"""Envoi d'emails SMTP et utilitaires de template (Office 365 / Brevo / Gmail)."""
from __future__ import annotations

import re
import smtplib
from datetime import datetime
from email.mime.application import MIMEApplication
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from typing import TYPE_CHECKING

if TYPE_CHECKING:
    from src.db import Absence, Apprenti


def parse_sender(sender: str) -> tuple[str, str]:
    """Extrait (nom, email) depuis 'Nom Affiché <email>' ou 'email'."""
    m = re.match(r'^(.+?)\s*<([^>]+)>\s*$', sender.strip())
    if m:
        return m.group(1).strip(), m.group(2).strip()
    return "", sender.strip()


def render_template(template: str, variables: dict) -> str:
    """Substitue les variables {prenom}, {nom}, etc. dans le template."""
    try:
        return template.format_map(variables)
    except KeyError:
        return template


def build_template_vars(
    apprenti: "Apprenti",
    absences: list["Absence"],
    semestre_label: str = "",
) -> dict:
    """Construit le dictionnaire de variables pour les templates email."""
    nb_total      = len(absences)
    nb_excusees   = sum(1 for a in absences if a.statut == "excusee")
    nb_non_exc    = sum(1 for a in absences if a.statut == "non_excusee")
    nb_a_traiter  = sum(1 for a in absences if a.statut == "a_traiter")
    return {
        "prenom":          apprenti.prenom,
        "nom":             apprenti.nom,
        "nom_complet":     f"{apprenti.nom} {apprenti.prenom}",
        "classe":          apprenti.classe,
        "nb_absences":     nb_total,
        "nb_excusees":     nb_excusees,
        "nb_non_excusees": nb_non_exc,
        "nb_a_traiter":    nb_a_traiter,
        "semestre":        semestre_label or "",
        "date_du_jour":    datetime.now().strftime("%d.%m.%Y"),
    }


def send_email(
    smtp_host: str,
    smtp_port: int,
    smtp_login: str,
    smtp_password: str,
    smtp_sender: str,
    to_email: str,
    subject: str,
    body: str,
    attachments: "list[tuple[bytes, str]] | None" = None,
) -> None:
    """Envoie un email avec pièces jointes PDF optionnelles.

    smtp_login   : identifiant d'authentification SMTP (peut différer de l'expéditeur).
    smtp_sender  : adresse expéditeur, format 'Nom <email>' ou 'email'.
    attachments  : liste de (pdf_bytes, filename).
    Lève une exception en cas d'échec (SMTPException, OSError).
    """
    _from_name, _from_email = parse_sender(smtp_sender)

    msg = MIMEMultipart()
    msg["From"]    = f"{_from_name} <{_from_email}>" if _from_name else _from_email
    msg["To"]      = to_email
    msg["Subject"] = subject
    msg.attach(MIMEText(body, "plain", "utf-8"))

    for pdf_bytes, pdf_filename in (attachments or []):
        part = MIMEApplication(pdf_bytes, _subtype="pdf")
        part.add_header("Content-Disposition", "attachment", filename=pdf_filename)
        msg.attach(part)

    with smtplib.SMTP(smtp_host, smtp_port, timeout=20) as smtp:
        smtp.ehlo()
        smtp.starttls()
        smtp.ehlo()
        smtp.login(smtp_login, smtp_password)
        smtp.sendmail(_from_email, [to_email], msg.as_string())