#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <ctype.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>
#include <fcntl.h>
#include <libgen.h>

#define MAXLINE		1024	/* max size of inputed command line*/
#define MAXARGS     128		/* max args on a command line */

/* Global variables */
extern char **environ;      /* defined in libc */
char prompt[] = "myshell> ";    /* command line prompt */
char *shellname;


/* Function Declarations: */
int parseline(const char *cmdline, char **argv);
int checkGrammar(const char*cmdline);
void usage();
void app_error(char *msg);



int main(int argc, char **argv) 
{
    char pName[MAXLINE];
    char cmdline[MAXLINE];
    int emit_prompt = 1; /* emit prompt (default) */
    int pid, bg;
    char *argvexec[MAXARGS];
    
        shellname = argv[0];
    /* Execute the shell's read/eval loop */
    while (1) 
    {
	/* Read command line */
	if (emit_prompt) {
	    printf("%s", prompt);                   
	    fflush(stdout);
	}
	strcpy(cmdline, "");
	if ((fgets(cmdline, MAXLINE, stdin) == NULL) && ferror(stdin))
	    app_error("fgets error");
	if (feof(stdin)) { /* End of file (ctrl-d) */
	    fflush(stdout);
	    exit(0);
	}
	
	/* Evaluate the command line */
	bg = parseline(cmdline, argvexec);

	if(bg == -1)
	{
	    /* ignore command for whatever reason.. */
	    continue;
	}
	
	/*
	  Insert SYSCALLS that make the shell execute programs and wait correctlly here!
	*/





	/*
	  STOP INSERTING HERE!
	*/
	
	
	fflush(stdout);
	fflush(stderr);
    }
    
    
    exit(0); /* control never reaches here */
}





/* 
 * parseline - Parse the command line and build the argv array.
 * 
 *
 *  This function takes in a long string which is our command line and parses it
 *  into tokens that can be sent directly to exec. Also calls checkGrammar().
 *
 * Parameters:
 *   cmdline:  The command line, in the form:
 *
 *                command [arguments...] [&]
 *
 *   argv:     will become populated with the tokens that the command line was  
 *             parsed into, much like the real argv that you get in main. 
 *             
 *             NOTE: for this argv, you do NOT need an argc. After
 *             the last argument in the array there will be a NULL. That is how you know
 *             you have reached the end of the array.   
 *
 * Returns:
 *   1:        if the user has requested a BG job
 *   0:        if the user has requested a FG job  
 *  -1:        if cmdline is incorrectly formatted
 * 
 */
int parseline(const char *cmdline, char **argv) 
{
    return 0;
}


/* Checks that & appears at the end of the line if it appears at all */
int checkGrammar(const char* cmdline)
{
    return 1;
}




/* Prints the error message if the command line is not well formed. */
void usage()
{
	printf("%s: Parse error! Invalid command line.\n", shellname);
}

/* Prints whatever error message is supplied to msg to standard out. */
void app_error(char *msg)
{
    fprintf(stderr, "%s\n", msg);
    exit(1);
}