"""Framer implementations.

The implementation is responsible for encoding/decoding requests/responses.

According to the selected type of modbus frame a prefix/suffix is added/removed
"""
from __future__ import annotations

from enum import Enum

from pymodbus.exceptions import ModbusIOException
from pymodbus.logging import Log
from pymodbus.pdu import DecodePDU, ModbusPDU


class FramerType(str, Enum):
    """Type of Modbus frame."""

    ASCII = "ascii"
    RTU = "rtu"
    SOCKET = "socket"
    TLS = "tls"


class FramerBase:
    """Intern base."""

    EMPTY = b''
    MIN_SIZE = 0

    def __init__(
        self,
        decoder: DecodePDU,
    ) -> None:
        """Initialize a ADU (framer) instance."""
        self.decoder = decoder

    def decode(self, _data: bytes) -> tuple[int, int, int, bytes]:
        """Decode ADU.

        returns:
            used_len (int) or 0 to read more
            dev_id,
            tid,
            modbus request/response (bytes)
        """
        return 0, 0, 0, self.EMPTY

    def encode(self, data: bytes, _dev_id: int, _tid: int) -> bytes:
        """Encode ADU.

        returns:
            modbus ADU (bytes)
        """
        return data

    def buildFrame(self, message: ModbusPDU) -> bytes:
        """Create a ready to send modbus packet.

        :param message: The populated request/response to send
        """
        data = message.function_code.to_bytes(1,'big') + message.encode()
        frame = self.encode(data, message.dev_id, message.transaction_id)
        return frame

    def processIncomingFrame(self, data: bytes) -> tuple[int, ModbusPDU | None]:
        """Process new packet pattern.

        This takes in a new request packet, adds it to the current
        packet stream, and performs framing on it. That is, checks
        for complete messages, and once found, will process all that
        exist.
        """
        used_len = 0
        while True:
            data_len, pdu = self._processIncomingFrame(data[used_len:])
            used_len += data_len
            if not data_len:
                return used_len, None
            if pdu:
                return used_len, pdu

    def _processIncomingFrame(self, data: bytes) -> tuple[int, ModbusPDU | None]:
        """Process new packet pattern.

        This takes in a new request packet, adds it to the current
        packet stream, and performs framing on it. That is, checks
        for complete messages, and once found, will process all that
        exist.
        """
        Log.debug("Processing: {}", data, ":hex")
        if not data:
            return 0, None
        used_len, dev_id, tid, frame_data = self.decode(data)
        if not frame_data:
            return used_len, None
        if (result := self.decoder.decode(frame_data)) is None:
            raise ModbusIOException("Unable to decode request")
        result.dev_id = dev_id
        result.transaction_id = tid
        Log.debug("Frame advanced, resetting header!!")
        return used_len, result