import smtplib

from email.message import EmailMessage
from itertools import groupby

from django.core.management.base import BaseCommand, CommandError
from tasks.models import Tool, Task, Event, Reminder


class Command(BaseCommand):
    help = 'Sends any notifications for upcoming and overdue tasks'

    def _send_email(self, to, subject, content):
        msg = EmailMessage()
        msg.set_content(content)
        msg['Subject'] = subject
        msg['From'] = 'adam@adamgoldsmith.name'
        msg['To'] = to

        with smtplib.SMTP("localhost") as server:
            server.send_message(msg)

    def _active_reminders(self):
        for reminder in Reminder.objects.all():
            if reminder.should_remind:
                yield reminder

    def _format_reminder_lines(self, reminders):
        for reminder in reminders:
            next_date = reminder.task.next_recurrence.strftime('%Y-%m-%d')
            yield f"  - {reminder.task.name} - {next_date}"

    def handle(self, *args, **options):
        reminders_per_user = {
            user: sorted(reminders, key=lambda r: r.task.next_recurrence)
            for user, reminders in groupby(self._active_reminders(), lambda r: r.user)
        }

        for user, reminders in reminders_per_user.items():
            self.stdout.write(self.style.SUCCESS(
                f'Sending notification for {len(reminders)} task(s) to {user}'))

            contents = "The following tasks are upcoming or overdue:\n\n" + \
                ('\n'.join(self._format_reminder_lines(reminders)))

            self._send_email(
                user.email,
                f'[CMS Tool Maintenance] {len(reminders)} tasks are upcoming or overdue!',
                contents)