from dataclasses import dataclass, field
from typing import ClassVar, Callable
from ctypes import c_uint32, c_int32, c_uint8
import struct
from optable import OPCODES, OpcodeDescription, OpL, OpA, OpF, OpD
from enum import IntFlag, auto

class VMFlags(IntFlag):
    AFTER_BRANCH = auto()

class Condition:
    def __init__(self, cond: int):
        self.i: bool = bool(cond & (1 << 3))
        self.v: bool = bool(cond & (1 << 2))
        self.n: bool = bool(cond & (1 << 1))
        self.z: bool = bool(cond & (1 << 0))

class VMCC(IntFlag):
    OVERFLOW = 1 << 2
    NEGATIVE = 1 << 1
    ZERO     = 1 << 0

@dataclass
class VM:
    instr_callbacks: ClassVar[dict[OpcodeDescription, Callable]]

    def __init__(self, mem):
        self.mem: bytearray = mem
        self.cc: VMCC = VMCC(0)
        self.pc: c_uint32 = c_uint32(0)
        self.registers: list[c_int32] = [c_int32(0) for _ in range(256)]
        self.breakpoints: set[int] = field(default_factory=set)
        self._vm_flags: VMFlags = VMFlags(0)
        self.__init_callbacks__()

    def __init_callbacks__(self):
        VM.instr_callbacks = {
                # ariphmetic
                OpD(OpF(0), OpL.MATH, OpA.ADD):
                self._math_callback_gen(lambda lhs, rhs: lhs + rhs),

                OpD(OpF.QUICK, OpL.MATH, OpA.ADD):
                self._math_quick_callback_gen(lambda lhs, rhs: lhs + rhs),

                OpD(OpF(0), OpL.MATH, OpA.SUB):
                self._math_callback_gen(lambda lhs, rhs: lhs - rhs),

                OpD(OpF.QUICK, OpL.MATH, OpA.SUB):
                self._math_quick_callback_gen(lambda lhs, rhs: lhs - rhs),

                OpD(OpF(0), OpL.MATH, OpA.MUL):
                self._math_callback_gen(lambda lhs, rhs: lhs * rhs),

                OpD(OpF.QUICK, OpL.MATH, OpA.MUL):
                self._math_quick_callback_gen(lambda lhs, rhs: lhs * rhs),

                OpD(OpF(0), OpL.MATH, OpA.DIV):
                self._math_callback_gen(lambda lhs, rhs: lhs // rhs),

                OpD(OpF.QUICK, OpL.MATH, OpA.DIV):
                self._math_quick_callback_gen(lambda lhs, rhs: lhs // rhs),

                # logical ops
                OpD(OpF.UNEXPANDED, OpL.MATH, OpA.AND): 
                self._math_callback_gen(lambda lhs, rhs: lhs & rhs),

                OpD(OpF.UNEXPANDED, OpL.MATH, OpA.OR): 
                self._math_callback_gen(lambda lhs, rhs: lhs | rhs),

                OpD(OpF.UNEXPANDED, OpL.MATH, OpA.XOR):
                self._math_callback_gen(lambda lhs, rhs: lhs ^ rhs),

                OpD(OpF.UNEXPANDED, OpL.MATH, OpA.MASK):
                self._math_callback_gen(
                    lambda lhs, rhs: lhs & ((~rhs + (1 << 32)) % (1 << 32))
                    ),

                # block 2
                OpD(OpF(0), OpL.MEM, OpA.LOAD):
                self._load_callback,
                OpD(OpF.QUICK, OpL.MEM, OpA.LOAD):
                self._load_callback,
                OpD(OpF(0), OpL.MEM, OpA.STORE):
                self._store_callback,
                OpD(OpF.QUICK, OpL.MEM, OpA.STORE):
                self._store_callback,

                # block 3
                OpD(OpF(0), OpL.BRANCH, OpA.BRANCH):
                    self._branch_callback,
                OpD(OpF.QUICK, OpL.BRANCH, OpA.BRANCH):
                    self._branch_callback,
                OpD(OpF(0), OpL.BRANCH, OpA.IND_BRANCH):
                    self._branch_indexed_callback
                }

    def step(self) -> None:
        """
        Make one step (only step into)
        """
        # По какой-то причине адрессация работает
        # так, будто мы на 1 слово впереди опкода
        if not VMFlags.AFTER_BRANCH:
            self.pc = c_uint32(self.cc.value + 1)
        # сбрасываем флаг AFTER_BRANCH
        self._vm_flags &= ~(VMFlags.AFTER_BRANCH)
        opcode = self.mem[self.pc.value]
        opdesc = self._fetch_opcode_desc(opcode)
        args = self._parse_arguments(opdesc)
        self._run_callback(opdesc, args)

    def continue_(self) -> None:
        """
        Continue from current breakpoint
        """
        while ((self.pc.value < len(self.mem) // 4)
               and not self.pc.value in self.breakpoints):
            self.step()
        print("breakpoint")
        input()

    def run(self) -> None:
        """
        Run from very beginning
        """
        self.pc = c_uint32(0)
        while (self.pc.value < len(self.mem) // 4):
            self.continue_()

    def _fetch_opcode_desc(self, opcode: int):
        return OPCODES[opcode]
    
    def _parse_arguments(self, opdesc: OpcodeDescription) -> tuple[int, ...]:
        addr = self.pc.value
        main_part = struct.unpack(">BBBb", self.mem[addr:addr+4])

        if not OpF.UNEXPANDED in opdesc.flags or OpF.QUICK in opdesc.flags:
            upper_part = struct.unpack(">i", self.mem[addr+4:addr+8])
            return (*main_part, *upper_part)
        return main_part

    def _run_callback(
            self,
            opdesc: OpcodeDescription,
            args: tuple[int, ...]
            ) -> None:
        if opdesc.layout == OpL.MATH:
            assert len(args) == 4
            _, r3, r1, r2_or_i8 = args
            self.instr_callbacks[opdesc](
                    r3, r1, r2_or_i8
                    )
        if opdesc.layout == OpL.MEM:
            if OpF.QUICK in opdesc.flags:
                assert len(args) == 4
                _, r3, r1, i8 = args
                self.instr_callbacks[opdesc](
                        r3, r1, i8
                        )
            else:
                assert len(args) == 5
                _, r3, r1, _, disp = args
                self.instr_callbacks[opdesc](
                        r3, r1, disp
                        )

        if opdesc.layout == OpL.BRANCH:
            if OpF.QUICK in opdesc.flags:
                assert len(args) == 4
                _, cond, _, i8 = args
                self.instr_callbacks[opdesc](
                        cond, i8
                        )
            elif opdesc.action == OpA.IND_BRANCH:
                assert len(args) == 5
                _, cond, r1, _, disp = args
                self.instr_callbacks[opdesc](
                        cond, r1, disp
                        )
            else:
                assert len(args) == 5
                _, cond, _, _, disp = args
                self.instr_callbacks[opdesc](
                        cond, disp
                        )

    def _math_callback_gen(
            self,
            operation: Callable[[int, int], int]
            ) -> Callable[["VM", int,  int ,int], None]:
        """
        Поскольку математические операции конструируются
        по одному шаблону, я завел функцию высшего порядка,
        которая будет их генерировать
        """
        def callback(self, r3: int, r1: int, r2: int):
            lhs = self.registers[r1].value
            rhs = self.registers[r2].value
            self.registers[r3] = c_int32(operation(lhs, rhs))
            
        return callback

    def _math_quick_callback_gen(
            self,
            operation: Callable[[int, int], int]
            ) -> Callable[["VM", int,  int ,int], None]:
        """
        Поскольку математические операции конструируются
        по одному шаблону, я завел функцию высшего порядка,
        которая будет их генерировать.

        В отлиие от _math_callback_gen, эта уже предназначена для
        операций с пометкой QUICK
        """
        def callback(self, r3: int, r1: int, i8: int) -> None:
            self.cc = VMCC(0)
            lhs = self.registers[r1].value
            result = operation(lhs, i8)
            if result < 0:
                self.cc |= VMCC.NEGATIVE
            elif result == 0:
                self.cc |= VMCC.ZERO
            # самая дорогая проверка на переполнение)
            try:
                struct.pack('i', result)
            except struct.error:
                self.cc |= VMCC.OVERFLOW
            self.registers[r3] = c_int32(result)
        return callback

    def _load_callback(self, r3: int, r1: int, disp: int) -> None:
        addr = (self.registers[r1].value + disp) * 4
        self.registers[r3] = c_int32(
                struct.unpack(">i", self.mem[addr:addr+4])[0]
                )

    def _store_callback(self, r3: int, r1: int, disp: int) -> None:
        addr = (self.registers[r1].value + disp) * 4
        self.mem[addr:addr+4] = struct.pack(">i", self.registers[r3].value)

    def _branch_callback(self, cond: int, disp: int) -> None:
        c = Condition(cond)
        vm_c = Condition(self.cc.value)
        if (c.v & vm_c.v) & (c.n & vm_c.n) & (c.z & vm_c.z) == c.i:
            self._vm_flags |= VMFlags.AFTER_BRANCH
            self.pc = c_uint32(self.pc.value + disp)

    def _branch_indexed_callback(self, cond: int, r1: int, disp: int) -> None:
        c = Condition(cond)
        vm_c = Condition(self.cc.value)
        if (c.v & vm_c.v) & (c.n & vm_c.n) & (c.z & vm_c.z) == c.i:
            self._vm_flags |= VMFlags.AFTER_BRANCH
            addr = self.registers[r1].value + disp
            self.pc = c_uint32(addr)