"""
Data flow monitor — checks IMS and ThingsBoard data freshness.

Returns per-source status (green / yellow / red) with age and messages.
Used by the /api/health/data-sources endpoint and the email alerter.
"""

from __future__ import annotations

import logging
from datetime import datetime, timezone
from typing import Any

from config.settings import (
    IMS_STALE_YELLOW_MIN,
    IMS_STALE_RED_MIN,
    TB_STALE_YELLOW_MIN,
    TB_STALE_RED_MIN,
    ENERGY_STALE_YELLOW_MIN,
    ENERGY_STALE_RED_MIN,
)
from src.data.data_providers import DataHub

log = logging.getLogger("solarwine.monitor")


def _classify(age_minutes: float | None, yellow: float, red: float) -> str:
    """Return green / yellow / red based on age thresholds."""
    if age_minutes is None:
        return "red"
    if age_minutes < yellow:
        return "green"
    if age_minutes < red:
        return "yellow"
    return "red"


def _status_message(source: str, status: str, age: float | None) -> str:
    if status == "green":
        return f"{source} data is fresh"
    if age is not None:
        return f"{source} data is {age:.0f} min old"
    return f"{source} data is unavailable"


class DataFlowMonitor:
    """Computes per-source data flow status."""

    def check_all(self, hub: DataHub) -> dict[str, Any]:
        now_iso = datetime.now(timezone.utc).isoformat()
        sources: dict[str, dict] = {}

        # --- IMS Weather ---
        sources["ims_weather"] = self._check_ims(hub)

        # --- ThingsBoard Sensors ---
        sources["tb_sensors"] = self._check_tb_sensors(hub)

        # --- ThingsBoard Energy ---
        sources["tb_energy"] = self._check_tb_energy(hub)

        # Overall status: worst of all sources
        statuses = [s["status"] for s in sources.values()]
        if "red" in statuses:
            overall = "red"
        elif "yellow" in statuses:
            overall = "yellow"
        else:
            overall = "green"

        return {
            "overall": overall,
            "checked_at": now_iso,
            "sources": sources,
        }

    def _check_ims(self, hub: DataHub) -> dict:
        try:
            wx = hub.weather.get_current()
            if wx and "error" not in wx:
                age = float(wx.get("age_minutes", -1))
                if age < 0:
                    log.warning("IMS weather returned negative age_minutes — data provider issue")
                    age = None
                status = _classify(age, IMS_STALE_YELLOW_MIN, IMS_STALE_RED_MIN)
                return {
                    "status": status,
                    "age_minutes": round(age, 1) if age is not None else None,
                    "last_reading": wx.get("timestamp_local") or wx.get("timestamp_utc"),
                    "message": _status_message("IMS weather", status, age),
                }
            return {
                "status": "red",
                "age_minutes": None,
                "last_reading": None,
                "message": f"IMS weather error: {wx.get('error', 'unavailable')}",
            }
        except Exception as exc:
            log.warning("IMS health check failed: %s", exc)
            return {
                "status": "red",
                "age_minutes": None,
                "last_reading": None,
                "message": f"IMS weather unreachable: {exc}",
            }

    def _check_tb_sensors(self, hub: DataHub) -> dict:
        try:
            snap = hub.vine_sensors.get_snapshot(light=True)
            if snap and "error" not in snap:
                stale = snap.get("staleness_minutes")
                age = float(stale) if stale is not None else None
                status = _classify(age, TB_STALE_YELLOW_MIN, TB_STALE_RED_MIN)
                return {
                    "status": status,
                    "age_minutes": round(age, 1) if age is not None else None,
                    "last_reading": snap.get("timestamp"),
                    "message": _status_message("ThingsBoard sensors", status, age),
                }
            return {
                "status": "red",
                "age_minutes": None,
                "last_reading": None,
                "message": f"TB sensors error: {snap.get('error', 'unavailable')}",
            }
        except Exception as exc:
            log.warning("TB sensors health check failed: %s", exc)
            return {
                "status": "red",
                "age_minutes": None,
                "last_reading": None,
                "message": f"TB sensors unreachable: {exc}",
            }

    def _check_tb_energy(self, hub: DataHub) -> dict:
        try:
            en = hub.energy.get_current()
            if en and "error" not in en:
                power = en.get("power_kw")
                # Energy doesn't always expose age_minutes — infer from cache TTL
                age = float(en["age_minutes"]) if "age_minutes" in en else None
                status = _classify(age, ENERGY_STALE_YELLOW_MIN, ENERGY_STALE_RED_MIN)
                if age is None:
                    # If no age but we have data, assume green (just fetched)
                    status = "green"
                return {
                    "status": status,
                    "age_minutes": round(age, 1) if age is not None else None,
                    "power_kw": round(float(power), 2) if power is not None else None,
                    "message": _status_message("Energy telemetry", status, age),
                }
            return {
                "status": "red",
                "age_minutes": None,
                "power_kw": None,
                "message": f"Energy error: {en.get('error', 'unavailable')}",
            }
        except Exception as exc:
            log.warning("Energy health check failed: %s", exc)
            return {
                "status": "red",
                "age_minutes": None,
                "power_kw": None,
                "message": f"Energy unreachable: {exc}",
            }