import django.db.models.deletion
from django.db import migrations, models


CUISINE_SEEDS = [
    ('家常菜', 0),
    ('本帮菜', 10),
    ('江浙菜', 20),
    ('川菜', 30),
    ('粤菜', 40),
    ('鲁菜', 50),
    ('湘菜', 60),
    ('西北菜', 70),
    ('面点小吃', 80),
]


def seed_cuisines(apps, schema_editor):
    """Create Cuisine rows and save dish->cuisine mapping to a temp table."""
    Cuisine = apps.get_model('meals', 'Cuisine')

    name_to_id = {}
    for name, order in CUISINE_SEEDS:
        obj, _ = Cuisine.objects.get_or_create(name=name, defaults={'sort_order': order})
        name_to_id[name] = obj.pk

    from django.db import connection
    with connection.cursor() as cursor:
        cursor.execute("SELECT id, cuisine FROM meals_dish WHERE cuisine IS NOT NULL AND cuisine != ''")
        rows = cursor.fetchall()

    for _, cuisine_name in rows:
        if cuisine_name not in name_to_id:
            obj, _ = Cuisine.objects.get_or_create(name=cuisine_name, defaults={'sort_order': 90})
            name_to_id[cuisine_name] = obj.pk

    with connection.cursor() as cursor:
        cursor.execute("CREATE TABLE _temp_dish_cuisine (dish_id INTEGER, cuisine_id INTEGER)")
        for dish_id, cuisine_name in rows:
            cuisine_id = name_to_id.get(cuisine_name)
            if cuisine_id:
                cursor.execute(
                    "INSERT INTO _temp_dish_cuisine (dish_id, cuisine_id) VALUES (%s, %s)",
                    [dish_id, cuisine_id],
                )


def update_cuisine_fk(apps, schema_editor):
    """Populate Dish.cuisine_id from the temp table, then clean up."""
    from django.db import connection
    with connection.cursor() as cursor:
        cursor.execute(
            "UPDATE meals_dish SET cuisine_id = "
            "(SELECT cuisine_id FROM _temp_dish_cuisine "
            "WHERE _temp_dish_cuisine.dish_id = meals_dish.id) "
            "WHERE EXISTS (SELECT 1 FROM _temp_dish_cuisine "
            "WHERE _temp_dish_cuisine.dish_id = meals_dish.id)"
        )
        cursor.execute("DROP TABLE _temp_dish_cuisine")


def reverse_seed(apps, schema_editor):
    """Reverse: clean up temp table and delete Cuisine rows."""
    from django.db import connection
    with connection.cursor() as cursor:
        cursor.execute("DROP TABLE IF EXISTS _temp_dish_cuisine")
    Cuisine = apps.get_model('meals', 'Cuisine')
    Cuisine.objects.all().delete()


class Migration(migrations.Migration):
    """Step 2: Seed cuisines from existing data, then alter Dish.cuisine to FK."""

    dependencies = [
        ('meals', '0006_cuisine_dish_cuisine_fk'),
    ]

    operations = [
        migrations.RunPython(seed_cuisines, reverse_seed),
        migrations.AlterField(
            model_name='dish',
            name='cuisine',
            field=models.ForeignKey(
                blank=True,
                null=True,
                on_delete=django.db.models.deletion.SET_NULL,
                related_name='dishes',
                to='meals.cuisine',
                verbose_name='菜系',
            ),
        ),
        migrations.RunPython(update_cuisine_fk, migrations.RunPython.noop),
    ]