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import { AngularFirestore, AngularFirestoreCollection } from '@angular/fire/firestore';
import { LoadingBarService } from '@ngx-loading-bar/core';
import { BehaviorSubject, Observable } from 'rxjs';
import { scan, take, tap } from 'rxjs/operators';
import { APP_CONFIG, InterfaceAppConfig } from '../app-config';
/**
* options to reproduce firestore queries consistently
*/
interface QueryConfig {
/** path to collection */
path: string;
/** field to orderBy */
field: string;
/** limit per query */
limit?: number;
/** reverse order? */
reverse?: boolean;
/** prepend to source? */
prepend?: boolean;
}
/**
* Pagination Service
*/
@Injectable()
export class PaginationService {
/** observable data */
data: Observable<any>;
/** is done? */
done = new BehaviorSubject<boolean>(false);
/** is loading? */
loading = new BehaviorSubject<boolean>(false);
/** private source data */
private readonly _data = new BehaviorSubject([]);
/** QueryConfig */
private query: QueryConfig;
/**
* constructor of PaginationService
* @param afs: AngularFirestore
* @param ngZone: NgZone
* @param loadingBar: LoadingBarService
* @param appConfig: APP_CONFIG
*/
constructor(private readonly afs: AngularFirestore,
private readonly ngZone: NgZone,
private readonly loadingBar: LoadingBarService,
@Inject(APP_CONFIG) private readonly appConfig: InterfaceAppConfig) {
}
/**
* initial query sets options and defines the Observable
* @param path: path to collection
* @param field: field to orderBy
* @param opts: options
* @param isReset: do you want to reset before init?
*/
init(path, field, opts?, isReset?): void {
this.query = {
path,
field,
limit: 2,
reverse: false,
prepend: false,
...opts
};
if (isReset || isReset === undefined) {
this.reset();
}
setTimeout(() => {
const first = this.afs.collection(this.query.path, ref =>
ref
.orderBy(this.query.field, this.query.reverse ? 'desc' : 'asc')
.limit(this.query.limit));
this.mapAndUpdate(first);
// create the observable array for consumption in components
this.data = this._data.asObservable()
.pipe(scan((acc, val) =>
this.query.prepend ? val.concat(acc) : acc.concat(val)));
}, 0);
}
/**
* Retrieves additional data from firestore
*/
more(): any {
const cursor = this.getCursor();
if (cursor) {
const more = this.afs.collection(this.query.path, ref =>
ref
.orderBy(this.query.field, this.query.reverse ? 'desc' : 'asc')
.limit(this.query.limit)
.startAfter(cursor));
this.mapAndUpdate(more);
} else {
this.done.next(true);
}
}
/**
* Reset the pagination
*/
reset(): void {
this._data.next([]);
this.done.next(false);
// istanbul ignore next
if (!this.appConfig.isUnitTest) {
// I do not want to add 'tick(x)' to all of end of unit test cases just for loading bar
this.loadingBar.complete();
}
this.loading.next(false);
}
/**
* Determines the doc snapshot to paginate query
*/
private getCursor(): any {
const current = this._data.value;
if (current.length) {
return this.query.prepend ? current[0].doc : current[current.length - 1].doc;
}
return;
}
/**
* Maps the snapshot to usable format the updates source
* @param col: AngularFirestoreCollection
*/
private mapAndUpdate(col: AngularFirestoreCollection<any>): any {
if (this.done.value || this.loading.value) {
return;
}
// loading
// istanbul ignore next
if (!this.appConfig.isUnitTest) {
// I do not want to add 'tick(x)' to all of end of unit test cases just for loading bar
this.loadingBar.start();
}
this.loading.next(true);
// map snapshot with doc ref (needed for cursor)
return col.snapshotChanges()
.pipe(tap(arr => {
let values = arr.map(snap => {
const id = snap.payload.doc.id;
const data = snap.payload.doc.data();
const doc = snap.payload.doc;
return {id, ...data, doc};
});
// if prepending, reverse array
values = this.query.prepend ? values.reverse() : values;
// update source with new values, done loading
this._data.next(values);
// istanbul ignore next
if (!this.appConfig.isUnitTest) {
// I do not want to add 'tick(x)' to all of end of unit test cases just for loading bar
this.loadingBar.complete();
}
this.loading.next(false);
// no more values, mark done
if (!values.length) {
this.done.next(true);
}
}))
.pipe(take(1))
.subscribe();
}
}
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