/**
 * 应用级运行宿主，生命周期跨越页面导航；同一账号下复用 workspace runtime 和共享读取器。
 * 账号/退出登录变化先递增 authEpoch 使旧回调失效，再异步关闭退休 runtime；关闭失败仍保留退休实例供重试。
 * registry 是共享定义，工作文档归 project engine，读取预览也不能成为第二份可写文档。
 */
import {createModelPreview,type LiveModelPreview} from './model-preview.ts';
import type { Id, Registry } from '../canvas-core/types.ts';
import { fault, readMap } from '../canvas-core/values.ts';
import type { WorkspaceRuntime } from './workspace.ts';
import { createScopedLoader, type LoadPort, type ScopedLoader } from './loader.ts';
import type { CanonicalReadUpdate } from './contracts.ts';

/** Host lifetime matches the signed-in application, independently of navigation. */
/** 宿主注入 workspace/loader 工厂；current 闭包绑定精确账号与 epoch，作为异步结果准入围栏。 */
export function createRuntimeHost(options: { registry: Registry; workspace(accountId: Id, workspaceId: Id, authEpoch: number, current: () => boolean): WorkspaceRuntime; modelLoader?(accountId:Id,workspaceId:Id,authEpoch:number,current:()=>boolean):LoadPort<CanonicalReadUpdate>; onError?: (error: unknown) => void; onObserverError?: (error: unknown) => void }) {
  let accountId: Id | null = null, authEpoch = 0, disposed = false;
  // active 表只含当前身份，retired 持有尚未成功关闭的旧 runtime，不能因换账号就丢掉待保存内容。
  const workspaces = new Map<Id, WorkspaceRuntime>(), retired = new Set<WorkspaceRuntime>();
  const readers = new Map<Id, ScopedLoader<CanonicalReadUpdate>>();
  /** 并行尝试关闭退休实例，成功才移出集合；汇总失败而不提前释放失败实例。 */
  const closeRetired = async () => {
    const results = await Promise.allSettled([...retired].map(async runtime => { await runtime.close(); retired.delete(runtime); }));
    const errors = results.flatMap(result => result.status === 'rejected' ? [result.reason] : []);
    if (errors.length) throw new AggregateError(errors, 'host_close_failed');
  };
  /** 同步撤销当前身份：先换 epoch，再关闭读取句柄/移走 workspace；实际存储收尾另行等待。 */
  function retire() { authEpoch++; accountId = null; for (const reader of readers.values()) reader.close();readers.clear();for (const runtime of workspaces.values()) retired.add(runtime); workspaces.clear(); }
  /** 账号变化才退休旧作用域；后台关闭错误走 onError，报告失败不能改变新账号的身份事实。 */
  function activate(account: Id) {
    if (disposed) throw fault('host_disposed');
    if (accountId !== account) {
      retire(); accountId = account;
      void closeRetired().catch(error => { try { options.onError?.(error); } catch { /* Reporting cannot change scope. */ } });
    }
  }
  return Object.freeze({
    /** 只读共享定义，不含各 workspace 的可变运行状态。 */
    registry: options.registry,
    /** 返回绑定当前 epoch 的校验函数；同账号退出再登录也因 epoch 变化而使旧函数失效。 */
    bindAccount(account: Id) { activate(account); const epoch = authEpoch; return () => !disposed && accountId === account && authEpoch === epoch; },
    /** 捕获当前身份摘要，供导航/宿主检查，不携带认证凭证。 */
    identity: () => Object.freeze({ accountId, authEpoch }),
    /** 返回当前 workspace 表的安全只读快照，外部不能手动增删运行实例。 */
    getWorkspaces: () => readMap(workspaces),
    /** 通过共享 scoped loader 读 canonical 源；增量可产生只读预览，terminal 完整后才返回最终模型。 */
    async loadModel(account:Id,workspace:Id,canvas:Id,settings:{signal?:AbortSignal;navigationGeneration?:number;onPreview?:(preview:LiveModelPreview)=>void}={}) {
      activate(account);
      const readEpoch=authEpoch;
      if(!options.modelLoader)throw fault('model_loader_unavailable');
      let reader=readers.get(workspace);
      // 同 workspace 复用并发读取；maxCacheEntries=0 不把一次已完成读取当成长期授权缓存。
      if(!reader){const epoch=authEpoch,current=()=>!disposed&&accountId===account&&authEpoch===epoch;reader=createScopedLoader({load:options.modelLoader(account,workspace,epoch,current),current:()=>current(),maxCacheEntries:0});readers.set(workspace,reader);}
      // 每个订阅者自己解算预览/seen 游标，观察者异常只终止该预览，不更改共享读取事实。
      const preview=settings.onPreview?createModelPreview(options.registry):undefined;let seen=0,previewFailed=false;let declaredCanvasIds:readonly Id[]=[];
      /** 先检查身份/取消，再消费尚未处理的块；头部范围证据决定 loading 版本与可用覆盖范围。 */
      const onUpdate=(state:import('./loader.ts').LoadSnapshot<CanonicalReadUpdate>)=>{
        if(!preview||previewFailed||disposed||accountId!==account||authEpoch!==readEpoch||settings.signal?.aborted)return;
        try{for(;seen<state.chunks.length;seen++){const chunk=state.chunks[seen],value=preview.update(chunk.value);if(chunk.value.status==='receiving'&&value){if(chunk.sequence===0)declaredCanvasIds=Object.freeze(chunk.value.canvases.map(canvas=>canvas.id));settings.onPreview?.(Object.freeze({...value,versions:readMap(new Map(Object.entries(chunk.serverVersions))),loading:Object.freeze({...(value.canvasElementCounts?value.elementOwners?{version:6 as const,canvasElementCounts:value.canvasElementCounts,elementOwners:value.elementOwners,sourceCanvases:value.sourceCanvases!}:{version:3 as const,canvasElementCounts:value.canvasElementCounts}:{version:1 as const}),sourceToken:chunk.snapshotToken,declaredCanvasIds,receivedElements:value.receivedElements,totalElements:value.totalElements})}));}}}
        catch(error){previewFailed=true;try{options.onObserverError?.(error);}catch{}}
      };
      // key 纳入账号、workspace、格式、查询与 authEpoch；view 导航代次不替代授权代次。
      const handle=reader.acquire({accountId:account,workspaceId:workspace,projectId:null,canvasId:canvas,viewKey:'canonical-project',format:'canonical-model-v1',queryFingerprint:'full-project',source:'foundry',authEpoch,navigationGeneration:settings.navigationGeneration??0},{signal:settings.signal,onUpdate});
      // ready 后再查身份和 terminal/complete；finally 始终释放本订阅，不能泄漏 reader 引用。
      try{const snapshot=await handle.ready;if(disposed||accountId!==account||authEpoch!==readEpoch)throw fault('identity_changed');const last=snapshot.chunks.at(-1);if(!last||!last.complete||last.value.status==='receiving')throw fault('incomplete_load');return last.value.status==='ready'?Object.freeze({...last.value,sourceToken:last.snapshotToken}):last.value;}finally{handle.release();preview?.close();}
    },
    /** 按当前账号激活并懒创建 workspace；导航到同工作区不会重新创建资源池或项目。 */
    workspace(account: Id, workspace: Id) {
      activate(account);
      let runtime = workspaces.get(workspace);
      if (!runtime) {
        const epoch = authEpoch;
        runtime = options.workspace(account, workspace, epoch, () => !disposed && accountId === account && authEpoch === epoch);
        workspaces.set(workspace, runtime);
      }
      return runtime;
    },
    /** 退出身份但保留 host 可再次绑定；返回旧 runtime 收尾 Promise，让宿主处理未保存错误。 */
    retireIdentity() { retire(); return closeRetired(); },
    /** 永久关闭 host 并退休全部作用域；失败仍可再次调用 close 重试退休集合。 */
    close() { disposed = true; retire(); return closeRetired(); },
  });
}
/** 公共宿主 API 由工厂返回值推导，避免接口声明与实现两份维护。 */
export type RuntimeHost = ReturnType<typeof createRuntimeHost>;