/**
 * 画布路由的客户端生命周期桥。把路径引用解析成board/profile，再选择新版engine、渐进预览或旧snapshot编辑器。
 * 页面只持显示与导航状态，项目由RuntimeHost/WorkspaceRuntime拥有；卸载中断本页订阅，但已开始的项目加载可转后台完成。
 */
"use client";

import { useEffect, useRef, useState } from "react";
import type {Viewport} from '@xyflow/react';
import type {LiveModelPreview} from '@/lib/canvas-runtime/model-preview';
import { useRouter, useSearchParams } from "next/navigation";
import { api, errorText } from "@/lib/api";
import { readDemoBoards } from "@/lib/demo-workspace";
import { matchesRef, type Board } from "@/lib/workspace";
import { loadCanvasEntry } from "@/lib/canvas-entry";
import {createBrowserCanvasMigration,type LegacyMigrationContext} from "@/lib/browser-canvas-migration";
import {readCanvasMigration} from "@/lib/canvas-migration";
import type { ProjectEngine } from "@/lib/canvas-runtime/workspace";
import { useCanvasRuntimeHost, useCanvasRenderers } from "./canvas-runtime-host";
import type { CanvasSnapshot } from "@/lib/canvas-sync";
import styles from "./workspace.module.css";
import { useActiveBoard } from "./active-board";
import dynamic from "next/dynamic";
/** 旧编辑器只在浏览器加载，避免服务端执行依赖DOM的画布实现。 */
const GraphCanvas = dynamic(() => import("@/components/canvas/graph-canvas"), { ssr: false, loading: () => <p role="status">正在准备画布…</p> });

/** 新版编辑器同样独立客户端bundle，模型选择由loadCanvasEntry结果决定，而非界面手动猜格式。 */
const HeadlessGraphCanvas = dynamic(() => import("@/components/canvas/headless-graph-canvas"), { ssr: false, loading: () => <p role="status">正在准备画布…</p> });
/** 只读渐进预览先出现，已知内容足够后可升级为partial engine，保持原视口。 */
const LoadingGraphCanvas=dynamic(()=>import("@/components/canvas/loading-graph-canvas"),{ssr:false});
/** route将结果绑定到这次路径；engine/snapshot/migration分别来自实际选择的协议路径。 */
type Loaded = { board: Board; snapshot?: CanvasSnapshot; route: string; engine?: ProjectEngine; migration?:LegacyMigrationContext };
/** 当前页面只借用host与renderer，retry触发重新读取；不在页面state复制业务文档或history。 */
export default function GraphPage({ workspaceId, boardId }: { workspaceId: string; boardId: string }) {
  const renderers=useCanvasRenderers();
  const demo = useSearchParams().get("demo") === "1";
  const router = useRouter();
  const runtimeHost = useCanvasRuntimeHost();
  const route = workspaceId + ":" + boardId;
  const { board: activeBoard, setBoard: setActiveBoard } = useActiveBoard();
  const [loaded, setLoaded] = useState<Loaded | null>(null);
  const [preview,setPreview]=useState<{board:Board;value:LiveModelPreview;route:string}|null>(null);
  // 预览视口暂存于ref，切成可编辑视图时交作initialViewport；新路由重置，不当文档编辑保存。
  const previewViewport=useRef<Viewport|undefined>(undefined);
  const [error, setError] = useState("");
  const [retry, setRetry] = useState(0);
  const navigationGeneration=useRef(0);
  /** 每条路由/重试新建读取生命周期，清旧显示；active、AbortController和host身份护栏共同隔离迟到结果。 */
  useEffect(() => {
    setLoaded(null);setPreview(null);previewViewport.current=undefined; setError("");
    // 演示目录走旧本地画布，不发canonical读取、不绑定真实账户项目。
    if (demo) {
      const item = readDemoBoards(workspaceId).find((board) => matchesRef(board, boardId));
      if (item) setLoaded({ board: item, route });
      else setError("图谱不存在。");
      return;
    }
    let active = true;
    const controller = new AbortController();
    // 保存开始时身份，并在profile解析后取得currentIdentity闭包，后续await返回均据此判断是否还能采用结果。
    const startingIdentity=runtimeHost.identity();let currentIdentity:(()=>boolean)|undefined;
    // latest合并待采用的预览，pumping串行openPartial/persist，防快流把多个partial打开交错到同一项目。
    let latest:{value:LiveModelPreview;board:Board;accountId:string}|undefined,pumping:Promise<void>|undefined,partialEngine:ProjectEngine|undefined,partialRuntime:ReturnType<typeof runtimeHost.workspace>|undefined;
    /** 后台任务失败仅在页面仍活跃时显示，离开页面不再更新本页error。 */
    const reportBackground=(error:unknown)=>{if(active)setError(errorText(error));};
    /** 已建立partial engine且身份仍有效时，交工作区继续完整读取；视图离开不等于关闭可恢复项目。 */
    const completeInBackground=()=>{if(partialEngine?.loading.getState()&&currentIdentity?.())void partialRuntime?.resumeLoading(partialEngine.getSnapshot().document.projectId).catch(reportBackground);};
    /** 串行采用最新预览，先openPartial再发布UI并保存；期间新预览覆盖latest等待槽而非并行改根。 */
    function pump(){
      if(pumping)return pumping;
      const task=(async()=>{while(latest){const next=latest;latest=undefined;if(!currentIdentity?.())return;const runtime=runtimeHost.workspace(next.accountId,next.board.workspace_id);partialRuntime=runtime;const engine=await runtime.openPartial(next.value.document,next.value.versions,next.value.loading);partialEngine=engine;if(active&&currentIdentity?.()){setLoaded(previous=>previous?.route===route&&previous.engine===engine?previous:{board:next.board,engine,route});setPreview(null);}else{completeInBackground();return;}await engine.persist();}})();
      pumping=task.finally(()=>{pumping=undefined;if(latest&&active)void pump().catch(reportBackground);});return pumping;
    }

    // 导航代次递增传入共享loader，查询身份与取消订阅由host/loader维护；入口优先canonical防旧writer误开。
    loadCanvasEntry({ request: api, workspaceRef: workspaceId, boardRef: boardId, registry: runtimeHost.registry, signal: controller.signal,navigationGeneration:++navigationGeneration.current,
      /** 只有本board已在前缀中才显示；有元素后推动partial engine，尚未建立engine时用只读预览。 */
      onPreview:(value,board,profile)=>{if(active&&currentIdentity?.()&&value.document.canvases.has(board.id)){if(!partialEngine)setPreview({board,value,route});if(value.document.elements.size){latest={value,board,accountId:profile.id};void pump().catch(reportBackground);}}},
      /** profile解析后绑定账户并读取模型；若开始后的authEpoch已变且当前账户不同于响应账户，拒绝旧导航认领。 */
      readModel:input=>{const identity=runtimeHost.identity();if(identity.authEpoch!==startingIdentity.authEpoch&&identity.accountId!==input.accountId)throw new Error('identity_changed');currentIdentity=runtimeHost.bindAccount(input.accountId);return runtimeHost.loadModel(input.accountId,input.workspaceId,input.canvasId,{signal:input.signal,navigationGeneration:input.navigationGeneration,onPreview:input.onPreview});},
    }).then(async result => {
      if (!active||currentIdentity&&!currentIdentity()) return;
      // 迁移完成回调只递增retry重开入口，不在旧组件内手工切换文档格式。
      if (result.mode === 'legacy') {
        const migration:LegacyMigrationContext={accountId:result.profile.id,rootId:result.migration?.rootId,registry:runtimeHost.registry,isCurrentIdentity:()=>!!currentIdentity?.(),onApplied:()=>{if(active&&currentIdentity?.())setRetry(value=>value+1);}};
        setLoaded({board:result.board,snapshot:result.snapshot,route,migration});setPreview(null);return;
      }
      // 服务已返回新模型但本地仍有同根pending时，查询并收尾原迁移记录，不生成新迁移请求。
      const pending=readCanvasMigration(localStorage,{accountId:result.profile.id,workspaceId:result.board.workspace_id});
      if(pending?.phase==='pending'&&pending.rootId===result.model.document.projectId){
        try{await createBrowserCanvasMigration({scope:{accountId:result.profile.id,workspaceId:result.board.workspace_id},registry:runtimeHost.registry,isCurrentIdentity:()=>active&&!!currentIdentity?.(),signal:controller.signal}).resume();}
        catch(error){reportBackground(error);}
      }
      // 完整模型到来先等partial采用链结束，再open同一项目，避免尾部覆盖尚在发布的前缀根。
      while(pumping)await pumping;
      if(!active||!currentIdentity?.())return;
      const engine = await runtimeHost.workspace(result.profile.id, result.board.workspace_id).open(result.model.document, result.model.versions,{sourceToken:result.model.sourceToken});
      if (active&&(!currentIdentity||currentIdentity())){setLoaded({ board: result.board, engine, route });setPreview(null);}
    })
      .catch((error) => { if (active) { setError(errorText(error)); if (error.message === "invalid_session") router.replace("/login"); } });
    // 清掉未采用预览并中断本页读取；已拥有的partial项目交后台，绝不在这里直接engine.close。
    return () => { active = false;latest=undefined; controller.abort();completeInBackground(); };
  }, [workspaceId, boardId, route, demo, retry, router, runtimeHost]);
  // 即使effect清理/新读取尚未完成，只显示route匹配的结果，不短暂闪出上个board。
  const current = loaded?.route === route ? loaded : null;
  const currentPreview=preview?.route===route?preview:null;
  const board = current?.board??currentPreview?.board;
  /** 发布当前board元数据供侧栏标题使用，卸载/换board归还该Context显示状态，不删除服务端board。 */
  useEffect(() => {
    if (board) setActiveBoard({ id: board.id, slug: board.slug, workspace_id: board.workspace_id, workspace_ref: workspaceId, title: board.title });
    return () => setActiveBoard(null);
  }, [board, workspaceId, setActiveBoard]);
  // 本board在侧栏改名后优先读共享新标题；其它board的活动状态不能覆盖当前名称。
  const displayBoard = board && activeBoard?.id === board.id && activeBoard.workspace_id === board.workspace_id ? { ...board, title: activeBoard.title } : board;
  // 显示优先级：engine→只读预览→旧snapshot→读取占位；重试错误提示与已显示前缀可并存。
  return <main className={styles.graph} aria-label={displayBoard ? displayBoard.title + " · 无限图谱" : "无限图谱"} aria-busy={!current && !error}>
    {displayBoard && current?.engine ? <HeadlessGraphCanvas key={displayBoard.workspace_id + ":" + displayBoard.id} board={displayBoard} engine={current.engine} renderers={renderers} initialViewport={previewViewport.current} /> : displayBoard&&currentPreview ? <LoadingGraphCanvas key={displayBoard.workspace_id+":"+displayBoard.id} preview={currentPreview.value} canvasId={displayBoard.id} workspaceId={displayBoard.workspace_id} registry={runtimeHost.registry} renderers={renderers} onViewport={viewport=>{previewViewport.current=viewport;}} /> : displayBoard ? <GraphCanvas key={(current?.migration?.accountId??"demo")+":"+displayBoard.workspace_id+":"+displayBoard.id} board={displayBoard} snapshot={current?.snapshot} migration={current?.migration} /> : <div className={styles.graphSurface} aria-label="正在读取画布" />}
    {error ? <div className={styles.graphStatus} role="alert">{error} <button onClick={() => setRetry((value) => value + 1)}>重新加载</button></div> : !board && <p className={styles.graphStatus} role="status">正在打开图谱…</p>}
  </main>;
}