import java.util.Scanner;
import java.io.File;

/**
* A class to model a simple 4-bit Virtual Machine.
* @author cs416
* @version 2
*/
public class VM {

    private int ip;
    private int is;
    private int r0;
    private int r1;
    private int[] memory;
    //additional variables as needed

    
    /**
     * Load the program instructions from the specified file path.
     * throws an IllegalStateException if the program file cannot be loaded.
     * reads instructions from the file until end of file or a maximum of 16
     * values have been read
     * @param progFilePath the path of the program file to load into the VM
     */
    public VM(String progFilePath) throws IllegalStateException {
	throw new UnsupportedOperationException("TO BE IMPLEMENTED");
    }

    /**
     * For testing purposes - initialize the VM to the array.
     * The array is in the format {ip, is, r0, r1, m0, m1, .... m15}
     * @param m the imitialization array
     */
    public VM(int[] m) {
        ip = m[0];
        is = m[1];
        r0 = m[2];
        r1 = m[3];
        memory = new int[16];
        System.arraycopy(m, 4, memory, 0, 16);
    }

    /**
     * Turn debug mode on (VM details are printed during step.
     */
    public void debugModeOn() {
        throw new UnsupportedOperationException("TO BE IMPLEMENTED");
    }

    /**
     * Turn debug mode off (VM details not printed during step).
     */
    public void debugModeOff() {
	throw new UnsupportedOperationException("TO BE IMPLEMENTED");
    }

    /**
     * Is the VM running.
     * @return boolean
     */
    public boolean isRunning() {
	throw new UnsupportedOperationException("TO BE IMPLEMENTED");
    }

    /**
     * Perform a single step (fetch & execute) of the VM.
     */
    public void step() {
	throw new UnsupportedOperationException("TO BE IMPLEMENTED");
    }

    /**
     * String representation of the CPU.
     * @return String
     */
    @Override
    public String toString() {
        return String.join(
            "\n",
            ".--------. .--------.",
            String.format("| IP: %2d | | IS: %2d |", ip, is),
            "'--------' '--------'",
            ".--------. .--------.",
            String.format("| R0: %2d | | R1: %2d |", r0, r1),
            "'--------' '--------'",
            "",
            ".-------------------.",
            String.format("| %2d | %2d | %2d | %2d |", memory[0], memory[1],
                memory[2], memory[3]),
            "|----+----+----+----|",
            String.format("| %2d | %2d | %2d | %2d |", memory[4], memory[5],
                memory[6], memory[7]),
            "|----+----+----+----|",
            String.format("| %2d | %2d | %2d | %2d |", memory[8], memory[9],
                memory[10], memory[11]),
            "|----+----+----+----|",
            String.format("| %2d | %2d | %2d | %2d |", memory[12], memory[13],
                memory[14], memory[15]),
            "'----+----+----+----'"
        );
    }
}