"""message safety v2 normative schema

Revision ID: 0001_message_safety_v2
"""

from alembic import op
from app.db import Base

revision = "0001_message_safety_v2"
down_revision = None
branch_labels = None
depends_on = None


def upgrade() -> None:
    op.execute("CREATE SCHEMA IF NOT EXISTS message_safety")
    Base.metadata.create_all(bind=op.get_bind())
    op.execute(
        """
        CREATE OR REPLACE FUNCTION message_safety.guard_config_immutable()
        RETURNS trigger LANGUAGE plpgsql AS $$
        BEGIN
          IF OLD.version IS DISTINCT FROM NEW.version
             OR OLD.schema_version IS DISTINCT FROM NEW.schema_version
             OR OLD.config IS DISTINCT FROM NEW.config
             OR OLD.config_sha256 IS DISTINCT FROM NEW.config_sha256 THEN
            RAISE EXCEPTION 'immutable config fields cannot be changed';
          END IF;
          RETURN NEW;
        END $$;
        """
    )
    op.execute(
        """
        CREATE TRIGGER config_immutable
        BEFORE UPDATE ON message_safety.config_versions
        FOR EACH ROW EXECUTE FUNCTION message_safety.guard_config_immutable();
        """
    )
    op.execute(
        """
        CREATE OR REPLACE FUNCTION message_safety.guard_terminal_task()
        RETURNS trigger LANGUAGE plpgsql AS $$
        BEGIN
          IF OLD.status IN ('allowed','denied','failed')
             AND ROW(OLD.*) IS DISTINCT FROM ROW(NEW.*) THEN
            RAISE EXCEPTION 'terminal safety task is immutable';
          END IF;
          RETURN NEW;
        END $$;
        """
    )
    op.execute(
        """
        CREATE TRIGGER task_terminal_immutable
        BEFORE UPDATE ON message_safety.safety_tasks
        FOR EACH ROW EXECUTE FUNCTION message_safety.guard_terminal_task();
        """
    )


def downgrade() -> None:
    op.execute("DROP SCHEMA message_safety CASCADE")