"""Alert rule evaluation for DMARC report data."""

from __future__ import annotations

from datetime import datetime, timedelta, timezone
from typing import Any, Dict, List, Optional

from sqlalchemy import case, func
from sqlalchemy.orm import Session

from app.models.domain import Domain
from app.models.report import DMARCReport, ReportRecord
from app.models.setting import Setting
from app.services.alert_history import record_alert_evaluation
from app.services.notifications import NotificationResult, send_notification


def _truthy(value: Optional[str], default: bool = True) -> bool:
    if value in (None, ""):
        return default
    return str(value).strip().lower() in {"1", "true", "yes", "on"}


def _int_setting(value: Optional[str], default: int) -> int:
    try:
        return int(value or default)
    except (TypeError, ValueError):
        return default


def _settings(db: Session) -> Dict[str, Optional[str]]:
    rows = db.query(Setting).filter(Setting.category == "notifications").all()
    return {row.key: row.value for row in rows}


def _days_ago_ts(days: int) -> int:
    return int((datetime.now(timezone.utc) - timedelta(days=days)).timestamp())


def _new_source_alerts(db: Session, window_days: int = 7) -> List[Dict[str, Any]]:
    cutoff_ts = _days_ago_ts(window_days)
    previous_sources = {
        (row.domain, row.source_ip)
        for row in (
            db.query(Domain.name.label("domain"), ReportRecord.source_ip.label("source_ip"))
            .join(DMARCReport, DMARCReport.domain_id == Domain.id)
            .join(ReportRecord, ReportRecord.report_id == DMARCReport.id)
            .filter(DMARCReport.begin_date < cutoff_ts)
            .distinct()
            .all()
        )
    }

    current_sources = (
        db.query(
            Domain.name.label("domain"),
            ReportRecord.source_ip.label("source_ip"),
            func.sum(ReportRecord.count).label("message_count"),
        )
        .join(DMARCReport, DMARCReport.domain_id == Domain.id)
        .join(ReportRecord, ReportRecord.report_id == DMARCReport.id)
        .filter(DMARCReport.begin_date >= cutoff_ts)
        .group_by(Domain.name, ReportRecord.source_ip)
        .order_by(func.sum(ReportRecord.count).desc())
        .all()
    )

    alerts = []
    for row in current_sources:
        if (row.domain, row.source_ip) in previous_sources:
            continue
        count = int(row.message_count or 0)
        alerts.append(
            {
                "rule": "new_sender_source",
                "severity": "warning",
                "domain": row.domain,
                "source_ip": row.source_ip,
                "message_count": count,
                "title": "New sending source",
                "detail": f"{row.source_ip} first appeared for {row.domain} with {count} messages.",
            }
        )
    return alerts


def _failure_threshold_alerts(
    db: Session, threshold: int, window_days: int = 1
) -> List[Dict[str, Any]]:
    cutoff_ts = _days_ago_ts(window_days)
    rows = (
        db.query(
            Domain.name.label("domain"),
            func.sum(ReportRecord.count).label("failed_messages"),
        )
        .join(DMARCReport, DMARCReport.domain_id == Domain.id)
        .join(ReportRecord, ReportRecord.report_id == DMARCReport.id)
        .filter(DMARCReport.begin_date >= cutoff_ts)
        .filter(func.coalesce(ReportRecord.dkim, "fail") != "pass")
        .filter(func.coalesce(ReportRecord.spf, "fail") != "pass")
        .group_by(Domain.name)
        .having(func.sum(ReportRecord.count) >= threshold)
        .all()
    )
    return [
        {
            "rule": "dmarc_failures_above_threshold",
            "severity": "error",
            "domain": row.domain,
            "failed_messages": int(row.failed_messages or 0),
            "threshold": threshold,
            "title": "DMARC failures above threshold",
            "detail": (
                f"{row.domain} had {int(row.failed_messages or 0)} DMARC failures "
                f"in the last {window_days} day(s)."
            ),
        }
        for row in rows
    ]


def _missing_report_alerts(db: Session, missing_days: int) -> List[Dict[str, Any]]:
    cutoff_ts = _days_ago_ts(missing_days)
    latest_rows = (
        db.query(
            Domain.name.label("domain"),
            func.max(DMARCReport.end_date).label("last_report_ts"),
        )
        .outerjoin(DMARCReport, DMARCReport.domain_id == Domain.id)
        .group_by(Domain.id, Domain.name)
        .all()
    )
    alerts = []
    for row in latest_rows:
        last_report_ts = int(row.last_report_ts or 0)
        if last_report_ts >= cutoff_ts:
            continue
        alerts.append(
            {
                "rule": "missing_reports",
                "severity": "warning",
                "domain": row.domain,
                "missing_days": missing_days,
                "last_report_at": (
                    datetime.fromtimestamp(last_report_ts, tz=timezone.utc).isoformat()
                    if last_report_ts
                    else None
                ),
                "title": "Missing DMARC reports",
                "detail": f"{row.domain} has no DMARC report in the last {missing_days} day(s).",
            }
        )
    return alerts


def _compliance_drop_alerts(
    db: Session, drop_points: int, window_days: int = 2
) -> List[Dict[str, Any]]:
    cutoff_ts = _days_ago_ts(window_days)
    rows = (
        db.query(
            Domain.name.label("domain"),
            DMARCReport.begin_date.label("begin_date"),
            func.sum(ReportRecord.count).label("total"),
            func.sum(
                case(
                    (
                        (ReportRecord.dkim == "pass") | (ReportRecord.spf == "pass"),
                        ReportRecord.count,
                    ),
                    else_=0,
                )
            ).label("passed"),
        )
        .join(DMARCReport, DMARCReport.domain_id == Domain.id)
        .join(ReportRecord, ReportRecord.report_id == DMARCReport.id)
        .filter(DMARCReport.begin_date >= cutoff_ts)
        .group_by(Domain.name, DMARCReport.begin_date)
        .order_by(Domain.name, DMARCReport.begin_date)
        .all()
    )

    by_domain: Dict[str, List[Dict[str, float]]] = {}
    for row in rows:
        total = int(row.total or 0)
        passed = int(row.passed or 0)
        rate = round((passed / total) * 100, 1) if total else 0.0
        by_domain.setdefault(row.domain, []).append({"date": row.begin_date, "rate": rate})

    alerts = []
    for domain, points in by_domain.items():
        if len(points) < 2:
            continue
        previous = points[-2]
        current = points[-1]
        drop = round(previous["rate"] - current["rate"], 1)
        if drop < drop_points:
            continue
        alerts.append(
            {
                "rule": "compliance_drop",
                "severity": "error" if drop >= 25 else "warning",
                "domain": domain,
                "previous_rate": previous["rate"],
                "current_rate": current["rate"],
                "drop": drop,
                "threshold": drop_points,
                "title": "Compliance dropped",
                "detail": f"{domain} compliance fell by {drop} percentage points.",
            }
        )
    return alerts


def evaluate_alert_rules(db: Session) -> List[Dict[str, Any]]:
    """Evaluate all enabled alert rules against persisted DMARC data."""
    settings = _settings(db)
    alerts: List[Dict[str, Any]] = []

    if _truthy(settings.get("notifications.alert_new_sources_enabled")):
        alerts.extend(_new_source_alerts(db))

    if _truthy(settings.get("notifications.alert_failure_threshold_enabled")):
        threshold = _int_setting(settings.get("notifications.alert_failure_threshold_count"), 100)
        alerts.extend(_failure_threshold_alerts(db, threshold))

    if _truthy(settings.get("notifications.alert_missing_reports_enabled")):
        missing_days = _int_setting(settings.get("notifications.alert_missing_reports_days"), 2)
        alerts.extend(_missing_report_alerts(db, missing_days))

    if _truthy(settings.get("notifications.alert_compliance_drop_enabled")):
        drop_points = _int_setting(settings.get("notifications.alert_compliance_drop_points"), 10)
        alerts.extend(_compliance_drop_alerts(db, drop_points))

    return alerts


def send_current_alerts(db: Session) -> Dict[str, Any]:
    """Evaluate current alert rules and send one summary notification when needed."""
    alerts = evaluate_alert_rules(db)
    record_alert_evaluation(db, alerts)
    if not alerts:
        return {
            "alerts": [],
            "notification": NotificationResult(
                success=True, skipped=True, message="No alerts."
            ).to_dict(),
        }

    lines = [f"{alert['title']}: {alert['detail']}" for alert in alerts[:10]]
    if len(alerts) > 10:
        lines.append(f"...and {len(alerts) - 10} more alert(s).")
    result = send_notification(
        db,
        title=f"DMARQ alert summary: {len(alerts)} alert(s)",
        body="\n".join(lines),
    )
    return {"alerts": alerts, "notification": result.to_dict()}