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. */
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;
  const workspaces = new Map<Id, WorkspaceRuntime>(), retired = new Set<WorkspaceRuntime>();
  const readers = new Map<Id, ScopedLoader<CanonicalReadUpdate>>();
  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');
  };
  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(); }
  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({
    registry: options.registry,
    bindAccount(account: Id) { activate(account); const epoch = authEpoch; return () => !disposed && accountId === account && authEpoch === epoch; },
    identity: () => Object.freeze({ accountId, authEpoch }),
    getWorkspaces: () => readMap(workspaces),
    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);
      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);}
      const preview=settings.onPreview?createModelPreview(options.registry):undefined;let seen=0,previewFailed=false;let declaredCanvasIds:readonly Id[]=[];
      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{}}
      };
      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});
      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();}
    },
    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;
    },
    retireIdentity() { retire(); return closeRetired(); },
    close() { disposed = true; retire(); return closeRetired(); },
  });
}
export type RuntimeHost = ReturnType<typeof createRuntimeHost>;