#include "./stdinc.h"

//
// Purpose:	Homework 3, Problem 6
// Usage:	t_exec [-v] [-d] < Command
//			-v	verbose mode
//			-d	debug mode (output some details)
//				(not part of the assignment)

// --| constants |--
const int	MAX_LINE = 50;
const int	BUFSZ = 100;
const char	*WHITE = " \t\n";       // white space characters

// --| prototypes |--
void eval(char *word[]);
void getArgs(int argc, char *argv[]);
int getTokens(char *cmnd, char *word[], const char *delim);

// --| globals |--
int	verbose = 0;
int	debug = 0;

// --| in-line functions |--
static inline			// display prompt and get command
char * getcmnd(char *cmnd) {
  char *	s;
  printf("> ");
  s = fgets(cmnd, MAX_LINE, stdin);
  if (cmnd[strlen(cmnd)-1] != '\n') {
    fprintf(stderr, "*** Ooops, line too long\n");
    exit(1);
  }
  printf("%s", cmnd);		fflush(stdout);
  return s;
}

int
main (int argc, char *argv[]) {
  char	cmnd[MAX_LINE];	// command-line
  char	*word[BUFSZ];	// word[k] points to kth word
  int	nwords;		// #words in command line
  int	i;

  getArgs(argc, argv);

  while (getcmnd(cmnd) != NULL) {
    nwords = getTokens(cmnd, word, WHITE);

    if (strcmp(word[0], "quit") == 0)	break;
    eval(word);
  }
  return 0;

}

void
getArgs(int argc, char *argv[]) {
  int	c;
  int	ok = 1;
       
  while ((c = getopt(argc, argv, "dv")) != -1) {
    switch(c) {
      case 'd':
        debug = 1;
      	break;
      case 'v':
        verbose = 1;
      	break;
      default:	
        ok = 0;
	DEBUG( (stderr, "getArgs:  Unknown flag %c\n", c) );
        break;
    }
  }
  if (!ok) {
    fprintf(stderr, "Usage:  t_exec [-v] [-d] < Command\n");
    exit(1);
  }
}

// --| get tokens |--
// Semantics:	(nwords, word[]) = getTokens(cmnd,delim)
//	where	cmnd	is the command line
//		delim	is the deliminator string
//		nwords	is number of words in command line
//		word[]	is array of ptrs to words in command line
// Usage:	int nwords = getTokens(cmnd, word, " \t\n");
//		where	char cmnd[];
//			char *word[];
int
getTokens(char *cmnd, char *word[], const char *delim) {
  int	nwords = 0;
  char	*p = cmnd;
  char	*token;

  while ((token=strtok(p,delim)) != NULL) {
    word[nwords] = token;
    DEBUG( (stderr, "\tword[%d] = %s\n", nwords, token) );
    nwords++;
    p = NULL;
  }
  word[nwords] = NULL;
  return nwords;
}

// --| evaluate a command |--
void
eval(char *word[]) {
  pid_t		pid;
  int		status;
  struct timeval tv1, tv2;
  double	t;		// elapsed time in msec

  gettimeofday(&tv1, 0);
  if ( (pid = Fork()) == 0) {	// child
    if (verbose) {
      int	i = 0;
      fprintf(stderr, "\tverbose output:\n");
      fprintf(stderr, "\t\tfile:\t%s\n", word[0]);
      while (word[i] != NULL) {
        fprintf(stderr, "\t\targv[%d]:\t%s\n", i, word[i]);
	i++;
      }
    }
    Execvp(word[0], word);
    exit(0);
  }
  Waitpid(pid, &status,0);
  gettimeofday(&tv2, 0);
  t = (1000.0*tv2.tv_sec + tv2.tv_usec/1000.0)
  				- (1000.0*tv1.tv_sec + tv1.tv_usec/1000.0);
  fprintf (stderr, "Elapsed Time:  %d sec, %d msec\n", (int) t/1000, (int) t%1000);
}