/**
 * 工作区画布目录的读取与展示树派生。完整分页包含子分区，随后用parent_board_id构建侧栏关系。
 * 显示树可保守容纳孤儿/循环记录，不据此修改服务端owner，也不替代文档模型中的canvas树校验。
 */
import { matchesRef, type Board } from "./workspace.ts";

/** 页面注入的通用JSON请求能力，传入signal供导航/卸载取消。 */
type Request = <T>(path: string, options?: RequestInit) => Promise<T>;
/** Include children and finish pagination before building ownership paths. */
/** 分页取齐board后返回按ID去重的列表，后出现的同ID记录更新内容。
 * next_offset必须严格前进且安全，seen防重复游标，不能只拿首页就推断某canvas没有父分区。 */
export async function loadBoardDirectory(request: Request, workspace: string, signal?: AbortSignal) {
  // Map 是本次读取的临时去重表，全部分页成功才返回；某页失败不发布已积累的半份目录。
  const boards = new Map<string, Board>();
  let offset = 0;
  const seen = new Set<number>();
  while (true) {
    if (seen.has(offset)) throw new Error("invalid_pagination");
    seen.add(offset);
    const page = await request<{ items: Board[]; next_offset?: number | null }>(`workspaces/${encodeURIComponent(workspace)}/materials?kind=board&sort=modified&include_subgraphs=true&limit=100&offset=${offset}`, { signal });
    for (const board of page.items) boards.set(board.id, board);
    if (page.next_offset == null) return [...boards.values()];
    if (!Number.isSafeInteger(page.next_offset) || page.next_offset <= offset) throw new Error("invalid_pagination");
    offset = page.next_offset;
  }
}
/** 侧栏派生分支：保留原board记录引用，children是本次展示树容器。 */
export type BoardBranch = { board: Board; children: BoardBranch[] };
/** 每条记录沿父链检查循环；父缺失或成环时作为展示根，避免递归挂载成无限树。
 * 同层顺序沿用输入列表，不在此另做排序或写回parent_board_id。 */
export function boardDirectory(boards: Board[]): BoardBranch[] {
  // 重复 ID 采用最后一条数据、沿用首次插入顺序；分支节点是新对象，board 本身仍借用输入引用。
  const entries = new Map(boards.map((board) => [board.id, { board, children: [] as BoardBranch[] }]));
  const roots: BoardBranch[] = [];
  for (const entry of entries.values()) {
    const seen = new Set([entry.board.id]);
    let parent = entry.board.parent_board_id;
    let cyclic = false;
    while (parent && entries.has(parent)) {
      if (seen.has(parent)) { cyclic = true; break; }
      seen.add(parent); parent = entries.get(parent)!.board.parent_board_id;
    }
    const owner = entry.board.parent_board_id && entries.get(entry.board.parent_board_id);
    if (owner && !cyclic) owner.children.push(entry); else roots.push(entry);
  }
  return roots;
}
/** 按ID或slug找到当前项，包含自身向上收集祖先ID，重复ID即停，供侧栏自动展开。 */
export function activeBoardAncestors(boards: Board[], ref?: string) {
  const result = new Set<string>();
  let item = boards.find((board) => matchesRef(board, ref));
  while (item && !result.has(item.id)) { result.add(item.id); item = boards.find((board) => board.id === item!.parent_board_id); }
  return result;
}
/** 忽略首尾空白并做本地小写匹配；父标题命中保留整子树，否则保留命中后代及其路径祖先。 */
export function filterBoardDirectory(branches: BoardBranch[], query: string): BoardBranch[] {
  const term = query.trim().toLocaleLowerCase();
  if (!term) return branches;
  return branches.flatMap((branch) => {
    if (branch.board.title.toLocaleLowerCase().includes(term)) return [branch];
    // 只重建需要裁剪 children 的祖先容器；直接命中的分支复用原对象，不深复制整棵树。
    const children = filterBoardDirectory(branch.children, term);
    return children.length ? [{ ...branch, children }] : [];
  });
}