deterministicVer0

#include<iostream>
#include<fstream> //needed for reading from .txt file
#include<vector>
#include<string>

// Yes there are global variables working 
std::ifstream instructionFile; 
std::string programFile;
std::string inputString;
char curState = '0';
std::vector<char> TAPE(1,'B'); //will treat the infinate tape as a vector for is ability to dynamically change size as needed.
std::vector<char>::iterator RW;;

//called when the iterator goes out of the bounds of TAPE
//will grow either left or right depending on D
void expandTape(const char D){
//    std::cout << "H" << std::endl;        //debug
    if(D == 'R') {
        TAPE.emplace_back('B');
    }
    else if(D == 'L') {
        TAPE.emplace(TAPE.begin(),'B');
        RW = TAPE.begin();
        RW++;
    }
}

//address issue of generating more space in the vector.
bool delta(const char &Q, const char &Gamma){

//step 0; open text file.
instructionFile.open(programFile);

//begin itterating through the text file, line by line untill the end of txt file or we found a match
bool found = false;
std::string instruction;
char state, tape_symbol, new_state, new_tape_symbol, direction;


while(instructionFile && !found){
//  look at two characters (ignoring white space)
    instructionFile >> state >> tape_symbol;
    if(state != '/'){                       //if the instruction is not a comment
        if(Q == state && Gamma == tape_symbol){
            found = true;   //we've found the corrisponding delta combination 
            instructionFile >> new_state >> new_tape_symbol >> direction;  //fetch where the TM should go to next.
//            std::cout << new_state << " " << new_tape_symbol << " " << direction << std::endl;        //debug
            *RW = new_tape_symbol;  //write to TAPE
            curState = new_state;   //update state
            if(direction == 'R') {RW++;}    //move RW head.
            else{RW--;}
            if(RW == TAPE.begin() || RW == TAPE.end()) {expandTape(direction);}
//
        }
    }
    instructionFile.ignore(INT_MAX, '\n');  //goto next line
}
instructionFile.close();    //error arise when you don't close the document;


if(!found){ //only occures if there is no matching state and tape symbol. TM crashes.
    std::cout << "TM has crashed! no instruction for (" << Q << "," << Gamma << ")" << std::endl;
}
return found;
}

void getID() {
    std::vector<char>::iterator Read = TAPE.begin();
    while(Read != TAPE.end()) {
        if(Read == RW) {std::cout << "[" << curState << "]";}  //if the display iterator and RW head are at the same position, we need to display curState.
        std::cout << *Read;
        Read++;
    } 
    std::cout << std::endl;
}

int main(){
//--------- fetching file -------------------
std::cout << "Enter program file (Enter \"Q\" to exit): ";
std::cin >> programFile;
if(programFile == "Q") {return 0;}
else{instructionFile.open(programFile);}

while(!instructionFile.is_open())
{
std::cout << programFile << " was not found" << std::endl; 
std::cout << "Enter program file (Enter \"Q\" to exit): ";
std::cin >> programFile;    //getting the text file containig the instructions
if(programFile == "Q") {return 0;}
else{instructionFile.open(programFile);}
}
instructionFile.close();    //we don't need it yet.


//------ GETTING INPUT STRING ----------------
std::cout << "enter input string: ";
std::cin >> inputString;

//---------- FILLING TM TAPE ---------------
for(int i = 0; i < inputString.size(); i++)
{
    TAPE.push_back(inputString[i]);
}
TAPE.push_back('B'); //capping off the front of the tape.
RW = TAPE.begin();   // createmoved to the first input symbol 
RW++;
getID();        //dispay itnital ID

//---------- DELTA --------------------
bool good = true;
while(good){
    good = delta(curState,*RW);
    if(curState == 'f'){
        good = false;
        getID();
        std::cout << inputString << " was accepted by TM!" << std::endl;

    } else {
        getID();
    }

    int _ = 1;
}
}