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


char * copy_string(char  * input)
{
  int length = 0;
  while(input[length] != 0)
  {
    length++;
  }
  char * result = (char *) malloc(sizeof(char) * (length + 1));
  int i;
  for (i = 0; i <= length; i++)
  {
    result[i] = input[i];
  }
  return result;
}


struct phone_entry
{
  char * name;
  char * phone;
};


struct phonebook
{
  int max_entries;
  int current_entries;
  phone_entry * entries;
};


struct phonebook initialize_phonebook(int max_entries)
{
  struct phonebook result;
  result.max_entries = max_entries;
  result.current_entries = 0;
  result.entries = (phone_entry *) malloc(sizeof(phone_entry) * max_entries); 

  return result;
}

// asks the user to enter the name and number for some person
// to be fixed.
void enter_number(struct phonebook * my_book)
{
  if (my_book->current_entries >= my_book->max_entries)
  {
    printf("you surpassed the maximum number of entries\n");
  }

  char * buffer = (char *) malloc(sizeof(char) * 1000);

  struct phone_entry entry;
  printf("please enter name\n");
  scanf("%s", buffer);
  entry.name = copy_string(buffer);

  printf("please enter phone\n");
  scanf("%s", buffer);
  entry.phone = copy_string(buffer);

  my_book->entries[my_book->current_entries] = entry;
  my_book->current_entries++;

  free(buffer);
}


void print_phonebook(phonebook my_book)
{
  printf("\nall phone entries:\n");
  int i;
  for (i = 0; i < my_book.current_entries; i++)
  {
    printf("entry %d\n", i);
    printf("name: %s\n", my_book.entries[i].name);
    printf("number: %s\n", my_book.entries[i].phone);
    printf("\n");
  }
}


char * get_filename()
{
  return "phones.txt";
}


int save_phonebook(struct phonebook * my_book)
{
  char * filename = get_filename();
  FILE * file = fopen(filename, "w");
  if (file == 0)
  {
    printf("could not open file %s for writing\n", filename);
    return 0;
  }

  int i;
  for (i = 0; i < my_book->current_entries; i++)
  {
    fprintf(file, "%s %s\n", my_book->entries[i].name, my_book->entries[i].phone);
  }
  fclose(file);

  return 1;
}


int load_phonebook(struct phonebook * my_book)
{
  char * filename = get_filename();
  FILE * file = fopen(filename, "r");
  if (file == 0)
  {
    printf("could not open file %s for reading\n", filename);
    return 0;
  }

  my_book->current_entries = 0;
  char * buffer = (char *) malloc(sizeof(char) * 1000);
  int success = 1;
  while(1)
  {
    phone_entry entry;
    
    int items = fscanf(file, "%s", buffer);
    if (items != 1)
    {
      break;
    }

    if (my_book->current_entries >= my_book->max_entries)
    {
      printf("phonebook capacity has been exceeded, cannot store phone number for %s\n", buffer);
      success = 0;
      break;
    }

    entry.name = copy_string(buffer);
    
    items = fscanf(file, "%s", buffer);
    if (items != 1)
    {
      printf("failed to read phone number for name %s\n", entry.name);
      success = 0;
      free(entry.name);
      break;
    }
    entry.phone = copy_string(buffer);
    my_book->entries[my_book->current_entries] = entry;
    my_book->current_entries++;
  }
  fclose(file);
  free(buffer);

  return success;
}


int string_equal(char * a, char * b)
{
  int i = 0;
  while(1)
  {
    if ((a[i] == 0) && (b[i] == 0))
    {
      return 1;
    }
    else if ((a[i] == 0) || (b[i] == 0))
    {
      return 0;
    }
    else if (a[i] != b[i])
    {
      return 0;
    }
    i++;
  }
}


void search_name(struct phonebook * book)
{
  char * buffer = (char *) malloc(sizeof(char) * 1000);
  printf("enter name to search for:\n");
  scanf("%s", buffer);

  int i;
  for (i = 0; i < book->current_entries; i++)
  {
    struct phone_entry entry = book->entries[i];
    if (string_equal(entry.name, buffer))
    {
      printf("entry %d\n", i);
      printf("name: %s\n", book->entries[i].name);
      printf("number: %s\n", book->entries[i].phone);
      printf("\n");
    }
  }
}


int main()
{
  int max_entries = 100;
  struct phonebook book = initialize_phonebook(max_entries);
  if (load_phonebook(&book) == 0)
  {
    printf("failed to load phonebook\n");
    book = initialize_phonebook(max_entries);
  }

  while(1)
  {
    int choice;
    printf("\n1. enter a new number\n");
    printf("2. print all entries\n");
    printf("3. save to a file\n");
    printf("4. search name\n");
    printf("0. exit\n");
    printf("enter your choice:\n");
    scanf("%d", &choice);

    switch(choice)
    {
    case 0:
      exit(0);
      break;

    case 1:
      enter_number(&book);
      break;

    case 2:
      print_phonebook(book);
      break;

    case 3:
      save_phonebook(&book);
      break;

    case 4:
      search_name(&book);
      break;

    default:
      printf("%d is not a valid choice\n", choice);
      break;

    }


  }
}