/**
 * Adds an optional self-reference so a chat message can reply to another.
 * Kept as a plain column (no FK): when the replied-to message is later deleted
 * the id is retained but the join yields null, letting the UI show a subtle
 * "deleted message" reference instead of breaking the insert.
 *
 * Idempotent: also runs against fresh databases created from schema.sql, where
 * the column already exists.
 *
 * @module
 */

import type { DatabaseSync } from "node:sqlite";

/** Applies this migration to `db`. */
export function up(db: DatabaseSync): void {
  const cols = db.prepare(`PRAGMA table_info(chat_messages);`).all() as {
    name: string;
  }[];
  if (!cols.some((c) => c.name === "reply_to_id")) {
    db.exec(`ALTER TABLE chat_messages ADD COLUMN reply_to_id TEXT;`);
  }
}