/**
 * GroupResolver 的 HTTP 实现(契约 C2,Group 团队服务到位后启用,
 * 经 HUB_GROUP_SERVICE_URL 配置)。
 *
 * 语义红线:
 *  - 失败 → FileLibError(503, group_unavailable)。依赖故障不是"无权限",
 *    绝不伪装成 404/403(计划 D13)。
 *  - 我方绝不自己推祖先:返回什么用什么,不在本地补逻辑。
 */

import { FileLibError } from "./model.js";
import type { GroupResolver } from "./groupResolver.js";

export interface HttpGroupResolverConfig {
  readonly baseUrl: string;
  readonly timeoutMs?: number;
  /** 测试可注入假 fetch;生产用全局 fetch。 */
  readonly fetchFn?: typeof fetch;
}

export function createHttpGroupResolver(config: HttpGroupResolverConfig): GroupResolver {
  const timeoutMs = config.timeoutMs ?? 2_000;
  const fetchFn = config.fetchFn ?? fetch;
  return {
    async resolveMemberGroupIds(userId) {
      const url = `${config.baseUrl.replace(/\/$/, "")}/groups/resolve-member-groups?userId=${encodeURIComponent(userId)}`;
      let response: Response;
      try {
        response = await fetchFn(url, { signal: AbortSignal.timeout(timeoutMs) });
      } catch (error) {
        throw new FileLibError(503, "group_unavailable", `group service unreachable: ${String(error)}`);
      }
      if (!response.ok) {
        throw new FileLibError(503, "group_unavailable", `group service returned ${response.status}`);
      }
      let body: unknown;
      try {
        body = await response.json();
      } catch {
        throw new FileLibError(503, "group_unavailable", "group service returned malformed JSON");
      }
      const groupIds = (body as { groupIds?: unknown }).groupIds;
      if (!Array.isArray(groupIds) || groupIds.some((id) => typeof id !== "string")) {
        throw new FileLibError(503, "group_unavailable", "group service returned malformed payload");
      }
      return groupIds as readonly string[];
    },
  };
}