/**
 * 模型读取前缀的只读预览。直接把已校验document投影给ReactFlow，允许浏览视口，不创建可写engine或临时history/ledger。
 * 这个组件不负责持久化前缀；后续可编辑partial engine的建立与交接由路由及runtime处理。
 */
"use client";

import {useEffect,useMemo,useRef} from 'react';
import {Background,BackgroundVariant,ReactFlow,useReactFlow,type Viewport,type NodeTypes, type NodeProps,Handle,Position} from '@xyflow/react';
import type {Registry} from '@/lib/canvas-core/types';
import type {ModelPreview} from '@/lib/canvas-runtime/model-preview';
import type {ReactRenderers} from '@/lib/canvas-bindings/react-flow';
import {createLoadingRendererCatalog} from '@/lib/canvas-bindings/renderers';
import {projectCanvas} from '@/lib/canvas-bindings/projection';
import {CanvasRendererCommandsContext,type CanvasRendererCommands} from '@/lib/canvas-bindings/react-flow';
import {UnsupportedNode,UnsupportedEdge} from './unsupported-elements';
import styles from './canvas.module.css';

/** 已知类型缺少专用preview renderer时展示准备占位；保留已投影连线需要的Handle，禁止新连接。 */
function PreparingNode({data}:NodeProps){return <div style={{width:'100%',height:'100%',padding:14,border:'1px solid #ded7ce',borderRadius:8,background:'#fffdfa'}} aria-label="正在准备元素"><span>{typeof data.title==='string'?data.title:'正在准备元素…'}</span>{(data.__previewHandles as {id?:string;type:'source'|'target'}[]??[]).map((handle,index)=><Handle key={index} type={handle.type} id={handle.id} position={handle.type==='source'?Position.Right:Position.Left} isConnectable={false}/>)}</div>;}
/** 所有预览命令统一拒绝为model_loading，避免复用的renderer意外修改数据。 */
const reject=()=>({status:'rejected' as const,code:'model_loading',targets:[]});
/** 冻结命令接口仅提供拒绝结果；inert与ReactFlow只读设置之外，命令层再提供一道限制。 */
const commands:CanvasRendererCommands=Object.freeze({dispatch:reject,transaction:reject});
/** 首次存在节点且视口初始化后fitView一次，限制最大缩放为1，并把结果交给外层用于视图交接。 */
function InitialPreviewViewport({onViewport,nodeCount}:{onViewport(viewport:Viewport):void;nodeCount:number}){
 // fitted是本组件挂载期标记；清理只禁止迟到通知，不取消已经发起的fitView，也不重置fitted。
 const flow=useReactFlow(),fitted=useRef(false),notify=useRef(onViewport);notify.current=onViewport;
 useEffect(()=>{if(!flow.viewportInitialized||fitted.current||!nodeCount)return;fitted.current=true;let active=true;void flow.fitView({padding:.2,maxZoom:1}).then(()=>{if(active)notify.current(flow.getViewport());});return()=>{active=false;};},[flow,nodeCount]);
 return null;
}
/** Render the validated read prefix directly. No temporary editor, ACK, ledger or
 * writable engine is constructed, and no partial model enters durable storage. */
/** renderer catalog限制加载期可用渲染路径；无法解释引用关系时沿用opaque占位，不能猜测缺失内容。 */
export default function LoadingGraphCanvas({preview,canvasId,registry,renderers,workspaceId,onViewport}: {preview:ModelPreview;canvasId:string;workspaceId:string;registry:Registry;renderers:ReactRenderers;onViewport(viewport:Viewport):void}){
 // Without a declared reference schema, use the existing opaque placeholder
 // until the complete document is available to the installed renderer.
 const catalog=useMemo(()=>createLoadingRendererCatalog(registry,renderers.catalog),[registry,renderers]);
 // 对已收到文档做只读投影；从现有边补齐各节点Handle描述，不推断尚未读取到的连线。
 const projection=useMemo(()=>{
  const value=projectCanvas(preview.document,canvasId,registry,new Set(),()=>undefined,undefined,catalog);
  const handles=new Map<string,{id?:string;type:'source'|'target'}[]>();for(const edge of value.edges)for(const type of ['source','target'] as const){const id=edge[type],rows=handles.get(id)??[];rows.push({type,id:edge[type==='source'?'sourceHandle':'targetHandle']??undefined});handles.set(id,rows);}
  // 节点禁用拖动/选择/焦点/连接及指针，边禁用选择/焦点；已知组件声明assetId资源字段才设置预览URL。
  return{nodes:value.nodes.map(node=>({...node,draggable:false,selectable:false,focusable:false,connectable:false,style:{...node.style,pointerEvents:'none' as const},data:{...node.data,__previewHandles:handles.get(node.id)??[],...(registry.resolve(preview.document.elements.get(node.id)!)==='known'&&typeof node.data.assetId==='string'&&registry.components.get(preview.document.elements.get(node.id)!.componentId)?.resourceFields?.includes('assetId')?{src:`/api/foundry/workspaces/${encodeURIComponent(workspaceId)}/assets/${encodeURIComponent(node.data.assetId)}?variant=preview`}:{})}})),edges:value.edges.map(edge=>({...edge,selectable:false,focusable:false}))};
 },[preview.document,canvasId,workspaceId,registry,catalog]);
 // 普通rendererId优先使用专用preview，否则节点PreparingNode、边UnsupportedEdge；节点再套inert隔离内部控件。
 const nodeTypes=useMemo<NodeTypes>(()=>{const result:NodeTypes={};for(const [id,Renderer]of Object.entries({...Object.fromEntries(Object.keys(renderers.nodeTypes).map(id=>[id,renderers.previewNodeTypes[id]??PreparingNode])),unsupported:UnsupportedNode}))result[id]=props=><div inert style={{width:'100%',height:'100%'}}><Renderer {...props}/></div>;return result;},[renderers]),edgeTypes=useMemo(()=>({...Object.fromEntries(Object.keys(renderers.edgeTypes).map(id=>[id,renderers.previewEdgeTypes[id]??UnsupportedEdge])),unsupported:UnsupportedEdge}),[renderers]);
 // 仍允许拖动或滚动平移，关闭滚轮缩放和Delete删除；onMoveEnd记录视口，进度只显示读取数量。
 return <div className={styles.editor} data-canvas-loading-preview aria-label="正在加载的画布，只读预览">
  <CanvasRendererCommandsContext.Provider value={commands}>
   <ReactFlow nodes={projection.nodes} edges={projection.edges} nodeTypes={nodeTypes} edgeTypes={edgeTypes} nodesDraggable={false} nodesConnectable={false} elementsSelectable={false} nodesFocusable={false} edgesFocusable={false} panOnDrag panOnScroll zoomOnScroll={false} minZoom={.1} maxZoom={4} deleteKeyCode={null} onMoveEnd={(_,viewport)=>onViewport(viewport)}>
    <InitialPreviewViewport onViewport={onViewport} nodeCount={projection.nodes.length}/>
    <Background variant={BackgroundVariant.Dots} gap={24} size={1} />
   </ReactFlow>
  </CanvasRendererCommandsContext.Provider>
  <p role="status" style={{position:'absolute',left:'50%',transform:'translateX(-50%)',bottom:16,pointerEvents:'none'}}>正在加载… {preview.receivedElements}/{preview.totalElements}，加载期间可浏览</p>
 </div>;
}