map-age-cleaner/dist/index.js

Automatically cleanup expired items in a Map

"use strict";
const pDefer = require("p-defer");
function mapAgeCleaner(map, property = 'maxAge') {
    let processingKey;
    let processingTimer;
    let processingDeferred;
    const cleanup = async () => {
        if (processingKey !== undefined) {
            // If we are already processing an item, we can safely exit
            return;
        }
        const setupTimer = async (item) => {
            processingDeferred = pDefer();
            const delay = item[1][property] - Date.now();
            if (delay <= 0) {
                // Remove the item immediately if the delay is equal to or below 0
                map.delete(item[0]);
                processingDeferred.resolve();
                return;
            }
            // Keep track of the current processed key
            processingKey = item[0];
            processingTimer = setTimeout(() => {
                // Remove the item when the timeout fires
                map.delete(item[0]);
                if (processingDeferred) {
                    processingDeferred.resolve();
                }
            }, delay);
            // tslint:disable-next-line:strict-type-predicates
            if (typeof processingTimer.unref === 'function') {
                // Don't hold up the process from exiting
                processingTimer.unref();
            }
            return processingDeferred.promise;
        };
        try {
            for (const entry of map) {
                await setupTimer(entry);
            }
        }
        catch (_a) {
            // Do nothing if an error occurs, this means the timer was cleaned up and we should stop processing
        }
        processingKey = undefined;
    };
    const reset = () => {
        processingKey = undefined;
        if (processingTimer !== undefined) {
            clearTimeout(processingTimer);
            processingTimer = undefined;
        }
        if (processingDeferred !== undefined) { // tslint:disable-line:early-exit
            processingDeferred.reject(undefined);
            processingDeferred = undefined;
        }
    };
    const originalSet = map.set.bind(map);
    map.set = (key, value) => {
        if (map.has(key)) {
            // If the key already exist, remove it so we can add it back at the end of the map.
            map.delete(key);
        }
        // Call the original `map.set`
        const result = originalSet(key, value);
        // If we are already processing a key and the key added is the current processed key, stop processing it
        if (processingKey && processingKey === key) {
            reset();
        }
        // Always run the cleanup method in case it wasn't started yet
        cleanup(); // tslint:disable-line:no-floating-promises
        return result;
    };
    cleanup(); // tslint:disable-line:no-floating-promises
    return map;
}
module.exports = mapAgeCleaner;