/**
 * 旧版画布的联合读取工具，并行取得目录元数据与v2快照。
 * 它不协商canonical新模型，迁移感知的页面入口应使用canvas-entry中的分流流程。
 */
import { CANVAS_ACCEPT } from "./canvas-v2.ts";
import { decodeSnapshot, type CanvasSnapshot, type CanvasRequest } from "./canvas-sync.ts";
import { matchesRef, type Board } from "./workspace.ts";

/** 逐段编码路由引用，校验board身份和工作区，再解码快照；AbortSignal传给两次请求。
 * 返回数据不直接更新UI，导航是否仍有效由调用方控制。 */
export async function loadBoardCanvas(request: CanvasRequest, workspaceRef: string, boardRef: string, signal?: AbortSignal) {
  const path = `workspaces/${encodeURIComponent(workspaceRef)}/materials/${encodeURIComponent(boardRef)}`;
  const [board, snapshot] = await Promise.all([request<Board>(path, { signal }), request<CanvasSnapshot>(path + "/canvas", { signal, headers: { Accept: CANVAS_ACCEPT } })]);
  if (board.kind !== "board" || !matchesRef(board, boardRef) || typeof board.workspace_id !== "string" || !board.workspace_id) throw new Error("invalid_reference");
  return { board, snapshot: decodeSnapshot(snapshot) };
}