#!/usr/bin/env python3

import sys

if len(sys.argv) != 2:
    print(f"Usage: {sys.argv[0]} [filename]")
    sys.exit(1)

def decode_jump(ins: int) -> str:
    if (ins & 0x7) == 0:
        return ""
    if (ins & 0x7) == 0x7:
        return "; j"

    jl = (ins & (1<<2)) != 0
    je = (ins & (1<<1)) != 0
    jg = (ins & (1<<0)) != 0

    # implied: and not jg
    if (jl and je): return "; jle"
    # implied: and not je
    if (jl and jg): return "; jne"
    # implied: and not je
    if (je and jg): return "; jge"

    # implied: only one flag is 1
    if (jl): return "; jl"
    if (je): return "; je"
    if (jg): return "; jg"

    return "; <unknown>"


def decode_ins(ins: int) -> str:
    opcode = (ins >> 8) & 0x03
    ar_n_log = (ins & (1<<10)) != 0
    opcode |= (ar_n_log << 2)

    if opcode == 0b000: return "AND"
    if opcode == 0b001: return "OR"
    if opcode == 0b010: return "XOR"
    if opcode == 0b011: return "NEG"
    if opcode == 0b100: return "ADD"
    if opcode == 0b101: return "INC"
    if opcode == 0b110: return "SUB"
    if opcode == 0b111: return "DEC"

    return "<?>"

def decode(ins: int) -> str:
    if (ins & 0x8000 == 0):
        # mov? ldr? ldi? aaaaaaaaaaa....
        return f"mov A, #{ins}"
    else:
        use_mem = (ins & (1<<12)) != 0
        zx = (ins & (1<<7)) != 0
        sw = (ins & (1<<6)) != 0
        dA = (ins & (1<<5)) != 0
        dD = (ins & (1<<4)) != 0
        dM = (ins & (1<<3)) != 0

        codename = decode_ins(ins)
        return f"{codename:<5}<unknown>{decode_jump(ins)}"

try:
    with open(sys.argv[1], "rb") as f:
        while True:
            insb = f.read(2)
            if not insb: break
            ins = int.from_bytes(insb)
            print(f"\t{insb[0]:02x} {insb[1]:02x}\t{decode(ins)}")

except FileNotFoundError:
    print(f"File not found.")
    sys.exit(1)
# head, tail...
except BrokenPipeError:
    sys.exit(0)