from collections import defaultdict
from dataclasses import dataclass
from pprint import pprint
import os
import inspect

@dataclass(frozen=True)
class CodeOperand:
    operand: str
    lsb: int
    length: int

@dataclass(frozen=True)
class Code:
    code_bits: int
    mask_bits: int
    operands: list[CodeOperand]

@dataclass(frozen=True)
class Instruction:
    instruction: str
    operands: str
    variables: list[str]
    code: Code
    operation: str

def unparse_instruction_code(ins):
    code = list(f'{ins.code.code_bits:016b}')
    for operand in ins.code.operands.values():
        for i in range(operand.lsb, operand.lsb + operand.length):
            code[15 - i] = operand.operand
    return ''.join(code)

_operands = {
    "Rn",
    "Rm",
    "R0",
    "GBR",
    "SR",
    "VBR",
    "MACH",
    "MACL",
    "R0",
}

def _b16_str(n):
    for i in reversed(range(16)):
        yield chr(ord('0') + ((n >> i) & 1))

def b16_str(n):
    return ''.join(_b16_str(n))

_operand_bits = {
    'i',
    'n',
    'm',
    'd',
}

def assert_contiguous(bits):
    assert len(bits) == len(set(bits))
    for i, bit in enumerate(bits[:-1]):
        assert abs(bit - bits[i+1]) == 1
    return bits

def parse_code(code):
    operands_list = defaultdict(list)
    code_bits_list = []
    mask_bits_list = []
    for i, digit in enumerate(reversed(code)):
        if digit not in {'0','1'}:
            assert digit in _operand_bits, (digit, code)
            operands_list[digit].append(i)
            mask_bits_list.append(i)
        else:
            code_bits_list.append((i, int(digit)))

    code_bits = 0
    for i, digit in code_bits_list:
        code_bits |= (digit << i)
    mask_bits = 0xffff
    for i in mask_bits_list:
        mask_bits &= ~(1 << i)
    operands = {
        operand:
        CodeOperand(
            operand=operand,
            lsb=min(assert_contiguous(bits)),
            length=len(bits)
        )
        for operand, bits in operands_list.items()
    }
    return Code(
        code_bits=code_bits,
        mask_bits=mask_bits,
        operands=operands
    )

def get_variable(token):
    variables = {
        'Rm': 'm',
        'Rn': 'n',
        'disp': 'd',
        'imm': 'i',
        'label': 'd',
        # SH4
        "Rm_BANK": 'm',
        "Rn_BANK": 'n',
        # SH4 floating point
        "FRm": 'm',
        "FRn": 'n',
        "DRm": 'm',
        "DRn": 'n',
        "XDm": 'm',
        "XDn": 'n',
        "FVm": 'm',
        "FVn": 'n',
    }
    non_variables = {
        "GBR",
        "VBR",
        "MACH",
        "MACL",
        "SR",
        "PR",
        "PC",
        "R0",
        # SH4
        "SSR",
        "SPC",
        "DBR",
        "SGR",
        # SH4 floating point
        "FPUL",
        "FR0",
        "FPSCR",
        "XMTRX",
    }
    if token in variables:
        yield variables[token]
    elif token in non_variables:
        return
    else:
        assert False, token

def parse_tokens(operands):
    if operands == '':
        return
    span = 0
    i = 0
    while i != len(operands):
        c = operands[i]
        if c in {'(', '#', '@', '-'}:
            span = i + 1
        elif c in {',', ')', '+'}:
            if span != i:
                yield operands[span:i]
            span = i + 1
        i += 1
    assert operands[-1] != ','
    if span != len(operands):
        yield operands[span:]

def parse_variables(operands):
    for token in parse_tokens(operands):
        yield from get_variable(token)

def parse_instruction(*, instruction, operands, code, operation, **kwargs):
    code = parse_code(code)
    try:
        variables = tuple(parse_variables(operands))
    except:
        print(instruction)
        raise

    return (
        instruction,
        operands,
        variables,
        code,
        operation,
    )

def untabulate_instructions(filename, columns):
    with open(filename, 'r') as f:
        buf = f.read()

    instructions = []

    for line in buf.split('\n'):
        def column(s):
            start, end = columns[s]
            return line[start:end]

        if not line.strip():
            continue
        assert '\t' not in line, line
        if line and line[0] == ' ':
            assert len(line.strip()) == len(column("operation").strip())
            instructions[-1] = Instruction(
                instruction = instructions[-1].instruction,
                operands = instructions[-1].operands,
                variables = instructions[-1].variables,
                code = instructions[-1].code,
                operation = " ".join([
                    instructions[-1].operation, line.strip()
                ])
            )
            continue
        instruction = Instruction(*parse_instruction(**dict([
            (name, line[start:end].strip())
            for name, (start, end) in columns.items()
        ])))
        instructions.append(instruction)

    return instructions

def column_bounds(columns):
    for ix, (name, start) in enumerate(columns):
        if ix == len(columns) - 1:
            end = None
        else:
            end = columns[ix+1][1]
        yield name, (start, end)


directory = os.path.dirname(os.path.abspath(inspect.getfile(inspect.currentframe())))

def untabulate_instructions_sh2():
    columns = dict(column_bounds([
        ("instruction", 0  ),
        ("operands"   , 8  ),
        ("code"       , 23 ),
        ("operation"  , 42 ),
        ("state"      , 88 ),
        ("t_bit"      , 102)
    ]))

    return untabulate_instructions(os.path.join(directory, "..", "sh2.txt"), columns)

def untabulate_instructions_sh4():
    columns = dict(column_bounds([
        ("instruction", 0  ),
        ("operands"   , 8  ),
        ("operation"  , 24 ),
        ("code"       , 80 ),
        ("privileged" , 104),
        ("t_bit"      , 116)
    ]))

    return untabulate_instructions(os.path.join(directory, "..", "sh4.txt"), columns)