Negotiate and decode snapshot-bound canonical model streams

src/lib/canvas-service/model-stream.ts

@@ -0,0 +1,62 @@
+import type { CanvasRecord, ElementRecord, Id, Registry } from '../canvas-core/types.ts';
+import { createDocument, validateDocument } from '../canvas-core/document.ts';
+import { fault, freeze, readMap, validJson } from '../canvas-core/values.ts';
+import type { CanonicalReadUpdate } from '../canvas-runtime/contracts.ts';
+
+export const modelStreamType = 'application/vnd.foundry.canvas-model+ndjson;version=1';
+const maxBytes=64*1024*1024,maxLine=8*1024*1024,maxLines=4096;
+const uuid=/^[a-f\d]{8}-[a-f\d]{4}-[a-f\d]{4}-[a-f\d]{4}-[a-f\d]{12}$/i;
+const object=(value:unknown):Record<string,unknown>=>{if(!value||typeof value!=='object'||Array.isArray(value)||!validJson(value))throw fault('invalid_model_stream');return value as Record<string,unknown>;};
+/** Bounded NDJSON framing. EOF is required even after a terminal record. */
+async function* lines(source:AsyncIterable<Uint8Array>,signal:AbortSignal){
+ const decoder=new TextDecoder('utf-8',{fatal:true});let pending='',total=0,lineBytes=0,count=0;
+ for await(const bytes of source){
+  signal.throwIfAborted();if(!(bytes instanceof Uint8Array))throw fault('invalid_model_stream');total+=bytes.byteLength;if(total>maxBytes)throw fault('model_stream_budget');
+  let start=0;
+  for(let index=0;index<bytes.length;index++)if(bytes[index]===10){
+   lineBytes+=index-start;if(lineBytes>maxLine)throw fault('model_stream_budget');
+   pending+=decoder.decode(bytes.subarray(start,index),{stream:true});pending+=decoder.decode();if(++count>maxLines||!pending)throw fault('invalid_model_stream');
+   yield{raw:JSON.parse(pending),byteLength:lineBytes+1};pending='';lineBytes=0;start=index+1;
+  }
+  lineBytes+=bytes.length-start;if(lineBytes>maxLine)throw fault('model_stream_budget');pending+=decoder.decode(bytes.subarray(start),{stream:true});
+ }
+ signal.throwIfAborted();pending+=decoder.decode();if(pending||lineBytes)throw fault('incomplete_model_stream');
+}
+export async function* decodeModelStream(source:AsyncIterable<Uint8Array>,canvasId:Id,registry:Registry,signal:AbortSignal){
+ let sequence=0,token='',projectId='',expected=0,ended=false;
+ let terminal: {sequence:number;snapshotToken:string;projectId:string;versions:ReadonlyMap<Id,number>;complete:boolean;byteLength:number;coverage:string[];value:CanonicalReadUpdate}|undefined;
+ let canvases:CanvasRecord[]=[],versions:ReadonlyMap<Id,number>=new Map(),tombstones:ReadonlyMap<Id,number>=new Map();
+ const elements:ElementRecord[]=[],ids=new Set<Id>(),canvasIds=new Set<Id>();
+ for await(const line of lines(source,signal)){
+  const raw=object(line.raw);
+  if(ended||raw.streamVersion!==1||raw.sequence!==sequence++||typeof raw.snapshotToken!=='string'||!raw.snapshotToken||raw.snapshotToken.length>256)throw fault('invalid_model_stream');
+  if(sequence===1){
+   if(raw.kind!=='header'||raw.documentFormatVersion!==1||typeof raw.projectId!=='string'||!uuid.test(raw.projectId)||!Number.isSafeInteger(raw.elementCount)||(raw.elementCount as number)<0||!Array.isArray(raw.canvases)||raw.canvases.length>256)throw fault('invalid_model_stream');
+   token=raw.snapshotToken;projectId=raw.projectId;expected=raw.elementCount as number;canvases=raw.canvases as CanvasRecord[];
+   for(const canvas of canvases){object(canvas);if(typeof canvas.id!=='string'||!uuid.test(canvas.id)||canvasIds.has(canvas.id))throw fault('invalid_model_stream');canvasIds.add(canvas.id);}
+   if(!canvasIds.has(canvasId)||!canvasIds.has(projectId))throw fault('project_mismatch');
+   const versionMap=new Map<Id,number>(),dead=new Map<Id,number>();
+   for(const [id,value]of Object.entries(object(raw.versions))){if(!uuid.test(id)||!Number.isSafeInteger(value)||(value as number)<1)throw fault('invalid_canonical_version');versionMap.set(id,value as number);}
+   if([...canvasIds].some(id=>!versionMap.has(id)))throw fault('invalid_model_stream');
+   if(!Array.isArray(raw.removedCanvasIds)||new Set(raw.removedCanvasIds).size!==raw.removedCanvasIds.length||raw.removedCanvasIds.some(id=>typeof id!=='string'||canvasIds.has(id)||!versionMap.has(id))||versionMap.size!==canvasIds.size+raw.removedCanvasIds.length)throw fault('invalid_model_stream');
+   for(const [id,value]of Object.entries(object(raw.tombstones))){if(!id||!Number.isSafeInteger(value)||(value as number)<1)throw fault('invalid_model_stream');dead.set(id,value as number);}
+   versions=readMap(versionMap);tombstones=readMap(dead);
+   const value:CanonicalReadUpdate=freeze({status:'receiving',projectId,canvases,elements:[],tombstones,versions,receivedElements:0,totalElements:expected});
+   yield{sequence:0,snapshotToken:token,projectId,versions,complete:false,byteLength:line.byteLength,coverage:['model-header'],value};continue;
+  }
+  if(raw.snapshotToken!==token)throw fault('load_snapshot_changed');
+  if(raw.kind==='elements'){
+   if(!Array.isArray(raw.elements)||!raw.elements.length||raw.elements.length>64||elements.length+raw.elements.length>expected)throw fault('invalid_model_stream');
+   for(const item of raw.elements){const element=object(item) as unknown as ElementRecord;if(typeof element.id!=='string'||!element.id||ids.has(element.id)||!canvasIds.has(element.ownerCanvasId))throw fault('invalid_model_stream');ids.add(element.id);elements.push(element);}
+   const value:CanonicalReadUpdate=freeze({status:'receiving',projectId,canvases:[],elements:raw.elements as ElementRecord[],tombstones:readMap(new Map()),versions,receivedElements:elements.length,totalElements:expected});
+   yield{sequence:sequence-1,snapshotToken:token,projectId,versions,complete:false,byteLength:line.byteLength,coverage:raw.elements.map(item=>`element:${(item as ElementRecord).id}`),value};
+  }else if(raw.kind==='complete'){
+   if(raw.elementCount!==expected||elements.length!==expected)throw fault('incomplete_model_stream');
+   const document=createDocument(projectId,canvases,elements,tombstones);validateDocument(document,registry);ended=true;
+   const value:CanonicalReadUpdate=Object.freeze({status:'ready',document,versions});
+   terminal={sequence:sequence-1,snapshotToken:token,projectId,versions,complete:true,byteLength:line.byteLength,coverage:[...canvasIds].map(id=>`canvas:${id}`),value};
+  }else throw fault('invalid_model_stream');
+ }
+ if(!ended||!terminal)throw fault('incomplete_model_stream');
+ yield terminal;
+}