#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <bsd/string.h>
#include <stdlib.h>

typedef struct {
  char key[20];
  char value[20];
} list_entry;

char *dictionary_file_name = "./my-dict";
char *tmp_name = "./.my-dict.tmp";

int add_entry(char **args)
{
  char *key = args[0], *value = args[1];
  FILE *dict = fopen(dictionary_file_name, "rb");
  FILE *out = fopen(tmp_name, "wb");
  if (!out) {
    perror(tmp_name);           /* permission denied, for example */
    return -1;
  }

  int found = 0;                /* Have we found the entry? */
  if (dict) {   /* XXX what if we failed because permission denied? */
    for (;;) {
      list_entry my_entry;
      if (!fread(&my_entry, sizeof my_entry, 1, dict)) break;
      if (0 == strcmp(my_entry.key, key)) {
        if (strlcpy(my_entry.value, value, sizeof my_entry.value) >= sizeof my_entry.value) abort();
        found = 1;
      }
      fwrite(&my_entry, sizeof my_entry, 1, out); /* XXX error checking, e.g., disk full */
    }
    fclose(dict);
  }

  if (!found) {
    list_entry my_entry;
    if (strlcpy(my_entry.key, args[0], sizeof my_entry.key) >= sizeof my_entry.key) abort();
    if (strlcpy(my_entry.value, args[1], sizeof my_entry.value) >= sizeof my_entry.value) abort();
    fwrite(&my_entry, sizeof my_entry, 1, out); /* XXX what is wrong with you */
  }

  fflush(out);
  fsync(fileno(out));    /* ensure data is actually written to file */
  fclose(out);
  if (rename(tmp_name, dictionary_file_name)) {
    perror("rename");
    return -1;
  }

  return 0;                     /* success */
}

list_entry *find_entry(char *keyname)
{
  static list_entry my_entry;
  FILE *dict = fopen(dictionary_file_name, "rb");
  if (!dict) {
    perror(dictionary_file_name);
    return 0;
  }

  for (;;) {
    if (!fread(&my_entry, sizeof my_entry, 1, dict)) break;
    if (0 == strcmp(my_entry.key, keyname)) {
      return &my_entry;
    }
  }
  
  return 0;
}
  

int main(int argc, char **argv)
{
  if (argc < 2) {
    fprintf(stderr, "Usage: %s --add key value  # to add key=value to the db\n",
            argv[0]);
    fprintf(stderr, "or: %s key                 # to look up the key\n",
            argv[0]);
    return -1;
  }
  
  if (0 == strcmp(argv[1], "--add")) {
    return add_entry(argv+2);
  } else {
    list_entry *result = find_entry(argv[1]);
    if (result) {
      printf("%s = %s\n", result->key, result->value);
      return 0;
    } else {
      printf("Not found\n");
      return -1;
    } 
  }
}