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import { PromiseOrValue } from "@implab/core-amd/interfaces";
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import { isPromise } from "@implab/core-amd/safe";
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import { observe, Observable } from "./observable";
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export interface OrderedUpdate<T> {
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/** The item is being updated */
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readonly item: T;
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/** The previous index of the item, -1 in case it is inserted */
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readonly prevIndex: number;
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/** The new index of the item, -1 in case it is deleted */
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readonly newIndex: number;
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}
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export type QueryResults<T> = Observable<OrderedUpdate<T>>;
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interface DjObservableResults<T> {
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/**
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* Allows observation of results
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*/
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observe(listener: (object: T, previousIndex: number, newIndex: number) => void, includeUpdates?: boolean): {
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remove(): void;
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};
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}
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interface Queryable<T, Q, O> {
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query(query?: Q, options?: O): PromiseOrValue<T[]>;
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}
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export const isDjObservableResults = <T>(v: object): v is DjObservableResults<T> =>
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v && (typeof (v as { observe?: unknown; }).observe === "function");
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export const query = <T, Q, O>(store: Queryable<T, Q, O>, includeUpdates = true) =>
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(query?: Q, options?: O & { observe?: boolean }) => {
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return observe<OrderedUpdate<T>>(({ next, complete, error, isClosed }) => {
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const processResults = (items: T[]) =>
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items.forEach((item, newIndex) => next({ item, newIndex, prevIndex: -1 }));
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try {
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const results = store.query(query, options);
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if (isPromise(results)) {
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results.then(processResults).then(undefined, error);
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} else {
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processResults(results);
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}
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if (!isClosed() && (options?.observe !== false) && isDjObservableResults<T>(results)) {
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const h = results.observe((item, prevIndex, newIndex) => next({ item, prevIndex, newIndex }), includeUpdates);
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return () => h.remove();
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} else {
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complete();
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}
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} catch (err) {
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error(err);
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}
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});
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};
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