import logging
import smtplib
from datetime import datetime
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.utils import formataddr
from typing import Sequence

from sqlalchemy.orm import Session

from app.core.config import settings
from app.core.email_utils import parse_recipient_list
from app.models.system import SendLog
from app.services.config_store import get_config

logger = logging.getLogger("newsletter.smtp")


def get_smtp_settings(db: Session) -> dict[str, str]:
    return {
        "enabled": get_config(db, "smtp.enabled", "false"),
        "host": get_config(db, "smtp.host", ""),
        "port": get_config(db, "smtp.port", "587"),
        "username": get_config(db, "smtp.username", ""),
        "password": get_config(db, "smtp.password", ""),
        "from_email": get_config(db, "smtp.from_email", ""),
        "from_name": get_config(db, "smtp.from_name", ""),
        "reply_to": get_config(db, "smtp.reply_to", ""),
        "use_tls": get_config(db, "smtp.use_tls", "true"),
        "recipients": get_config(db, "smtp.recipients", ""),
        # Zeitplan
        "schedule_enabled": get_config(db, "smtp.schedule_enabled", "false"),
        "schedule_acknowledged": get_config(db, "smtp.schedule_acknowledged", "false"),
        "schedule_frequency": get_config(db, "smtp.schedule_frequency", "monthly"),
        "schedule_time": get_config(db, "smtp.schedule_time", "08:00"),
        "schedule_weekdays": get_config(db, "smtp.schedule_weekdays", "0"),
        "schedule_dom": get_config(db, "smtp.schedule_dom", "1"),
        "last_scheduled_date": get_config(db, "smtp.last_scheduled_date", ""),
        # Generierungs-Vorgaben für den geplanten Versand
        "gen_period": get_config(db, "smtp.gen_period", "last_month"),
        "gen_days": get_config(db, "smtp.gen_days", "30"),
        "gen_article_type": get_config(db, "smtp.gen_article_type", "new"),
        "gen_category": get_config(db, "smtp.gen_category", ""),
        "gen_excluded_users": get_config(db, "smtp.gen_excluded_users", settings.default_excluded_users),
    }


def schedule_is_due(settings: dict[str, str], now: datetime) -> bool:
    """Prüft, ob laut Zeitplan jetzt ein Versand fällig ist (mit Tages-Dedupe)."""
    if settings["enabled"].lower() != "true":
        return False
    if (settings.get("schedule_enabled") or "false").lower() != "true":
        return False
    if (settings.get("schedule_acknowledged") or "false").lower() != "true":
        return False
    freq = (settings.get("schedule_frequency") or "off").lower()
    if freq == "off":
        return False

    schedule_time = settings.get("schedule_time") or "08:00"
    if now.strftime("%H:%M") < schedule_time:
        return False

    today = now.strftime("%Y-%m-%d")
    if settings.get("last_scheduled_date") == today:
        return False

    if freq == "daily":
        return True
    if freq == "weekly":
        weekdays = {d.strip() for d in (settings.get("schedule_weekdays") or "").split(",") if d.strip() != ""}
        return str(now.weekday()) in weekdays
    if freq == "monthly":
        try:
            dom = int(settings.get("schedule_dom") or "1")
        except ValueError:
            dom = 1
        return now.day == max(1, min(dom, 28))
    return False


def send_newsletter(
    db: Session,
    subject: str,
    html_content: str,
    text_content: str,
    recipients: Sequence[str],
    scheduled: bool = False,
) -> tuple[str, str]:
    settings = get_smtp_settings(db)
    if settings["enabled"].lower() != "true":
        detail = "SMTP ist deaktiviert. Bitte in der SMTP-Konfiguration aktivieren."
        _log(db, subject, recipients, "skipped", detail, scheduled)
        return "skipped", detail
    if not settings["host"] or not settings["from_email"] or not recipients:
        detail = "SMTP unvollständig konfiguriert (Host, Absender oder Empfänger fehlen)."
        _log(db, subject, recipients, "failed", detail, scheduled)
        return "failed", detail

    try:
        validated_recipients = parse_recipient_list(",".join(recipients))
    except ValueError as exc:
        detail = f"Ungültige Empfängerliste: {exc}"
        _log(db, subject, recipients, "failed", detail, scheduled)
        return "failed", detail

    msg = MIMEMultipart("alternative")
    msg.attach(MIMEText(text_content, "plain", "utf-8"))
    msg.attach(MIMEText(html_content, "html", "utf-8"))
    msg["Subject"] = subject
    if settings.get("from_name"):
        msg["From"] = formataddr((settings["from_name"], settings["from_email"]))
    else:
        msg["From"] = settings["from_email"]
    msg["To"] = settings["from_email"]
    msg["Bcc"] = ", ".join(validated_recipients)
    if settings.get("reply_to"):
        msg["Reply-To"] = settings["reply_to"]

    try:
        port = int(settings["port"])
        with smtplib.SMTP(settings["host"], port, timeout=20) as server:
            if settings["use_tls"].lower() == "true":
                server.starttls()
            if settings["username"]:
                server.login(settings["username"], settings["password"])
            server.sendmail(settings["from_email"], validated_recipients, msg.as_string())
        detail = f"Versand erfolgreich an {len(validated_recipients)} Empfänger."
        _log(db, subject, validated_recipients, "sent", detail, scheduled)
        return "sent", detail
    except Exception as exc:
        logger.exception("SMTP-Versand fehlgeschlagen")
        detail = "Versandfehler: E-Mail konnte nicht zugestellt werden. Details stehen im Server-Log."
        _log(db, subject, validated_recipients, "failed", detail, scheduled)
        return "failed", detail


def mark_scheduled_sent(db: Session, now: datetime) -> None:
    from app.services.config_store import set_config

    set_config(db, "smtp.last_scheduled_date", now.strftime("%Y-%m-%d"))


def _log(db: Session, subject: str, recipients: Sequence[str], status: str, detail: str, scheduled: bool) -> None:
    db.add(
        SendLog(
            subject=subject,
            recipients=", ".join(recipients) if recipients else "-",
            status=status,
            detail=detail,
            scheduled=scheduled,
        )
    )
    db.commit()