61 lines
1.6 KiB
JavaScript
61 lines
1.6 KiB
JavaScript
/*
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Copyright 2021 The Matrix.org Foundation C.I.C.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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export class ListObserver {
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constructor() {
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this._queue = [];
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this._backlog = [];
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}
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next() {
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if (this._backlog.length) {
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return Promise.resolve(this._backlog.shift());
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} else {
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return new Promise(resolve => {
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this._queue.push(resolve);
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});
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}
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}
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_fullfillNext(value) {
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if (this._queue.length) {
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const resolve = this._queue.shift();
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resolve(value);
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} else {
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this._backlog.push(value);
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}
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}
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onReset() {
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this._fullfillNext({type: "reset"});
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}
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onAdd(index, value) {
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this._fullfillNext({type: "add", index, value});
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}
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onUpdate(index, value, params) {
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this._fullfillNext({type: "update", index, value, params});
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}
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onRemove(index, value) {
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this._fullfillNext({type: "remove", index, value});
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}
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onMove(fromIdx, toIdx, value) {
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this._fullfillNext({type: "move", fromIdx, toIdx, value});
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}
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}
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