55 lines
4.2 KiB
TypeScript
55 lines
4.2 KiB
TypeScript
import type {Id,Target,Geometry} from '../canvas-core/types.ts';
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import type {SessionSnapshot,GestureState} from '../canvas-core/gestures.ts';
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import {equal} from '../canvas-core/values.ts';
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import type {ExternalSource} from './selectors.ts';
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export type GestureSelection={readonly preview:Geometry|undefined;readonly active:boolean};
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/** Derived view/target subscriptions. Values retain no document or full per-hook session. */
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export function createSessionSources(source:ExternalSource<SessionSnapshot>){
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type Observer={update(snapshot:SessionSnapshot):boolean;notify():void};
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const modes=new Map<Id,Map<Id,Set<Observer>>>(),gestures=new Map<Id,Set<Observer>>();
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const targetIndexes=new WeakMap<readonly Target[],ReadonlyMap<Id,number>>();
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let stop:(()=>void)|undefined,previous:SessionSnapshot|undefined;
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function targets(gesture:GestureState){let index=targetIndexes.get(gesture.targets);if(!index){index=new Map(gesture.targets.map(target=>[target.id,target.incarnation]));targetIndexes.set(gesture.targets,index);}return index;}
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function changed(){
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if(!previous)return;const before=previous,next=source.getSnapshot();previous=next;
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const candidates=new Set<Observer>(),add=(items:Set<Observer>|undefined)=>{for(const item of items??[])candidates.add(item);};
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if(before.views!==next.views)for(const[viewId,byId]of modes){
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const old=before.views.get(viewId)?.modes,current=next.views.get(viewId)?.modes;if(old===current)continue;
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for(const id of new Set([...(old?.keys()??[]),...(current?.keys()??[])]))if(old?.get(id)!==current?.get(id))add(byId.get(id));
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}
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const old=before.gesture,current=next.gesture;
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if(old!==current){
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const ids=new Set<Id>();
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if(!old||!current||old.token!==current.token||old.viewId!==current.viewId||old.targets!==current.targets){for(const gesture of [old,current])for(const target of gesture?.targets??[])ids.add(target.id);}
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else if(old.preview!==current.preview){for(const[id,value]of old.preview)if(current.preview.get(id)!==value)ids.add(id);for(const[id,value]of current.preview)if(old.preview.get(id)!==value)ids.add(id);}
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for(const id of ids)add(gestures.get(id));
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}
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const notifications:Observer[]=[];for(const observer of candidates)if(observer.update(next))notifications.push(observer);
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let failed=false,error:unknown;for(const observer of notifications)try{observer.notify();}catch(caught){if(!failed){failed=true;error=caught;}}if(failed)throw error;
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}
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function channel<T>(read:(snapshot:SessionSnapshot)=>T,register:(observer:Observer)=>()=>void):ExternalSource<T>{
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let initialized=false,value:T;
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return Object.freeze({
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getSnapshot(){const next=read(source.getSnapshot());if(!initialized||!equal(value,next))value=next;initialized=true;return value;},
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subscribe(notify:()=>void){
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let observed=read(source.getSnapshot()),failed=false;
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const observer:Observer={notify,update(snapshot){try{const next=read(snapshot);if(!failed&&equal(observed,next))return false;observed=next;failed=false;}catch{failed=true;}return true;}};
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const remove=register(observer);
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if(!stop){previous=source.getSnapshot();try{stop=source.subscribe(changed);}catch(error){remove();previous=undefined;throw error;}}
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let active=true;return()=>{if(!active)return;active=false;remove();if(!modes.size&&!gestures.size){stop?.();stop=undefined;previous=undefined;}};
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},
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});
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}
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return Object.freeze({
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mode(viewId:Id,id:Id):ExternalSource<string|null>{return channel(snapshot=>snapshot.views.get(viewId)?.modes.get(id)??null,observer=>{
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let byId=modes.get(viewId);if(!byId){byId=new Map();modes.set(viewId,byId);}let bucket=byId.get(id);if(!bucket){bucket=new Set();byId.set(id,bucket);}bucket.add(observer);
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return()=>{bucket!.delete(observer);if(!bucket!.size)byId!.delete(id);if(!byId!.size)modes.delete(viewId);};
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});},
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gesture(viewId:Id,target:Target):ExternalSource<GestureSelection>{const{id,incarnation}=target;return channel(snapshot=>{
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const gesture=snapshot.gesture,matched=!!gesture&&targets(gesture).get(id)===incarnation;
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return{preview:matched?gesture!.preview.get(id):undefined,active:matched&&gesture!.viewId===viewId};
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},observer=>{let bucket=gestures.get(id);if(!bucket){bucket=new Set();gestures.set(id,bucket);}bucket.add(observer);return()=>{bucket!.delete(observer);if(!bucket!.size)gestures.delete(id);};});},
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});
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}
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