package rpn;

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

public class RPN {

    private Stack stack = new Stack();
    private Queue <Character> output = new LinkedList<>();
    private Integer result = new Integer(-1);
    private Scanner scanner;
    private HashMap<Character, Integer> operators = new HashMap<Character, Integer>();

    // converting to RPN
    private void convert() throws IOException {
        // opening
        scanner = new Scanner(new File("C:/Users/Dominika/source/repos/onp/src/files/calculations.txt"));
        initPriority();

        // if file exists, read a char
        char read = 0;
        int counter = 0;
        while (scanner.hasNext()) {
            read = (char) scanner.next().charAt(counter);
            counter++;
            if (Character.isDigit(read)) {
                output.add(read);
            } else if (isFunction(read)) {
                stack.push(read);
            } else if (isOperand(read)) {
                checkOperand(read);
            }
        }

        while (!stack.empty()) {
            output.add((char) stack.peek());
            stack.pop();
        }

        // closing
        scanner.close();
    }

    private void checkOperand(char read) {
        if (read == '+' || read == '-') {
            if ((char) stack.peek() == '*' || (char) stack.peek() == '/') {
                output.add((char) stack.peek());
                stack.pop();
                checkOperand(read);
            }
        } else {
            stack.push(read);
        }
    }

    private void initPriority() {
        operators.put('*', 3);
        operators.put('/', 3);
        operators.put('+', 1);
        operators.put('-', 1);
    }

    private boolean isOperand(char c) {
        if (c == '+' || c == '-' || c == '*' || c == '/') {
            return true;
        } else return false;
    }

    private boolean isFunction(char c) {
        if (c == 's' || c == 't' || c == 'c') {
            return true;
        } else return false;
    }

    public static void main(String[] args) throws IOException {
        RPN rpn = new RPN();
        rpn.convert();
    }
}