"""Clock-phase normal envelopes frozen before replay; never inspect future readings."""
from datetime import datetime
from math import isfinite

CALIBRATION_VERSION = "scada-monitor-calibration@2"
DIAGNOSTIC_POLICY = "normal-phase-envelope@1"


def weighted_diagnosis(document: dict) -> bool:
    return (document.get("monitoring_config") or {}).get("decision_policy") == "weighted"


def current_calibration(document: dict, start: datetime) -> dict | None:
    calibration = document.get("monitoring_calibration") or {}
    if (calibration.get("version") == CALIBRATION_VERSION
            and calibration.get("diagnostic_policy") == DIAGNOSTIC_POLICY
            and calibration.get("knowledge_cutoff") == start.isoformat()):
        return calibration
    return None


def diagnostic_signal(document: dict, event: dict) -> bool:
    """Never revive a persisted fixed-percentage event as new diagnosis evidence."""
    if event.get("category") == "data_quality":
        return False
    if not weighted_diagnosis(document):
        return True
    rules = (document.get("config") or {}).get("rules", [])
    rule = next((item for item in rules if item["rule_id"] == event["rule_id"]), None)
    return bool(rule and (rule["kind"] == "bounds" or event.get("diagnostic_policy") == DIAGNOSTIC_POLICY))


def normal_profile_bounds(profile: dict | None, at: datetime) -> tuple[float, float] | None:
    if not profile:
        return None
    interval = profile.get("interval_seconds", 0)
    if not profile.get("phase_origin"):
        return None
    origin = datetime.fromisoformat(profile["phase_origin"])
    lower, upper = profile.get("lower", []), profile.get("upper", [])
    offset = (at - origin).total_seconds()
    if interval <= 0 or offset < 0 or offset % interval or not lower or len(lower) != len(upper):
        return None
    slot = int(offset // interval) % len(lower)
    low, high = lower[slot], upper[slot]
    if low is None or high is None or not isfinite(low) or not isfinite(high):
        return None
    return float(low), float(high)