"""
Management command to initialize AssetHistory for existing assets in the database.
Creates a 'create' history entry for each asset using:
- installation_date if available
- 01/01/2000 as fallback

Usage: python manage.py initialize_asset_history [--dry-run] [--batch-size=1000]
"""

from django.core.management.base import BaseCommand
from django.contrib.contenttypes.models import ContentType
from django.utils import timezone
from django.db import transaction
from datetime import datetime
from assets.models import AssetHistory


class Command(BaseCommand):
    help = 'Initialize AssetHistory for existing assets (creates __created__ entries)'

    def add_arguments(self, parser):
        parser.add_argument(
            '--dry-run',
            action='store_true',
            help='Show what would be done without actually creating history entries'
        )
        parser.add_argument(
            '--batch-size',
            type=int,
            default=1000,
            help='Number of history entries to create in each batch (default: 1000)'
        )
        parser.add_argument(
            '--app-label',
            type=str,
            default='assets',
            help='App label to process (default: assets)'
        )

    def handle(self, *args, **options):
        dry_run = options['dry_run']
        batch_size = options['batch_size']
        app_label = options['app_label']
        
        self.stdout.write(self.style.SUCCESS('=' * 70))
        self.stdout.write(self.style.SUCCESS('Asset History Initialization'))
        self.stdout.write(self.style.SUCCESS('=' * 70))
        
        if dry_run:
            self.stdout.write(self.style.WARNING('\n[!] DRY RUN MODE - No changes will be made\n'))
        
        # Default creation date for assets without installation_date
        default_date = timezone.make_aware(datetime(2000, 1, 1, 0, 0, 0))
        
        # Get all asset models from the specified app
        asset_content_types = ContentType.objects.filter(app_label=app_label)
        
        total_assets = 0
        total_created = 0
        total_skipped = 0
        
        for content_type in asset_content_types:
            model_class = content_type.model_class()
            
            # Skip if model doesn't exist or isn't an asset-like model
            if not model_class or not hasattr(model_class, 'code'):
                continue
            
            model_name = content_type.model
            self.stdout.write(f'\nProcessing {content_type.app_label}.{model_name}...')
            
            # Get all assets of this type
            assets = model_class.objects.all()
            asset_count = assets.count()
            
            if asset_count == 0:
                self.stdout.write(self.style.WARNING(f'   No assets found'))
                continue
            
            self.stdout.write(f'   Found {asset_count} assets')
            
            # Get existing history entries for this model
            existing_history = set(
                AssetHistory.objects.filter(
                    content_type=content_type,
                    action_type='create'
                ).values_list('object_id', flat=True)
            )
            
            # Prepare batch of history entries
            history_entries = []
            processed = 0
            created = 0
            skipped = 0
            
            for asset in assets.iterator(chunk_size=batch_size):
                processed += 1
                
                # Skip if already has creation history
                if asset.id in existing_history:
                    skipped += 1
                    continue
                
                # Determine creation date
                if hasattr(asset, 'installation_date') and asset.installation_date:
                    # Combine date with time
                    dt = datetime.combine(asset.installation_date, datetime.min.time())
                    # Make timezone-aware if not already
                    if timezone.is_aware(dt):
                        creation_date = dt
                    else:
                        creation_date = timezone.make_aware(dt)
                else:
                    creation_date = default_date
                
                # Create creation history entry
                history_entry = AssetHistory(
                    content_type=content_type,
                    object_id=asset.id,
                    timestamp=creation_date,
                    user=None,  # System-generated
                    field_name='__created__',
                    old_value=None,
                    new_value=asset.code,
                    action_type='create'
                )
                history_entries.append(history_entry)
                
                # Add initial status entry if asset has a status
                if hasattr(asset, 'status') and asset.status:
                    status_entry = AssetHistory(
                        content_type=content_type,
                        object_id=asset.id,
                        timestamp=creation_date,
                        user=None,  # System-generated
                        field_name='status',
                        old_value=None,
                        new_value=asset.status,
                        action_type='status_change'
                    )
                    history_entries.append(status_entry)
                
                created += 1
                
                # Batch insert when we reach batch_size
                if len(history_entries) >= batch_size:
                    if not dry_run:
                        with transaction.atomic():
                            AssetHistory.objects.bulk_create(history_entries)
                    history_entries = []
                    self.stdout.write(f'   ✓ Processed {processed}/{asset_count} assets...', ending='\r')
            
            # Insert remaining entries
            if history_entries and not dry_run:
                with transaction.atomic():
                    AssetHistory.objects.bulk_create(history_entries)
            
            # Summary for this model
            self.stdout.write(f'   ✓ Processed {processed}/{asset_count} assets')
            if created > 0:
                self.stdout.write(self.style.SUCCESS(f'   [+] Created {created} history entries'))
            if skipped > 0:
                self.stdout.write(self.style.WARNING(f'   [-] Skipped {skipped} (already have history)'))
            
            total_assets += asset_count
            total_created += created
            total_skipped += skipped
        
        # Final summary
        self.stdout.write('\n' + '=' * 70)
        self.stdout.write(self.style.SUCCESS('Summary:'))
        self.stdout.write('=' * 70)
        self.stdout.write(f'Total assets processed: {total_assets}')
        self.stdout.write(self.style.SUCCESS(f'History entries created: {total_created}'))
        self.stdout.write(self.style.WARNING(f'Assets skipped (existing history): {total_skipped}'))
        
        if dry_run:
            self.stdout.write('\n' + self.style.WARNING('[!] DRY RUN - No changes were made'))
            self.stdout.write(self.style.WARNING('    Run without --dry-run to apply changes'))
        else:
            self.stdout.write('\n' + self.style.SUCCESS('[+] Asset history initialization complete!'))
        
        self.stdout.write('')