"""flow_proposal l1 source linkage

Revision ID: 1fd88a68b145
Revises: cb9e282267d2
Create Date: 2026-05-29 19:33:09.188681

"""
from typing import Sequence, Union

from alembic import op
import sqlalchemy as sa
from sqlalchemy.dialects import postgresql


# revision identifiers, used by Alembic.
revision: str = '1fd88a68b145'
down_revision: Union[str, None] = 'cb9e282267d2'
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.add_column(
        "flow_proposals",
        sa.Column("l1_session_id", postgresql.UUID(as_uuid=True), nullable=True),
    )
    op.create_index(
        "ix_flow_proposals_l1_session_id",
        "flow_proposals",
        ["l1_session_id"],
    )
    op.create_foreign_key(
        "fk_flow_proposals_l1_session_id",
        "flow_proposals",
        "l1_walk_sessions",
        ["l1_session_id"],
        ["id"],
        ondelete="SET NULL",
    )
    op.alter_column("flow_proposals", "source_session_id", nullable=True)
    op.create_check_constraint(
        "ck_flow_proposals_exactly_one_source",
        "flow_proposals",
        "(source_session_id IS NOT NULL) <> (l1_session_id IS NOT NULL)",
    )


def downgrade() -> None:
    op.drop_constraint(
        "ck_flow_proposals_exactly_one_source",
        "flow_proposals",
        type_="check",
    )
    op.alter_column("flow_proposals", "source_session_id", nullable=False)
    op.drop_constraint(
        "fk_flow_proposals_l1_session_id",
        "flow_proposals",
        type_="foreignkey",
    )
    op.drop_index("ix_flow_proposals_l1_session_id", "flow_proposals")
    op.drop_column("flow_proposals", "l1_session_id")