import re
import urllib.error
import urllib.parse
import urllib.request
from io import BytesIO

from PyPDF2 import PdfFileReader, PdfFileMerger
from django.conf import settings
from django.contrib.staticfiles.storage import staticfiles_storage
from django.core.cache import cache
from django.core.mail import EmailMessage, EmailMultiAlternatives
from django.db.models.signals import post_save
from django.template.loader import get_template
from django.urls import reverse
from django.utils import timezone
from premailer import Premailer
from registration.signals import user_activated
from reversion import revisions as reversion
from z3c.rml import rml2pdf

from RIGS import models


def send_eventauthorisation_success_email(instance):
    # Generate PDF first to prevent context conflicts
    context = {
        'object': instance.event,
        'receipt': True,
        'current_user': False,
    }

    template = get_template('event_print.xml')
    merger = PdfFileMerger()

    rml = template.render(context)

    buffer = rml2pdf.parseString(rml)
    merger.append(PdfFileReader(buffer))
    buffer.close()

    terms = urllib.request.urlopen(settings.TERMS_OF_HIRE_URL)
    merger.append(BytesIO(terms.read()))

    merged = BytesIO()
    merger.write(merged)

    # Produce email content
    context = {
        'object': instance,
    }

    if instance.event.person is not None and instance.email == instance.event.person.email:
        context['to_name'] = instance.event.person.name
    elif instance.event.organisation is not None and instance.email == instance.event.organisation.email:
        context['to_name'] = instance.event.organisation.name

    subject = "N%05d | %s - Event Authorised" % (instance.event.pk, instance.event.name)

    client_email = EmailMultiAlternatives(
        subject,
        get_template("eventauthorisation_client_success.txt").render(context),
        to=[instance.email],
        reply_to=[settings.AUTHORISATION_NOTIFICATION_ADDRESS],
    )

    css = staticfiles_storage.path('css/email.css')
    html = Premailer(get_template("eventauthorisation_client_success.html").render(context),
                     external_styles=css).transform()
    client_email.attach_alternative(html, 'text/html')

    escapedEventName = re.sub(r'[^a-zA-Z0-9 \n\.]', '', instance.event.name)

    client_email.attach('N%05d - %s - CONFIRMATION.pdf' % (instance.event.pk, escapedEventName),
                        merged.getvalue(),
                        'application/pdf'
                        )

    if instance.event.mic:
        mic_email_address = instance.event.mic.email
    else:
        mic_email_address = settings.AUTHORISATION_NOTIFICATION_ADDRESS

    mic_email = EmailMessage(
        subject,
        get_template("eventauthorisation_mic_success.txt").render(context),
        to=[mic_email_address]
    )

    # Now we have both emails successfully generated, send them out
    client_email.send(fail_silently=True)
    mic_email.send(fail_silently=True)

    # Set event to booked now that it's authorised
    instance.event.status = models.Event.BOOKED
    instance.event.save()


def on_revision_commit(sender, instance, created, **kwargs):
    if created:
        send_eventauthorisation_success_email(instance)


post_save.connect(on_revision_commit, sender=models.EventAuthorisation)


def send_admin_awaiting_approval_email(user, request, **kwargs):
    # Bit more controlled than just emailing all superusers
    for admin in models.Profile.admins():
        # Check we've ever emailed them before and if so, if cooldown has passed.
        if admin.last_emailed is None or admin.last_emailed + settings.EMAIL_COOLDOWN <= timezone.now():
            context = {
                'request': request,
                'link_suffix': reverse("admin:RIGS_profile_changelist") + '?is_approved__exact=0',
                'number_of_users': models.Profile.users_awaiting_approval_count(),
                'to_name': admin.first_name
            }

            email = EmailMultiAlternatives(
                "%s new users awaiting approval on RIGS" % (context['number_of_users']),
                get_template("admin_awaiting_approval.txt").render(context),
                to=[admin.email],
                reply_to=[user.email],
            )
            css = staticfiles_storage.path('css/email.css')
            html = Premailer(get_template("admin_awaiting_approval.html").render(context),
                             external_styles=css).transform()
            email.attach_alternative(html, 'text/html')
            email.send()

            # Update last sent
            admin.last_emailed = timezone.now()
            admin.save()


user_activated.connect(send_admin_awaiting_approval_email)


def update_cache(sender, instance, created, **kwargs):
    cache.clear()


for model in reversion.get_registered_models():
    post_save.connect(update_cache, sender=model)