rate-keeper/dist/index.js

A lightweight utility for easily adding rate limiting to functions, ideal for preventing API rate limit violations.

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.DropPolicy = void 0;
exports.default = RateKeeper;
const globalRateData = new Map();
/**
 * @enum {DropPolicy} Defines the behavior of the queue when the maximum size has been reached.
 */
var DropPolicy;
(function (DropPolicy) {
    DropPolicy[DropPolicy["Reject"] = 0] = "Reject";
    DropPolicy[DropPolicy["DropOldest"] = 1] = "DropOldest";
})(DropPolicy || (exports.DropPolicy = DropPolicy = {}));
class LimitData {
    constructor(settings) {
        this.queue = [];
        this.timer = null;
        this.settings = settings;
    }
}
function getRateData(settings) {
    const { id } = settings;
    if (globalRateData.has(id)) {
        return globalRateData.get(id);
    }
    else {
        const newLimitData = new LimitData(settings);
        globalRateData.set(id, newLimitData);
        return newLimitData;
    }
}
/**
 * @param {(...args: Args) => Result} action The action to be rate-limited.
 * @param {number} rateLimit The minimum interval in milliseconds between each execution.
 * @param {QueueSettings} settings Optional. Queue settings for rate limiting and execution.
 * @returns {(...args: Args) => Promise<Result>} An asynchronous function that executes the action and returns a promise with the result.
 */
function RateKeeper(action, rateLimit, settings = { id: 0 }) {
    const limitData = settings.id === 0 ? new LimitData(settings) : getRateData(settings);
    function processQueue() {
        var _a, _b;
        (_b = (_a = limitData.queue.shift()) === null || _a === void 0 ? void 0 : _a.action) === null || _b === void 0 ? void 0 : _b.call(_a);
        if (limitData.queue.length === 0 && limitData.timer !== null) {
            clearInterval(limitData.timer);
            limitData.timer = null;
        }
    }
    function publicFunc(...args) {
        var _a;
        const { maxQueueSize, dropPolicy } = limitData.settings;
        let resolve;
        let reject;
        const promise = new Promise((res, rej) => {
            resolve = res;
            reject = rej;
        });
        // Handle queue size limit
        if (maxQueueSize !== undefined && limitData.queue.length >= maxQueueSize) {
            if (dropPolicy === DropPolicy.Reject) {
                // Reject new task by immediately resolving with a rejection
                return Promise.reject(new Error("Queue is at max capacity."));
            }
            else if (dropPolicy === DropPolicy.DropOldest) {
                // Drop the oldest task in the queue
                (_a = limitData.queue.shift()) === null || _a === void 0 ? void 0 : _a.reject(new Error("Queue is at max capacity."));
            }
        }
        // Add the new task to the queue
        limitData.queue.push({
            action: () => resolve(action(...args)),
            reject: (reason) => { reject(reason); }
        });
        // Start the timer if it isn’t already running
        if (limitData.timer === null) {
            processQueue();
            limitData.timer = setInterval(processQueue, rateLimit);
        }
        return promise;
    }
    return publicFunc;
}
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