//Encryption using Caesar Cipher of shift 13 i.e. Rot13
/*Assumptions:
 * The decryption programme '-' means space.
 * Any character from 52 to 64 from ASCII table is not in the text
 * Any character from 91 to 96 from ASCII table is not in the text
 * */


//Need to import these for file reading
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.stream.Collectors;

//For out.println
import static java.lang.System.out;

//This small programme assigns the variable 'rawText' to the text in test.txt file.
public class ReadFile {
    public static void main(String[] args) throws IOException {
        String rawText = Files.lines(Paths.get("c:\\fileToBeEncrypted.txt")).collect(Collectors.joining(""));

        int lenOfText = rawText.length();

        int i , bigL, bigL2, smallL, smallL2;
        for (i = 0; i < lenOfText; i++) {

        	//Refer to ASCII table

        	//First two 'if' and 'else if' checks are for Capital letters
        	if (rawText.charAt(i) + 0 <= 77) {
        		bigL = rawText.charAt(i) + 13;

        		//Convert number to character from ASCII table
        		out.print((char) bigL);


        	//In ASCII table 'N' is 78, if we add 13 to 78 then we get 91 which is '['.
            //However we want to go back to A, B, ... so we add 13 and subtract 26 which means overall we subtract 13.
           	} else if (rawText.charAt(i) + 0 > 77 && rawText.charAt(i) + 0 <= 90) {
        		bigL2 = rawText.charAt(i) - 13;
        		out.print((char) bigL2);


        	//Now we check for small letters and deal with them the same way as capital letters
            } else if (rawText.charAt(i) + 0 >= 97 && rawText.charAt(i) + 0 <= 109) {
            	smallL = rawText.charAt(i) + 13;


        		out.print((char) smallL);


            }else if (rawText.charAt(i) + 0 >= 110 && rawText.charAt(i) + 0 <= 122) {
            	smallL2 = rawText.charAt(i) - 13;

        		out.print((char) smallL2);
            }
        }
    }
}