/**
=========================================
Author         :  Eyad Hossam Al-Den,   |  Sarah Abou-Senna
e-mail         :  eyadhossamm@gmail.com |  sara_usa_1999@hotmail.com
ID             :  20176007              |  20175006
program        :  Software Engineering
task#          :  Assignment 4

preferable/necessary to compile in C++11 or later.
=========================================
*/

#include <iostream>
#include <string>                                                           //added for compatibility for anything older than C++11
#include <sstream>
#include <limits>
#include <fstream>
#include <vector>

using namespace std;

struct COURSE
{
    string courseName;
    int grade;
};

struct Student
{
    string name;
    int id;
    string email;
    COURSE courses[3];
};

vector<Student> students;
ifstream file;
void ReadFile();

/**==============BASIC SHIFTING ENCRYPTION/DECRYPTION FUNCTIONS==============*/
//Shifting Encryption
string shiftEncryption(string input, int shifts)
{
    for(int i=0; i<input.length(); i++) {
        if (input[i] != ' ')
            input[i] = static_cast<char>(input[i] + shifts);                    //changes the i-th character to its (i+shifts)-th character.
    }
    return input;
}
//Shifting Decryption
string shiftDecryption(string input, int shifts)
{
    for(int i=0; i<input.length(); i++) {
        if (input[i] != ' ')
            input[i] = static_cast<char>(input[i] - shifts);                    //changes the i-th character to its (i-shifts)-th character.
    }
    return input;
}
/**==============END OF SHIFTING ENCRYPTION/DECRYPTION==============*/


/**==============BONUS ENCRYPTION/DECRYPTION TECHNIQUES==============*/
//Transposition Encryption/Decryption, the same function does both tasks because it's essentially the same exact thing.
string transposition(string input)
{
    string output = ""; int flag = 0;
    for(int i=0; i<=input.length(); i++)
    {
        string temp = "";
        if(!isalpha(input[i]))
        {
            temp = input.substr(flag, i-flag);
            flag = i+1;
            for(int j=0; j<temp.length(); j++)
            {
                output += temp[temp.length() - j - 1];
            }
            output += input[i];
        }
    }
    return output;
}


/**==============RAIL FENCE CIPHER==============*/
//Rail Fence Encryption technique
string railFenceEncryption(string input, int depth)
{
    string encryptedOutput = ""; bool moveDown = false;
    int row = 0, column = 0;
    char rail[depth][input.length()];                                       //initialize the depth*len(input)

    for(int i=0; i<depth; i++)
        for(int j=0; j<input.length(); j++)
            rail[i][j] = '#';                                               //assign '#' to each of the depth*len(input) matrix's elements, basically the "fence".

    for(int i=0; i<input.length(); i++)
    {
        if(row == 0 || row == depth - 1)                                    //check if you are at either the topmost or bottommost row
            moveDown = !moveDown;                                           //go in the other direction if you are at either of those two

        rail[row][column++] = input[i];                                     //move and replace elements along the diagonal with input[i]

        if(moveDown) row++;                                                 //if you are moving down, increase rows, if not, decrease rows (moving up)
        else row--;
    }

    for(int i=0; i<depth; i++)
        for(int j=0; j<input.length(); j++)
            if(rail[i][j] != '#')                                           //basically checks if you are on a diagonal or not
                encryptedOutput += rail[i][j];                              //if you are, append the character of the element you are at to the output string

    return encryptedOutput;
}
//Rail Fence Decryption technique
string railFenceDecryption(string input, const int depth)                         //most code is repeated from the encryption function, code is somewhat self-explanatory.
{
    string decryptedOutput = ""; bool moveDown = false;
    int row = 0, column = 0, pos = 0;
    char rail[depth][input.length()];

    for(int i=0; i<depth; i++)
        for(int j=0; j<input.length(); j++)
            rail[i][j] = '#';                                               //same as before, construct the 'fence'

    for(int i=0; i<input.length(); i++)
    {
        if(row == depth - 1) moveDown = false;
        else if(row == 0) moveDown = true;

        rail[row][column++] = '.';                                          //mark indexes with a period '.'

        if(moveDown) row++;
        else row--;
    }


    for(int i=0; i<depth; i++)
        for(int j=0; j<input.length(); j++)
            if(rail[i][j] == '.' && pos<input.length())                     //replace rail[i][j] with input[pos++] if (i,j) are on a rail
                rail[i][j] = input[pos++];

    row = 0, column = 0;
    for(int i=0; i<input.length(); i++)
    {
        if(row == depth - 1) moveDown = false;
        else if(row == 0) moveDown = true;

        if(rail[row][column] != '.')
            decryptedOutput += rail[row][column++];

        if(moveDown) row++;
        else row--;
    }

    return decryptedOutput;
}
/**==============END OF RAIL-FENCE CIPHER==============*/
/**===================MENU FUNCTIONS===================*/
void showEncryptionMethods()
{
    cout << "Input file location (e.g. : D:\\example.txt):" << endl;
    string fileLocation = "";
    cin >> fileLocation;
    file.open(fileLocation);
    if(file.fail())
    {
        cerr << "Opening file failed. Check entered path and try again." << endl;
        return;
    }else ReadFile();

    ofstream outFile;
    outFile.open("EncryptedFile.txt");

    string encryptionMethod = "", input = ""; int key = 0;
    cout << "Choose a method of encryption to encrypt this string with [shifting/transposition/rail-fence]: " << endl;
    cin >> encryptionMethod;
    if(encryptionMethod == "shifting")
    {
        cin.ignore(numeric_limits<streamsize>::max(), '\n' );
        cout << "Enter number of shifts: " << endl;
        cin >> key;
        for(int i = 0; i < students.size(); i++)
        {
            outFile << shiftEncryption(students[i].name, key) << endl;
            outFile << students[i].id << endl;
            outFile << shiftEncryption(students[i].email, key) << endl;
            for(int j = 0; j < 3; j++)
                outFile << shiftEncryption(students[i].courses[j].courseName, key) << ' ' << students[i].courses[j].grade << endl;
        }
        outFile.close();
    }
    else if(encryptionMethod == "transposition")
    {
        cin.ignore(numeric_limits<streamsize>::max(), '\n' );
        for(int i = 0; i < students.size(); i++)
        {
            outFile << transposition(students[i].name) << endl;
            outFile << students[i].id << endl;
            outFile << transposition(students[i].email) << endl;
            for(int j = 0; j < 3; j++)
                outFile << transposition(students[i].courses[j].courseName) << students[i].courses[j].grade << endl;
        }
    }
    else if(encryptionMethod == "rail-fence")
    {
        cin.ignore(numeric_limits<streamsize>::max(), '\n' );
        cout << "Enter depth of fence: " << endl;
        cin >> key;
        for(int i = 0; i < students.size(); i++)
        {
            outFile << railFenceEncryption(students[i].name, key) << endl;
            outFile << students[i].id << endl;
            outFile << railFenceEncryption(students[i].email, key) << endl;
            for(int j = 0; j < 3; j++)
                outFile << railFenceEncryption(students[i].courses[j].courseName, key) << students[i].courses[j].grade << endl;
        }
    }
    else
    {
        cout << "Invalid input, try again." << endl;
    }
    outFile.close();
}
void showDecryptionMethods()
{
    cout << "Input file location (e.g. : D:\\example.txt):" << endl;
    string fileLocation = "";
    cin >> fileLocation;
    file.open(fileLocation);
    if(file.fail())
    {
        cerr << "Opening file failed. Check entered path and try again." << endl;
        return;
    }else ReadFile();

    ofstream outFile;
    outFile.open("DecryptedFile.txt");

    string decryptionMethod = "", input = ""; int key = 0;
    cout << "Choose a method of decryption to decrypt this string with [shifting/transposition/rail-fence]: " << endl;
    cin >> decryptionMethod;
    if(decryptionMethod == "shifting")
    {
        cin.ignore(numeric_limits<streamsize>::max(), '\n' );
        cout << "Enter number of shifts: " << endl;
        cin >> key;
        for(int i = 0; i < students.size(); i++)
        {
            outFile << shiftDecryption(students[i].name, key) << endl;
            outFile << students[i].id << endl;
            outFile << shiftDecryption(students[i].email, key) << endl;
            for(int j = 0; j < 3; j++)
                outFile << shiftDecryption(students[i].courses[j].courseName, key) << students[i].courses[j].grade << endl;
        }
    }
    else if(decryptionMethod == "transposition")
    {
        cin.ignore(numeric_limits<streamsize>::max(), '\n' );
        for(int i = 0; i < students.size(); i++)
        {
            outFile << transposition(students[i].name) << endl;
            outFile << students[i].id << endl;
            outFile << transposition(students[i].email) << endl;
            for(int j = 0; j < 3; j++)
                outFile << transposition(students[i].courses[j].courseName) << students[i].courses[j].grade << endl;
        }
    }
    else if(decryptionMethod == "rail-fence")
    {
        cin.ignore(numeric_limits<streamsize>::max(), '\n' );
        cout << "Enter depth of fence: " << endl;
        cin >> key;
        for(int i = 0; i < students.size(); i++)
        {
            outFile << railFenceDecryption(students[i].name, key) << endl;
            outFile << students[i].id << endl;
            outFile << railFenceDecryption(students[i].email, key) << endl;
            for(int j = 0; j < 3; j++)
                outFile << railFenceDecryption(students[i].courses[j].courseName, key) << students[i].courses[j].grade << endl;
        }
    }
    else
    {
        cout << "Invalid input, try again." << endl;
    }
    outFile.close();
}

/**==============END OF MENU FUNCTIONS==============*/
int main()
{
    string command = "";
    while(true)
    {
        cout << "choose (write) a function to perform [encrypt/decrypt/exit]: " << endl;
        cin >> command;
        for(int i=0; i<command.length(); i++)
            command[i] = tolower(command[i]);
        if(command == "exit") break;
        else if(command == "encrypt") showEncryptionMethods();
        else if(command == "decrypt") showDecryptionMethods();
        else cout << "invalid input, try again." << endl;

        cout << endl;
    }
    return 0;
}

void ReadFile()
{
    string currStr = "";
    while(file >> currStr)
    {
        string name = currStr;
        file >> currStr;
        name += " " + currStr;
        Student tempStudent;
        tempStudent.name = name;
        file >> tempStudent.id >> tempStudent.email;
        for (int i = 0; i < 3; i++)
        {
            file >> currStr;
            tempStudent.courses[i].courseName = currStr;
            file >> tempStudent.courses[i].grade;
        }
        students.push_back(tempStudent);
    }
}