"""Calculs C3 sur les relevés bruts.

Les intervalles sont volontairement calculés à la demande : MeterReading reste
la source de vérité et un reset ou un changement de compteur ne peut pas être
absorbé silencieusement dans une soustraction.
"""
from dataclasses import dataclass, asdict
from datetime import date, datetime, timedelta, timezone
from statistics import median, mean
from typing import Optional

from sqlalchemy.orm import joinedload

from ...extensions import db
from ..models.planning import (
    Meter, MeterReading, MeterAlert, MeterAlertEvidence, MeterAlertRule,
    MeterHeatingRegime, GasConversion, MeterTariff, CollegeClosure, ClosureWorkDay,
    MeterReadingSchedule, MeterReadingOccurrence,
)
from .planning_service import is_public_holiday


@dataclass
class ConsumptionInterval:
    meter_id: int
    reading_start: MeterReading
    reading_end: MeterReading
    start_date: datetime
    end_date: datetime
    raw_delta: float
    calendar_days: int
    consumption_per_day: float
    quality: str = "EXACT"
    context: dict = None

    def as_dict(self):
        data = asdict(self)
        data["reading_start"] = self.reading_start.id
        data["reading_end"] = self.reading_end.id
        data["start_date"] = self.start_date.isoformat()
        data["end_date"] = self.end_date.isoformat()
        return data


def _reading_datetime(reading):
    value = reading.reading_date or datetime.min.replace(tzinfo=timezone.utc)
    return value if value.tzinfo else value.replace(tzinfo=timezone.utc)


def _context_for(meter, start, end):
    counts = {"scolaire": 0, "vacances": 0, "fermeture": 0, "permanence": 0, "autre": 0}
    d = start.date()
    closures = CollegeClosure.query.filter(CollegeClosure.start_date <= end.date(), CollegeClosure.end_date >= start.date()).all()
    closure_ids = [row.id for row in closures]
    work_days = {row.work_date for row in ClosureWorkDay.query.filter(ClosureWorkDay.work_date >= start.date(), ClosureWorkDay.work_date < end.date()).all()} if closure_ids else set()
    while d < end.date():
        if meter.housing_unit_id:
            counts["scolaire"] += 1
        else:
            closure = next((row for row in closures if row.start_date <= d <= row.end_date), None)
            if closure:
                kind = (closure.closure_type or "vacances").lower()
                key = "permanence" if d in work_days or "perman" in kind else ("fermeture" if "fermet" in kind else "vacances")
                counts[key] += 1
            elif d.weekday() >= 5 or is_public_holiday(d)[0]:
                counts["fermeture"] += 1
            else:
                counts["scolaire"] += 1
        d += timedelta(days=1)
    regimes = {"NORMAL": 0, "REDUCED": 0, "STOP": 0}
    rows = MeterHeatingRegime.query.filter(
        MeterHeatingRegime.meter_id == meter.id,
        MeterHeatingRegime.valid_from <= end.date(),
        db.or_(MeterHeatingRegime.valid_to.is_(None), MeterHeatingRegime.valid_to >= start.date()),
    ).all()
    d = start.date()
    while d < end.date():
        row = next((r for r in rows if r.valid_from <= d and (r.valid_to is None or d <= r.valid_to)), None)
        if row:
            regimes[row.regime] += 1
        d += timedelta(days=1)
    return {"calendar": counts, "heating": regimes}


def consumption_intervals(meter, start=None, end=None):
    query = MeterReading.query.filter_by(meter_id=meter.id).order_by(MeterReading.reading_date, MeterReading.id).options(joinedload(MeterReading.read_by))
    if start:
        query = query.filter(MeterReading.reading_date >= start)
    if end:
        query = query.filter(MeterReading.reading_date <= end)
    readings = query.all()
    result = []
    for previous, current in zip(readings, readings[1:]):
        # A reset belongs to a new physical segment; never derive a delta over it.
        if previous.is_reset or current.is_reset or current.value < previous.value:
            continue
        days = max((_reading_datetime(current) - _reading_datetime(previous)).days, 1)
        interval = ConsumptionInterval(
            meter_id=meter.id, reading_start=previous, reading_end=current,
            start_date=_reading_datetime(previous), end_date=_reading_datetime(current),
            raw_delta=current.value - previous.value, calendar_days=days,
            consumption_per_day=(current.value - previous.value) / days,
        )
        interval.context = _context_for(meter, interval.start_date, interval.end_date)
        result.append(interval)
    return result


def aggregate_intervals(intervals, period="DAY"):
    """Agrégation simple par jour/semaine/mois sans modifier les relevés."""
    groups = {}
    for interval in intervals:
        d = interval.end_date.date()
        key = d if period == "DAY" else (d - timedelta(days=d.weekday()) if period == "WEEK" else (d.year, d.month))
        groups.setdefault(key, []).append(interval)
    return [{"period": key, "consumption": sum(i.raw_delta for i in rows), "calendar_days": sum(i.calendar_days for i in rows),
             "consumption_per_day": sum(i.raw_delta for i in rows) / max(sum(i.calendar_days for i in rows), 1), "intervals": rows}
            for key, rows in sorted(groups.items(), key=lambda x: x[0])]


def _metric_value(intervals, metric):
    """Retourne une métrique contextualisée par répartition temporelle."""
    if not intervals:
        return 0.0
    if metric == "consumption_interval":
        return sum(item.raw_delta for item in intervals)
    if metric == "consumption_per_day":
        return sum(item.raw_delta for item in intervals) / max(sum(item.calendar_days for item in intervals), 1)
    calendar_key = {"school_consumption": "scolaire", "vacation_consumption": "vacances", "closure_consumption": "fermeture"}
    heating_key = {"heating_normal": "NORMAL", "heating_reduced": "REDUCED", "heating_stop": "STOP"}
    key = calendar_key.get(metric)
    if key:
        days = sum((item.context or {}).get("calendar", {}).get(key, 0) for item in intervals)
    else:
        days = sum((item.context or {}).get("heating", {}).get(heating_key.get(metric, ""), 0) for item in intervals)
    total_days = sum(item.calendar_days for item in intervals)
    return sum(item.raw_delta for item in intervals) * days / total_days if total_days else 0.0


def remainder_for_interval(meter, interval):
    children = meter.children.all() if hasattr(meter.children, "all") else list(meter.children)
    if not children:
        return None
    total = 0.0
    quality = "EXACT"
    for child in children:
        rows = [i for i in consumption_intervals(child) if i.start_date <= interval.start_date and i.end_date >= interval.end_date]
        if rows:
            total += rows[-1].consumption_per_day * interval.calendar_days
            continue
        history = consumption_intervals(child)
        if len(history) >= 2:
            total += mean(i.consumption_per_day for i in history[-3:]) * interval.calendar_days
            quality = "ESTIMATED"
        else:
            quality = "PARTIAL"
    return {"value": interval.raw_delta - total, "quality": quality}


def _matches(value, operator, threshold):
    return {">": value > threshold, "<": value < threshold, ">=": value >= threshold, "<=": value <= threshold}[operator]


def evaluate_alert_rule(rule, interval, intervals=None, commit=True):
    if not rule.is_active:
        return None
    intervals = intervals or [interval]
    if rule.period in ("WEEK", "MONTH"):
        grouped = aggregate_intervals(intervals, rule.period)
        bucket = next((row["intervals"] for row in grouped if interval in row["intervals"]), [interval])
    else:
        bucket = [interval]
    value = _metric_value(bucket, rule.metric)
    if rule.context_filter:
        context = {
            "calendar": {key: sum((item.context or {}).get("calendar", {}).get(key, 0) for item in bucket)
                         for key in ("scolaire", "vacances", "fermeture", "permanence", "autre")},
            "heating": {key: sum((item.context or {}).get("heating", {}).get(key, 0) for item in bucket)
                        for key in ("NORMAL", "REDUCED", "STOP")},
        }
        if rule.context_filter in ("NORMAL", "REDUCED", "STOP"):
            if not (context.get("heating", {}).get(rule.context_filter) or 0): return None
        elif not (context.get("calendar", {}).get(rule.context_filter) or 0): return None
    zero_low = rule.detect_zero_or_low and (
        value == 0 or
        (rule.low_consumption_threshold is not None and value <= rule.low_consumption_threshold)
    )
    if not zero_low and not _matches(value, rule.operator, rule.threshold): return None
    alert_type = "ZERO_OR_LOW_CONSUMPTION" if zero_low else "MANUAL_THRESHOLD"
    open_alert = MeterAlert.query.filter_by(meter_id=rule.meter_id, alert_type=alert_type, metric=rule.metric, period=rule.period, context_key=rule.context_filter, rule_id=rule.id, status="OPEN").first()
    if not open_alert:
        open_alert = MeterAlert(meter_id=rule.meter_id, alert_type=alert_type, level=rule.level, metric=rule.metric, period=rule.period, context_key=rule.context_filter, rule_id=rule.id, observed_value=value, period_start=bucket[0].start_date.date(), period_end=bucket[-1].end_date.date())
        db.session.add(open_alert); db.session.flush()
    else:
        open_alert.observed_value = value
    evidence = MeterAlertEvidence.query.filter_by(alert_id=open_alert.id, reading_start_id=bucket[0].reading_start.id, reading_end_id=bucket[-1].reading_end.id).first()
    if not evidence:
        db.session.add(MeterAlertEvidence(alert_id=open_alert.id, reading_start_id=bucket[0].reading_start.id, reading_end_id=bucket[-1].reading_end.id, observed_value=value))
    if commit: db.session.commit()
    return open_alert


def statistical_anomaly(meter, interval, min_intervals=3, minimum_deviation_percent=30.0, rule=None, commit=True):
    if rule is not None:
        min_intervals = rule.min_comparable_intervals
        minimum_deviation_percent = rule.min_deviation_percent
    history = [i for i in consumption_intervals(meter) if i.end_date < interval.start_date and i.context == interval.context]
    history = [i for i in history if not MeterAlertEvidence.query.filter_by(reading_end_id=i.reading_end.id, excluded_from_baseline=True).first()]
    if len(history) < min_intervals: return None
    reference = median(i.consumption_per_day for i in history)
    if reference == 0 or interval.consumption_per_day <= reference: return None
    deviation = (interval.consumption_per_day - reference) / reference * 100
    if deviation < minimum_deviation_percent:
        return None
    rule_id = rule.id if rule else None
    alert = MeterAlert.query.filter_by(meter_id=meter.id, alert_type="STATISTICAL_ANOMALY", metric="consumption_per_day", period="DAY", context_key="comparable", rule_id=rule_id, status="OPEN").first()
    if not alert:
        alert = MeterAlert(meter_id=meter.id, alert_type="STATISTICAL_ANOMALY", level="WARNING", metric="consumption_per_day", period="DAY", context_key="comparable", rule_id=rule_id)
        db.session.add(alert); db.session.flush()
    alert.observed_value, alert.reference_value, alert.deviation_percent, alert.comparable_count = interval.consumption_per_day, reference, deviation, len(history)
    if not MeterAlertEvidence.query.filter_by(alert_id=alert.id, reading_start_id=interval.reading_start.id, reading_end_id=interval.reading_end.id).first():
        db.session.add(MeterAlertEvidence(alert_id=alert.id, reading_start_id=interval.reading_start.id, reading_end_id=interval.reading_end.id, observed_value=interval.consumption_per_day))
    if commit: db.session.commit()
    return alert


def gas_coefficient(meter, on_date):
    rows = GasConversion.query.filter_by(meter_id=meter.id).filter(GasConversion.valid_from <= on_date, db.or_(GasConversion.valid_to.is_(None), GasConversion.valid_to >= on_date)).order_by(GasConversion.valid_from.desc()).all()
    manual = next((row for row in rows if row.origin == "MANUAL"), None)
    return (manual or (rows[0] if rows else None)).coefficient_kwh_per_m3 if (manual or rows) else None


def create_bill_gas_conversion(*, meter, volume_m3, billed_kwh, valid_from, valid_to=None, commit=True):
    if volume_m3 is None or volume_m3 <= 0:
        raise ValueError("Le volume gaz facturé doit être strictement positif.")
    if billed_kwh is None or billed_kwh < 0:
        raise ValueError("Les kWh facturés ne peuvent pas être négatifs.")
    conversion = GasConversion(meter=meter, coefficient_kwh_per_m3=billed_kwh / volume_m3,
                               valid_from=valid_from, valid_to=valid_to, origin="BILL",
                               volume_m3=volume_m3, billed_kwh=billed_kwh)
    db.session.add(conversion)
    if commit: db.session.commit()
    return conversion


def close_meter_alert(*, alert, conclusion, comment=None, user_id=None, commit=True):
    allowed = {"CONFIRMED_LEAK", "NORMAL_EXPLAINED", "READING_ERROR", "BAD_THRESHOLD", "OTHER"}
    if conclusion not in allowed:
        raise ValueError("Conclusion d'alerte invalide.")
    alert.status = "CLOSED"
    alert.closed_at = datetime.now(timezone.utc)
    alert.conclusion = conclusion
    alert.comment = comment
    if conclusion in {"CONFIRMED_LEAK", "READING_ERROR"}:
        for evidence in alert.evidence:
            evidence.excluded_from_baseline = True
    if commit: db.session.commit()
    return alert


def visible_open_meter_alerts(user):
    """Retourne les alertes visibles dans Ma journée selon le RBAC métier."""
    query = MeterAlert.query.filter(MeterAlert.status.in_(("OPEN", "INVESTIGATING")))
    if user.is_admin():
        return query.order_by(MeterAlert.level.desc(), MeterAlert.opened_at.desc()).all()
    assigned_schedule = db.session.query(MeterReadingSchedule.meter_id).filter(
        MeterReadingSchedule.assigned_to_id == user.id
    )
    assigned_occurrence = db.session.query(MeterReadingOccurrence.schedule_id).filter(
        MeterReadingOccurrence.assigned_to_id == user.id
    )
    occurrence_meter = db.session.query(MeterReadingSchedule.meter_id).filter(
        MeterReadingSchedule.id.in_(assigned_occurrence)
    )
    return query.filter(MeterAlert.meter_id.in_(assigned_schedule.union(occurrence_meter))).order_by(
        MeterAlert.level.desc(), MeterAlert.opened_at.desc()
    ).all()


def _intervals_touching_reading(meter, reading):
    """Retourne uniquement les segments voisins d'un relevé modifié."""
    return [interval for interval in consumption_intervals(meter)
            if interval.reading_start.id == reading.id or interval.reading_end.id == reading.id]


def _invalidate_open_evidence_for(intervals, meter, changed_reading_ids=None):
    """Neutralise les preuves ouvertes qui ne correspondent plus à un segment valide.

    Les alertes déjà clôturées restent historiques. Les preuves ouvertes
    obsolètes sont retirées afin qu'une réévaluation puisse recréer une preuve
    valide sans collision ; la correction C1 conserve l'audit de la mesure.
    """
    changed_ids = set(changed_reading_ids or ())
    changed_ids.update({reading.id for item in intervals for reading in (item.reading_start, item.reading_end)})
    if not changed_ids:
        return []
    affected = []
    alerts = MeterAlert.query.filter_by(meter_id=meter.id).filter(MeterAlert.status == "OPEN").all()
    for alert in alerts:
        invalidated = False
        removed = []
        for evidence in alert.evidence:
            if evidence.reading_start_id in changed_ids or evidence.reading_end_id in changed_ids:
                # Le couple de relevés peut rester valide tout en ayant une
                # valeur différente : sa preuve précédente est alors obsolète.
                # On la retire uniquement d'une alerte encore ouverte ; les
                # alertes clôturées conservent leur audit historique.
                db.session.delete(evidence)
                removed.append(evidence)
                invalidated = True
        db.session.flush()
        remaining = [evidence for evidence in alert.evidence if evidence not in removed]
        if invalidated and not any(not evidence.excluded_from_baseline for evidence in remaining):
            alert.status = "CLOSED"
            alert.closed_at = datetime.now(timezone.utc)
            alert.conclusion = "READING_ERROR"
            alert.comment = "Alerte clôturée automatiquement après correction d'un relevé."
            affected.append(alert)
    return affected


def recalculate_meter_after_reading(*, meter, reading, commit=True):
    """Analyse le ou les nouveaux segments, sans rescanner l'historique des règles.

    Le relevé est déjà ajouté à la transaction appelante et doit avoir été
    flushé pour disposer de son identifiant.
    """
    impacted = _intervals_touching_reading(meter, reading)
    if not impacted:
        if commit:
            db.session.commit()
        return []
    rules = MeterAlertRule.query.filter_by(meter_id=meter.id, is_active=True).all()
    all_intervals = consumption_intervals(meter)
    for rule in rules:
        for interval in impacted:
            evaluate_alert_rule(rule, interval, intervals=all_intervals, commit=False)
    if commit:
        db.session.commit()
    return impacted


def recalculate_meter_after_correction(*, meter, reading, commit=True):
    """Réévalue seulement les deux segments pouvant dépendre du relevé corrigé."""
    ordered = (MeterReading.query.filter_by(meter_id=meter.id)
               .order_by(MeterReading.reading_date, MeterReading.id).all())
    reading_index = next((index for index, item in enumerate(ordered) if item.id == reading.id), None)
    neighbor_ids = {reading.id}
    if reading_index is not None:
        if reading_index:
            neighbor_ids.add(ordered[reading_index - 1].id)
        if reading_index + 1 < len(ordered):
            neighbor_ids.add(ordered[reading_index + 1].id)
    impacted = _intervals_touching_reading(meter, reading)
    _invalidate_open_evidence_for(impacted, meter, neighbor_ids)
    rules = MeterAlertRule.query.filter_by(meter_id=meter.id, is_active=True).all()
    all_intervals = consumption_intervals(meter)
    for rule in rules:
        for interval in impacted:
            evaluate_alert_rule(rule, interval, intervals=all_intervals, commit=False)
    if commit:
        db.session.commit()
    return impacted


def estimated_cost(meter, interval):
    tariff = MeterTariff.query.filter_by(meter_id=meter.id).filter(MeterTariff.valid_from <= interval.end_date.date(), db.or_(MeterTariff.valid_to.is_(None), MeterTariff.valid_to >= interval.end_date.date())).order_by(MeterTariff.valid_from.desc()).first()
    if not tariff: return None
    amount = interval.raw_delta
    if meter.meter_type == "gaz":
        coefficient = gas_coefficient(meter, interval.end_date.date())
        if coefficient is None and tariff.unit == "€/kWh": return None
        amount *= coefficient or 1
    return amount * tariff.unit_price