vigenere

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

int shift(char c);

int main(int argc, string argv[1]);
    int j;

{
    if (argc != 2) //if user doesn't run command-line argument of one or enter positive int
    {
        printf("Usage: ./vigenere key\n"); //prompt them to run it again
        return 1; //returning zero means everything went well
    }

    if (isalpha(argv[1])) //If user inputs an alpha key continue

        string p = get_string("plaintext: "); //prompt for plaintext and store

        {
            printf("ciphertext: "); //Print after collecting plaintext
        }

        for (int j = 0, n = strlen(argv[1];  j < n; j++)  //length of the entire string. Save n as strlen for use in loop
        {
            char cipher; //char within the string
            int shift(char cipher);

            if (isupper(p[i]))

            {
                cipher = ((p[i] + key[j]) % 26); //add key and rotate
                printf("%c", cipher); //print ciphertext after rotating
            }

            else if (islower(p[i]))

            {
                cipher = ((p[i] + key[j]) % 26); //add key and rotate
                printf("%c", cipher); //print ciphertext after rotating
            }

            else

            {
                printf("%c", p[i]); //Else, print unchanged
            }

        }
        printf("\n");
        return 0;


} //Closing brackets

//function definition
    int shift(char c);
        int j;
    {
        for (j = 0; j < strlen(argv[1]); j++)
            int c = (argv[1]); //NEW SHIFT function; user input at start of program
            int key = (argv[1][j]);

                for (key[j] % strlen(argv[1]))

                    if (islower(c))
                    {
                        key = ((key[j] - 97) % 26); //Shifting by alpha index
                    }
                    if (isupper(c))
                    {
                        key = ((key[j] - 65) % 26);
                    }
    }