"""Add base_units table and retarget unit_types.base_unit_id.

Revision ID: 009_base_units
Revises: 008_unit_type_fields
Create Date: 2026-08-05

"""

from typing import Sequence, Union

import sqlalchemy as sa
from alembic import op

revision: str = "009_base_units"
down_revision: Union[str, None] = "008_unit_type_fields"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.create_table(
        "base_units",
        sa.Column("id", sa.String(length=36), nullable=False),
        sa.Column("company_id", sa.String(length=36), nullable=False),
        sa.Column("code", sa.String(length=30), nullable=False),
        sa.Column("name", sa.String(length=100), nullable=False),
        sa.Column("description", sa.String(length=255), nullable=True),
        sa.Column("is_active", sa.Boolean(), nullable=False),
        sa.Column("sort_order", sa.Integer(), nullable=True),
        sa.Column("created_at", sa.DateTime(), nullable=False),
        sa.Column("updated_at", sa.DateTime(), nullable=False),
        sa.ForeignKeyConstraint(["company_id"], ["companies.id"], ondelete="CASCADE"),
        sa.PrimaryKeyConstraint("id"),
        sa.UniqueConstraint("company_id", "code", name="uq_base_units_company_code"),
    )
    op.create_index("ix_base_units_company_id", "base_units", ["company_id"], unique=False)

    conn = op.get_bind()
    inspector = sa.inspect(conn)
    fks = {fk["name"] for fk in inspector.get_foreign_keys("unit_types")}
    if "fk_unit_types_base_unit_id" in fks:
        op.drop_constraint("fk_unit_types_base_unit_id", "unit_types", type_="foreignkey")

    # Clear old self-referential IDs before pointing FK at base_units
    op.execute(sa.text("UPDATE unit_types SET base_unit_id = NULL"))

    op.create_foreign_key(
        "fk_unit_types_base_unit_id",
        "unit_types",
        "base_units",
        ["base_unit_id"],
        ["id"],
        ondelete="SET NULL",
    )


def downgrade() -> None:
    op.drop_constraint("fk_unit_types_base_unit_id", "unit_types", type_="foreignkey")
    op.execute(sa.text("UPDATE unit_types SET base_unit_id = NULL"))
    op.create_foreign_key(
        "fk_unit_types_base_unit_id",
        "unit_types",
        "unit_types",
        ["base_unit_id"],
        ["id"],
        ondelete="SET NULL",
    )
    op.drop_index("ix_base_units_company_id", table_name="base_units")
    op.drop_table("base_units")