"""Envoi des emails de définition / réinitialisation de mot de passe."""

from __future__ import annotations

import json
import os
from datetime import datetime
from pathlib import Path
from urllib.parse import quote

from src.email_sender import send_email

_ROOT = Path(__file__).resolve().parent.parent
_DATA_DIR = Path(os.getenv("DATA_DIR", str(_ROOT / "data")))
_SETTINGS_PATH = _DATA_DIR / "settings.json"
_TEMPLATES_DIR = _DATA_DIR / "email_templates"


def _load_settings() -> dict:
    if _SETTINGS_PATH.exists():
        try:
            return json.loads(_SETTINGS_PATH.read_text(encoding="utf-8"))
        except Exception:
            return {}
    return {}


def _read_template(name: str) -> str:
    path = _TEMPLATES_DIR / name
    if not path.exists():
        raise FileNotFoundError(
            f"Template manquant : {path}. Créez data/email_templates/{name}."
        )
    return path.read_text(encoding="utf-8")


def _read_optional_template(name: str) -> str | None:
    path = _TEMPLATES_DIR / name
    if not path.exists():
        return None
    return path.read_text(encoding="utf-8")


def _format_expiry(dt: datetime) -> str:
    return dt.strftime("%d.%m.%Y à %H:%M")


def _format_ttl_human(dt: datetime) -> str:
    """Renvoie 'dans X h' ou 'dans X jours'."""
    delta = dt - datetime.now()
    total_seconds = max(0, int(delta.total_seconds()))
    if total_seconds < 3600:
        mins = total_seconds // 60
        return f"valable {mins} minute{'s' if mins > 1 else ''}"
    hours = total_seconds // 3600
    if hours < 48:
        return f"valable {hours} heure{'s' if hours > 1 else ''}"
    days = hours // 24
    return f"valable {days} jour{'s' if days > 1 else ''}"


def send_password_email(
    *,
    kind: str,            # "welcome" | "reset"
    username: str,
    name: str,
    email: str,
    token: str,
    expires_at: datetime,
) -> None:
    """Envoie un email de définition (kind='welcome') ou de reset (kind='reset').

    Lève une exception en cas d'erreur (SMTP, template manquant, base_url manquante).
    """
    if kind not in ("welcome", "reset"):
        raise ValueError(f"kind must be 'welcome' or 'reset', got {kind!r}")
    if not email or "@" not in email:
        raise ValueError(f"Email invalide pour {username!r}")

    settings = _load_settings()
    base_url = (settings.get("app_base_url") or "").rstrip("/")
    if not base_url:
        raise ValueError(
            "URL de base manquante. Configurez `app_base_url` dans Paramètres."
        )

    smtp_host     = settings.get("smtp_host")
    smtp_port     = int(settings.get("smtp_port") or 587)
    smtp_login    = settings.get("smtp_login")
    smtp_password = settings.get("smtp_password")
    smtp_sender   = settings.get("smtp_sender")
    if not (smtp_host and smtp_login and smtp_password and smtp_sender):
        raise ValueError(
            "Configuration SMTP incomplète. Vérifiez Paramètres → SMTP."
        )

    link = f"{base_url}/password-set?token={quote(token)}"
    vars_ = {
        "name":       name,
        "username":   username,
        "link":       link,
        "expiry":     _format_expiry(expires_at),
        "ttl_human":  _format_ttl_human(expires_at),
    }
    template_text_name = "welcome.txt"  if kind == "welcome" else "reset.txt"
    template_html_name = "welcome.html" if kind == "welcome" else "reset.html"
    body_text = _read_template(template_text_name).format_map(vars_)
    html_raw  = _read_optional_template(template_html_name)
    body_html = html_raw.format_map(vars_) if html_raw else None

    subject = (
        "EPTM Dashboard — Définissez votre mot de passe"
        if kind == "welcome"
        else "EPTM Dashboard — Réinitialisation de votre mot de passe"
    )

    send_email(
        smtp_host=smtp_host,
        smtp_port=smtp_port,
        smtp_login=smtp_login,
        smtp_password=smtp_password,
        smtp_sender=smtp_sender,
        to_email=email,
        subject=subject,
        body=body_text,
        body_html=body_html,
        attachments=None,
    )