package net.benjaminurquhart.bfj;

import java.util.ArrayList;

import javax.script.ScriptException;

public class BFJ {

	public static void execute(String code) throws Exception{
		execute(code, 30000);
	}
	public static void execute(String code, int cellAmount) throws Exception{
		int[] buff = new int[cellAmount < 30000 ? 30000 : cellAmount];
		ArrayList<Integer> forward = new ArrayList<>(), backward = new ArrayList<>();
		int instruction = 0, data = 0, codeLen = code.length();
		for(int i = 0; i < codeLen; i++){
			if(code.charAt(i) == '[') forward.add(i);
			if(code.charAt(i) == ']') backward.add(i);
		}
		if(forward.size() != backward.size()){
			throw new ScriptException("Unmatched jump instruction at character " + (forward.size() < backward.size() ? backward.get(backward.size() - 1) : forward.get(forward.size() - 1)));
		}
		while(instruction < codeLen){
			switch(code.charAt(instruction)){
			case ',': buff[data] = System.in.read(); break;
			case '.': System.out.print((char)buff[data]); break;
			case '+': buff[data]++; break;
			case '-': buff[data]--; break;
			case '>' : data++; break;
			case '<' : data--; break;
			case '[': instruction = (buff[data] == 0 ? backward.get(forward.indexOf(instruction)) : instruction); break;
			case ']': instruction = (buff[data] != 0 ? forward.get(backward.indexOf(instruction)) : instruction); break;
			}
			instruction++;
		}
	}
	public static void main(String[] args) throws Exception{
		execute(",.+.-.");
	}
}