"""Row-Level Security for plugin-owned tables (SPEC §11.1 + privacy hardening).

Per-user isolation for ``plg_*`` tables is enforced by Postgres, not by remembering
a ``WHERE user_id = ?`` in every query. Each user-data table gets RLS enabled +
forced, with a policy comparing ``user_id`` to the transaction-local GUC
``app.current_user_id``. Plugin code reaches these tables only through
``sdk.session(user_id)`` (see :mod:`app.plugins.db`), which drops to the
least-privilege :data:`PLUGIN_ROLE` and binds that GUC — so even a query that
forgets to filter cannot see or write another user's rows.

Plugin migrations call :func:`enable_rls` right after creating a user-data table.
"""

from __future__ import annotations

# NOLOGIN, non-superuser, NOBYPASSRLS role plugin sessions SET LOCAL ROLE into
# (created by core migration 0014). RLS is skipped for superusers / table owners /
# BYPASSRLS roles, so plugin access must run as this restricted role to be enforced.
PLUGIN_ROLE = "webmail_plugin"

_USER_CTX = "current_setting('app.current_user_id', true)::uuid"


def rls_ddl(table: str, *, user_column: str = "user_id") -> list[str]:
    """SQL statements that lock ``table`` to the current user (SPEC §11.1).

    Pure/testable: returns the DDL rather than executing it. ``FORCE`` makes even
    the table owner subject to the policy; ``WITH CHECK`` blocks inserting/updating
    rows for a different user."""
    policy = f"{table}_user_isolation"
    return [
        f"ALTER TABLE {table} ENABLE ROW LEVEL SECURITY",
        f"ALTER TABLE {table} FORCE ROW LEVEL SECURITY",
        f"CREATE POLICY {policy} ON {table} "
        f"USING ({user_column} = {_USER_CTX}) "
        f"WITH CHECK ({user_column} = {_USER_CTX})",
        f"GRANT SELECT, INSERT, UPDATE, DELETE ON {table} TO {PLUGIN_ROLE}",
    ]


def enable_rls(table: str, *, user_column: str = "user_id") -> None:
    """Apply :func:`rls_ddl` via Alembic ``op`` — call from a plugin migration."""
    from alembic import op

    for statement in rls_ddl(table, user_column=user_column):
        op.execute(statement)