/**
 * BackgroundServerNudge — mid-run reminder when the user asked to start a
 * long-running dev server/watcher but no exec_background (or run_in_background)
 * has been used yet.
 *
 * Soft: max 1 fire. Pairs with evaluateInventedBackgroundServerCompletionGate.
 */

export const BACKGROUND_SERVER_NUDGE_MAX_ATTEMPTS = 1;

const SERVER_USER_RE =
  /(?:\bdev server\b|\bstart (?:the )?(?:server|service|watcher)\b|\brun (?:the )?server\b|开发服务器|启动服务|起服务|后台跑(?:服务|server)|long-running)/iu;

export interface BackgroundServerNudgeRequest {
  userText: string;
  toolCallsByName: Record<string, number>;
  messages?: Array<{ role?: string; content?: unknown }>;
  totalToolCalls: number;
  attempts: number;
}

export type BackgroundServerNudgeResult =
  | { fire: false }
  | { fire: true; correction: string };

function sawBackgroundStart(
  byName: Record<string, number>,
  messages: Array<{ role?: string; content?: unknown }> | undefined,
): boolean {
  if ((byName.exec_background ?? 0) > 0) return true;
  if (!messages?.length) return false;
  for (const m of messages) {
    if (!m || m.role !== 'assistant' || !Array.isArray(m.content)) continue;
    for (const block of m.content) {
      const b = block as { type?: string; name?: string; input?: unknown };
      if (b?.type !== 'tool_use' || b.name !== 'exec') continue;
      const input = b.input;
      if (input && typeof input === 'object') {
        const o = input as Record<string, unknown>;
        if (o.run_in_background === true || o.background === true) return true;
      }
    }
  }
  return false;
}

export function evaluateBackgroundServerNudge(
  request: BackgroundServerNudgeRequest,
): BackgroundServerNudgeResult {
  if (request.attempts >= BACKGROUND_SERVER_NUDGE_MAX_ATTEMPTS) return { fire: false };
  if (request.totalToolCalls < 1) return { fire: false };
  if (sawBackgroundStart(request.toolCallsByName, request.messages)) return { fire: false };

  const user = (request.userText || '').trim();
  if (!user || !SERVER_USER_RE.test(user)) return { fire: false };

  // Conceptual "how does the server work?" without asking to start it.
  if (
    /(?:how does|what is|文档|原理|介绍)/iu.test(user) &&
    !/(?:start|run|launch|启动|起)/iu.test(user)
  ) {
    return { fire: false };
  }

  return {
    fire: true,
    correction:
      '[System] The user asked to start a long-running server/watcher, and tools have already run without `exec_background` ' +
      '(or `exec` with run_in_background). Start it in the background and report the bg handle, or clearly say it was not started. ' +
      'Do not invent a running server.',
  };
}