@platform/state/lib/TreeState/TreeState.sync.mjs

A small, simple, strongly typed, [rx/observable] state-machine.

import { Subject } from 'rxjs';
import { filter, map, takeUntil } from 'rxjs/operators';
export function syncFrom(args) {
    const { target } = args;
    const parent = (args.parent || '').trim();
    if (!parent) {
        const err = `Cannot sync: parent node not specified.`;
        throw new Error(err);
    }
    if (!target.query.exists(parent)) {
        const err = `Cannot sync: the parent node '${parent}' does not exist in tree '${target.id}'.`;
        throw new Error(err);
    }
    const dispose$ = new Subject();
    const dispose = () => {
        dispose$.next();
        dispose$.complete();
    };
    target.dispose$.subscribe(() => dispose());
    if (args.until$) {
        args.until$.subscribe(() => dispose());
    }
    const source$ = args.source$.pipe(takeUntil(dispose$), filter((e) => e.type === 'TreeState/changed'), map((e) => e.payload));
    const change = (to) => {
        target.change((draft, ctx) => {
            const node = ctx.findById(parent);
            if (node) {
                ctx.children(node, (children) => {
                    const index = children.findIndex((child) => child.id === to.id);
                    if (index === -1) {
                        children.push(to);
                    }
                    else {
                        children[index] = to;
                    }
                });
            }
        });
    };
    if (args.initial) {
        change(args.initial);
    }
    source$.subscribe((e) => {
        change(e.to);
    });
    const syncer = {
        parent,
        get isDisposed() {
            return dispose$.isStopped;
        },
        dispose$,
        dispose,
    };
    return syncer;
}