shelving/store/EndpointStore.js

Toolkit for using data in JavaScript.

import { MINUTE, NONE } from "../util/constants.js";
import { isDeepEqual } from "../util/equal.js";
import { Store } from "./Store.js";
/**
 * Store object that loads a result from an API endpoint and manages its state.
 *
 * @todo Needs support for `EndpointOptions` to set headers etc.
 */
export class EndpointStore extends Store {
    static CANCELLED = Symbol("CANCELLED");
    endpoint;
    _payload;
    _abort = undefined;
    get payload() {
        return this._payload;
    }
    set payload(next) {
        const current = this._payload;
        // Did the payload actually change?
        if (!isDeepEqual(current, next)) {
            this._payload = next;
            // If there's already a fetch in progress, cancel it.
            if (this._abort) {
                this._abort.abort(EndpointStore.CANCELLED);
                this._abort = undefined;
            }
            // Trigger a fetch.
            this._call();
        }
    }
    /** Maximum age data can be before a fetch is triggered (defaults to 5 minutes). */
    maxAge = 5 * MINUTE;
    // Override to possibly trigger a fetch when value is read.
    get value() {
        // Queue `this.call()` if...
        // 1. Value is still loading.
        // 2. Value is stale (older than maxAge).
        if (this.loading || this.age > this.maxAge)
            if (!this.reason)
                this._call();
        return super.value;
    }
    set value(value) {
        super.value = value;
    }
    constructor(endpoint, payload) {
        super(NONE);
        this.endpoint = endpoint;
        this.payload = payload;
    }
    refetch() {
        return this._call();
    }
    /** Call the API now to fetch the data. */
    async _call() {
        if (this._abort)
            return; // Already fetching.
        this.reason = undefined; // Optimistically clear any error.
        try {
            this._abort = new AbortController();
            const value = await this.endpoint.fetch(this._payload, { signal: this._abort.signal });
            this.value = value;
        }
        catch (thrown) {
            console.error(thrown);
            if (thrown === EndpointStore.CANCELLED)
                return; // Cancelled on purpose.
            this.reason = thrown;
        }
        finally {
            this._abort = undefined;
        }
    }
}