from typing import Any, ClassVar, Type
from ..datainputstream import DataInputStream

class Packet:
    REGISTRY: ClassVar[dict[int, Type['Packet']]] = {}
    FIELDS: ClassVar[list[tuple[str, Any]]] = []
    PACKET_ID: ClassVar[int] = 0x00

    def __init__(self, **params):
        for k, v in params.items():
            setattr(self, k, v)

    @classmethod
    def read_from(cls, stream: DataInputStream) -> 'Packet':
        fields: dict = {}
        for key, datatype in cls.FIELDS:
            fields[key] = cls.read_field(stream, datatype)
        return cls(**fields)

    @staticmethod
    def read_field(stream: DataInputStream, datatype: Any):
        match datatype:
            case 'uint':
                return stream.read_uint()
            case 'int':
                return stream.read_int()
            case 'str':
                return stream.read_string()
            case 'str', length:
                return stream.read_string()[:length]
            case 'ulong':
                return stream.read_ulong()
            case 'long':
                return stream.read_long()
            case 'ushort':
                return stream.read_ushort()
            case 'short':
                return stream.read_short()
            case 'byte':
                return stream.read_byte()
            case 'float':
                return stream.read_float()
            case 'double':
                return stream.read_double()
            case 'bool':
                return stream.read_boolean()
            case 'bytes', length:
                return stream.read_bytes(length)
            case _:
                raise ValueError(f'unknown type {datatype}')

    def __init_subclass__(cls) -> None:
        Packet.REGISTRY[cls.PACKET_ID] = cls

    @classmethod
    def parse_packet(cls, stream: DataInputStream) -> 'Packet':
        packet_id: int = stream.read_byte()
        if packet_id not in cls.REGISTRY:
            stream._cursor -= 1
            raise ValueError(f'invalid packet 0x{packet_id:02x}')
        return cls.REGISTRY[packet_id].read_from(stream)

    def __repr__(self):
        pkt_name = self.REGISTRY[self.PACKET_ID].__name__
        fields = []
        for name, _ in self.FIELDS:
            fields.append(f'{name}={getattr(self, name)!r}')
        return f'<{pkt_name} {str.join(", ", fields)}'