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// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
import Foundation
public protocol PopupThrottler {
func canShowAlert(type: PopupType) -> Bool
func willShowAlert(type: PopupType)
}
public enum PopupType: Sendable {
/// Javascript alert()
case alert
/// Popup window (window.open)
case popupWindow
/// Max consecutive popups allowed within a given time period (below)
/// after which throttling begins.
var maxPopupThreshold: Int {
switch self {
case .alert: return 5
case .popupWindow: return 2
}
}
/// The time within which the popup threshold may be reached. After this
/// many seconds since the first alert, the time and alert count are reset.
var resetTime: TimeInterval {
switch self {
case .alert: return 20
case .popupWindow: return 2
}
}
public static let defaultResetTimes = [PopupType.alert: PopupType.alert.resetTime,
PopupType.popupWindow: PopupType.popupWindow.resetTime]
}
/// Utility for tracking various types of popups that may be presented
/// over a short time. Used to prevent Javascript abuse or DOS attacks.
public final class DefaultPopupThrottler: PopupThrottler {
private var alertCount = [PopupType.alert: 0, PopupType.popupWindow: 0]
private var lastAlertDate = [PopupType.alert: Date.distantPast, PopupType.popupWindow: Date.distantPast]
private let resetTime: [PopupType: TimeInterval]
public init(resetTime: [PopupType: TimeInterval] = PopupType.defaultResetTimes) {
self.resetTime = resetTime
}
// MARK: - Public API
public func canShowAlert(type: PopupType) -> Bool {
guard let count = alertCount[type] else { return true }
guard let date = lastAlertDate[type] else { return true }
guard let time = resetTime[type] else { return true }
let alertCountOK = count < type.maxPopupThreshold
let timeOK = date.timeIntervalSinceNow < (time * -1.0)
return alertCountOK || timeOK
}
public func willShowAlert(type: PopupType) {
guard let count = alertCount[type] else { return }
guard let date = lastAlertDate[type] else { return }
guard let time = resetTime[type] else { return }
let timeSinceLastAlert = date.timeIntervalSinceNow * -1.0
if timeSinceLastAlert >= time {
// Our reasonable time limit has passed, which means we can reset our
// alert count and allow any further alerts.
alertCount[type] = 1
lastAlertDate[type] = Date()
} else {
alertCount[type] = count + 1
}
}
}