommand line\n");
			for(i=0;i<MAXJOBS&&i<jobsc;i++) printf("%d\t%d\t%d\t%s",i+1,jobs[i].pid,jobs[i].status,jobs[i].commandline);
			printf("Enter the number of the command to recall, 0 for new prompt: ");
			scanf("%d",&jobsr);
			fflush(stdin);
			continue;
		}

		//add to the job list/command history	
		for(i=MAXJOBS-1;i>=0;i--){
			jobs[i+1]=jobs[i];
		}
		jobsc++;
		jobs[0].pid=0;
		jobs[0].status=-1;
		strcpy(jobs[0].commandline,buf);
		//parse the string
		strcpy(bufbak,buf);
		argsc=0;
		u= strtok_r(buf, " \n", &b);
		while (u) {
			args[argsc]= u;
			argsc++;
			u= strtok_r(NULL, " \n", &b);
		}
		args[argsc--]= NULL;

		//execute the command
		pid=fork();
		if(pid==0){
			//this is the child
			jobs[0].pid=getpid();
			execvp(args[0],args);
			printf("error executing %s from the command line %s\n",args[0],bufbak);
			exit(127);
			//without this exit, there will be two processes and the exit command would not success
			}
		else
			//this is the parent
			wait(&status);
	}while(strcmp(buf,"exit\n")!=0);

	//free(buf);
	printf("Goodbye!\n");
}
//signal catching function	
static void sig_int(int signum){	
	printf("\nSignal catched %d\n",signum);
	printf("\nCommand: ");
	//why is this string being printed before the signal catched string?
}