import { notFound } from "next/navigation";

import { BackendDownNotice } from "@/components/BackendDownNotice";
import { ForeshadowBoard } from "@/components/foreshadow/ForeshadowBoard";
import { fetchForeshadow, fetchProject } from "@/lib/api/server";
import type { ForeshadowView, ProjectResponse } from "@/lib/api/types";

interface PageProps {
  params: Promise<{ id: string }>;
}

// 伏笔看板页（UX §6.8）。Server Component 取项目 + 全量伏笔（GET .../foreshadow）；
// ForeshadowBoard（Client）按 status 分四泳道并承载登记/状态变更交互。
export default async function ForeshadowPage({ params }: PageProps) {
  const { id } = await params;

  // 仅当项目确实不存在（404）才判 notFound；后端不可用等其它失败降级为「后端不可达」提示，
  // 不把整页变成「找不到页面」。
  let project: ProjectResponse;
  try {
    project = await fetchProject(id);
  } catch (err) {
    if (isNotFoundError(err)) notFound();
    return <BackendDownNotice className="m-6" />;
  }

  // 伏笔看板（GET .../foreshadow）。瞬时错误降级为空看板，不阻塞进页。
  let initialItems: ForeshadowView[] = [];
  try {
    const board = await fetchForeshadow(id);
    initialItems = board.foreshadow ?? [];
  } catch {
    initialItems = [];
  }

  return <ForeshadowBoard project={project} initialItems={initialItems} />;
}

// fetchProject 抛错信息形如「请求失败 404: ...」；据此区分「项目不存在」与「后端不可用」。
function isNotFoundError(err: unknown): boolean {
  return err instanceof Error && err.message.includes("请求失败 404");
}