"""Reports: folder_id column for folder-based sorting

Revision ID: 0139
Revises: 0138
Create Date: 2026-08-21

Adds folder_id to report_templates for folder-based organization.
"""

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

# revision identifiers, used by Alembic.
revision = "0139"
down_revision = "0138"
branch_labels = None
depends_on = None


def _table_exists(conn, table_name: str) -> bool:
    """True when the table exists (dual-path convergence, Gate B).

    On a fresh install the report_generator plugin SQL migration has not
    run yet when Alembic reaches this revision — skip instead of failing.
    The plugin-side convergence migration adds the same column.
    """
    row = conn.execute(
        sa.text("SELECT to_regclass(:tname) IS NOT NULL"),
        {"tname": f"public.{table_name}"},
    ).scalar()
    return bool(row)


def upgrade() -> None:
    conn = op.get_bind()
    if not _table_exists(conn, "report_templates"):
        return
    op.add_column("report_templates", sa.Column("folder_id", PGUUID(as_uuid=True), nullable=True))
    op.create_index("ix_report_templates_folder", "report_templates", ["folder_id"])


def downgrade() -> None:
    conn = op.get_bind()
    if not _table_exists(conn, "report_templates"):
        return
    op.drop_index("ix_report_templates_folder", table_name="report_templates")
    op.drop_column("report_templates", "folder_id")