VMParser.java

package com.daniyaldianati.vmtranslator;

import java.util.Scanner;

public class VMParser {
    private Scanner scanner;
    private String current;

    public VMParser(Scanner s) {
        scanner = s;
    }

    public boolean hasNextCommand() {
        return scanner.hasNextLine();
    }

    public void parseNextLine() {
        // Keep reading until a valid, non-empty, non-comment line is found
        do {
            if (!scanner.hasNextLine()) {
                current = null;
                return;
            }
            current = scanner.nextLine().split("//")[0].trim(); // Strip comments & whitespace
        } while (current.isEmpty());
    }

    public CommandType commandType() {
        if (current == null || current.isEmpty()) {
            throw new IllegalStateException("No current command to analyze");
        }

        String cmd = current.split(" ")[0];
        switch (cmd) {
            case "push": return CommandType.C_PUSH;
            case "pop": return CommandType.C_POP;
            case "label": return CommandType.C_LABEL;
            case "goto": return CommandType.C_GOTO;
            case "if-goto": return CommandType.C_IF;
            case "function": return CommandType.C_FUNCTION;
            case "call": return CommandType.C_CALL;
            case "return": return CommandType.C_RETURN;
            default: return CommandType.C_ARITHMETIC;
        }
    }

    public String arg1() {
        if (commandType() == CommandType.C_RETURN) {
            throw new IllegalStateException("arg1() should not be called on return command");
        }

        String[] parts = current.split(" ");
        return (commandType() == CommandType.C_ARITHMETIC) ? parts[0] : parts[1];
    }

    public int arg2() {
        if (!(commandType() == CommandType.C_PUSH ||
              commandType() == CommandType.C_POP ||
              commandType() == CommandType.C_FUNCTION ||
              commandType() == CommandType.C_CALL)) {
            throw new IllegalStateException("arg2() should only be called on push/pop/function/call");
        }

        return Integer.parseInt(current.split(" ")[2]);
    }
}