"""Normalize ingredient.aisle and grocery_item.aisle to canonical labels.

Revision ID: 0015
Revises: 0014
Create Date: 2026-06-02
"""
from typing import Sequence, Union

import sqlalchemy as sa
from alembic import op

# revision identifiers, used by Alembic.
revision: str = "0015"
down_revision: Union[str, None] = "0014"
branch_labels: Union[Sequence[str], None] = None
depends_on: Union[Sequence[str], None] = None


CANONICAL_AISLES = (
    "Produce",
    "Meat & Seafood",
    "Dairy & Eggs",
    "Pantry",
    "Frozen",
    "Bakery",
    "Beverages",
    "Spices",
    "Other",
)

# Map from lowercased source value to canonical label. Keep the rule
# order narrow -> broad; longest matches win via SQL CASE.
NORMALIZATION_RULES = [
    ("canned goods", "Pantry"),
    ("canned", "Pantry"),
    ("freezer", "Frozen"),
    ("frozen", "Frozen"),
    ("produce", "Produce"),
    ("fruit", "Produce"),
    ("vegetable", "Produce"),
    ("dairy", "Dairy & Eggs"),
    ("eggs", "Dairy & Eggs"),
    ("cheese", "Dairy & Eggs"),
    ("milk", "Dairy & Eggs"),
    ("yogurt", "Dairy & Eggs"),
    ("meat", "Meat & Seafood"),
    ("seafood", "Meat & Seafood"),
    ("fish", "Meat & Seafood"),
    ("chicken", "Meat & Seafood"),
    ("beef", "Meat & Seafood"),
    ("pork", "Meat & Seafood"),
    ("meat_seafood", "Meat & Seafood"),
    ("bakery", "Bakery"),
    ("bread", "Bakery"),
    ("beverage", "Beverages"),
    ("beverages", "Beverages"),
    ("drinks", "Beverages"),
    ("spice", "Spices"),
    ("spices", "Spices"),
    ("seasoning", "Spices"),
    ("pantry", "Pantry"),
    ("dry", "Pantry"),
    ("snack", "Pantry"),
    ("snacks", "Pantry"),
]

CASE_EXPR = "CASE LOWER(COALESCE(aisle, '')) " + " ".join(
    f"WHEN '{src}' THEN '{dst}' " for src, dst in NORMALIZATION_RULES
) + " WHEN NULLIF(LOWER(COALESCE(aisle, '')), '') IS NULL THEN NULL " + " ELSE 'Other' END"


def _normalize(table: str) -> None:
    op.execute(
        f"CREATE TEMP TABLE {table}_aisle_backup AS "
        f"SELECT id, aisle FROM {table} WHERE aisle IS NOT NULL"
    )
    op.execute(f"UPDATE {table} SET aisle = {CASE_EXPR} WHERE aisle IS NOT NULL")


def upgrade() -> None:
    bind = op.get_bind()
    with op.batch_alter_table("ingredient") as batch:
        pass
    _normalize("ingredient")
    _normalize("grocery_item")
    bind.execute(
        sa.text(
            "SELECT set_config('app.aisle_backup_retention', 'aisle_migration_0015', false)"
        )
    )


def downgrade() -> None:
    # Best-effort downgrade: the backup temp tables only exist within the
    # upgrade transaction. Restoring the pre-normalization state is not
    # possible from this migration alone. Operators must restore from a
    # database snapshot taken before upgrade.
    raise NotImplementedError(
        "Cannot reverse aisle normalization without an external backup. "
        "Restore the database from a snapshot taken before 0015 was applied."
    )