#!/usr/bin/env python3

import struct


OPCODES = (
    None , 'SET', 'ADD', 'SUB', 'MUL', 'MLI', 'DIV', 'DVI',
    'MOD', 'MDI', 'AND', 'BOR', 'XOR', 'SHR', 'ASR', 'SHL',
    'IFB', 'IFC', 'IFE', 'IFN', 'IFG', 'IFA', 'IFL', 'IFU',
    None , None , 'ADX', 'SBX', None , None , 'STI', 'STD'
)

OPCODES_X = (
    None , 'JSR', None , None , None , None , None , None ,
    'INT', 'IAG', 'IAS', 'RFI', 'IAQ', None , None , None ,
    'HWN', 'HWQ', 'HWI', None , None , None , None , None ,
    None , None , None , None , None , None , None , None
)

ADDRESSING = (
    'A', 'B', 'C', 'X', 'Y', 'Z', 'I', 'J',
    '[A]', '[B]', '[C]', '[X]', '[Y]', '[Z]', '[I]', '[J]',
    '[A+n]', '[B+n]', '[C+n]', '[X+n]', '[Y+n]', '[Z+n]', '[I+n]', '[J+n]',
    'POP/PUSH', 'PEEK', 'PEEK n', 'SP', 'PC', 'EX', '[n]', 'n'
)

def read_word(f):
    b = f.read(2)
    if len(b) < 2:
        raise EOFError()
    return struct.unpack("<H", b)[0]

def disassemble(filename):
    with open(filename, 'rb') as f:
        pc = 0
        while True:
            try:
                w = read_word(f)
            except EOFError:
                break
            ins = [w]
            op = w & 0x1f
            b = (w >> 5) & 0x1f
            a = (w >> 10) & 0x3f
            if a < 0x20:
                a_str = ADDRESSING[a]
                if 'n' in a_str:
                    w = read_word(f)
                    ins.append(w)
                    a_str = a_str.replace('n', str(w))
            else:
                a_str = str(int(a) - 0x21)
            a_str = a_str.split('/')[0]
            if op == 0:
                mnemonic = "%s %s" % (OPCODES_X[b], a_str)
            else:
                b_str = ADDRESSING[b]
                if 'n' in b_str:
                    w = read_word(f)
                    ins.append(w)
                    b_str = b_str.replace('n', str(w))
                b_str = b_str.split('/')[-1]
                mnemonic = "%s %s, %s" % (OPCODES[op], b_str, a_str)
            print("%5d:\t%-20s; %s" % (pc, mnemonic, ' '.join(["%04x" % x for x in ins])))
            pc += len(ins)


if __name__ == '__main__':
    import sys

    if len(sys.argv) > 1:
        disassemble(sys.argv[1])