"""
Celery tasks for notifications.
"""

import logging
from celery import shared_task
from django.utils import timezone
from django.core.mail import send_mail
from django.template.loader import render_to_string
from django.conf import settings
from datetime import timedelta
from zoneinfo import ZoneInfo

logger = logging.getLogger(__name__)


@shared_task
def send_daily_task_email():
    """
    Send daily email to users with their tasks due today.
    Runs once per day and sends to users in their local morning time.
    """
    from django.contrib.auth import get_user_model
    from tasks.models import Task

    User = get_user_model()

    # Get all users who have email notifications enabled
    users = User.objects.filter(
        email_notifications=True,
        email_verified=True,
        is_active=True
    )

    emails_sent = 0
    current_utc_hour = timezone.now().hour

    for user in users:
        # Convert current UTC time to user's local time
        try:
            user_tz = ZoneInfo(user.timezone)
        except Exception:
            user_tz = ZoneInfo('UTC')

        user_local_time = timezone.now().astimezone(user_tz)
        user_local_hour = user_local_time.hour

        # Only send if it's between 6-7 AM in the user's timezone
        # (gives 1 hour window, task runs every hour)
        if not (6 <= user_local_hour < 7):
            continue

        # Get today's date in user's timezone
        today = user_local_time.date()

        # Check if we already sent an email today
        from .models import Notification
        already_sent_today = Notification.objects.filter(
            user=user,
            notification_type='daily_email',
            created_at__date=today
        ).exists()

        if already_sent_today:
            continue

        # Get tasks due today
        tasks_due_today = Task.objects.filter(
            user=user,
            due_date=today,
            status__in=['pending', 'in_progress']
        ).order_by('due_time', 'priority', 'title')

        # Get overdue tasks
        overdue_tasks = Task.objects.filter(
            user=user,
            due_date__lt=today,
            status__in=['pending', 'in_progress']
        ).order_by('due_date', 'due_time', 'priority', 'title')

        # Only send email if there are tasks
        if not tasks_due_today.exists() and not overdue_tasks.exists():
            continue

        # Prepare email content
        subject = f"Your tasks for {today.strftime('%A, %B %d, %Y')}"

        # Create plain text message
        message_lines = [
            f"Good morning! Here are your tasks for today:\n"
        ]

        if overdue_tasks.exists():
            message_lines.append(f"\n⚠️  OVERDUE TASKS ({overdue_tasks.count()}):")
            for task in overdue_tasks[:10]:  # Limit to 10
                due_str = task.due_date.strftime('%b %d')
                message_lines.append(f"  • {task.title} (due {due_str})")
            if overdue_tasks.count() > 10:
                message_lines.append(f"  ... and {overdue_tasks.count() - 10} more")

        if tasks_due_today.exists():
            message_lines.append(f"\n📅 DUE TODAY ({tasks_due_today.count()}):")
            for task in tasks_due_today:
                time_str = task.due_time.strftime('%I:%M %p') if task.due_time else ''
                priority_icon = {'high': '🔴', 'medium': '🟡', 'low': '🟢'}.get(task.priority, '')
                message_lines.append(f"  • {priority_icon} {task.title} {time_str}".strip())

        message_lines.append(f"\n\nView all tasks: https://{settings.SITE_DOMAIN}")
        message_lines.append("\nYou can change your email preferences in your profile settings.")

        message = '\n'.join(message_lines)

        # Send email
        try:
            send_mail(
                subject=subject,
                message=message,
                from_email=settings.DEFAULT_FROM_EMAIL,
                recipient_list=[user.email],
                fail_silently=False,
            )

            # Record that we sent the email (prevents duplicates)
            Notification.objects.create(
                user=user,
                notification_type='daily_email',
                title=subject,
                message=f"Daily email sent with {tasks_due_today.count()} tasks due today and {overdue_tasks.count()} overdue tasks"
            )

            emails_sent += 1
            logger.info(f"Sent daily task email to {user.email}")
        except Exception as e:
            logger.error(f"Failed to send daily email to {user.email}: {e}")

    logger.info(f"Daily task email job completed. Sent {emails_sent} emails.")
    return emails_sent


@shared_task
def process_recurring_tasks():
    """
    Process completed recurring tasks and create next instances.
    This runs daily as a safety net to catch any tasks that weren't
    automatically handled when marked as completed.
    """
    from tasks.models import Task

    # Find completed recurring tasks from the last 48 hours
    yesterday = timezone.now() - timedelta(days=2)

    completed_recurring_tasks = Task.objects.filter(
        status='completed',
        recurrence__in=['daily', 'weekly', 'biweekly', 'monthly', 'yearly', 'custom'],
        completed_at__gte=yesterday
    ).exclude(recurrence='none')

    tasks_created = 0
    for task in completed_recurring_tasks:
        # Check if a next recurrence already exists
        next_due_date = task.calculate_next_due_date()
        if next_due_date:
            # Check if we already created this recurrence
            existing = Task.objects.filter(
                user=task.user,
                title=task.title,
                due_date=next_due_date,
                recurrence=task.recurrence,
                status='pending'
            ).exists()

            if not existing:
                # Create the next recurrence
                new_task = task.create_next_recurrence()
                if new_task:
                    tasks_created += 1
                    logger.info(f"Created recurring task: {new_task.title} (due: {new_task.due_date})")

    if tasks_created > 0:
        logger.info(f"Created {tasks_created} recurring task instances")

    return tasks_created