"""Stream connection state machine."""

import enum
from i2p_streaming.options import StreamOptions


class ConnectionState(enum.Enum):
    NEW = 0
    SYN_SENT = 1
    SYN_RECEIVED = 2
    ESTABLISHED = 3
    CLOSE_WAIT = 4
    LAST_ACK = 5
    FIN_WAIT = 6
    CLOSING = 7
    TIME_WAIT = 8
    CLOSED = 9
    RESET = 10


class StreamConnection:
    """TCP-like connection state machine for I2P streaming."""

    def __init__(self, options: StreamOptions | None = None):
        self._options = options or StreamOptions()
        self.state = ConnectionState.NEW
        self.next_send_seq = 0
        self.next_recv_seq = 0
        self.send_window = self._options.initial_window_size
        self.recv_window = self._options.initial_window_size
        self.destination: bytes = b""

    def _require_state(self, *states: ConnectionState):
        if self.state not in states:
            raise RuntimeError(f"Invalid transition from {self.state}")

    def send_syn(self):
        self._require_state(ConnectionState.NEW)
        self.state = ConnectionState.SYN_SENT

    def receive_syn(self):
        self._require_state(ConnectionState.NEW)
        self.state = ConnectionState.SYN_RECEIVED

    def receive_syn_ack(self):
        self._require_state(ConnectionState.SYN_SENT)
        self.state = ConnectionState.ESTABLISHED

    def send_syn_ack(self):
        self._require_state(ConnectionState.SYN_RECEIVED)
        self.state = ConnectionState.ESTABLISHED

    def send_close(self):
        self._require_state(ConnectionState.ESTABLISHED, ConnectionState.CLOSE_WAIT)
        if self.state == ConnectionState.ESTABLISHED:
            self.state = ConnectionState.FIN_WAIT
        elif self.state == ConnectionState.CLOSE_WAIT:
            self.state = ConnectionState.LAST_ACK

    def receive_close(self):
        self._require_state(ConnectionState.ESTABLISHED, ConnectionState.FIN_WAIT)
        if self.state == ConnectionState.ESTABLISHED:
            self.state = ConnectionState.CLOSE_WAIT
        elif self.state == ConnectionState.FIN_WAIT:
            self.state = ConnectionState.CLOSING

    def receive_ack(self):
        self._require_state(ConnectionState.LAST_ACK)
        self.state = ConnectionState.CLOSED

    def receive_close_ack(self):
        self._require_state(ConnectionState.FIN_WAIT)
        self.state = ConnectionState.TIME_WAIT

    def timeout(self):
        self._require_state(ConnectionState.TIME_WAIT)
        self.state = ConnectionState.CLOSED

    def reset(self):
        self.state = ConnectionState.RESET

    def increment_send_seq(self):
        self.next_send_seq += 1

    def increment_recv_seq(self):
        self.next_recv_seq += 1