#define _POSIX_C_SOURCE 200809L

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char ** argv) {
  int suffix_present = 0, i, j;
  char *basename; char c;
  int basename_length = 0, last_slash = 0;
  int suffix_length = 0;

  /* 
    Basename takes two arguments, one for the path itself and an optional
    one for a suffix to remove (e.g. ".c" to remove the C file extension).
    Here, we check for that second argument to determine if we need to
    remove an extension.

    If there aren't multiple arguments, check if a path was even given. If
    not, the POSIX spec says to just return a newline.
  */
  if(argc > 2) {
    suffix_present = 1;
  }
  else if(argc == 1) {
    printf("\n");
    return 0;
  }

  /*
    If the path is just //, the POSIX spec also says to return newline
  */
  if(strcmp(argv[1], "//") == 0) {
    printf("\n");
    return 0;
  }

  i = 0;
  
  /* 
    Find the end of the path (probably could've just used strlen)
  */
  for(c = argv[1][i]; c != '\0'; c = argv[1][i]) {
    i++;
  }

  /*
    If the last character of the path is /, then remove it
  */
  if(argv[1][i-1] == '/') {
    argv[1][i-1] = '\0';
  }

  i = 0;
  
  /*
    Find the last slash in the path
  */
  for(c = argv[1][i]; c != '\0'; c = argv[1][i]) {
    if(c == '/') {
      last_slash = i;
    }
    i++;
  }

  i = last_slash + 1;

  /*
    Figure out how long the basename is
  */
  for(c = argv[1][i]; c != '\0'; c = argv[1][i]) {
    basename_length++; i++;
  }

  /* 
    Allocate memory for the basename; fail out if we can't
  */
  basename = calloc(basename_length + 1, sizeof(*basename));
  if(basename == NULL) {
    fprintf(stderr, "%s: Could not allocate sufficient memory\n", argv[0]);
    return 1;
  }

  i = last_slash + 1;

  /*
    Transfer the basename to the array
  */
  for(c = argv[1][i]; c != '\0'; c = argv[1][i]) {
    basename[i - (last_slash + 1)] = c;
    i++;
  }

  basename[basename_length] = '\0'; /* don't forget the null! */

  /*
    If we need to remove a suffix, check if the end of the string is
    actually equal to the suffix and, if it is, replace the first character
    of the suffix with a null character.
  */
  if(suffix_present && strcmp(basename, argv[2]) != 0) {
    i = 0;
    for(c = argv[2][i]; c != '\0'; c = argv[2][i]) {
      suffix_length++;
      i++;
    }
    
    j = suffix_length - 1;

    for(i = basename_length - 1; i > 0; i--) {
      if(basename[i] != argv[2][j]) {
	break;
      }
      else if(j == 0) {
        basename[i] = '\0';
	i = 0;
      }
      j--;
    }
  }

  /*
    Print the basename, free the memory, and quit!
  */
  printf("%s\n", basename);

  free(basename);

  return 0;
}