//C++ Library
#include <iostream>
#include <cstring>
#include <string>
#include <fstream>
#include <sstream>

//C Library
#include <unistd.h>
#include <stdio.h>
#include <termios.h>
#include <stdlib.h>
using namespace std;  //using standard namespace

//Functions
/**Create OR Login User Function Headers**/
int getch();
string getpass(const char*, bool);
void createUser();
bool validatePass(char[]);
bool validateShadow(string, string);
bool checkUser(string);
bool checkPasswd(string);
void addSalt(string);
void addShadow(string, string, int);
void addPasswd(string, string, int);

/**File System Function Headers**/
void SystemMenu(string);
bool checkFile(string);
void createFile(string, int, int);
int getUserLevel(string);
int getFileLevel(string);
void readFile(string, int);
void writeFile(string, int);
void listFile();
void saveFile();

//Main Function
int main (int argc, char* argv[])
{
	//Variable
	string username;
	string password;

	//Create files for those computer don't have these files
	system("touch salt.txt");
	system("touch shadow.txt");
	system("touch passwd.txt");
	system("touch Files.store");

	cout<<"\tWelcome to File System"<<endl;
	cout<<"======================================"<<endl;
	if(argc == 1) //If run with ./FileSystem
	{
		cout<<"Login to File System\n======================"<<endl;
		enteruser:
		cout<<"Username		: ";
		cin>>username;
		if(checkUser(username) == false && checkPasswd(username) == false) //Check if user name and password does not exist, prompt user to enter again
		{
			cout<<"User Does Not Exist. Please Try Again. "<<endl;
			goto enteruser;
		}
		else  //Else ask for password and continue to login
		{
			cin.ignore(); //To reserve a line
			password=getpass("Password: ",true); //getpass("Display", if true = hide password, false = display password)

			if (validateShadow(username, password) == true) //Validate username and password/login
			{
				sleep (5); //Delay
				SystemMenu(username);
			}
			else  //If fail to match hash value
			{
				cout<<"Password Incorrect!"<<endl;
				cout<<"Hash Value Does Not Match. \nProgram Terminating......."<<endl;
			}
		}

	}
	else if(strcmp(argv[1], "-i") == 0) //Run with ./FileSystem -i
	{
		cout<<"Username		: ";
		cin>>username;
		if(checkUser(username) == false)
		{
			cout<<"User Does Not Exist. Proceed to Create User Account. "<<endl;
			createUser();
		}
		else
			cout<<"User already Exist inside System. \nProgram Terminating......."<<endl;

	}
}

//Create User
void createUser()
{
	//Variable
	string username;
	string pwd1;
	string pwd2;
	char *passwd;

	cout<<"\tRegister"<<endl;
	cout<<"======================================"<<endl;
	cout<<"Username		: ";
	cin>>username;
	cin.ignore(); //use to reserve for a next string input
	tryagain:

	pwd1=getpass("Please enter the password: ",true); //Hide input password by using getpass() function

	//convert string to char
	passwd = new char [pwd1.length()];
	strcpy(passwd, pwd1.c_str());

	if (validatePass(passwd) == true)
	{
		int count=1;
		enter_again:
		if(count<4)
		{
			pwd2=getpass("Enter password again: ",true);

			if(pwd1 ==	pwd2)
			{
				int clearance;
				cout<<"Successful created"<<endl;
				addSalt(username);

				enterclearance:
				cout<<"User Clearance(0/1/2)	: ";
				cin>>clearance;
				if(clearance < 0 ||clearance > 2)
				{
					cout<<"Invalid clearance."<<endl;
					goto enterclearance;
				}
				else
				{
					addShadow(username, pwd1, clearance);
					addPasswd(username, pwd1, clearance);
				}
			}
			else
			{
				cout<<"Password invalid. Please try again.("<<3-count<<")"<<endl;
				count++;
				goto enter_again;
			}
		}
		else
		{
			cout<<"Enter password again."<<endl;
			goto tryagain;
		}

	}
	else
	{
		cout<<"Enter password again."<<endl;
		goto tryagain;
	}
}

//Check User, salt file
bool checkUser(string user)
{
	string line;
	ifstream inFile("salt.txt");
	if (!inFile.is_open())
        cout<<"Unable to open file!";

	while(getline(inFile, line))
	{
		stringstream ss;
        ss.str(line);
        string str1;
		for(int x = 0;x<2;x++)
		{
			getline(ss, str1, ':');
            if(x==0)
            {
				  string name =str1;
				  if(name == user)
				  {
					   return true;
					   break;
				  }
			}
		}
	}

	return false;
}

//Check Password, passwd file
bool checkPasswd(string user)
{
	string line;
	ifstream inFile("passwd.txt");
	if (!inFile.is_open())
        cout<<"Unable to open passwd.txt!"<<endl;

	while(getline(inFile, line))
	{
		stringstream ss;
        ss.str(line);
        string str1;
		for(int x = 0;x<2;x++)
		{
			getline(ss, str1, ':');
            if(x==0)
            {
				  string name =str1;
				  if(name == user)
				  {
					   return true;
					   break;
				  }
			}
		}
	}
	return false;
}

//Check for validate password
bool validatePass(char pass[])
{
	//Password policy: one symbol, an upper case, lower case, digit, min 8 character
	bool size = false, upper = false, alpha = false, digit =false, punct = false;
	if( strlen(pass) == 8)  //to ensure password is 8 character
	{
		size = true;
	}

	for (int i = 0; pass[i]; ++i)
	{
		if(isupper(pass[i]))  //upper case
			upper = true;
		else if(isalpha(pass[i]))  //alphabet
			alpha = true;
		else if(isdigit(pass[i]))  //digit
			digit = true;
		else if(ispunct(pass[i]) )  //symbol
			punct = true;
	}

	//Show error message
	if(size == false)
	{
		cout<<"Min 8 character."<<endl;
	}

	if(upper == false)
	{
		cout<<"At least 1 upper case character."<<endl;
	}

	if(alpha == false)
	{
		cout<<"At least 1 letter character."<<endl;
	}

	if(digit == false)
	{
		cout<<"At least 1 digit number."<<endl;
	}

	if(punct == false)
	{
		cout<<"At least 1 symbol character."<<endl;
	}

	if(upper && alpha && digit && punct && size)
		return true;
	else
		return false;
}

//Create shadow password
bool validateShadow(string username, string pass)
{
	char mkpass_cmd[]  = "mkpasswd -m md5 ";    //MD5 command
	string line, salt_num, name;


	//get salt password from salt.txt
	ifstream inFile("salt.txt");
	if (!inFile.is_open())
        cout<<"Unable to open file!";

	while(getline(inFile, line))
	{
		stringstream ss;
        ss.str(line);
        string str1;
		for(int x = 0;x<2;x++)
		{
			getline(ss, str1, ':');
			if(x==0)
            {
				 name =str1;
			}
			else if (x==1)
			{
				if(name == username)
				{
					salt_num = str1.c_str();
				}
			}
		}
	}

	//convert salt and userpassword to Passhash
	system("touch temp.txt");			//create a temp file to store system output
	char salt[20];
	strcpy(salt, salt_num.c_str());
	//Combine mkpass_cmd with Password
	strcat (mkpass_cmd, pass.c_str());
	//Combine mkpass_cmd with -s
	strcat (mkpass_cmd, " -s ");
	//Combine mkpass_cmd with salt value
	strcat (mkpass_cmd, salt);
	strcat (mkpass_cmd, " >temp.txt");
	system(mkpass_cmd);

	//open temp file and take out the output
	ifstream intemp("temp.txt");
	string hash;
	getline(intemp, hash);
	system("rm temp.txt");	//remove temp file

	system("clear"); //clear screen

	//Output to user interface
	cout<<username<<" Found in salt.txt and passwd.txt. "<<endl;
	cout<<"\nSalt Retrieved: "<<salt_num<<endl;
	cout<<"\nhashing......"<<endl;
	cout<<"\nHash Value: "<<hash<<endl;
	cout<<"\n\n\nLoading........."<<endl;
	//open shadow file
	string salt_hash;
	ifstream inShadow("shadow.txt");
	if (!inShadow.is_open())
        cout<<"Unable to open file!";

	while(getline(inShadow, line))
	{
		stringstream ss;
        ss.str(line);
        string str1;
		for(int x = 0;x<2;x++)
		{
			getline(ss, str1, ':');
            if(x==0)
            {
				 name =str1;
			}
			else if (x==1)
			{
				if(name == username)
				{
					salt_hash = str1.c_str();
				}
			}
		}
	}

	//Compare Generated Hash Value with Hash Value inside shadow.txt
	if(salt_hash == hash)
	{
		return true;
	}
	else
		return false;

}

//Hide input character(C language), instead of using <conio.h> library
int getch()
{
    int ch;
    struct termios t_old, t_new;

    tcgetattr(STDIN_FILENO, &t_old);
    t_new = t_old;
    t_new.c_lflag &= ~(ICANON | ECHO);
    tcsetattr(STDIN_FILENO, TCSANOW, &t_new);

    ch = getchar();

    tcsetattr(STDIN_FILENO, TCSANOW, &t_old);
    return ch;
}

//Declaration of a function to hide input character
string getpass(const char *prompt, bool show_asterisk=true)
{
  const char BACKSPACE=127;
  const char RETURN=10;

  string password;
  unsigned char ch=0;

  cout <<prompt;

  while((ch=getch())!=RETURN)
    {
       if(ch==BACKSPACE) //when backspace is pressed, delete password
         {
            if(password.length()!=0)
              {
                 if(show_asterisk) //\b is hide it to the back
                 cout <<"\b \b";
                 password.resize(password.length()-1);
              }
         }
       else
         {
             password+=ch;
             if(show_asterisk)
                 cout <<'*';  //Show * for every single character instead of real password
         }
    }
  cout <<endl;
  return password;
}

//Random 8 digits function
void addSalt(string username)
{
	srand(time(NULL));
	int salt = rand() % 90000000 + 10000000; //random 8 digits
	ofstream outfile("salt.txt", ios::app); //outfile
	outfile<<username<<":"<<salt<<endl;
	outfile.close();
}

//Write to shadow file
void addShadow(string username, string pass, int clearance)
{
	string line;
	string salt_num;
	string name;
	char mkpass_cmd[]  = "mkpasswd -m md5 "; //md5 command
	//open salt file
	ifstream inFile("salt.txt");
	if (!inFile.is_open())
        cout<<"Unable to open file!";

    //extract each line from text file
	while(getline(inFile, line))
	{
		stringstream ss;
        ss.str(line);
        string str1;
		for(int x = 0;x<2;x++)
		{
			getline(ss, str1, ':'); //split it out when meet :
            if(x==0)
            {
				name =str1;
			}
			else if (x==1)
			{
				if(name == username)
				{
					salt_num = str1.c_str();  //c_str() is a conversion function from stringstream to string
				}
			}
		}
	}
	system("touch temp.txt");			//create a temp file to store  system output
	char salt[20];
	strcpy(salt, salt_num.c_str());
	//Combine mkpass_cmd with Password
	strcat (mkpass_cmd, pass.c_str());
	//Combine mkpass_cmd with -s
	strcat (mkpass_cmd, " -s ");
	//Combine mkpass_cmd with salt value
	strcat (mkpass_cmd, salt);
	strcat (mkpass_cmd, " >temp.txt");
	system(mkpass_cmd);

	//open temp file and take out the output
	ifstream intemp("temp.txt");
	string hash;
	getline(intemp, hash);
	system("rm temp.txt");	//remove temp file


	ofstream outfile("shadow.txt", ios::app);
	outfile<<username<<":"<<hash<<":"<<clearance<<endl;
	outfile.close();
}

//Add password
void addPasswd(string username, string password, int clearance)
{
	string line, name, salt, shadow;

	//Open file
	ifstream inSalt("salt.txt");
	ifstream inShadow("shadow.txt");
	ofstream outPasswd;

	if (!inShadow.is_open())
		cout << "Unable to open shadow.txt!";

	while (getline(inShadow, line))
	{
		stringstream ss;
		ss.str(line);
		string str1;
		for (int i = 1; i<=2; i++)
		{
			getline(ss, str1, ':');
			if (i == 1)
			{
				name = str1;
			}
			else if (i == 2)
			{
				if (name == username)
				{
					shadow = str1;
				}
			}
		}
	}

	outPasswd.open("passwd.txt", ios::app);
	outPasswd<<username<<":"<<shadow<<":"<<":"<<":"<<username<<":"<<":"<<":"<<endl;
	outPasswd.close();

	inSalt.close();
	inShadow.close();
	outPasswd.close();


}

/**File System Functions**/
void SystemMenu(string username)
{
	char selection;
	string filename, line;
	int filelevel;

	int userlevel = getUserLevel(username);
	do
	{
		system("clear");
		menu:
		cout<<endl<<endl;

		//Main Menu
		cout<<"\tFile System Main Menu\n  ==============================="<<endl;
		cout<<"||\t(C)reate New  File\t ||"<<endl;
		cout<<"||\t(R)ead   From File\t ||"<<endl;
		cout<<"||\t(W)rite  To   File\t ||"<<endl;
		cout<<"||\t(L)ist   All  Files\t ||"<<endl;
		cout<<"||\t(S)ave   All  Records\t ||"<<endl;
		cout<<"||\t(E)xit   File System\t ||"<<endl;
		cout<<"  ==============================="<<endl;
		cout<<"Select Action (C/R/W/L/S/E): ";
		cin>>selection;

		//Accept input upper case and lower case
		if (selection == 'C' || selection == 'c')
		{
			system ("clear");
			//Create File with File Security Level
			cout<<"Please Enter the Name and Classification of your File: "<<endl;
			cout<<"File Name: ";
			cin>>filename;
			enterlvl:
			cout<<"Security level(0 or 1 or 2): ";
			cin>>filelevel;

			if (filelevel <0 || filelevel > 2)
			{
				cout<<"Invalid File Security Level. Please Enter Again."<<endl;
				goto enterlvl; //repeat
			}
			else if (checkFile(filename) == true)
			{
				cout<<filename<<" Already Exist in File System. Please Try Again."<<endl;
				goto menu; //repeat
			}
			else
				createFile(filename, filelevel, userlevel);  //create new file

			sleep(5);
		}
		if (selection == 'R' || selection == 'r')
		{
			system ("clear");
			//Read or Write File
			cout<<"Please Enter the File Name to Read "<<endl;
			cout<<"File Name: ";
			cin>>filename;
			if (checkFile(filename) == true)
				readFile(filename, userlevel);
			else
			{
				cout<<filename<<" Does Not Exist in File System. "<<endl;
				goto menu; //repeat
			}

			sleep(5);
		}
		if (selection == 'W' || selection == 'w')
		{
			system ("clear");
			//Read or Write File
			cout<<"Please Enter the File Name to Write "<<endl;
			cout<<"File Name: ";
			cin>>filename;
			if (checkFile(filename) == true)
				writeFile(filename, userlevel);
			else
			{
				cout<<filename<<" Does Not Exist in File System. "<<endl;
				goto menu;  //repeat
			}

			sleep(5);
		}
		if (selection == 'L' || selection == 'l')
		{
			system ("clear");
			listFile();
			goto menu; //repeat
		}
		if (selection == 'S' || selection == 's')
		{
			system ("clear");
			saveFile();
			goto menu;
		}
		if (selection == 'E' || selection == 'e')
		{
			system ("clear");
			char exit;
			cout<<"Shut Down the File System? (Y/N): ";
			cin>>exit;
			if (exit == 'Y' || exit == 'y')
			{
				cout<<"Listing all Files in Record ..... Before Shut Down\n\n"<<endl;
				listFile();
				break;
			}
			else if (exit == 'N' || exit == 'n')
				goto menu;
		}

	}while (selection != 'E' || selection != 'e');
}

//Check all exists files
bool checkFile(string file)
{
	string line, filename;
	bool file_exist = false;
	ifstream inFiles("Files.store");

	if (!inFiles.is_open())
		cout<<"Unable to Open File Records"<<endl;

	while (getline(inFiles,line))
    {
        stringstream ss;
        string str1;
        ss.str(line);
        for (int i=1; i<=2; i++)
        {
            getline(ss,str1,':');
            if (i == 1)     	//1st column of string
				filename = str1;	//Set File Name

			if (file == filename)//If file exist inside Files.store
				file_exist = true;
		}
	}
	//Close inFiles
	inFiles.close();
	return file_exist;
}

//Create file
void createFile(string file, int filelvl, int userlvl)
{
	string line, filename;

	ofstream outFiles;

	if (userlvl >= filelvl)
	{
		outFiles.open("Files.store", ios::app);
		outFiles<<file<<":"<<filelvl<<endl;
		outFiles.close();
		cout<<file<<" have been Successfully Created with Security Level "<<filelvl<<". "<<endl;
	}
	else
		cout<<file<<" Create Denied due to Current User Level. "<<endl;

	cout<<"\n\n\nLoading........."<<endl;
}

int getUserLevel(string username)
{
	int userlvl;
	string line, user;
	ifstream inShadow("shadow.txt");

	if (!inShadow.is_open())
		cout<<"Unable to Open shadow.txt"<<endl;

	while (getline(inShadow,line))
    {
        stringstream ss;
        string str1;
        ss.str(line);
        for (int i=1; i<=3; i++)
        {
            getline(ss,str1,':');
            if (i == 1)
				user = str1;
            if (i == 3)     	//3rd column of string
            {
				if (user == username)
					userlvl = atoi(str1.c_str());	//Set File Level
			}
		}
	}
	//Close inShadow
	inShadow.close();
	return userlvl;
}

int getFileLevel(string file)
{
	int filelvl;
	string line, filename;
	ifstream inFiles("Files.store");

	if (!inFiles.is_open())
		cout<<"Unable to Open File Records"<<endl;

	while (getline(inFiles,line))
    {
        stringstream ss;
        string str1;
        ss.str(line);
        for (int i=1; i<=2; i++)
        {
            getline(ss,str1,':');
            if (i == 1)
				filename = str1;
            if (i == 2)     	//2nd column of string
            {
				if (filename == file)
					filelvl = atoi(str1.c_str());	//Set File Level
			}
		}
	}
	//Close inFiles
	inFiles.close();
	return filelvl;
}

void readFile(string file, int userlvl)
{
	int filelvl = getFileLevel(file);

		if (userlvl == filelvl || userlvl > filelvl)
			cout<<"Read Access Granted for "<<file<<endl;
		else
			cout<<"Read Access Denied for "<<file<<endl;

		cout<<"\n\n\nLoading........."<<endl;
}

void writeFile(string file, int userlvl)
{
	int filelvl = getFileLevel(file);

		if (userlvl == filelvl)
			cout<<"Write Access Granted for "<<file<<endl;
		else
			cout<<"Write Access Denied for "<<file<<endl;

		cout<<"\n\n\nLoading........."<<endl;
}

void listFile()
{
	string line;
	ifstream inFiles("Files.store");

	if (!inFiles.is_open())
		cout<<"Unable to Open File Records"<<endl;

	cout<<"File System Records\n-------------------"<<endl;
	while (getline(inFiles,line))
    {
        stringstream ss;
        string str1;
        ss.str(line);
        for (int i=1; i<=2; i++)
        {
            getline(ss,str1,':');
            if (i == 1)
				cout<<str1<<endl;
		}
	}
	//Close inFiles
	inFiles.close();
}

void saveFile()
{
	cout<<"File Save Successful."<<endl;
}