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//
// RelayCacheIO.swift
// RelayCacheIO
//
// Created by pronebird on 27/07/2021.
// Copyright © 2021 Mullvad VPN AB. All rights reserved.
//
import Foundation
extension RelayCache {
enum IO {}
}
extension RelayCache.IO {
/// The default cache file location bound by app group container.
static func defaultCacheFileURL(
forSecurityApplicationGroupIdentifier appGroupIdentifier: String
) -> URL? {
let containerURL = FileManager.default.containerURL(
forSecurityApplicationGroupIdentifier: appGroupIdentifier
)
return containerURL?.appendingPathComponent("relays.json")
}
/// The path to pre-bundled `relays.json` file.
static var preBundledRelaysFileURL: URL? {
return Bundle.main.url(forResource: "relays", withExtension: "json")
}
/// Safely read the cache file from disk using file coordinator.
static func read(cacheFileURL: URL) throws -> RelayCache.CachedRelays {
var result: Result<RelayCache.CachedRelays, RelayCache.Error>?
let fileCoordinator = NSFileCoordinator(filePresenter: nil)
let accessor = { (fileURLForReading: URL) -> Void in
// Decode data from disk
do {
let data = try Data(contentsOf: fileURLForReading)
let relays = try JSONDecoder().decode(RelayCache.CachedRelays.self, from: data)
result = .success(relays)
} catch let error as DecodingError {
result = .failure(.decodeCache(error))
} catch {
result = .failure(.readCache(error))
}
}
var error: NSError?
fileCoordinator.coordinate(readingItemAt: cacheFileURL,
options: [.withoutChanges],
error: &error,
byAccessor: accessor)
if let error = error {
result = .failure(.readCache(error))
}
return try result!.get()
}
/// Safely read the cache file from disk using file coordinator and fallback to prebundled
/// relays in case if the relay cache file is missing.
static func readWithFallback(cacheFileURL: URL, preBundledRelaysFileURL: URL)
throws -> RelayCache.CachedRelays
{
do {
return try Self.read(cacheFileURL: cacheFileURL)
} catch {
let error = error as! RelayCache.Error
switch error {
case .decodeCache, .readCache(CocoaError.fileReadNoSuchFile):
return try RelayCache.IO.readPrebundledRelays(fileURL: preBundledRelaysFileURL)
default:
throw error
}
}
}
/// Read pre-bundled relays file from disk.
static func readPrebundledRelays(fileURL: URL) throws -> RelayCache.CachedRelays {
do {
let data = try Data(contentsOf: fileURL)
let relays = try REST.Coding.makeJSONDecoder()
.decode(REST.ServerRelaysResponse.self, from: data)
return RelayCache.CachedRelays(
relays: relays,
updatedAt: Date(timeIntervalSince1970: 0)
)
} catch let error as DecodingError {
throw RelayCache.Error.decodePrebundledRelays(error)
} catch {
throw RelayCache.Error.readPrebundledRelays(error)
}
}
/// Safely write the cache file on disk using file coordinator.
static func write(cacheFileURL: URL, record: RelayCache.CachedRelays) throws {
var resultError: RelayCache.Error?
let fileCoordinator = NSFileCoordinator(filePresenter: nil)
let accessor = { (fileURLForWriting: URL) -> Void in
do {
let data = try JSONEncoder().encode(record)
try data.write(to: fileURLForWriting)
} catch let error as EncodingError {
resultError = .encodeCache(error)
} catch {
resultError = .writeCache(error)
}
}
var error: NSError?
fileCoordinator.coordinate(writingItemAt: cacheFileURL,
options: [.forReplacing],
error: &error,
byAccessor: accessor)
if let resultError = resultError {
throw resultError
}
}
}
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