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simulators/bots/vesda.py

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+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
+        }