package inclass;

import java.util.*;

public class Assembler {

	public static LinkedList<Integer> wordlist = new LinkedList<Integer>();

	public static int makeI(byte opcode, byte rs, byte rt, short immed) {
		int result = 0;
		result |= opcode << 26;
		result |= rs << 21;
		result |= rt << 16;
		result |= immed;

		return result;
	}

	public static int makeR(byte opcode, int rs, int rt, int rd, byte shamt, byte funct) {
		int result = 0;
		result |= opcode << 26;
		result |= rs << 21;
		result |= rt << 16;
		result |= rd << 11;
		result |= shamt << 6;
		result |= funct;

		return result;
	}

	public static byte reg2bin(String w) {
		byte reg = 0;
		switch (w) {
		case "$zero":
			reg = 0;
			break;
		case "$v0":
			reg = 2;
			break;
		case "$v1":
			reg = 3;
			break;
		case "$a0":
			reg = 4;
			break;
		case "$a1":
			reg = 5;
			break;
		case "$a2":
			reg = 6;
			break;
		case "$a3":
			reg = 7;
			break;
		case "$t0":
			reg = 8;
			break;
		case "$t1":
			reg = 9;
			break;
		case "$t2":
			reg = 10;
			break;
		case "$t3":
			reg = 11;
			break;
		case "$t4":
			reg = 12;
			break;
		case "$t5":
			reg = 13;
			break;
		case "$t6":
			reg = 14;
			break;
		case "$t7":
			reg = 15;
			break;
		case "$s0":
			reg = 16;
			break;
		case "$s1":
			reg = 17;
			break;
		case "$s2":
			reg = 18;
			break;
		case "$s3":
			reg = 19;
			break;
		case "$s4":
			reg = 20;
			break;
		case "$s5":
			reg = 21;
			break;
		case "$s6":
			reg = 22;
			break;
		case "$s7":
			reg = 23;
			break;

		}

		return reg;
	}

	public static void main(String[] args) {
		Scanner kb = new Scanner(System.in);
		System.out.println("Assembler - C. Grey");

		String op = null;
		byte opcode = 0;
		String rs, rt, rd;
		byte shamt = 0;
		byte func = 0;
		byte rscode = 0;
		byte rtcode = 0;
		byte rdcode = 0;
		int word = 0;
		short immed = 0;
		short branch_address;

		System.out.println("Begin assembly");

		do {

			/*
			 * op = null; rs = null; rt = null; rd = null; shamt = 0; func = 0; opcode = 0;
			 * rscode = 0; rtcode = 0; rdcode = 0; word = 0;
			 */

			op = kb.next();

			if (op.equalsIgnoreCase("HALT")) {

				continue;
			}

			else {

				rd = kb.next();
				rs = kb.next();
				rt = kb.next();

			}

			if (isNumeric(rd) == true) {
				immed = Short.parseShort(rd);
				rscode = reg2bin(rs);
				rtcode = reg2bin(rt);
			}

			else if (isNumeric(rs) == true) {
				immed = Short.parseShort(rs);
				rtcode = reg2bin(rt);
				rdcode = reg2bin(rd);
			}

			else if (isNumeric(rt) == true) {
				immed = Short.parseShort(rt);
				rdcode = reg2bin(rd);
				rscode = reg2bin(rs);
			}

			else {

				rdcode = reg2bin(rd);
				rscode = reg2bin(rs);
				rtcode = reg2bin(rt);
			}

			switch (op) {

			case "ADD":
				opcode = 0;
				func = 32;
				shamt = 0;
				word = makeR(opcode, rscode, rtcode, rdcode, shamt, func);
				break;
			case "AND":
				opcode = 0;
				func = 36;
				shamt = 0;
				word = makeR(opcode, rscode, rtcode, rdcode, shamt, func);
				break;
			case "ADDI":
				opcode = 8;
				word = makeI(opcode, rscode, rtcode, immed);
				break;
			case "ANDI":
				opcode = 12;
				word = makeI(opcode, rscode, rtcode, immed);
				break;
			case "BEQ":
				opcode = 4;
				word = makeI(opcode, rscode, rtcode, immed);
				break;
			case "LW":
				opcode = 35;
				word = makeI(opcode, rscode, rtcode, immed);
				break;



			}

			wordlist.add(word);

		} while (!op.equalsIgnoreCase("HALT"));

		for (int i = 0; i < wordlist.size(); i++) {
			System.out.println(
					"***: " + String.format("%32s", Integer.toBinaryString(wordlist.get(i))).replace(" ", "0"));
		}

		System.out.println("Assembly complete. Program required " + wordlist.size() + " words of memory.");
	}

	public static boolean isNumeric(String str) {
		try {
			Double.parseDouble(str);
			return true;
		} catch (NumberFormatException e) {
			return false;
		}
	}

}