"""Binary control packet codec shared by the daemon and local clients."""

from __future__ import annotations

from dataclasses import dataclass
import struct
import time


CONTROL_PACKET_VERSION = 1
CONTROL_PACKET_STRUCT = struct.Struct("!BBHIfQ")

EVENT_NAME_TO_ID = {
    "pose_home": 1,
    "pose_hold": 2,
    "mode_stride": 3,
    "surge_up": 6,
    "surge_down": 7,
    "sway_left": 8,
    "sway_right": 9,
    "spin_left": 10,
    "spin_right": 11,
    "set_surge": 12,
    "set_sway": 13,
    "set_spin": 14,
    "set_lift": 15,
    "lift_up": 16,
    "lift_down": 17,
    "trim_reset": 18,
    "session_quit": 19,
}
EVENT_ID_TO_NAME = {value: key for key, value in EVENT_NAME_TO_ID.items()}
ANALOG_EVENT_CODES = {"set_surge", "set_sway", "set_spin"}


@dataclass(slots=True)
class ControlPacket:
    seq_id: int
    event_id: int
    drive_value: float = 1.0
    sent_at_ns: int = 0

    @property
    def event_name(self) -> str:
        return EVENT_ID_TO_NAME.get(self.event_id, f"unknown_{self.event_id}")

    def encode(self) -> bytes:
        sent_at_ns = self.sent_at_ns or time.time_ns()
        return CONTROL_PACKET_STRUCT.pack(
            CONTROL_PACKET_VERSION,
            self.event_id,
            0,
            int(self.seq_id),
            float(self.drive_value),
            int(sent_at_ns),
        )

    @classmethod
    def decode(cls, payload: bytes) -> "ControlPacket":
        if len(payload) != CONTROL_PACKET_STRUCT.size:
            raise ValueError(
                f"invalid control packet length {len(payload)}; "
                f"want {CONTROL_PACKET_STRUCT.size}"
            )
        version, event_id, _reserved, seq_id, drive_value, sent_at_ns = (
            CONTROL_PACKET_STRUCT.unpack(payload)
        )
        if version != CONTROL_PACKET_VERSION:
            raise ValueError(f"unsupported control packet version {version}")
        return cls(
            seq_id=int(seq_id),
            event_id=int(event_id),
            drive_value=float(drive_value),
            sent_at_ns=int(sent_at_ns),
        )


def make_control_packet(
    seq_id: int,
    event_name: str,
    drive_value: float = 1.0,
    sent_at_ns: int | None = None,
) -> ControlPacket:
    event_id = EVENT_NAME_TO_ID[event_name]
    return ControlPacket(
        seq_id=seq_id,
        event_id=event_id,
        drive_value=drive_value,
        sent_at_ns=time.time_ns() if sent_at_ns is None else sent_at_ns,
    )