#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <ctype.h>  // for isspace()
#include <unistd.h>

// counts the number of blank lines and // comment lines

int main(int argc, char **argv) {
  int fin;

  // Take the filename from command line argument
  if (argc != 2) {
    fprintf(stderr, "usage: %s filename\n", argv[0]);
    return EXIT_FAILURE;
  }

  // Open the file
  fin = open(argv[1], O_RDONLY);
  if (fin < 0 ) {
    fprintf(stderr, "%s -- ", argv[1]);
    perror("open failed");
    return EXIT_FAILURE;
  }

  // set up state machine
  typedef
    enum state_t {START, POSSIBLE_COMMENT, COMMENT, OTHER, NUM_STATES}
  State;

  typedef
    enum linetype_t {BLANK_LINE, COMMENT_LINE, OTHER_LINE, NUM_LINE_TYPES}
  LineType;

  State fsaState = START;
  int count[NUM_LINE_TYPES] = { 0, 0, 0};

  char c;
  ssize_t readCnt;
  while ( 1 ) {
    readCnt = read(fin, &c, 1);
    if ( readCnt == 0 ) break; // EOF
    if ( readCnt == -1 && errno == EINTR ) continue;  // try again
    
    switch(fsaState) {
    case START:
      if ( c == '\n' ) count[BLANK_LINE]++;
      else if (isspace(c) );
      else if (c == '/') fsaState = POSSIBLE_COMMENT;
      else {
	fsaState = OTHER;
	count[OTHER_LINE]++;
      }
      break;
    case POSSIBLE_COMMENT:
      if ( c == '/' ) {
	fsaState = COMMENT;
	count[COMMENT_LINE]++;
      }
      else if (c == '\n') {
	fsaState = START;
	count[OTHER_LINE]++;
      }
      else {
	fsaState = OTHER;
	count[OTHER_LINE]++;
      }
      break;
    case COMMENT:
      if ( c == '\n' ) fsaState = START;
      break;
    case OTHER:
      if ( c == '\n' ) fsaState = START;
      break;
    default:
      fprintf(stderr, "Internal error\n");
      return EXIT_FAILURE;
    }
  }
  close(fin);

  if ( readCnt < 0 ) {
    perror(NULL);
    return EXIT_FAILURE;
  }

  printf("Blank lines:   %d\n", count[BLANK_LINE]);
  printf("Comment lines: %d\n", count[COMMENT_LINE]);
  printf("Other lines:   %d\n", count[OTHER_LINE]);

  return EXIT_SUCCESS;
}