#include <cs50.h>
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>

int validate (char* key);
char* ciphrate (char* text, char* key);

int main (int argc, string argv[])
{
    int valid = validate(argv[1]); //call function to validate the key is 26 char long, no char repeated and no numebers on it
    if (valid != 0)
    {                       //prints an error code
        if(valid == 1)
        {
            printf("Usage ./usability KEY\n");
        }
        else if (valid == 2)
        {
            printf("The key must contain 26 alphabetic characters\n");
        }
        else if (valid == 3)
        {
            printf("The key must contain no repeated characters\n");
        }
        else if (valid == 4)
        {
            printf("The key must not contain digits\n");
        }

        return 1; //return a code error
    }

    char* plaintxt = get_string("Plaintext: "); //ask for text to encipher

    printf("\n");
    char* ciphertxt = ciphrate(plaintxt, argv[1]); //call function to encipher the text

    printf("Ciphertext: %s\n", ciphertxt); //prints the result text

    return 0;
}

int validate (char* key)
{
    int lenght = strlen(key);  //checks for key lenght
    int chars = 0, a = 0, b = 0, c = 0; //some variables

    if (lenght != 26) //checks if lenght isn't equal to 26
    {
        return 2; //second error code output
    }
    for(int k = 0; k < 26; k++)
    {
        a = isdigit(key[k]); //check every char for a digit and add a value to a

    }
    if (a != 0) //if there's a digit
        {
            return 4; //fourth error code output
        }

    for(int i = 0; i < 26; i++)
    {
        c = islower(key[i]);
        if (c != 0)
        {
            key[i] = toupper(key[i]); //transform all chars to uppercase
        }
        b = b + key[i];
    }
    if (b != 2015) //the sum of all A - Z chars is 2015
    {
        return 3; //third error code output
    }

    return 0; //no error code output
}


char* ciphrate (char* text, char* key)
{
    int text_lenght = strlen(text);
    char* ciphrated_text = NULL;

    for(int i = 0; i < text_lenght; i++)
    {
        int d = 0, e = 0,f = 0;
        d = isupper(text[i]); //checks if cahr is uppercase or lower
        e = islower(text[i]);
        if(d == 0)
        {
            f = text[i] - 65;           //if it's uppercase then substract 65 (for knowing in witch place of the alphabet it's located)
            ciphrated_text[i] = key[f]; //and then assign the letter in the key that is in that possition
        }
        else if(e == 0)
        {
            f = text[i] - 97;                   //if it's a lowercase then substract 97 (same reason as in uppercase)
            ciphrated_text[i] = key[f] + 32;    //assign the letter in the key and add 32 so it's still a lowercase
        }
    }

    return ciphrated_text; //return the ciphrated text
}