from __future__ import annotations

from dataclasses import dataclass

from .frames import HEARTBEAT_FRAME, NEUTRAL_ACK_FRAME, frame_checksum_ok


REPORT_COMMAND_BYTES = frozenset({0x00, 0x01, 0x02})


@dataclass(frozen=True)
class AckDecision:
    should_ack: bool
    frame: bytes = NEUTRAL_ACK_FRAME
    reason: str = ""


@dataclass(frozen=True)
class AckPolicy:
    """Decides whether an RCP-origin frame should get a continuation ACK."""

    ack_frame: bytes = NEUTRAL_ACK_FRAME
    ack_reports: bool = True
    ack_heartbeats: bool = True
    ack_unlabeled_checksum_frames: bool = True

    def decide(self, frame: bytes, label: str = "") -> AckDecision:
        if not frame_checksum_ok(frame):
            return AckDecision(False, self.ack_frame, "checksum_bad")

        if frame == HEARTBEAT_FRAME:
            if self.ack_heartbeats:
                return AckDecision(True, self.ack_frame, "heartbeat_report")
            return AckDecision(False, self.ack_frame, "heartbeat_ignored")

        if frame[0] in REPORT_COMMAND_BYTES:
            if self.ack_reports:
                return AckDecision(True, self.ack_frame, f"report_cmd_{frame[0]:02X}")
            return AckDecision(False, self.ack_frame, "reports_disabled")

        if label == "checksum_ok_unlabeled" and self.ack_unlabeled_checksum_frames:
            return AckDecision(True, self.ack_frame, "unlabeled_checksum_ok")

        return AckDecision(False, self.ack_frame, f"non_report_cmd_{frame[0]:02X}")