116 lines
3.3 KiB
Swift
116 lines
3.3 KiB
Swift
//
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// Copyright 2023 Signal Messenger, LLC
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// SPDX-License-Identifier: AGPL-3.0-only
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//
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import Foundation
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/// An interface for fetching and storing usernames. Note that with the
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/// exception of the local user, any stored data about an account's username is
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/// only as fresh as the last time we looked it up - usernames should be
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/// considered transient.
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public protocol UsernameLookupManager {
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typealias ACI = UUID
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typealias Username = String
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/// Fetch the most recently-known username for the given ACI, if any.
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func fetchUsername(
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forAci aci: ACI,
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transaction: DBReadTransaction
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) -> Username?
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/// Fetch usernames for the given addresses, returning an array with a
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/// username corresponding to each passed address, if one is available.
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func fetchUsernames(
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forAddresses addresses: AnySequence<SignalServiceAddress>,
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transaction: DBReadTransaction
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) -> [Username?]
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/// Save the given username, or lack thereof, for the given ACI.
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func saveUsername(
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_ username: Username?,
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forAci aci: ACI,
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transaction: DBWriteTransaction
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)
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}
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/// A ``UsernameLookupManager`` implementation that uses on-disk persistence
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/// paired with an in-memory cache.
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class UsernameLookupManagerImpl: UsernameLookupManager {
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private enum CachedLookupResult {
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case found(username: Username)
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case notFound
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var usernameValue: Username? {
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switch self {
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case let .found(username):
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return username
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case .notFound:
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return nil
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}
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}
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}
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// MARK: - Init
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private let cachedLookups: AtomicDictionary<ACI, CachedLookupResult>
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init() {
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cachedLookups = .init(lock: .init())
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}
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// MARK: - UsernameLookupManager
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func fetchUsername(
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forAci aci: ACI,
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transaction: DBReadTransaction
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) -> Username? {
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if let cachedLookup = cachedLookups[aci] {
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return cachedLookup.usernameValue
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}
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if let persistedUsername = UsernameLookupRecord.fetchOne(
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forAci: aci,
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transaction: SDSDB.shimOnlyBridge(transaction)
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)?.username {
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cachedLookups[aci] = .found(username: persistedUsername)
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return persistedUsername
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}
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cachedLookups[aci] = .notFound
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return nil
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}
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func fetchUsernames(
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forAddresses addresses: AnySequence<SignalServiceAddress>,
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transaction: DBReadTransaction
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) -> [Username?] {
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addresses.map { address -> Username? in
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guard let aci = address.uuid else { return nil }
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return fetchUsername(forAci: aci, transaction: transaction)
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}
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}
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func saveUsername(
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_ username: Username?,
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forAci aci: ACI,
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transaction: DBWriteTransaction
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) {
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if let username {
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cachedLookups[aci] = .found(username: username)
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UsernameLookupRecord(aci: aci, username: username)
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.upsert(transaction: SDSDB.shimOnlyBridge(transaction))
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} else {
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cachedLookups[aci] = .notFound
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UsernameLookupRecord.deleteOne(
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forAci: aci,
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transaction: SDSDB.shimOnlyBridge(transaction)
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)
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}
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}
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}
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