The fromLiveQueryArray function is a utility function for Reactive Programming in JavaScript. It takes a Live Query, which is a special kind of query that dynamically updates as its results change, and converts it into an Observable.

from-live-query.ts

/*
 * MIT License
 * 
 * Copyright (c) 2023 James Woodall (jamesikanos@gmail.com)
 * 
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 * of this software and associated documentation files (the "Software"), to deal
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 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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 */

import { LiveQuery } from "remult";
import { Observable, map, shareReplay } from "rxjs";

/**
 * Converts a Remult Live Query into an Observable, emitting an array of values whenever the query changes
 * @param liveQuery The query to subscribe to
 * @returns An observable emitting an array of values whenever the query changes
 */
export function fromLiveQueryArray<T>(liveQuery: LiveQuery<T>): Observable<T[]> {

    return new Observable<T[]>(subscribe => {
        let items: T[] = [];

        const liveQuerySubscription = liveQuery.subscribe(next => {
            items = next.applyChanges(items);

            subscribe.next(items);
        });

        return () => {
            // Unsubscribe from the query
            liveQuerySubscription();
        };
    }).pipe(
        // Share the query, but unsubscribe when the last subscriber has left
        shareReplay({ bufferSize: 1, refCount: true })
    );
}

/**
 * Converts a Remult Live Query into an Observable, emitting the first value whenever the query changes. This is useful if you're only keeping track of a single value
 * @param liveQuery The query to subscribe to
 * @returns 
 */
export function fromLiveQueryFirst<T>(liveQuery: LiveQuery<T>): Observable<T> {
    return fromLiveQueryArray(liveQuery).pipe(map(j => j[0]));
}