/* phone.c - Interpret a phone number given a word.
 * Assume that the word has exactly 7 letters, and is in all caps.
 */
#include <stdio.h>
#include <ctype.h>   // functions manipulating characters like toupper.
#include <string.h>  // contains strlen()
#include <stdlib.h>  // contains exit()
#define GOOD 1
#define BAD  0

// Let's insert function prototypes, to tell the C compiler that these
// functions are defined later in the file.
void capitalize(char *);
int verify(char *);
void convert(char *, char *);

main()
{
  char word[8], phone_number[9];
  int status;

  // Let's use the fgets() function to read the input word into our string.
  // That way, we can explicitly control how many characters we read.
  // fgets() takes 3 parameters:
  // 1.  The character array we want to initialize.
  // 2.  The number of characters to read, including the terminating null char.
  // 3.  Where to read from.  For standard input, it's:  stdin.  But we can
  //     also have used fgets() to read from a file.

  printf("What is the word representing a phone number?  ");
  fgets(word, 8, stdin);
  printf("You entered %s\n", word);

  // Let's convert all characters to uppercase.
  capitalize(word);

  // Let's make sure the word consists entirely of capital letters.
  // Otherwise it's bad input.
  status = verify(word);

  if (status == GOOD)
  {
    // Now, we can convert.
    convert(word, phone_number);

    // Output
    printf("Your word %s becomes the phone number %s.\n", word, phone_number);
  }

  else
  {
    printf("Sorry, your input is not valid.  Need 7 letter word.\n");
  }
}

// Capitalize every character in s.  Use ctype's toupper(), which returns
// the uppercase version of the parameter we give to it.
void capitalize(char * s)
{
  int i;

  for (i = 0; i < strlen(s); ++i)
    s[i] = toupper(s[i]);
}

// Make sure everybody is an uppercase letter.  Use ctype's isupper().
// Also make sure the length of the string is 7.
// If the input is valid, return GOOD, else return BAD.
int verify(char * s)
{
  // YOU NEED TO MODIFY THIS FUNCTION SO IT DOESN'T ALWAYS REJECT INPUT.
  
  return BAD;
}

// For each char in word, turn it into a digit character.  Also remember
// to put in the hyphen.
// This function needs to put its answer in the phone parameter.
void convert(char * word, char * phone)
{
  int i, position = 0;
  char digit;

  for (i = 0; i < strlen(word); ++i)
  {
    switch(word[i])
    {
      case 'A' : case 'B' : case 'C' : digit = '2'; break;
      case 'D' : case 'E' : case 'F' : digit = '3'; break;
      case 'G' : case 'H' : case 'I' : digit = '4'; break;
      case 'J' : case 'K' : case 'L' : digit = '5'; break;
      case 'M' : case 'N' : case 'O' : digit = '6'; break;
      case 'P' : case 'Q' : case 'R' : case 'S' : digit = '7'; break;
      case 'T' : case 'U' : case 'V' : digit = '8'; break;
      case 'W' : case 'X' : case 'Y' : case 'Z' : digit = '9'; break;
      default:
        printf("Error - unknown letter %c\n", word[i]);
        exit(1);
    }

    phone[position++] = digit;
    if (position == 3)
      phone[position++] = '-';
  }

  // Put a null character at the end!
  phone[8] = '\0';
}