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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
protocol FaviconURLCache {
func getURLFromCache(cacheKey: String) async throws -> URL
func cacheURL(cacheKey: String, faviconURL: URL) async
func clearCache() async
}
actor DefaultFaviconURLCache: FaviconURLCache {
private enum CacheConstants {
static let cacheKey = "favicon-url-cache"
static let daysToExpiration = 30
}
static let shared = DefaultFaviconURLCache()
private let fileManager: URLCacheFileManager
private var urlCache = [String: FaviconURL]()
private var preserveTask: Task<Void, Never>?
private let preserveDebounceTime: UInt64 = 10_000_000_000 // 10 seconds
init(fileManager: URLCacheFileManager = DefaultURLCacheFileManager()) {
self.fileManager = fileManager
Task {
await retrieveCache()
}
}
func getURLFromCache(cacheKey: String) async throws -> URL {
guard let favicon = urlCache[cacheKey],
let url = URL(string: favicon.faviconURL, invalidCharacters: false)
else { throw SiteImageError.noURLInCache }
// Update the element in the cache so it's time to expire is reset
// We don't need to wait for this to finish
Task {
await cacheURL(cacheKey: cacheKey, faviconURL: url)
}
return url
}
func cacheURL(cacheKey: String, faviconURL: URL) async {
let favicon = FaviconURL(cacheKey: cacheKey,
faviconURL: faviconURL.absoluteString,
createdAt: Date())
urlCache[cacheKey] = favicon
preserveCache()
}
func clearCache() async {
urlCache = [String: FaviconURL]()
preserveCache()
}
private func preserveCache() {
preserveTask?.cancel()
preserveTask = Task {
try? await Task.sleep(nanoseconds: preserveDebounceTime)
guard !Task.isCancelled,
let data = archiveCacheData()
else { return }
await fileManager.saveURLCache(data: data)
}
}
private func archiveCacheData() -> Data? {
let cacheArray = urlCache.map { _, value in return value }
let archiver = NSKeyedArchiver(requiringSecureCoding: false)
do {
try archiver.encodeEncodable(cacheArray, forKey: CacheConstants.cacheKey)
} catch {
// Intentionally ignoring failure, a fail to save
// is not catastrophic and the cache can always be rebuilt
}
return archiver.encodedData
}
private func retrieveCache() async {
guard let data = await fileManager.getURLCache(),
let unarchiver = try? NSKeyedUnarchiver(forReadingFrom: data),
let cacheList = unarchiver.decodeDecodable([FaviconURL].self, forKey: CacheConstants.cacheKey)
else {
// Intentionally ignoring failure, a fail to retrieve
// is not catastrophic and the cache can always be rebuilt
return
}
// Ignore elements that are past the expiration time
let today = Date()
urlCache = cacheList.reduce(into: [String: FaviconURL]()) {
if numberOfDaysBetween(start: $1.createdAt, end: today) >= CacheConstants.daysToExpiration {
return
}
$0[$1.cacheKey] = $1
}
}
private func numberOfDaysBetween(start: Date, end: Date) -> Int {
let calendar = NSCalendar.current
let startDate = calendar.startOfDay(for: start)
let endDate = calendar.startOfDay(for: end)
let numberOfDays = calendar.dateComponents([.day], from: startDate, to: endDate)
return numberOfDays.day ?? 0
}
}