package com.example.cipher;


/**
 * Created by Mehul Patel on 2/13/16.
 */

import java.util.*;
import java.io.*;

public class Cipher{

    public static boolean isFile(String file){
        File tmp = new File(file);
        boolean exists = tmp.exists();
        if (exists)
            return true;
        System.out.println("Bad filename");
        return false;
    }

    public static String getFileContent(String file) {
        String str = "";
        try{
            FileReader fileReader = new FileReader(file);
             String line = "";
            BufferedReader bufferedReader = new BufferedReader(fileReader);
            while((line = bufferedReader.readLine()) != null) {
                str += line;
            }
            bufferedReader.close();


        } catch(FileNotFoundException ex) {
            System.out.println( "Bad filename");
        } catch (IOException e) {
            System.out.println("Something went wrong");
        }
        return str;
   }

    public static String encryptMain(char c, char key_s) {
        String s = "";
        int key =  (key_s >= 'a') ?  (int) key_s - (int) 'a' : (int) key_s - (int) 'A';
        if (c >= 'A' && c <= 'Z') s += (char)((c - 'A' + key) % 26 + 'A');
        else if (c >= 'a' && c <= 'z')  s += (char)((c - 'a' + key) % 26 + 'a');
        else  s += c;
        return s;
    }

    public static String decryptMain(char c, char key_s) {
        String s = "";
        int key =  (key_s >= 'a') ?  (int) key_s - (int) 'a' : (int) key_s - (int) 'A';
        if (c >= 'A' && c <= 'Z')  s += (char)(Math.abs(((c - 'A' - key) % 26))+ 'A');
        else if (c >= 'a' && c <= 'z')  s += (char)(Math.abs(((c - 'a' - key) % 26)) + 'a');
        else s += c;
        return s;
    }

    public static void encrypt() throws FileNotFoundException, UnsupportedEncodingException {

        Scanner input = new Scanner(System.in);
        System.out.print("Enter your key\n");
        String key = input.next();
        String ifs;
        while (true){
            System.out.println("Enter your input filename");
            ifs = input.next();
            if (isFile(ifs)) break;
        }
        String file_content = getFileContent(ifs);
        String output_content = "";
        int j = 0;
        for(int i = 0; i < file_content.length(); i++) {
            char a = file_content.charAt(i);
            if(j >= key.length())  j = 0;
            char b = key.charAt(j);
            output_content += encryptMain(a,b);
            j++;
        }
        System.out.print("Enter your output filename\n");
        String ofs = input.next(); //name of output txt file

        PrintWriter writer = new PrintWriter(ofs, "UTF-8");
        writer.print(output_content);
        writer.close();

        System.out.println("Successfully encrypted!!");


    }
    public static void decrypt() throws FileNotFoundException, UnsupportedEncodingException {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter your key\n");
        String key = input.next();

        String ifs;
        while (true){
            System.out.println("Enter your input filename");
            ifs = input.next();
            if (isFile(ifs)) break;
        }
        String file_content = getFileContent(ifs);
        String output_content = " ";
        int j = 0;
        for(int i = 0; i < file_content.length(); i++) {
            char a = file_content.charAt(i);
            if(j >= key.length())  j = 0;
            char b = key.charAt(j);
            output_content += decryptMain(a,b);
            j++;
        }

        System.out.print("Enter your output filename\n");
        String ofs = input.next(); //name of output txt file

        PrintWriter writer = new PrintWriter(ofs, "UTF-8");
        writer.print(output_content);
        writer.close();

        System.out.println("Successfully decrypted!!");
    }

    public static void main(String[] args) throws FileNotFoundException, UnsupportedEncodingException {
       Scanner input = new Scanner(System.in);

        System.out.println("Welcome to the encryption problem\n" +
                "What would you like to do?" );
        int choice = -1;
        while(choice != 0) {
            System.out.print("What would you like to do?\n" +
                    "1 - Encrypt a file\n" +
                    "2 - Decrypt a file\n" +
                    "0 - Exit\n" +
                    "Your Choice: ");
            choice = input.nextInt();
            if(choice == 1) encrypt();
            if(choice == 2) decrypt();
        }



    }

}