#include <iostream>
using namespace std;

int main() {
    int Choice, option;
    
    cout << "1.Caesar Cipher \n 2.Vernam Cipher \n 3.Vigenere Cipher \n 4.Transposition Cipher \n 5.RSA \n";
    cout << "Choose one of the options above: ";
    
    cin >> Choice;
    
    switch(Choice) {
        case 1:
            cout <<"1.Encrypt a message \n";
            cout <<"2.Decrypt a message \n";
            cout <<"Choose one option from above: ";
            cin >>option;
            
            if(option == 1) {
                string message, cipher;
                char chr;
                int shift, x;
                
                cout <<"Enter your message: ";
                cin >> message;
                
                cout <<"Enter the shift value: ";
                cin >> shift;
        
                for(int i=0; i<message.length(); i++) {
                    chr = message[i];
        
                    if (int(chr) <= 90){
                        x = ((int(chr) + shift - 65) % 26 + 65);
                        cipher[i] = char(x);
                    }
            
                    else {
                        
                        x = ((int(chr) + shift - 97) % 26 + 97);
                        cipher[i] = char(x);
                    }
                }
                cout<<"Your cipher text is: ";
                for(int i=0; i<message.length(); i++) {
                    cout<<cipher[i];
                }
            }
            else if(option == 2) {
                string message, cipher;
                char chr;
                int shift, x;
                
                cout<<"Enter your cipher text: ";
                cin>>cipher;
                
                cout<<"Enter the shift value: ";
                cin>>shift;
                
                for(int i=0; i<cipher.length(); i++) {
                    chr = cipher[i];
                    
                    if(int(chr) < 90) {
                         x = ((int(chr) - shift - 65) % 26 + 65);
                         message[i] = char(x);
                    }
                    else {
                         x = ((int(chr) - shift - 97) % 26 + 97);
                         message[i] = char(x);
                    }
                }
                cout<<"Your decrypted message is: ";
                for(int i=0; i<cipher.length(); i++) {
                    cout<<message[i];
                }
            }
        break;
        case 2:
            cout <<"1.Encrypt a message \n";
            cout <<"2.Decrypt a message \n";
            cout <<"Choose one option from above: ";
            cin >>option;
            
            if(option == 1) {
                string message, cipher, key;
                char chr, keychar;
                int x;
                
                cout <<"Enter your message: ";
                cin >> message;
                
                cout <<"Enter the key: ";
                cin >>key;
                
                for(int i=0; i<message.length(); i++){
                    char chr = message[i];
                    char keychar = key[i];
            
                    if (int(chr) < 90){
                        x = ((int(chr) + int(keychar) - 130) % 26 + 65);
                        cipher[i] = char(x);
                    }
                
                    else{
                       x = ((int(chr) + int(keychar) - 194) % 26 + 97);
                       cipher[i] = char(x);
                    }
                }     
                cout<<"Your cipher text is: ";
                for(int i=0; i<message.length(); i++) {
                    cout<<cipher[i];
                }
            }
            if(option == 2) {
                string cipher, message, key;
                char chr, keychar;
                int x;
                
                cout <<"Enter the cipher text: ";
                cin >> cipher;
                
                cout <<"Enter the key: ";
                cin >>key;
                
                for(int i=0; i<cipher.length(); i++){
                    chr = cipher[i];
                    keychar = key[i];
            
                    if (int(chr) < 90){
                        x = ((int(chr) - int(keychar) - 130) % 26 + 65);
                        message[i] = char(x);
                    }
                    else{
                       x = ((int(chr) - int(keychar)) % 26 + 97);
                       message[i] = char(x);
                    }
                }
                cout<<"Your decrypted message is: ";
                for(int i=0; i<cipher.length(); i++) {
                    cout<<message[i];
                }
            }
        break;
        case 3:
            cout <<"1.Encrypt a message \n";
            cout <<"2.Decrypt a message \n";
            cout <<"Choose one option from above: ";
            cin >>option;
            
            if(option == 1) {
                string message, cipher, key;
                char chr, keychar;
                int x;
                
                cout <<"Enter your message: ";
                cin >> message;
                
                cout <<"Enter the key: ";
                cin >>key;
                
                char newkey[message.length()];
                int length = 0;
                
                
                while(length < message.length()) {
                    for(int i=0; i<key.length(); i++) {
                        if(length <= message.length()) {
                            newkey[length] = key[i];
                            length += 1;
                        }
                        else
                            break;
                    }
                }
                
                for(int i=0; i<message.length(); i++){
                    chr = message[i];
                    keychar = newkey[i];
            
                    if (int(chr) < 90){
                        x = ((int(chr) + int(keychar) - 130) % 26 + 65);
                        cipher[i] = char(x);
                    }
                
                    else{
                       x = ((int(chr) + int(keychar) - 194) % 26 + 97);
                       cipher[i] = char(x);
                    }
                }     
                cout<<"Your cipher text is: ";
                for(int i=0; i<message.length(); i++) {
                    cout<<cipher[i];
                }
            }
            if(option == 2) {
                string cipher, message, key;
                char chr, keychar;
                int x;
                
                cout <<"Enter the cipher text: ";
                cin >> cipher;
                
                cout <<"Enter the key: ";
                cin >>key;
                
                char newkey[cipher.length()];
                int length = 0;
                
                
                while(length < cipher.length()) {
                    for(int i=0; i<key.length(); i++) {
                        if(length <= cipher.length()) {
                            newkey[length] = key[i];
                            length += 1;
                        }
                        else
                            break;
                    }
                }
                
                for(int i=0; i<cipher.length(); i++){
                    chr = cipher[i];
                    keychar = newkey[i];
            
                    if (int(chr) < 90){
                        x = ((int(chr) - int(keychar) - 130) % 26);
                        if(x<0){
                           x += 91;
                       }
                       else{
                           x += 65;
                       }
                        message[i] = char(x);
                    }
                    else{
                       x = ((int(chr) - int(keychar)) %26);
                       if(x<0){
                           x += 123;
                       }
                       else{
                           x += 97;
                       }
                       message[i] = char(x);
                    }
                }
                cout<<"Your decrypted message is: ";
                for(int i=0; i<cipher.length(); i++) {
                    cout<<message[i];
                }
            }
        break;
    }
    return 0;
}