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import { Observable } from "rxjs";
export type DataStatus = "syncing" | "synced" | "offline";
export type Subscriber<TData> = (data: TData) => void;
export interface DataAndStatus<TData> {
data: TData | null;
status: DataStatus;
}
export class DataLine2<TData> {
constructor(
private config: {
saveData: (data: TData) => Promise<void>;
getSavedData: () => Promise<TData | null>;
// return null for offline
fetchData: (savedData: TData | null) => Promise<TData | null>;
}
) {}
private _current: DataAndStatus<TData> | null = null;
private _observers: Subscriber<DataAndStatus<TData>>[] = [];
get currentData(): DataAndStatus<TData> | null {
return this._current;
}
get isDestroyable(): boolean {
const { _observers, currentData } = this;
return (
_observers.length === 0 &&
(currentData == null || currentData.status !== "syncing")
);
}
private next(data: DataAndStatus<TData>): void {
this._current = data;
this._observers.forEach((o) => o(data));
}
subscribe(subsriber: Subscriber<DataAndStatus<TData>>): void {
this.sync(); // TODO: Should I sync at this point or let the user sync explicitly.
this._observers.push(subsriber);
const { currentData } = this;
if (currentData != null) {
subsriber(currentData);
}
}
unsubscribe(subsriber: Subscriber<DataAndStatus<TData>>): void {
const index = this._observers.indexOf(subsriber);
if (index > -1) this._observers.splice(index, 1);
}
getObservalble(): Observable<DataAndStatus<TData>> {
return new Observable<DataAndStatus<TData>>((observer) => {
const f = (data: DataAndStatus<TData>): void => {
observer.next(data);
};
this.subscribe(f);
return () => {
this.unsubscribe(f);
};
});
}
sync(): void {
const { currentData } = this;
if (currentData != null && currentData.status === "syncing") return;
this.next({ data: currentData?.data ?? null, status: "syncing" });
void this.config.getSavedData().then((savedData) => {
if (currentData == null && savedData != null) {
this.next({ data: savedData, status: "syncing" });
}
return this.config.fetchData(savedData).then((data) => {
if (data == null) {
this.next({
data: savedData,
status: "offline",
});
} else {
return this.config.saveData(data).then(() => {
this.next({ data: data, status: "synced" });
});
}
});
});
}
save(data: TData): void {
const { currentData } = this;
if (currentData != null && currentData.status === "syncing") return;
this.next({ data: currentData?.data ?? null, status: "syncing" });
void this.config.saveData(data).then(() => {
this.next({ data: data, status: "synced" });
});
}
getSavedData(): Promise<TData | null> {
return this.config.getSavedData();
}
}
export class DataHub2<TKey, TData> {
private readonly subscriptionLineMap = new Map<string, DataLine2<TData>>();
private keyToString: (key: TKey) => string;
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(
private config: {
saveData: (key: TKey, data: TData) => Promise<void>;
getSavedData: (key: TKey) => Promise<TData | null>;
fetchData: (key: TKey, savedData: TData | null) => Promise<TData | null>;
keyToString?: (key: TKey) => string;
}
) {
this.keyToString =
config.keyToString ??
((value): string => {
if (typeof value === "string") return value;
else
throw new Error(
"Default keyToString function only pass string value."
);
});
}
private cleanLines(): void {
const toDelete: string[] = [];
for (const [key, line] of this.subscriptionLineMap.entries()) {
if (line.isDestroyable) {
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): DataLine2<TData> {
const keyString = this.keyToString(key);
const newLine: DataLine2<TData> = new DataLine2<TData>({
saveData: (data) => this.config.saveData(key, data),
getSavedData: () => this.config.getSavedData(key),
fetchData: (savedData) => this.config.fetchData(key, savedData),
});
this.subscriptionLineMap.set(keyString, newLine);
if (this.subscriptionLineMap.size === 1) {
this.cleanTimerId = window.setInterval(this.cleanLines.bind(this), 20000);
}
return newLine;
}
getLine(key: TKey): DataLine2<TData> {
const keyString = this.keyToString(key);
return this.subscriptionLineMap.get(keyString) ?? this.createLine(key);
}
}
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