import random
from bots.base import BaseBot


# VESDA alarm level thresholds (obscuration % per metre)
LEVELS = [
    ("normal", 0.0,  0.08),
    ("alert",  0.08, 0.20),
    ("action", 0.20, 0.50),
    ("fire",   0.50, 1.00),
]


def _level(obscuration: float) -> str:
    for name, lo, hi in LEVELS:
        if lo <= obscuration < hi:
            return name
    return "fire"


class VesdaBot(BaseBot):
    """VESDA aspirating smoke detector for a fire zone."""

    interval = 30

    def __init__(self, site_id: str, zone_id: str, room_id: str) -> None:
        super().__init__()
        self.site_id = site_id
        self.zone_id = zone_id
        self.room_id = room_id
        self._base_obscuration = random.uniform(0.005, 0.015)   # normal background
        self._alert  = False
        self._fire   = False

    def get_topic(self) -> str:
        return f"bms/{self.site_id}/fire/{self.zone_id}"

    def set_scenario(self, name: str | None) -> None:
        super().set_scenario(name)
        self._alert = (name == "VESDA_ALERT")
        self._fire  = (name == "VESDA_FIRE")

    def get_payload(self) -> dict:
        if self._fire:
            # Escalate rapidly to fire level
            obs = min(0.85, 0.50 + self._scenario_step * 0.03) + random.gauss(0, 0.01)
        elif self._alert:
            # Sit in alert/action band
            obs = min(0.45, 0.08 + self._scenario_step * 0.012) + random.gauss(0, 0.005)
        else:
            # Normal background with tiny random drift
            obs = self._base_obscuration + random.gauss(0, 0.002)
            obs = max(0.001, obs)

        level = _level(obs)

        return {
            "zone_id":        self.zone_id,
            "room_id":        self.room_id,
            "level":          level,
            "obscuration_pct_m": round(obs * 100, 3),
            "detector_1_ok":  True,
            "detector_2_ok":  True,
            "power_ok":       True,
            "flow_ok":        not self._fire,    # flow sensor trips in severe fire
        }