from django.contrib.staticfiles import finders
from django.contrib import messages
from django.core.mail import EmailMultiAlternatives, get_connection
from django.http import HttpRequest
from django.db.models.query import QuerySet
from django.utils.safestring import SafeText
from django.template.loader import render_to_string

from ..models.students import Student

from smtplib import SMTPException
from email.mime.image import MIMEImage

from typing import List

def send_mail_password(request: HttpRequest, queryset: QuerySet[Student]) -> None:
    img: MIMEImage | None = None
    filename: str
    candidates = finders.find("cantorair.png")
    if not candidates:
        messages.error(request=request, message="Cannot Load CantorAir Logo")
        return
    elif isinstance(candidates, list):
        filename = candidates.pop()
    else:
        filename = candidates

    with open(filename, "rb") as f:
        img = MIMEImage(f.read())
        img.add_header("Content-ID", "logo_image")
        img.add_header("Content-Disposition", "inline", filename="cantorair.png")     
    
    # build mail list filling template
    queryset = queryset.filter(mail_sent=False)
    mails: List[EmailMultiAlternatives] = []
    for student in queryset:
        if not student.user or not student.email: # skip student if has not an associated user
            continue
        try:
            username: str = student.user.username
            password: str = student.default_password()
            address: str = student.email

            text_message: str = f"Cantor Air Flight Scheduler\nUsername:{username}\nPassword:{password}\n"

            html_message: SafeText = render_to_string(
                template_name="email/mail.html",
                context={"username": username, "password": password}
            )

            mail: EmailMultiAlternatives = EmailMultiAlternatives(
                subject="CantorAir Flight Scheduler 🛫",
                from_email="ema.trabattoni@gmail.com",
                body=text_message, 
                to = [ address ]
            )
            mail.attach(filename=img)
            mail.attach_alternative(content=html_message, mimetype="text/html")
            mails.append(mail)
            student.mail_sent = True
            student.save()
        except Exception as e:
            messages.error(request=request, message=f"General Error: {e}")
    
    if len(mails) == 0:
        messages.warning(request=request, message="No email will be sent")
        return 
    
    # Open only one conenction and send mass email
    try:
        sent: int = 0
        with get_connection() as conn:
            sent = conn.send_messages(mails)
    except SMTPException as e:
        messages.error(request=request, message=f"Send Mail SMTP error: {e.strerror}")
    except Exception as e:
        messages.error(request=request, message=f"Send Mail General error: {e}")
    else:
        messages.success(request=request, message=f"Successfully sent {sent} messages")
    
    return