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Add support for per-model Sync Data Providers initialization (#433)
Task/Issue URL: https://app.asana.com/0/0/1205093266805582/f Rework Sync initialization mechanism by moving sync data models initialization from DDGSync (where it was tied to account signup/login flow) to data models themselves. Sync Metadata is leveraged to store sync setup state per data model. Two values are possible: needs remote data fetch (a.k.a initial sync) or ready to sync. Decoupling account flow from data models initialization allows to initialize data models independently of user turning on sync, which is a requirement to support initial sync for new syncable models added with client app updates. Also DataProvider class has been added – it's a dedicated sync data providers superclass that also encapsulates common logic, making individual data providers simpler.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,241 @@ | ||
| // | ||
| // DataProvider.swift | ||
| // DuckDuckGo | ||
| // | ||
| // Copyright © 2023 DuckDuckGo. All rights reserved. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); | ||
| // you may not use this file except in compliance with the License. | ||
| // You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, | ||
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| // See the License for the specific language governing permissions and | ||
| // limitations under the License. | ||
| // | ||
|
|
||
| import Foundation | ||
| import Combine | ||
|
|
||
| /** | ||
| * Defines sync feature, i.e. type of synced data. | ||
| */ | ||
| public struct Feature: Hashable { | ||
| public var name: String | ||
|
|
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| public init(name: String) { | ||
| self.name = name | ||
| } | ||
| } | ||
|
|
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| /** | ||
| * Defines sync feature's setup state. | ||
| */ | ||
| public enum FeatureSetupState: String { | ||
| /// This value denotes a state where a feature requires "initial sync" to be performed, | ||
| /// i.e. fetching remote data and merging it with local, with data deduplication as needed. | ||
| case needsRemoteDataFetch | ||
| /// Default value where feature is included in regular sync | ||
| case readyToSync | ||
| } | ||
|
|
||
| /** | ||
| * Describes a data model that is supported by Sync. | ||
| * | ||
| * Any data model that is passed to Sync is supposed to be encrypted as needed. | ||
| */ | ||
| public struct Syncable { | ||
| public var payload: [String: Any] | ||
|
|
||
| public init(jsonObject: [String: Any]) { | ||
| payload = jsonObject | ||
| } | ||
| } | ||
|
|
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| /** | ||
| * Describes data source for objects to be synced with the server. | ||
| * | ||
| * This protocol should not be implemented from scratch. Instead, clients should | ||
| * inherit `DataProvider` abstract class which implements this protocol partially, | ||
| * only leaving syncable data management functions to be implemented: | ||
| * - `prepareForFirstSync` | ||
| * - `fetchChangedObjects` | ||
| * - `handleInitialSyncResponse` | ||
| * - `handleSyncResponse` | ||
| */ | ||
| public protocol DataProviding: AnyObject { | ||
|
|
||
| /** | ||
| * Feature that is supported by this provider. | ||
| * | ||
| * This is passed to `GET /{types_csv}`. | ||
| */ | ||
| var feature: Feature { get } | ||
|
|
||
| /** | ||
| * Describes feature's sync setup state and defines the behavior of a feature in Sync Operation. | ||
| * | ||
| * Regular sync flow consists of sending local changes (if exists) to the server, receiving server | ||
| * response with remote changes, and applying these changes locally. | ||
| * | ||
| * Sometimes a syncable model has to go through a setup phase (a.k.a. initial sync) before it's ready | ||
| * to be synced the regular way. Initial sync starts with remote data being fetched from the server | ||
| * and merged with local data (applying deduplication as needed). After that, the model is ready | ||
| * for regular sync. This happens for: | ||
| * - newly added features – when a new app release adds a new syncable model, | ||
| * - all features – when adding a device to an existing Sync account. | ||
| */ | ||
| var featureSyncSetupState: FeatureSetupState { get } | ||
|
|
||
| /** | ||
| * Returns a boolean value stating whether a feature is locally registered with Sync. | ||
| * | ||
| * All features are registered when Sync is turned on. Additionally, when the app is updated | ||
| * to a new version that adds a new syncable model, feature representing that model is | ||
| * also automatically registered. Newly registered features may require special handling | ||
| * (a.k.a. initial sync). | ||
| */ | ||
| var isFeatureRegistered: Bool { get } | ||
|
|
||
| /** | ||
| * Registers feature with Sync using provided `setupState`. | ||
| * | ||
| * This function stores feature metadata in Sync Metadata Store and enables feature to be synced. | ||
| */ | ||
| func registerFeature(withState setupState: FeatureSetupState) throws | ||
|
|
||
| /** | ||
| * Deregisters feature. | ||
| * | ||
| * This function removes feature metadata from Sync Metadata Store, effectively disabling Sync | ||
| * for the feature. Deregistered feature needs to be registered again in order to be included | ||
| * in Sync (which will cause initial sync with data merging and deduplication). | ||
| */ | ||
| func deregisterFeature() throws | ||
|
|
||
| /** | ||
| * Time of last successful sync of a given feature. | ||
| * | ||
| * Note that it's a String as this is the server timestamp and should not be treated as date | ||
| * and as such used in comparing timestamps. It's merely an identifier of the last sync operation. | ||
| */ | ||
| var lastSyncTimestamp: String? { get } | ||
|
|
||
| /** | ||
| * Prepare data models for first sync. | ||
| * | ||
| * This function is called before the initial sync is performed. | ||
| */ | ||
| func prepareForFirstSync() throws | ||
|
|
||
| /** | ||
| * Return objects that have changed since last sync, or all objects in case of the initial sync. | ||
| */ | ||
| func fetchChangedObjects(encryptedUsing crypter: Crypting) async throws -> [Syncable] | ||
|
|
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| /** | ||
| * Apply initial sync operation response. | ||
| * | ||
| * - Parameter received: Objects that were received from the server. | ||
| * - Parameter clientTimestamp: Local timestamp of the sync network request. | ||
| * - Parameter serverTimestamp: Server timestamp describing server data validity. | ||
| * - Parameter crypter: Crypter object to decrypt received data. | ||
| */ | ||
| func handleInitialSyncResponse(received: [Syncable], clientTimestamp: Date, serverTimestamp: String?, crypter: Crypting) async throws | ||
|
|
||
| /** | ||
| * Apply sync operation result. | ||
| * | ||
| * - Parameter sent: Objects that were sent to the server. | ||
| * - Parameter received: Objects that were received from the server. | ||
| * - Parameter clientTimestamp: Local timestamp of the sync network request. | ||
| * - Parameter serverTimestamp: Server timestamp describing server data validity. | ||
| * - Parameter crypter: Crypter object to decrypt sent and received data. | ||
| */ | ||
| func handleSyncResponse(sent: [Syncable], received: [Syncable], clientTimestamp: Date, serverTimestamp: String?, crypter: Crypting) async throws | ||
|
|
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| /** | ||
| * Called when sync operation fails. | ||
| * | ||
| * - Parameter error: Sync operation error. | ||
| */ | ||
| func handleSyncError(_ error: Error) | ||
| } | ||
|
|
||
| /** | ||
| * Base class for Sync data providers. | ||
| * | ||
| * Clients should subclass this class to implement data providers for syncable data models. | ||
| * New data provider must implement functions declared as `open`, without calling super. | ||
| */ | ||
| open class DataProvider: DataProviding { | ||
|
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| public let feature: Feature | ||
| public let syncDidUpdateData: () -> Void | ||
| public let syncErrorPublisher: AnyPublisher<Error, Never> | ||
|
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| public var isFeatureRegistered: Bool { | ||
| metadataStore.isFeatureRegistered(named: feature.name) | ||
| } | ||
|
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| public func registerFeature(withState setupState: FeatureSetupState) throws { | ||
| try metadataStore.registerFeature(named: feature.name, setupState: setupState) | ||
| } | ||
|
|
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| public func deregisterFeature() throws { | ||
| try metadataStore.deregisterFeature(named: feature.name) | ||
| } | ||
|
|
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| public var featureSyncSetupState: FeatureSetupState { | ||
| metadataStore.state(forFeatureNamed: feature.name) | ||
| } | ||
|
|
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| public var lastSyncTimestamp: String? { | ||
| get { | ||
| metadataStore.timestamp(forFeatureNamed: feature.name) | ||
| } | ||
| set { | ||
| if newValue == nil { | ||
| metadataStore.updateTimestamp(nil, forFeatureNamed: feature.name) | ||
| } else { | ||
| metadataStore.update(newValue, .readyToSync, forFeatureNamed: feature.name) | ||
| } | ||
| } | ||
| } | ||
|
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| public init(feature: Feature, metadataStore: SyncMetadataStore, syncDidUpdateData: @escaping () -> Void) { | ||
| self.feature = feature | ||
| self.metadataStore = metadataStore | ||
| self.syncDidUpdateData = syncDidUpdateData | ||
| self.syncErrorPublisher = syncErrorSubject.eraseToAnyPublisher() | ||
| } | ||
|
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| open func prepareForFirstSync() throws { | ||
| assertionFailure("\(#function) is not implemented") | ||
| } | ||
|
|
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| open func fetchChangedObjects(encryptedUsing crypter: Crypting) async throws -> [Syncable] { | ||
| assertionFailure("\(#function) is not implemented") | ||
| return [] | ||
| } | ||
|
|
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| open func handleInitialSyncResponse(received: [Syncable], clientTimestamp: Date, serverTimestamp: String?, crypter: Crypting) async throws { | ||
| assertionFailure("\(#function) is not implemented") | ||
| } | ||
|
|
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| open func handleSyncResponse(sent: [Syncable], received: [Syncable], clientTimestamp: Date, serverTimestamp: String?, crypter: Crypting) async throws { | ||
| assertionFailure("\(#function) is not implemented") | ||
| } | ||
|
|
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| public func handleSyncError(_ error: Error) { | ||
| syncErrorSubject.send(error) | ||
| } | ||
|
|
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| // MARK: - Private | ||
|
|
||
| private let syncErrorSubject = PassthroughSubject<Error, Never>() | ||
| private let metadataStore: SyncMetadataStore | ||
| } |
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