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/**
* Tracks frequency of occurances based on `id` (remote address), then allows or
* denies command execution based on comparison with `threshold`
*
* Version: v2.0.0
* Developer: Marzavec ( https://github.com/marzavec )
* License: WTFPL ( http://www.wtfpl.net/txt/copying/ )
*
*/
class RateLimiter {
/**
* Create a ratelimiter instance.
*/
constructor () {
this.records = {};
this.halflife = 30 * 1000; // milliseconds
this.threshold = 25;
this.hashes = [];
}
/**
* Finds current score by `id`
*
* @param {String} id target id / address
*
* @return {Object} Object containing the record meta
*/
search (id) {
let record = this.records[id];
if (!record) {
record = this.records[id] = {
time: Date.now(),
score: 0
}
}
return record;
}
/**
* Adjusts the current ratelimit score by `deltaScore`
*
* @param {String} id target id / address
* @param {Number} deltaScore amount to adjust current score by
*
* @return {Boolean} True if record threshold has been exceeded
*/
frisk (id, deltaScore) {
let record = this.search(id);
if (record.arrested) {
return true;
}
record.score *= Math.pow(2, -(Date.now() - record.time ) / this.halflife);
record.score += deltaScore;
record.time = Date.now();
if (record.score >= this.threshold) {
return true;
}
return false;
}
/**
* Statically set server to no longer accept traffic from `id`
*
* @param {String} id target id / address
*/
arrest (id, hash) {
let record = this.search(id);
record.arrested = true;
this.hashes[hash] = id;
}
/**
* Remove statically assigned limit from `id`
*
* @param {String} id target id / address
*/
pardon (id) {
if (typeof this.hashes[id] !== 'undefined') {
id = this.hashes[id];
}
let record = this.search(id);
record.arrested = false;
}
}
module.exports = RateLimiter;
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