"""Initial relations tables

Revision ID: relations_0001
Revises: None
Create Date: 2026-02-27
"""

import sqlalchemy as sa
from alembic import op

revision = "relations_0001"
down_revision = None
branch_labels = None
depends_on = None


def _table_exists(conn, name):
    result = conn.execute(sa.text(
        "SELECT 1 FROM information_schema.tables WHERE table_schema='public' AND table_name=:t"
    ), {"t": name})
    return result.scalar() is not None


def upgrade():
    if _table_exists(op.get_bind(), "container_relations"):
        return

    op.create_table(
        "container_relations",
        sa.Column("id", sa.Integer, primary_key=True, autoincrement=True),
        sa.Column("parent_type", sa.String(32), nullable=False),
        sa.Column("parent_id", sa.Integer, nullable=False),
        sa.Column("child_type", sa.String(32), nullable=False),
        sa.Column("child_id", sa.Integer, nullable=False),
        sa.Column("sort_order", sa.Integer, nullable=False, server_default="0"),
        sa.Column("label", sa.String(255), nullable=True),
        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
        sa.Column("deleted_at", sa.DateTime(timezone=True), nullable=True),
        sa.UniqueConstraint(
            "parent_type", "parent_id", "child_type", "child_id",
            name="uq_container_relations_parent_child",
        ),
    )
    op.create_index("ix_container_relations_parent", "container_relations", ["parent_type", "parent_id"])
    op.create_index("ix_container_relations_child", "container_relations", ["child_type", "child_id"])


def downgrade():
    op.drop_table("container_relations")