"""
Utility functions for user management.
"""

from datetime import timedelta
from django.conf import settings
from django.core.mail import send_mail
from django.template.loader import render_to_string
from django.utils import timezone
from .models import EmailVerificationToken


TOKEN_EXPIRY_HOURS = getattr(settings, 'EMAIL_VERIFICATION_TOKEN_EXPIRY_HOURS', 24)


def generate_verification_token(user):
    """
    Generate a new verification token for user.
    Invalidates any existing unused tokens before creating a new one.
    """
    # Invalidate any existing unused tokens
    EmailVerificationToken.objects.filter(
        user=user,
        is_used=False
    ).update(is_used=True)

    # Create new token
    token = EmailVerificationToken.objects.create(
        user=user,
        expires_at=timezone.now() + timedelta(hours=TOKEN_EXPIRY_HOURS)
    )
    return token


def send_verification_email(user, request=None):
    """
    Send email verification link to user.
    """
    token = generate_verification_token(user)

    # Build verification URL
    if request:
        domain = request.get_host()
        protocol = 'https' if request.is_secure() else 'http'
    else:
        domain = settings.SITE_DOMAIN
        protocol = 'https' if not settings.DEBUG else 'http'

    verification_url = f"{protocol}://{domain}/verify-email/{token.token}/"

    # Render email from template
    context = {
        'user': user,
        'verification_url': verification_url,
        'expiry_hours': TOKEN_EXPIRY_HOURS,
    }

    html_message = render_to_string('emails/verify_email.html', context)
    text_message = render_to_string('emails/verify_email.txt', context)

    send_mail(
        subject='Verify your KeepItGoing email',
        message=text_message,
        from_email=settings.DEFAULT_FROM_EMAIL,
        recipient_list=[user.email],
        html_message=html_message,
        fail_silently=False,
    )


def send_approval_notification(user):
    """
    Notify user their account has been approved.
    """
    protocol = 'https' if not settings.DEBUG else 'http'
    login_url = f"{protocol}://{settings.SITE_DOMAIN}/login/"

    context = {
        'user': user,
        'login_url': login_url,
    }

    html_message = render_to_string('emails/account_approved.html', context)
    text_message = render_to_string('emails/account_approved.txt', context)

    send_mail(
        subject='Your KeepItGoing account has been approved',
        message=text_message,
        from_email=settings.DEFAULT_FROM_EMAIL,
        recipient_list=[user.email],
        html_message=html_message,
        fail_silently=False,
    )


def notify_admins_new_user(user):
    """
    Notify all staff users about new registration awaiting approval.
    """
    from django.contrib.auth import get_user_model
    User = get_user_model()

    # Get all staff users
    staff_users = User.objects.filter(is_staff=True, is_active=True)
    staff_emails = [u.email for u in staff_users if u.email]

    if not staff_emails:
        return

    protocol = 'https' if not settings.DEBUG else 'http'
    admin_url = f"{protocol}://{settings.SITE_DOMAIN}/admin/users/user/{user.id}/change/"

    context = {
        'user': user,
        'admin_url': admin_url,
    }

    html_message = render_to_string('emails/admin_new_user.html', context)
    text_message = render_to_string('emails/admin_new_user.txt', context)

    send_mail(
        subject=f'New user registration: {user.email}',
        message=text_message,
        from_email=settings.DEFAULT_FROM_EMAIL,
        recipient_list=staff_emails,
        html_message=html_message,
        fail_silently=True,  # Don't fail registration if admin email fails
    )