import struct
from typing import List

from .clazz import Class, Code, Method
from .exceptions import PJVMException
from .old_jtypes import JObj


class Frame:
    ip: int = 0
    clazz: Class
    method: Method
    code: Code
    stack: List[JObj]
    this: JObj
    local_variables: List

    def __init__(self, clazz: Class, method: Method):
        self.clazz = clazz
        self.method = method
        self.code = self.method.code
        self.stack = []
        self.local_variables = [None for _ in range(self.code.max_locals)]

    def get_byte(self, idx: int) -> int:
        return struct.unpack('>b', self.code.code[idx:idx + 1])[0]

    def get_short(self, idx: int) -> int:
        return struct.unpack('>h', self.code.code[idx:idx + 2])[0]

    def get_int(self, idx: int) -> int:
        return struct.unpack('>i', self.code.code[idx:idx + 4])[0]

    def set_local(self, val: JObj, index: int):
        if index > self.code.max_locals:
            raise PJVMException("Local out of bound!")
        self.local_variables[index] = val

    def get_local(self, index: int) -> JObj:
        if index > self.code.max_locals:
            raise PJVMException("Local out of bound!")
        val = self.local_variables[index]
        if val is None:
            raise PJVMException("Local not set")
        return val