90 lines
2.5 KiB
TypeScript
90 lines
2.5 KiB
TypeScript
/*
|
|
Copyright 2020 Bruno Windels <bruno@windels.cloud>
|
|
|
|
Licensed under the Apache License, Version 2.0 (the "License");
|
|
you may not use this file except in compliance with the License.
|
|
You may obtain a copy of the License at
|
|
|
|
http://www.apache.org/licenses/LICENSE-2.0
|
|
|
|
Unless required by applicable law or agreed to in writing, software
|
|
distributed under the License is distributed on an "AS IS" BASIS,
|
|
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
See the License for the specific language governing permissions and
|
|
limitations under the License.
|
|
*/
|
|
|
|
import {BaseObservableValue} from "./BaseObservableValue";
|
|
import {BaseObservableMap, IMapObserver} from "../map/BaseObservableMap";
|
|
import {SubscriptionHandle} from "../BaseObservable";
|
|
|
|
function pickLowestKey<K>(currentKey: K, newKey: K): boolean {
|
|
return newKey < currentKey;
|
|
}
|
|
|
|
export class PickMapObservableValue<K, V> extends BaseObservableValue<V | undefined> implements IMapObserver<K, V>{
|
|
|
|
private key?: K;
|
|
private mapSubscription?: SubscriptionHandle;
|
|
|
|
constructor(
|
|
private readonly map: BaseObservableMap<K, V>,
|
|
private readonly pickKey: (currentKey: K, newKey: K) => boolean = pickLowestKey
|
|
) {
|
|
super();
|
|
}
|
|
|
|
private updateKey(newKey: K): boolean {
|
|
if (this.key === undefined || this.pickKey(this.key, newKey)) {
|
|
this.key = newKey;
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
onReset(): void {
|
|
this.key = undefined;
|
|
this.emit(this.get());
|
|
}
|
|
|
|
onAdd(key: K, value:V): void {
|
|
if (this.updateKey(key)) {
|
|
this.emit(this.get());
|
|
}
|
|
}
|
|
|
|
onUpdate(key: K, value: V, params: any): void {
|
|
this.emit(this.get());
|
|
}
|
|
|
|
onRemove(key: K, value: V): void {
|
|
if (key === this.key) {
|
|
this.key = undefined;
|
|
// try to see if there is another key that fullfills pickKey
|
|
for (const [key] of this.map) {
|
|
this.updateKey(key);
|
|
}
|
|
this.emit(this.get());
|
|
}
|
|
}
|
|
|
|
onSubscribeFirst(): void {
|
|
this.mapSubscription = this.map.subscribe(this);
|
|
for (const [key] of this.map) {
|
|
this.updateKey(key);
|
|
}
|
|
}
|
|
|
|
onUnsubscribeLast(): void {
|
|
this.mapSubscription!();
|
|
this.key = undefined;
|
|
}
|
|
|
|
get(): V | undefined {
|
|
if (this.key !== undefined) {
|
|
return this.map.get(this.key);
|
|
}
|
|
return undefined;
|
|
}
|
|
}
|