docs(canvas): explain legacy tree state and transaction coordination

Reviewed-on: #3

src/components/canvas/use-canvas-tree.ts

@@ -1,3 +1,9 @@
+/**
+ * 旧版画布树的状态与操作协调Hook。documents按boardId保存已加载快照，views把嵌套子画布投影为当前ReactFlow场景。
+ * 每个board有独立CanvasSync writer，本地历史和服务端结构事务共用两个栈，成员迁移另用串行内存队列。
+ * 该实现保留旧快照协议与本地草稿恢复，不等同于新版engine的统一提交根、持久ledger和恢复状态机。
+ * 调用方应按根/工作区身份重挂载；refs提供异步操作读取的最新状态，React state负责发布界面变化。
+ */
 "use client";
 import { useCallback, useEffect, useMemo, useRef, useState } from "react";
 import type { EdgeChange, NodeChange } from "@xyflow/react";
@@ -8,20 +14,34 @@ import { CANVAS_ACCEPT, type EdgeData } from "@/lib/canvas-v2";
 import { subgraphMovePath, subgraphMoveParticipants } from "@/lib/canvas-subgraphs";
 import { mergeCanvasDocuments, projectCanvasTree, transformEdgeData, referenceAfterMoves } from "@/lib/canvas-tree";
 
+/** 命令返回的快照额外携带board_id，用于把多画布结果安装回各自writer。 */
 type OwnedSnapshot = CanvasSnapshot & { board_id: string };
+/** 兼容多个旧命令端点的结果包络，可能返回父/子/多快照、事务身份、归档列表和版本；各使用路径再解码快照。 */
 export type CanvasCommandResult = { transaction_id?: string; parent?: OwnedSnapshot; child?: OwnedSnapshot; snapshots?: OwnedSnapshot[]; children?: OwnedSnapshot[]; canvas_version?: number; applied_versions?: Record<string, number>; archived_board_ids?: string[]; undo_receipt?: { expires_at: string }; [key: string]: unknown };
+/** 本地历史保存操作前整份画布，可附关联画布；pendingMove标记尚未上传图片的跨画布移动，便于后来按服务端归属撤销。 */
 type LocalHistory = { boardId: string; before: CanvasDocument; related?: Map<string, CanvasDocument>; pendingMove?: { id: string; source: string; target: string } };
+/** 服务端结构事务历史保存可重放的路径/负载、事务ID和参与画布；撤销请求服务端undo，重做重新执行原命令。 */
 type TransactionHistory = { boardId: string; path: string; payload: Record<string, unknown>; id: string; participants: string[] };
+/** 两种历史条目共用undo/redo栈，通过是否有id字段区分；不是每次pointermove都直接创建条目。 */
 type Entry = LocalHistory | TransactionHistory;
+/** 成员归属迁移的FIFO任务；run在准备后捕获固定body/key供不确定失败重试，refresh表示确定冲突后需刷新基线。 */
 type MemberJob = { source: string; target: string; ids: string[]; parent: string; frame: string; participants: string[]; error?: string; refresh?: boolean; run?: () => Promise<void>; resolve: () => void };
+/** 只为一次reducer运算建立临时空历史，借其past是否变化判断该动作是否应进入本Hook自己的历史栈。 */
 const history = (document: CanvasDocument): CanvasHistory => ({ past: [], present: document, future: [] });
 
+/** initial建立根画布，snapshot决定是否连接服务端writer；paused阻止保存/独占事务等准入，migration额外限制旧写入。
+ * parentBoardId用于补读祖先快照；导出、跨分区移动和事务可能按需加载更多画布。 */
 export function useCanvasTree(root: string, workspace: string, initial: CanvasDocument, snapshot?: CanvasSnapshot, paused = false, parentBoardId?: string, migration?: {accountId:string;isCurrentIdentity():boolean}) {
+  // 有迁移上下文时先关旧编辑入口，等迁移协调组件取得共享租约再开放；flush只有迁移准备阶段临时启用。
   const migrationGate=useRef(!!migration);
   const migrationFlush=useRef(false);
   const [migrationHeld,setMigrationState]=useState(!!migration);
+  /** 同步检查门闩和账号身份，事件处理无需等待React的migrationHeld重新渲染。 */
   const migrationBlocked=()=>migrationGate.current||!!migration&&!migration.isCurrentIdentity();
+  /** 同时更新同步门闩与界面状态；只更新state会留下同一事件轮次中的旧写入窗口。 */
   function setMigrationHeld(value:boolean){migrationGate.current=value;setMigrationState(value);}
+  /** 旧接口请求护栏：await前后检查账号，写请求受迁移门闩限制；迁移排空时只放行canvas PATCH。
+   * X-Expected-Account要求代理校验目标账号，避免切号后旧请求误用新会话。 */
   const api:CanvasRequest=async <T,>(path:string,options?:RequestInit)=>{
     if(migration&&!migration.isCurrentIdentity())throw new Error('identity_changed');
     if(migrationBlocked()&&options?.method&&options.method!=='GET'&&!(migrationFlush.current&&options.method==='PATCH'&&path.endsWith('/canvas')))throw new Error('canvas_busy');
@@ -29,33 +49,42 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
     const value=await requestAPI<T>(path,{...options,headers:Object.fromEntries(headers)});
     if(migration&&!migration.isCurrentIdentity())throw new Error('identity_changed');return value;
   };
+  // documents是已加载board的模型表，current立即跟随发布供异步回调读取；status/error是旧writer汇总显示值。
   const [documents, setDocuments] = useState(new Map([[root, initial]]));
   const current = useRef(documents); current.current = documents;
   const [status, setStatus] = useState("saved");
   const [error, setError] = useState("");
   const [busy, setBusy] = useState(false);
   const [memberJobs, setMemberJobs] = useState<MemberJob[]>([]);
+  // capability缓存查询Promise；members是实际内存队列，memberJobs只是供React显示的数组副本。
   const memberCapability = useRef<Promise<boolean> | null>(null);
   const members = useRef<MemberJob[]>([]), memberRunning = useRef(false), dragging = useRef(false);
+  /** 仅挂载期间发布队列副本；任务对象仍共享引用，修改error等字段后需显式通知。 */
   const showMembers = () => { if (mounted.current) setMemberJobs([...members.current]); };
+  /** 拖动期间延后自动保存，结束时发布新Map触发防抖重新评估；不在这里执行成员归属变化。 */
   function setDragging(value: boolean) { dragging.current = value; if (!value) publish(new Map(current.current)); }
+  /** 成员任务涉及的节点暂不能再被普通动作改动；队列非空时也保护子图入口几何及结构，避免请求基准漂移。 */
   function protectedNodes(boardId: string) {
     const ids = new Set(members.current.flatMap((job) => [job.source, job.target].includes(boardId) ? job.ids : []));
     if (members.current.length) for (const node of current.current.get(boardId)?.nodes || []) if (node.data.subgraph) ids.add(node.id);
     return ids;
   }
   const [pendingCommand, setPendingCommand] = useState(false);
+  // 不确定命令失败时保留同一execute闭包，pendingCommand驱动UI；locked只管当前独占异步操作。
   const retryOperation = useRef<(() => Promise<CanvasCommandResult>) | null>(null);
   const locked = useRef(false), mounted = useRef(true), pause = useRef(paused); pause.current = paused;
+  // writer持每画布ACK基线与保存队列，loading去重子画布读取；二者都不是documents的替代存储。
   const writers = useRef(new Map<string, CanvasSync>());
   const loading = useRef(new Set<string>());
   const [retryLoad, setRetryLoad] = useState(0);
   const [recoveries, setRecoveries] = useState(new Map<string, CanvasDocument>());
   const pendingRecovery = useRef(recoveries); pendingRecovery.current = recoveries;
+  /** 以当前服务端快照筛选有内容差异的本地恢复候选，按board记录，等待用户决定；不证明可安全覆盖模型。 */
   function inspectRecovery(boardId: string, value: CanvasSnapshot) {
     const local = readLocalRecovery(localStorage, `endoleap_canvas_v1:${workspace}:${boardId}`, value);
     if (local) { const next = new Map(pendingRecovery.current).set(boardId, local); pendingRecovery.current = next; setRecoveries(next); }
   }
+  /** 可编辑时按选择替换本地文档或采用现状，移除恢复候选和草稿记录；远端写入仍走后续writer。 */
   function resolveRecovery(boardId: string, restore: boolean) {
     if(migrationBlocked())return;
     const draft = pendingRecovery.current.get(boardId);
@@ -63,12 +92,16 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
     const next = new Map(pendingRecovery.current); next.delete(boardId); pendingRecovery.current = next; setRecoveries(next);
     localStorage.removeItem(`endoleap_canvas_v1:${workspace}:${boardId}:recovery`);
   }
+  // 两个ref数组作为历史栈，boardAliases记录重做子图创建后新旧boardID对应；tick用于仅栈变化时通知UI。
   const undo = useRef<Entry[]>([]), redo = useRef<Entry[]>([]);
   const boardAliases = useRef(new Map<string, string>());
   const [, tick] = useState(0);
+  // 根据根与documents派生投影索引，nodeRefs/edgeRefs把场景ID映射回所属board、本地ID和坐标变换。
   const views = useMemo(() => projectCanvasTree(root, documents), [root, documents]);
   const view = useRef(views); view.current = views;
+  /** 先更新同步ref，再在挂载期间发布React state；等待中的操作可立即读取新Map。 */
   function publish(next: Map<string, CanvasDocument>) { current.current = next; if (mounted.current) setDocuments(next); }
+  /** 将服务端快照作为writer基线：已有writer采用新ACK，否则在真实快照模式建立writer；这里只安装，不发保存。 */
   function install(boardId: string, value: CanvasSnapshot) {
     const writer = writers.current.get(boardId);
     if (writer) writer.adopt(value);
@@ -80,25 +113,33 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
   // Initialization never writes a snapshot to the server.
   if (snapshot && !writers.current.has(root)) install(root, snapshot);
   useEffect(() => { mounted.current = true; return () => { mounted.current = false; }; }, []);
+  /** 普通单画布动作入口：检查门闩，经reducer计算新文档，保留成员迁移保护字段，再按需要记历史并发布。 */
   const update = (boardId: string, action: CanvasAction) => {
     if (migrationBlocked() || locked.current || retryOperation.current) return;
     const before = current.current.get(boardId); if (!before) return;
     const result = canvasReducer(history(before), action);
     const protectedIDs = protectedNodes(boardId);
+    // 迁移中的普通节点只允许选中变化；未作为移动目标的子图入口保留原几何、subgraph/ports/presentation。
+    // reducer删掉的受保护节点也补回，避免异步成员请求到来时对象已被本地删除。
     if (protectedIDs.size) result.present = { ...result.present, nodes: result.present.nodes.map((node) => {
       const prior = before.nodes.find((item) => item.id === node.id);
       if (!prior || !protectedIDs.has(node.id)) return node;
       const moving = members.current.some((job) => [job.source, job.target].includes(boardId) && job.ids.includes(node.id));
       return prior.data.subgraph && !moving ? { ...node, position: prior.position, width: prior.width, height: prior.height, data: { ...node.data, subgraph: prior.data.subgraph, ports: prior.data.ports, presentation: prior.data.presentation } } : { ...prior, selected: node.selected };
     }).concat(before.nodes.filter((node) => protectedIDs.has(node.id) && !result.present.nodes.some((item) => item.id === node.id))) };
+    // reducer产生历史才入undo，普通更新路径最多留40项并清redo；其它事务/刷新路径不一定使用同一截断逻辑。
     if (result.past.length) { undo.current.push({ boardId, before }); undo.current = undo.current.slice(-40); redo.current = []; }
     publish(new Map(current.current).set(boardId, result.present));
   };
+  /** 默认对根发动作，也允许调用方显式指定已加载board。 */
   const dispatch = (action: CanvasAction, boardId = root) => update(boardId, action);
+  /** 从投影节点ID解析实际owner，再用原始节点ID构造动作，避免把场景复合ID写回快照。 */
   const nodeAction = (id: string, action: (id: string) => CanvasAction) => { const ref = view.current.nodeRefs.get(id); if (ref) update(ref.boardId, action(ref.id)); };
+  /** 按owner分组ReactFlow节点变化；忽略add/replace，将场景位置和尺寸还原为所属board局部坐标。 */
   const nodesChanged = (changes: NodeChange<CanvasNode>[]) => {
     if (migrationBlocked() || locked.current || retryOperation.current) return;
     const groups = new Map<string, NodeChange<CanvasNode>[]>();
+    // 同批父分区也在移动时先计算调整后的原点，避免对子节点重复施加父位移；尺寸再除投影scale。
     const moves = new Map(changes.flatMap((change) => change.type === "position" && change.position ? [[change.id, change.position] as const] : []));
     for (const change of changes) {
       if (change.type === "add" || change.type === "replace") continue;
@@ -106,6 +147,7 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
       const adjusted = referenceAfterMoves(root, current.current, view.current.boards, ref.boardId, moves);
       const next = { ...change, id: ref.id };
       if (next.type === "position" && next.position) next.position = { x: (next.position.x - adjusted.origin.x) / ref.scale, y: (next.position.y - adjusted.origin.y) / ref.scale };
+      // ResizeObserver只更新测量信息；非显式resizing不得把测量宽高当模型尺寸写回。
       if (next.type === "dimensions") {
         // ResizeObserver measurements are editor state. Only an explicit resize
         // gesture may write node dimensions back to the owning snapshot.
@@ -116,6 +158,7 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
     }
     for (const [boardId, changes] of groups) update(boardId, { type: "nodes", changes });
   };
+  /** 按edgeRefs分组选择/删除等变化，忽略add/replace；最终update仍统一检查写入准入。 */
   const edgesChanged = (changes: EdgeChange[]) => {
     const groups = new Map<string, EdgeChange[]>();
     for (const change of changes) {
@@ -124,13 +167,17 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
     }
     for (const [boardId, changes] of groups) update(boardId, { type: "edges", changes });
   };
+  /** 曲线路径从场景坐标反变换回owner局部空间，再派发edge-data；transient交reducer决定历史语义。 */
   const patchEdge = (id: string, data: EdgeData, transient = false) => {
     const ref = view.current.edgeRefs.get(id); if (ref) update(ref.boardId, { type: "edge-data", id: ref.id, data: transformEdgeData(data, ref, true)!, transient });
   };
+  /** 遍历已加载文档，只有目标owner/localID被选中，其余节点取消选择；不直接操作投影数组。 */
   const select = (id: string) => {
     for (const [boardId, document] of current.current) update(boardId, { type: "nodes", changes: document.nodes.map((node) => ({ type: "select", id: node.id, selected: view.current.nodeRefs.get(id)?.boardId === boardId && view.current.nodeRefs.get(id)?.id === node.id })) });
   };
+  /** 读取并解码一个board的旧v2快照，可传取消信号；api层仍检查迁移账号身份。 */
   const read = async (boardId: string, signal?: AbortSignal) => decodeSnapshot(await api<CanvasSnapshot>(canvasPath(workspace, boardId), { headers: { Accept: CANVAS_ACCEPT }, signal }));
+  /** 查询服务端是否支持成员迁移同时提交坐标；演示为false，成功结果复用，失败清缓存供按需重试。 */
   function supportsMemberPositions(): Promise<boolean> {
     if (!snapshot) return Promise.resolve(false);
     if (!memberCapability.current) {
@@ -141,9 +188,11 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
     }
     return memberCapability.current;
   }
+  // 能力预取失败不视作确定不支持，真正成员操作仍可重新请求。
   useEffect(() => {
     void supportsMemberPositions().catch(() => { /* A failed prefetch is retried on demand, never cached as unsupported. */ });
   }, [root, workspace, !!snapshot]);
+  /** 按需加载真实快照或演示本地草稿，装writer并检查恢复候选；recursive递归加载子图，祖先集合防环且限制深度。 */
   async function ensure(boardId: string, recursive = false, ancestors = new Set<string>()): Promise<void> {
     if (ancestors.has(boardId) || ancestors.size > 8) throw new Error("subgraph_cycle");
     let document = current.current.get(boardId);
@@ -153,14 +202,17 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
     }
     if (recursive) { const next = new Set(ancestors); next.add(boardId); for (const node of document.nodes) if (node.data.subgraph) await ensure(node.data.subgraph.boardId, true, next); }
   }
+  /** 独占期间完整加载根下可达子图，然后收集导出Map；不会把已加载但不可达的祖先或其它分支混入导出。 */
   async function exportDocuments() {
     return exclusive(async () => {
       await ensure(root, true);
       const reachable = new Map<string, CanvasDocument>();
+      /** 可达集合兼作去重；ensure已验证递归关系，此处只遍历当前已加载文档。 */
       const collect = (id: string) => { const document = current.current.get(id)!; reachable.set(id, document); for (const node of document.nodes) if (node.data.subgraph && !reachable.has(node.data.subgraph.boardId)) collect(node.data.subgraph.boardId); };
       collect(root); return reachable;
     });
   }
+  // 打开子画布时向上读取元数据与快照，补齐祖先关系；alive阻止离页后的采用，不在本effect中abort请求。
   useEffect(() => {
     if (!snapshot || !parentBoardId) return;
     let alive = true;
@@ -178,6 +230,7 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
   // Root identity is stable until this editor unmounts.
   // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [parentBoardId, root, workspace]);
+  // 场景可见且未折叠的子图按需异步读取，loading去重；回包时重新确认仍被当前文档引用。
   useEffect(() => {
     for (const [boardId, document] of documents) for (const node of document.nodes) {
       if (!view.current.boards.has(boardId)) continue;
@@ -192,6 +245,8 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
   // Values and writers are scoped to this mounted root/workspace.
   // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [documents, retryLoad]);
+  // 文档变化防抖：250ms本地备份、800ms远端保存。恢复待决画布跳过，防止覆盖用户尚未选择的草稿。
+  // 远端另等独占锁、命令重试、成员任务和拖动结束；本地备份不需要等这些普通操作全部结束。
   useEffect(() => {
     if (paused || migrationBlocked()) return;
     const backup = setTimeout(() => {
@@ -208,7 +263,9 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
     }, 800);
     return () => { clearTimeout(backup); clearTimeout(save); };
   }, [documents, paused, workspace, memberJobs, migrationHeld]);
+  // pagehide/卸载尽量做本地同步备份，不等待远端flush；暂停/迁移仍禁止写，存储满时保留已有记录。
   useEffect(() => {
+    /** 遍历最新内存文档，备份规范化payload与ACK版本/dirty；页面离开时错误不再触发界面更新。 */
     const backup = () => {
       if (pause.current || migrationBlocked()) return;
       for (const [boardId, document] of current.current) {
@@ -219,6 +276,8 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
     window.addEventListener("pagehide", backup);
     return () => { window.removeEventListener("pagehide", backup); backup(); };
   }, [workspace]);
+  /** 串行排空各writer，任一恢复待决或writer错误就失败；deferMemberPositions保留待移动节点原ACK坐标。
+   * 支持原子坐标的成员接口会在归属事务里提交新位置，避免先把新位置单独写入旧owner。 */
   async function flush(deferMemberPositions = false) {
     for (const [boardId, document] of current.current) {
       if (pendingRecovery.current.has(boardId)) throw new Error("draft_recovery_required");
@@ -228,6 +287,8 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
       await writer.enqueue(saving); await writer.settled(); if (writer.error) throw new Error(writer.error);
     }
   }
+  /** 迁移前必须已关门，无事务/成员/拖动/加载，且恢复已处理；加载整棵迁移树并核查上传占位。
+   * 先备份本页，再临时放行PATCH排空旧writer；所有writer确认无待保存内容后把备份标为clean。 */
   async function prepareMigration(projectRoot:string){
     if(!migrationGate.current)throw new Error('migration_gate_required');
     if(locked.current||retryOperation.current||members.current.length||dragging.current||loading.current.size)throw new Error('canvas_busy');
@@ -240,12 +301,14 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
     for(const[boardId,document]of current.current){
       const writer=writers.current.get(boardId);
       const local=readLocalRecovery(localStorage,`endoleap_canvas_v1:${workspace}:${boardId}`,writer?{version:writer.version,document:writer.document}:undefined);
+      // 本地另有不同恢复内容时转为用户选择，不能用当前内存直接覆盖它后迁移。
       if(local&&canvasFingerprint(local,false)!==canvasFingerprint(document,false)){
         const next=new Map(pendingRecovery.current).set(boardId,local);pendingRecovery.current=next;setRecoveries(next);throw new Error('draft_recovery_required');
       }
       // Preserve the current view even if it closes while PATCH is in flight.
       localStorage.setItem(`endoleap_canvas_v1:${workspace}:${boardId}:recovery`,JSON.stringify({document:canvasPayload(document),baseVersion:writer?.version||1,dirty:writer?writer.needsSave(document):false}));
     }
+    // 只在flush的try/finally窗口放开旧PATCH，其它写命令仍被api护栏拒绝。
     migrationFlush.current=true;
     try{await flush();}finally{migrationFlush.current=false;}
     if(!mounted.current||migration&&!migration.isCurrentIdentity())throw new Error('identity_changed');
@@ -255,15 +318,19 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
       localStorage.setItem(`endoleap_canvas_v1:${workspace}:${boardId}:recovery`,JSON.stringify({document:canvasPayload(document),baseVersion:writer?.version||1,dirty:false}));
     }
   }
+  /** 旧版内存独占执行器，阻断冲突准入并发布busy；异常记error后继续抛出，finally可靠释放锁。
+   * 它不是跨标签页锁，也不提供操作的整批服务端回滚。 */
   async function exclusive<T>(operation: () => Promise<T>) {
     if (migrationBlocked() || locked.current || pause.current || members.current.length) throw new Error("canvas_busy");
     locked.current = true; setBusy(true);
     try { return await operation(); } catch (error) { setError(error instanceof Error ? error.message : "request_failed"); throw error; }
     finally { locked.current = false; if (mounted.current) setBusy(false); }
   }
+  /** 服务端快照更新时恢复本地选中标记，避免结构事务结果抹掉当前视图选择。 */
   function keepSelection(document: CanvasDocument, local?: CanvasDocument): CanvasDocument {
     return { ...document, nodes: document.nodes.map((node) => ({ ...node, selected: local?.nodes.find((item) => item.id === node.id)?.selected })), edges: document.edges.map((edge) => ({ ...edge, selected: local?.edges.find((item) => item.id === edge.id)?.selected })) };
   }
+  /** 汇总命令返回的各类快照，按boardID去重，基于旧ACK做三方合并再安装新基线。 */
   function accept(result: CanvasCommandResult) {
     const next = new Map(current.current);
     const values = [...new Map([...(result.parent ? [result.parent] : []), ...(result.child ? [result.child] : []), ...(result.snapshots || []), ...(result.children || [])].map((value)=>[value.board_id,value])).values()];
@@ -272,6 +339,8 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
       const merged=local&&base?mergeCanvasDocuments(base,local,decoded.document):decoded.document;
       install(value.board_id,decoded);next.set(value.board_id,keepSelection(merged,local));
     }
+    // 子图归档后，将仍在内存上传的节点及相关边投到父画布，避免服务端快照中没有的占位被丢弃。
+    // 其余已归档文档及writer从当前表移除，不在这里删除上传任务的原文件。
     for (const id of result.archived_board_ids || []) {
       const local=current.current.get(id);
       const owner=[...current.current].find(([,doc])=>doc.nodes.some((node)=>node.data.subgraph?.boardId===id));
@@ -286,6 +355,8 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
     publish(next);
     return [...new Set(values.map((value) => value.board_id))];
   }
+  /** 结构/AI等旧命令入口：加载参与writer、flush，再冻结expected_versions、If-Match和幂等key。
+   * execute闭包在不确定失败后复用同一body/key/version；这些恢复信息只在内存，不保证刷新后继续。 */
   async function command(boardId: string, path: string, payload: Record<string, unknown>, participants?: string[], record = true, versionBoard = boardId) {
     if (retryOperation.current) throw new Error("canvas_busy");
     return exclusive(async () => {
@@ -295,21 +366,25 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
       await flush();
       const body = { ...payload, ...(participants ? { expected_versions: Object.fromEntries(participants.map((id) => [id, writers.current.get(id)?.version])) } : {}) };
       const key = crypto.randomUUID(), version = writers.current.get(versionBoard)?.version || 1;
+      /** 发送、采用回执、按需补读目标快照，并把有transaction_id的结果记入服务端事务历史。 */
       const execute = async (): Promise<CanvasCommandResult> => {
         try {
           const result = await api<CanvasCommandResult>(canvasPath(workspace, boardId) + "/" + path, { method: "POST", headers: { Accept: CANVAS_ACCEPT, "If-Match": `"${version}"`, "Idempotency-Key": key }, body: JSON.stringify(body) });
           const changed = accept(result);
+          // 改变子图/事务后通知侧栏刷新目录；没有快照但有版本结果时补读并保留期间的本地编辑。
           if (path.startsWith("subgraphs") || path.startsWith("transactions/")) window.dispatchEvent(new window.CustomEvent("endoleap:board-directory-changed", { detail: { workspace } }));
           if (!changed.length && result.canvas_version) {
             const target=typeof result.board_id === "string"?result.board_id:boardId,remote=await read(target),local=current.current.get(target),base=writers.current.get(target)?.document;
             const merged=base&&local?mergeCanvasDocuments(base,local,remote.document):remote.document;
             install(target,remote);publish(new Map(current.current).set(target,keepSelection(merged,local)));
           }
+          // record=false用于undo/redo等已有历史流程，避免将历史遍历再次当新操作压栈。
           if (record && result.transaction_id) { undo.current.push({ boardId, path, payload, id: result.transaction_id, participants: changed }); redo.current = []; tick((v) => v + 1); }
           retryOperation.current = null; setPendingCommand(false); setError("");
           return result;
         } catch (error) {
           const code = error instanceof Error ? error.message : "request_failed";
+          // 网络/上游/解码等不确定失败保留execute并阻断普通编辑；确定拒绝清重试入口，错误仍交调用方处理。
           if (error instanceof TypeError || error instanceof ApiError && error.status >= 500 || ["upstream_timeout", "upstream_unavailable", "request_failed", "Failed to fetch", "internal_error", "invalid_canvas_snapshot"].includes(code)) { retryOperation.current = execute; setPendingCommand(true); }
           else { retryOperation.current = null; setPendingCommand(false); }
           throw error;
@@ -320,12 +395,15 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
   }
   // Ownership changes pause autosaves, not unrelated local editing. Server
   // acknowledgements merge against the persisted base, preserving intervening edits.
+  /** 成员队列只跑队首；归属移动期间暂停autosave，允许不相关本地编辑，结果按捕获ACK合并。
+   * 只有成功才shift并resolve；失败任务留队首供重试，Promise不在失败时假装完成。 */
   async function runMembers() {
     if (migrationBlocked() || memberRunning.current || !members.current.length) return;
     const job = members.current[0]; memberRunning.current = true; job.error = undefined; showMembers();
     try {
       if (!job.run) {
         for (const id of job.participants) if (!writers.current.has(id)) await ensure(id);
+        // 412等确定冲突后的重新准备：读参与快照，先三方合并本地变化，再更新各writer基线。
         if (job.refresh) {
           const refreshed = await Promise.all(job.participants.map(async (id) => [id, await read(id)] as const));
           const next = new Map(current.current);
@@ -336,6 +414,7 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
           for (const [id, remote] of refreshed) install(id, remote);
           publish(next); job.refresh = false;
         }
+        // 支持坐标时flush延后待移动节点位置；否则先按旧保存行为排空，再捕获参与文档作为合并基线。
         const atomic = await supportsMemberPositions();
         await flush(atomic === true);
         const bases = new Map(job.participants.map((id) => [id, writers.current.get(id)!.document]));
@@ -344,17 +423,22 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
           const node = source.nodes.find((node) => node.id === id); if (!node) throw new Error("invalid_reference");
           return [id, node.position];
         }));
+        // 请求内容含参与版本和可选局部坐标；创建job.run后重试不得换body或幂等key，除非确定原请求未应用。
         const body = JSON.stringify({ source_board_id: job.source, target_board_id: job.target, node_ids: job.ids, ...(atomic ? { positions } : {}),
           expected_versions: Object.fromEntries(job.participants.map((id) => [id, writers.current.get(id)!.version])) });
         const key = crypto.randomUUID(), historyIndex = undo.current.length;
+        /** 一次准备生成的可重试闭包；要求回执覆盖所有参与画布，不能凭缺失快照移动本地owner。 */
         job.run = async () => {
           const result = await api<CanvasCommandResult>(canvasPath(workspace, job.parent) + `/subgraphs/${job.frame}/members`, {
             method: "POST", headers: { Accept: CANVAS_ACCEPT, "Idempotency-Key": key }, body });
           const snapshots = [...(result.parent ? [result.parent] : []), ...(result.snapshots || [])];
           const values = new Map(snapshots.map((value) => [value.board_id, { ...decodeSnapshot(value), board_id: value.board_id }]));
           if (!job.participants.every((id) => values.has(id))) throw new Error("invalid_canvas_snapshot");
+          /** 移动结果已含新坐标，合并前只把源节点暂存位置还原到基线，避免重复施加坐标变化。 */
           const normalize = (id: string, local: CanvasDocument) => id !== job.source ? local : { ...local, nodes: local.nodes.map((node) => job.ids.includes(node.id) ? { ...node, position: bases.get(id)!.nodes.find((item) => item.id === node.id)!.position } : node) };
+          /** 参与画布基于原ACK+归一化本地内容+返回快照重放，未参与文档原样保留。 */
           const rebaseLocal=(id:string,doc:CanvasDocument)=>values.has(id)?mergeCanvasDocuments(bases.get(id)!,normalize(id,doc),values.get(id)!.document):doc;
+          // 请求期间新增本地历史也基于新owner结果调整；开始前历史和服务端事务条目保持原语义。
           const rebasedHistory = undo.current.map((entry,index)=>index<historyIndex||"id" in entry?entry:{...entry,before:rebaseLocal(entry.boardId,entry.before),...(entry.related?{related:new Map([...entry.related].map(([id,doc])=>[id,rebaseLocal(id,doc)]))}:{})});
           const next = new Map(current.current);
           for (const [id, value] of values) {
@@ -369,6 +453,7 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
           for (const [id, value] of values) install(id, value);
           publish(next);
           undo.current = rebasedHistory;
+          // 将迁移事务插回开始时的historyIndex，保留请求期间后来编辑的顺序，并清除旧redo。
           if (result.transaction_id) { undo.current.splice(historyIndex, 0, { boardId: job.parent, path: `subgraphs/${job.frame}/members`, payload: { source_board_id: job.source, target_board_id: job.target, node_ids: job.ids, positions }, id: result.transaction_id, participants: [...values.keys()] }); redo.current = []; }
         };
       }
@@ -378,6 +463,7 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
       job.error = error instanceof Error ? error.message : "request_failed";
       // A definite rejection performed zero writes. A retry may prepare fresh
       // versions; ambiguous transport failures must retain the exact body/key.
+      // 确定拒绝可清冻结闭包重新准备；412还需刷新版本。不确定传输失败继续保留原job.run。
       if (error instanceof ApiError && error.status < 500) { job.run = undefined; job.refresh = error.status === 412; }
       showMembers();
     } finally {
@@ -385,24 +471,31 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
       if (members.current.length && !members.current[0].error) void runMembers();
     }
   }
+  /** 检查准入和重叠成员任务后入FIFO队列；返回Promise由成功出队时resolve，错误在memberJobs中供UI重试。 */
   function moveMembers(parent: string, frame: string, source: string, target: string, ids: string[], participants: string[]) {
     if (migrationBlocked() || locked.current || retryOperation.current || pause.current || members.current.some((job) => job.ids.some((id) => ids.includes(id)) && [job.source, job.target].includes(source))) return Promise.reject(new Error("canvas_busy"));
     return new Promise<void>((resolve) => {
       members.current.push({ parent, frame, source, target, ids, participants, resolve }); showMembers(); void runMembers();
     });
   }
+  /** 将上传资源/尺寸绑定到所有当前文档及本地历史，避免撤销恢复旧Blob占位。
+   * 无asset时保留pendingUpload；尺寸仅在纯图片仍为320×240默认值时采用，不覆盖用户已调整大小。 */
   function resolveImageUpload(id: string, asset?: { url: string; id: string }, size?: {width:number;height:number}) {
     if(migrationBlocked())return;
+    /** 只匹配pendingUpload身份，移除或保留占位标记，并按文档schema选择是否写assetId。 */
     const resolve = (document: CanvasDocument): CanvasDocument => ({ ...document, nodes: document.nodes.map((node) => {
       if (node.pendingUpload !== id) return node;
       const fitted=node.data.kind==="plain-image"&&node.width===320&&node.height===240?size:undefined;
       const {pendingUpload,...ready}=node;
       return { ...ready, ...(!asset?{pendingUpload}:{}), ...(fitted?{...fitted,style:{...ready.style,...fitted}}:{}), data: { ...ready.data, ...(asset?{src:asset.url,...(document.schema_version===2?{assetId:asset.id}:{})}:{}) } };
     }) });
+    /** 仅改本地快照历史（含related），服务端事务条目仍由服务端重放解释。 */
     const rebase = (entry: Entry): Entry => "id" in entry ? entry : { ...entry, before: resolve(entry.before), ...(entry.related ? {related:new Map([...entry.related].map(([id,doc])=>[id,resolve(doc)]))} : {}) };
     undo.current = undo.current.map(rebase); redo.current = redo.current.map(rebase);
     publish(new Map([...current.current].map(([board,doc])=>[board,resolve(doc)])));
   }
+  /** 未上传且无关联边的图片可先在内存跨分区移动；校验容量/ID后按两owner原点和scale换算。
+   * 保存双画布before及pendingMove历史，上传完成后若进入服务端，撤销可能需要真实成员事务。 */
   function movePendingImage(source: string, target: string, id: string) {
     if(migrationBlocked())throw new Error("canvas_busy");
     const from = current.current.get(source)!, to = current.current.get(target)!;
@@ -413,6 +506,7 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
     undo.current.push({boardId:source,before:from,related:new Map([[target,to]]),pendingMove:{id,source,target}});redo.current=[];
     publish(new Map(current.current).set(source,{...from,nodes:from.nodes.filter((node)=>node.id!==id)}).set(target,{...to,nodes:[...to.nodes,moved]}));
   }
+  /** 独占等待writer停止后读新快照并三方合并；内容指纹改变才记本地历史，再安装新ACK。 */
   async function refresh(boardId: string) {
     return exclusive(async () => {
       const writer = writers.current.get(boardId); if (!writer) return;
@@ -423,6 +517,8 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
       install(boardId, remote); publish(new Map(current.current).set(boardId, merged));
     });
   }
+  /** 显式采用生成结果前，针对目标节点把基线text/src/assetId/ai对齐到远端，再合并其它本地编辑。
+   * 合并结果先排空保存，后续apply命令才能在明确版本上覆盖目标；此方法本身不发送生成结果采用请求。 */
   async function prepareApply(boardId: string, nodeId: string) {
     await exclusive(async () => {
       const writer = writers.current.get(boardId); if (!writer) throw new Error("invalid_reference");
@@ -436,12 +532,17 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
       setError("");
     });
   }
+  /** 查看栈顶并检查准入，成功后才移动栈项；本地条目替换before，事务条目调用服务端undo或重做。
+   * 重做可能创建新子board，使用alias将后续历史引用转到新身份，避免继续操作已归档旧子图。 */
   async function undoAction(isRedo = false) {
     const stack = isRedo ? redo.current : undo.current, destination = isRedo ? undo.current : redo.current;
     const original = stack.at(-1); if (!original || migrationBlocked() || locked.current || retryOperation.current || members.current.length) return;
+    /** 沿别名链解析最新boardID并防循环；只用于历史重放，不篡改任意元素ID。 */
     const alias = (id: string) => { const seen = new Set<string>(); while (boardAliases.current.has(id) && !seen.has(id)) { seen.add(id); id = boardAliases.current.get(id)!; } return id; };
+    /** 重做本地快照时更新子图board引用，其它节点内容保留。 */
     const remapDocument = (document: CanvasDocument) => ({ ...document, nodes: document.nodes.map((node) => node.data.subgraph ? { ...node, data: { ...node.data, subgraph: { boardId: alias(node.data.subgraph.boardId) } } } : node) });
     const entry: Entry = isRedo ? "id" in original ? { ...original, boardId: alias(original.boardId), participants: original.participants.map(alias), payload: { ...original.payload, ...(typeof original.payload.source_board_id === "string" ? { source_board_id: alias(original.payload.source_board_id) } : {}), ...(typeof original.payload.target_board_id === "string" ? { target_board_id: alias(original.payload.target_board_id) } : {}), ...Object.fromEntries(["source", "target"].flatMap((key) => { const endpoint = original.payload[key] as { board_id?: string } | undefined; return endpoint?.board_id ? [[key, { ...endpoint, board_id: alias(endpoint.board_id) }]] : []; })) } } : { ...original, boardId: alias(original.boardId), before: remapDocument(original.before), ...(original.related?{related:new Map([...original.related].map(([id,doc])=>[alias(id),remapDocument(doc)]))}:{}) } : original;
+    // 待上传图片若已存在于writer基线，纯本地快照切换已不够，需按归属路径逐跳请求成员移动后再转栈。
     if (!("id" in entry) && entry.pendingMove) {
       const move=entry.pendingMove,desired=alias(isRedo?move.target:move.source);
       const owner=[...current.current].find(([,doc])=>doc.nodes.some((node)=>node.id===move.id));
@@ -452,6 +553,7 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
         stack.pop();destination.push(entry);tick((v)=>v+1);return;
       }
     }
+    // 服务端事务撤销调用transactions/{id}/undo；重做执行原命令并保存新的事务ID/参与快照身份。
     if ("id" in entry) {
       if (isRedo) {
         const result = await command(entry.boardId, entry.path, entry.payload, entry.path === "subgraphs" ? undefined : entry.participants, false);
@@ -464,6 +566,7 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
         await command(entry.boardId, `transactions/${entry.id}/undo`, {}, entry.participants, false);
         stack.pop(); destination.push(entry);
       }
+    // 普通本地历史用当前文档作为反向条目，连同related画布一起发布，保证下一次redo可还原。
     } else {
       const before = current.current.get(entry.boardId); if (!before) return;
       const next=new Map(current.current).set(entry.boardId, entry.before), related=new Map<string,CanvasDocument>();
@@ -472,6 +575,9 @@ export function useCanvasTree(root: string, workspace: string, initial: CanvasDo
     }
     tick((v) => v + 1);
   }
+  /** 重试普通writer并触发子图读取effect；不在这里自动重发成员任务或未确认command，它们有各自入口。 */
   const retry = async () => { setError(""); setRetryLoad((v) => v + 1); for (const writer of writers.current.values()) await writer.retry(); };
+  // 对外暴露投影、动作、恢复、事务及writer引用，旧版UI依赖此组合接口；busy合并独占、待确认命令与迁移门闩。
+  // transactionBusy/canUndo/canRedo反映成员队列与栈是否有项，最终undoAction仍再次检查实际准入。
   return { migrationHeld,setMigrationHeld,prepareMigration,isMigrationHeld:migrationBlocked, documents, current, views, resolveImageUpload, movePendingImage, memberJobs, protectedNodes, setDragging, moveMembers, retryMembers: () => void runMembers(), transactionBusy: !!memberJobs.length, pendingCommand, retryPending: () => retryOperation.current ? exclusive(retryOperation.current) : Promise.resolve(null), prepareApply, recoveries, resolveRecovery, ensure, exportDocuments, dispatch, nodeAction, nodesChanged, edgesChanged, patchEdge, select, flush, command, refresh, read, busy: busy || pendingCommand || migrationHeld, error, status, retry, undo: () => undoAction(), redo: () => undoAction(true), canUndo: !memberJobs.length && !!undo.current.length, canRedo: !memberJobs.length && !!redo.current.length, writers, rootDocument: documents.get(root)!, setError };
 }