"""
Management command to fix timezone-aware datetime fields.

This command converts naive datetime fields to timezone-aware datetimes
using the Asia/Riyadh timezone.

Usage:
    python manage.py fix_timezone_data
"""

from django.core.management.base import BaseCommand
from django.utils import timezone
from django.apps import apps
import pytz

class Command(BaseCommand):
    help = 'Convert naive datetime fields to timezone-aware datetimes'

    def add_arguments(self, parser):
        parser.add_argument(
            '--dry-run',
            action='store_true',
            help='Show what would be updated without making changes',
        )

    def handle(self, *args, **options):
        dry_run = options['dry_run']
        riyadh_tz = pytz.timezone('Asia/Riyadh')
        
        self.stdout.write(self.style.SUCCESS('Starting timezone data migration...'))
        if dry_run:
            self.stdout.write(self.style.WARNING('DRY RUN MODE - No changes will be made'))
        
        # List of models and their datetime fields to fix
        models_to_fix = [
            ('hr', 'Attendance', ['check_in', 'check_out']),
            ('hr', 'LeaveRequest', ['reviewed_at']),
            ('appointments', 'Appointment', ['confirmation_sent_at', 'arrival_at', 'start_at', 'end_at', 'no_show_at', 'cancel_at', 'reschedule_at']),
            ('appointments', 'AppointmentReminder', ['scheduled_for', 'sent_at']),
            ('appointments', 'AppointmentConfirmation', ['confirmed_at', 'sent_at', 'expires_at', 'last_reminder_at']),
            ('finance', 'Payment', ['payment_date', 'processed_at']),
            ('finance', 'Invoice', ['zatca_submission_date']),
            ('finance', 'CSID', ['issue_date', 'expiry_date', 'revocation_date', 'last_used']),
            ('core', 'Consent', ['signed_at']),
            ('documents', 'ClinicalNote', ['finalized_at']),
            ('integrations', 'Message', ['sent_at', 'delivered_at']),
            ('notifications', 'Notification', ['sent_at', 'read_at']),
            ('referrals', 'Referral', ['responded_at', 'completed_at']),
        ]
        
        total_updated = 0
        
        for app_label, model_name, fields in models_to_fix:
            try:
                model = apps.get_model(app_label, model_name)
                
                for field_name in fields:
                    # Check if field exists
                    if not hasattr(model, field_name):
                        continue
                    
                    # Get all records with naive datetime in this field
                    records = model.objects.all()
                    updated_count = 0
                    
                    for record in records:
                        field_value = getattr(record, field_name)
                        
                        # Skip if field is None or already timezone-aware
                        if field_value is None or timezone.is_aware(field_value):
                            continue
                        
                        # Convert naive datetime to timezone-aware
                        # Assume the naive datetime was in Riyadh timezone
                        aware_datetime = riyadh_tz.localize(field_value)
                        
                        if not dry_run:
                            setattr(record, field_name, aware_datetime)
                            record.save(update_fields=[field_name])
                        
                        updated_count += 1
                    
                    if updated_count > 0:
                        total_updated += updated_count
                        self.stdout.write(
                            self.style.SUCCESS(
                                f'  ✓ {app_label}.{model_name}.{field_name}: {updated_count} records {"would be " if dry_run else ""}updated'
                            )
                        )
            
            except LookupError:
                self.stdout.write(
                    self.style.WARNING(f'  ⚠ Model {app_label}.{model_name} not found, skipping...')
                )
            except Exception as e:
                self.stdout.write(
                    self.style.ERROR(f'  ✗ Error processing {app_label}.{model_name}: {str(e)}')
                )
        
        if total_updated > 0:
            self.stdout.write(
                self.style.SUCCESS(
                    f'\n{"Would update" if dry_run else "Updated"} {total_updated} datetime fields to timezone-aware'
                )
            )
        else:
            self.stdout.write(
                self.style.SUCCESS('\nNo naive datetime fields found - all data is already timezone-aware!')
            )
        
        if dry_run:
            self.stdout.write(
                self.style.WARNING('\nThis was a dry run. Run without --dry-run to apply changes.')
            )