// Copyright: Ankitects Pty Ltd and contributors
// License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html

/* eslint
@typescript-eslint/no-non-null-assertion: "off",
*/

import type { Writable, Subscriber, Unsubscriber, Updater } from "svelte/store";
import { noop } from "../lib/functional";

export interface NodeStore<T extends Node> extends Writable<T> {
    setUnprocessed(node: T): void;
}

export function nodeStore<T extends Node>(
    node?: T,
    preprocess: (node: T) => void = noop,
): NodeStore<T> {
    const subscribers: Set<Subscriber<T>> = new Set();

    function setUnprocessed(newNode: T): void {
        if (!node || !node.isEqualNode(newNode)) {
            node = newNode;

            for (const subscriber of subscribers) {
                subscriber(node);
            }
        }
    }

    function set(newNode: T): void {
        preprocess(newNode);
        setUnprocessed(newNode);
    }

    function update(fn: Updater<T>): void {
        set(fn(node!));
    }

    function subscribe(subscriber: Subscriber<T>): Unsubscriber {
        subscribers.add(subscriber);

        if (node) {
            subscriber(node);
        }

        return () => subscribers.delete(subscriber);
    }

    return { set, setUnprocessed, update, subscribe };
}

export default nodeStore;