"""Samsung connection state shared by BLE and RFCOMM adapters.

The caller supplies received bytes and writes returned packets. This module
owns sequence numbers, framing, connection-info validation, and readiness;
it has no threads, Bluetooth dependencies, timers, or UI dependencies.
"""

from dataclasses import dataclass

from controller.protocol import Decoder, Encoder, Frame


@dataclass(frozen=True)
class Update:
    frames: tuple[Frame, ...]
    outgoing: tuple[bytes, ...]
    became_ready: bool = False


class Session:
    """A fresh instance represents exactly one speaker connection."""

    def __init__(self, strict_checksums=False):
        self.encoder = Encoder()
        self.decoder = Decoder(strict_checksums=strict_checksums)
        self.ready = False
        self._complete_sequence = None

    def start(self):
        return self.command(b"\x01")

    def command(self, payload):
        return self.encoder.encode(payload)

    def receive(self, chunk):
        frames = tuple(self.decoder.feed(chunk))
        outgoing = []
        became_ready = False
        for frame in frames:
            # Speaker notifications have their own sequence counter. Only an
            # ACK for our link-complete request establishes session readiness.
            if frame.kind == 0 and frame.sequence == self._complete_sequence and not self.ready:
                self.ready = True
                became_ready = True
            if (
                frame.kind == 1
                and frame.payload
                and frame.payload[0] == 2
                and self._complete_sequence is None
            ):
                payload = frame.payload
                if len(payload) < 7 or len(payload) < 7 + payload[5]:
                    raise ValueError("Malformed speaker connection response")
                outgoing.append(self.command(b"\x04"))
                self._complete_sequence = self.encoder.sequence
        return Update(frames, tuple(outgoing), became_ready)