@croct/cache/staleWhileRevalidate.js

An abstraction layer for caching.

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.StaleWhileRevalidateCache = void 0;
const time_1 = require("@croct/time");
const defaultClockProvider_1 = require("@croct/time/defaultClockProvider");
class StaleWhileRevalidateCache {
    constructor(config) {
        this.cacheProvider = config.cacheProvider;
        this.freshPeriod = config.freshPeriod;
        this.clock = config.clock ?? defaultClockProvider_1.DefaultClockProvider.getClock();
        this.errorHandler = config.errorHandler ?? (() => { });
    }
    async get(key, loader) {
        const now = time_1.Instant.now(this.clock);
        const retrieveAndSave = async () => {
            const entry = {
                value: await loader(key),
                timestamp: now,
            };
            await this.cacheProvider.set(key, entry);
            return entry;
        };
        const possiblyStaleEntry = await this.cacheProvider.get(key, retrieveAndSave);
        if (now.isAfter(possiblyStaleEntry.timestamp.plusSeconds(this.freshPeriod))) {
            // If expired revalidate on the background and return cached value
            retrieveAndSave().catch(this.errorHandler);
        }
        return possiblyStaleEntry.value;
    }
    set(key, value) {
        return this.cacheProvider.set(key, {
            value: value,
            timestamp: time_1.Instant.now(this.clock),
        });
    }
    delete(key) {
        return this.cacheProvider.delete(key);
    }
}
exports.StaleWhileRevalidateCache = StaleWhileRevalidateCache;