CREATE TABLE IF NOT EXISTS audit_log (
    id bigserial PRIMARY KEY,
    table_name text NOT NULL,
    op text NOT NULL,
    pk jsonb,
    old_data jsonb,
    new_data jsonb,
    actor_id bigint,
    ip text,
    ua text,
    changed_at timestamptz NOT NULL DEFAULT now()
);

CREATE INDEX IF NOT EXISTS idx_audit_log_table_time ON audit_log (table_name, changed_at DESC);

CREATE OR REPLACE FUNCTION audit_row_change()
RETURNS trigger
LANGUAGE plpgsql
AS $$
DECLARE
    v_actor_id bigint;
    v_ip text;
    v_ua text;
    v_pk jsonb;
BEGIN
    v_actor_id := NULLIF(current_setting('app.current_user_id', true), '')::bigint;
    v_ip := NULLIF(current_setting('app.current_ip', true), '');
    v_ua := NULLIF(current_setting('app.current_ua', true), '');

    IF TG_OP = 'INSERT' THEN
        v_pk := jsonb_build_object('id', NEW.id);
        INSERT INTO audit_log(table_name, op, pk, old_data, new_data, actor_id, ip, ua)
        VALUES (TG_TABLE_NAME, TG_OP, v_pk, NULL, to_jsonb(NEW), v_actor_id, v_ip, v_ua);
        RETURN NEW;
    ELSIF TG_OP = 'UPDATE' THEN
        v_pk := jsonb_build_object('id', NEW.id);
        INSERT INTO audit_log(table_name, op, pk, old_data, new_data, actor_id, ip, ua)
        VALUES (TG_TABLE_NAME, TG_OP, v_pk, to_jsonb(OLD), to_jsonb(NEW), v_actor_id, v_ip, v_ua);
        RETURN NEW;
    ELSE
        v_pk := jsonb_build_object('id', OLD.id);
        INSERT INTO audit_log(table_name, op, pk, old_data, new_data, actor_id, ip, ua)
        VALUES (TG_TABLE_NAME, TG_OP, v_pk, to_jsonb(OLD), NULL, v_actor_id, v_ip, v_ua);
        RETURN OLD;
    END IF;
END;
$$;

DROP TRIGGER IF EXISTS audit_sales_orders ON sales_orders;
CREATE TRIGGER audit_sales_orders
AFTER INSERT OR UPDATE OR DELETE ON sales_orders
FOR EACH ROW
EXECUTE FUNCTION audit_row_change();

DROP TRIGGER IF EXISTS audit_purchase_orders ON purchase_orders;
CREATE TRIGGER audit_purchase_orders
AFTER INSERT OR UPDATE OR DELETE ON purchase_orders
FOR EACH ROW
EXECUTE FUNCTION audit_row_change();

DROP TRIGGER IF EXISTS audit_stock_movements ON stock_movements;
CREATE TRIGGER audit_stock_movements
AFTER INSERT OR UPDATE OR DELETE ON stock_movements
FOR EACH ROW
EXECUTE FUNCTION audit_row_change();