"""Product variants — per-product material variant support

Revision ID: 022
Revises: 021
Create Date: 2026-03-03
"""
from alembic import op
import sqlalchemy as sa
from sqlalchemy.dialects.postgresql import UUID, JSONB

revision = "022"
down_revision = "021"
branch_labels = None
depends_on = None


def upgrade() -> None:
    # --- New table: product_variants ---
    op.create_table(
        "product_variants",
        sa.Column("id", UUID(as_uuid=True), primary_key=True, server_default=sa.text("gen_random_uuid()")),
        sa.Column("product_id", UUID(as_uuid=True), sa.ForeignKey("products.id", ondelete="CASCADE"), nullable=False, index=True),
        sa.Column("name", sa.String(500), nullable=False),
        sa.Column("gewuenschte_bildnummer", sa.String(500), nullable=True),
        sa.Column("components", JSONB, nullable=False, server_default="[]"),
        sa.Column("is_default", sa.Boolean, nullable=False, server_default="false"),
        sa.Column("source_excel", sa.String(1000), nullable=True),
        sa.Column("created_at", sa.DateTime, server_default=sa.func.now(), nullable=False),
        sa.Column("updated_at", sa.DateTime, server_default=sa.func.now(), nullable=False),
    )
    # Unique constraint: (product_id, lower(name))
    op.create_index(
        "uq_product_variants_product_name",
        "product_variants",
        [sa.text("product_id"), sa.text("lower(name)")],
        unique=True,
    )

    # --- Alter products ---
    op.add_column("products", sa.Column("arbeitspaket", sa.String(500), nullable=True))

    # Drop existing unique constraint on pim_id — PIM-ID is a class-level
    # identifier shared by many products so it must NOT be unique.
    op.drop_constraint("products_pim_id_key", "products", type_="unique")
    op.create_index(
        "uq_products_produkt_baureihe",
        "products",
        [sa.text("lower(produkt_baureihe)")],
        unique=True,
        postgresql_where=sa.text("produkt_baureihe IS NOT NULL AND is_active = true"),
    )

    # --- Alter order_lines ---
    op.add_column(
        "order_lines",
        sa.Column(
            "variant_id",
            UUID(as_uuid=True),
            sa.ForeignKey("product_variants.id", ondelete="SET NULL"),
            nullable=True,
        ),
    )

    # --- Backfill: create default variants for existing products ---
    op.execute("""
        INSERT INTO product_variants (id, product_id, name, components, is_default, source_excel, created_at, updated_at)
        SELECT
            gen_random_uuid(),
            p.id,
            COALESCE(p.name, p.pim_id),
            COALESCE(p.components, '[]'::jsonb),
            true,
            p.source_excel,
            NOW(),
            NOW()
        FROM products p
        WHERE p.name IS NOT NULL OR p.pim_id IS NOT NULL
    """)


def downgrade() -> None:
    op.drop_column("order_lines", "variant_id")
    op.drop_index("uq_products_produkt_baureihe", "products")
    op.create_unique_constraint("products_pim_id_key", "products", ["pim_id"])
    op.drop_column("products", "arbeitspaket")
    op.drop_index("uq_product_variants_product_name", "product_variants")
    op.drop_table("product_variants")