@virtualstate/navigation/esnext/state/state.js

Native JavaScript [navigation](https://developer.mozilla.org/en-US/docs/Web/API/Navigation_API) implementation

import { getNavigation } from "../get-navigation.js";
import { Push } from "@virtualstate/promise";
import { isPromise, ok } from "../is.js";
export function setState(state, navigation = getNavigation()) {
    const currentEntryChangePromise = new Promise(resolve => {
        navigation.addEventListener("currententrychange", resolve, { once: true });
    });
    const returned = navigation.updateCurrentEntry({
        state
    });
    const promises = [currentEntryChangePromise];
    if (isPromise(returned)) {
        promises.push(returned);
    }
    return Promise.all(promises);
}
export function getState(navigation = getNavigation()) {
    return navigation.currentEntry.getState();
}
const states = new WeakMap();
export function state(navigation = getNavigation()) {
    const existing = states.get(navigation);
    // Using a stable object for a navigation instance
    // allows for this state object to be used in memo'd functions
    if (isExisting(existing)) {
        return existing;
    }
    // Returning an object like this allows callers to bind
    // a navigation to the stateGenerator function, each time
    // a new asyncIterator is created, the transition or currentEntry
    // at that point will be used, meaning that this object
    // too can be freely used as a static source across
    // an application.
    const result = {
        [Symbol.asyncIterator]() {
            return stateGenerator(navigation);
        }
    };
    states.set(navigation, result);
    return result;
    function isExisting(existing) {
        return !!existing;
    }
}
export async function* stateGenerator(navigation = getNavigation()) {
    let lastState = undefined, wasState = false;
    let currentEntry = navigation.currentEntry;
    if (navigation.transition) {
        currentEntry = await navigation.transition?.finished;
    }
    const push = new Push();
    ok(currentEntry, "Expected a currentEntry");
    pushState();
    navigation.addEventListener("navigate", onNavigate);
    navigation.addEventListener("navigatesuccess", onNavigateSuccess);
    navigation.addEventListener("navigateerror", onNavigateError, { once: true });
    navigation.addEventListener("currententrychange", pushState);
    currentEntry.addEventListener("dispose", close, { once: true });
    yield* push;
    function pushState() {
        if (navigation.currentEntry.id !== currentEntry.id) {
            return close();
        }
        const state = currentEntry.getState();
        if (wasState || typeof state !== "undefined") {
            if (lastState === state) {
                return;
            }
            push.push(state);
            lastState = state;
            wasState = true;
        }
    }
    function onNavigate(event) {
        // Indicate that we have intercepted navigation
        // and are using it as a state tracker
        event.intercept?.({
            handler: () => Promise.resolve()
        });
    }
    function onNavigateSuccess() {
        if (navigation.currentEntry.id !== currentEntry.id) {
            close();
        }
    }
    function onNavigateError(event) {
        const { error } = event;
        push.throw(error);
    }
    function close() {
        navigation.removeEventListener("navigate", onNavigate);
        navigation.removeEventListener("navigatesuccess", onNavigateSuccess);
        navigation.removeEventListener("navigateerror", onNavigateError);
        navigation.removeEventListener("currententrychange", pushState);
        currentEntry.removeEventListener("dispose", close);
        push.close();
    }
}
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