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import { pull } from "lodash";
import { Observable, BehaviorSubject, combineLatest } from "rxjs";
import { map } from "rxjs/operators";
export type Subscriber<TData> = (data: TData) => void;
export type WithSyncStatus<T> = T & { syncing: boolean };
export class DataLine<TData> {
private _current: TData | undefined = undefined;
private _syncPromise: Promise<void> | null = null;
private _syncingSubject = new BehaviorSubject<boolean>(false);
private _observers: Subscriber<TData>[] = [];
constructor(
private config: {
sync: () => Promise<void>;
destroyable?: (value: TData | undefined) => boolean;
disableInitSync?: boolean;
}
) {
if (config.disableInitSync !== true) {
setTimeout(() => void this.sync());
}
}
private subscribe(subscriber: Subscriber<TData>): void {
this._observers.push(subscriber);
if (this._current !== undefined) {
subscriber(this._current);
}
}
private unsubscribe(subscriber: Subscriber<TData>): void {
if (!this._observers.includes(subscriber)) return;
pull(this._observers, subscriber);
}
getObservable(): Observable<TData> {
return new Observable<TData>((observer) => {
const f = (data: TData): void => {
observer.next(data);
};
this.subscribe(f);
return () => {
this.unsubscribe(f);
};
});
}
getSyncStatusObservable(): Observable<boolean> {
return this._syncingSubject.asObservable();
}
getDataWithSyncStatusObservable(): Observable<WithSyncStatus<TData>> {
return combineLatest([
this.getObservable(),
this.getSyncStatusObservable(),
]).pipe(
map(([data, syncing]) => ({
...data,
syncing,
}))
);
}
get value(): TData | undefined {
return this._current;
}
next(value: TData): void {
this._current = value;
this._observers.forEach((observer) => observer(value));
}
get isSyncing(): boolean {
return this._syncPromise != null;
}
sync(): Promise<void> {
if (this._syncPromise == null) {
this._syncingSubject.next(true);
this._syncPromise = this.config.sync().then(() => {
this._syncingSubject.next(false);
this._syncPromise = null;
});
}
return this._syncPromise;
}
syncWithAction(
syncAction: (line: DataLine<TData>) => Promise<void>
): Promise<void> {
if (this._syncPromise == null) {
this._syncingSubject.next(true);
this._syncPromise = syncAction(this).then(() => {
this._syncingSubject.next(false);
this._syncPromise = null;
});
}
return this._syncPromise;
}
get destroyable(): boolean {
const customDestroyable = this.config?.destroyable;
return (
this._observers.length === 0 &&
!this.isSyncing &&
(customDestroyable != null ? customDestroyable(this._current) : true)
);
}
}
export class DataHub<TKey, TData> {
private sync: (key: TKey, line: DataLine<TData>) => Promise<void>;
private keyToString: (key: TKey) => string;
private destroyable?: (key: TKey, value: TData | undefined) => boolean;
private readonly subscriptionLineMap = new Map<string, DataLine<TData>>();
private cleanTimerId = 0;
// setup is called after creating line and if it returns a function as destroyer, then when the line is destroyed the destroyer will be called.
constructor(config: {
sync: (key: TKey, line: DataLine<TData>) => Promise<void>;
keyToString?: (key: TKey) => string;
destroyable?: (key: TKey, value: TData | undefined) => boolean;
}) {
this.sync = config.sync;
this.keyToString =
config.keyToString ??
((value): string => {
if (typeof value === "string") return value;
else
throw new Error(
"Default keyToString function only pass string value."
);
});
this.destroyable = config.destroyable;
}
private cleanLines(): void {
const toDelete: string[] = [];
for (const [key, line] of this.subscriptionLineMap.entries()) {
if (line.destroyable) {
toDelete.push(key);
}
}
if (toDelete.length === 0) return;
for (const key of toDelete) {
this.subscriptionLineMap.delete(key);
}
if (this.subscriptionLineMap.size === 0) {
window.clearInterval(this.cleanTimerId);
this.cleanTimerId = 0;
}
}
private createLine(key: TKey, disableInitSync = false): DataLine<TData> {
const keyString = this.keyToString(key);
const { destroyable } = this;
const newLine: DataLine<TData> = new DataLine<TData>({
sync: () => this.sync(key, newLine),
destroyable:
destroyable != null ? (value) => destroyable(key, value) : undefined,
disableInitSync: disableInitSync,
});
this.subscriptionLineMap.set(keyString, newLine);
if (this.subscriptionLineMap.size === 1) {
this.cleanTimerId = window.setInterval(this.cleanLines.bind(this), 20000);
}
return newLine;
}
getObservable(key: TKey): Observable<TData> {
return this.getLineOrCreate(key).getObservable();
}
getSyncStatusObservable(key: TKey): Observable<boolean> {
return this.getLineOrCreate(key).getSyncStatusObservable();
}
getDataWithSyncStatusObservable(
key: TKey
): Observable<WithSyncStatus<TData>> {
return this.getLineOrCreate(key).getDataWithSyncStatusObservable();
}
getLine(key: TKey): DataLine<TData> | null {
const keyString = this.keyToString(key);
return this.subscriptionLineMap.get(keyString) ?? null;
}
getLineOrCreate(key: TKey): DataLine<TData> {
const keyString = this.keyToString(key);
return this.subscriptionLineMap.get(keyString) ?? this.createLine(key);
}
getLineOrCreateWithoutInitSync(key: TKey): DataLine<TData> {
const keyString = this.keyToString(key);
return (
this.subscriptionLineMap.get(keyString) ?? this.createLine(key, true)
);
}
optionalInitLineWithSyncAction(
key: TKey,
syncAction: (line: DataLine<TData>) => Promise<void>
): Promise<void> {
const optionalLine = this.getLine(key);
if (optionalLine != null) return Promise.resolve();
const line = this.createLine(key, true);
return line.syncWithAction(syncAction);
}
}
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