Use an operation queue to renew the Reddit access token so that we don't do it multiple times in a refresh cycle

Account/Sources/Account/FeedProvider/Reddit/RedditFeedProvider.swift

@@ -10,6 +10,7 @@ import Foundation
 import os.log
 import OAuthSwift
 import Secrets
+import RSCore
 import RSParser
 import RSWeb
 
@@ -34,7 +35,7 @@ public enum RedditFeedType: Int {
 	case subreddit = 3
 }
 
-public final class RedditFeedProvider: FeedProvider {
+public final class RedditFeedProvider: FeedProvider, RedditFeedProviderTokenRefreshOperationDelegate {
 
 	var log = OSLog(subsystem: Bundle.main.bundleIdentifier!, category: "RedditFeedProvider")
 
@@ -48,14 +49,16 @@ public final class RedditFeedProvider: FeedProvider {
 		"all": NSLocalizedString("All", comment: "All")
 	]
 	
+	private let operationQueue = MainThreadOperationQueue()
 	private var parsingQueue = DispatchQueue(label: "RedditFeedProvider parse queue")
 	
 	public var username: String?
 	
-	private var oauthToken: String
+	var oauthTokenLastRefresh: Date?
-	private var oauthRefreshToken: String
+	var oauthToken: String
+	var oauthRefreshToken: String
 
-    private var oauthSwift: OAuth2Swift?
+    var oauthSwift: OAuth2Swift?
 	private var client: OAuthSwiftClient? {
 		return oauthSwift?.client
 	}
@@ -259,6 +262,13 @@ public final class RedditFeedProvider: FeedProvider {
 		return components.url
 	}
 
+	static func storeCredentials(username: String, oauthToken: String, oauthRefreshToken: String) throws {
+		let tokenCredentials = Credentials(type: .oauthAccessToken, username: username, secret: oauthToken)
+		try CredentialsManager.storeCredentials(tokenCredentials, server: Self.server)
+		let tokenSecretCredentials = Credentials(type: .oauthRefreshToken, username: username, secret: oauthRefreshToken)
+		try CredentialsManager.storeCredentials(tokenSecretCredentials, server: Self.server)
+	}
+	
 }
 
 // MARK: OAuth1SwiftProvider
@@ -412,41 +422,22 @@ private extension RedditFeedProvider {
     func handleFailure(error: OAuthSwiftError, completion: @escaping (Error?) -> Void) {
 		if case .tokenExpired = error {
 
-			os_log(.debug, log: self.log, "Access token expired, attempting to renew...")
+			let op = RedditFeedProviderTokenRefreshOperation(delegate: self)
 			
-			oauthSwift?.renewAccessToken(withRefreshToken: oauthRefreshToken) { [weak self] result in
+			op.completionBlock = { operation in
-				guard let strongSelf = self, let username = strongSelf.username else {
+				let refreshOperation = operation as! RedditFeedProviderTokenRefreshOperation
+				if let error = refreshOperation.error {
+					completion(error)
+				} else {
 					completion(nil)
-					return
-				}
-				
-				switch result {
-				case .success(let tokenSuccess):
-					strongSelf.oauthToken = tokenSuccess.credential.oauthToken
-					strongSelf.oauthRefreshToken = tokenSuccess.credential.oauthRefreshToken
-					do {
-						try Self.storeCredentials(username: username, oauthToken: strongSelf.oauthToken, oauthRefreshToken: strongSelf.oauthRefreshToken)
-						os_log(.debug, log: strongSelf.log, "Access token renewed.")
-					} catch {
-						completion(error)
-						return
-					}
-					completion(nil)
-				case .failure(let oathError):
-					completion(oathError)
 				}
 			}
 			
+			operationQueue.add(op)
+			
 		} else {
 			completion(error)
 		}
     }
 
-	static func storeCredentials(username: String, oauthToken: String, oauthRefreshToken: String) throws {
-		let tokenCredentials = Credentials(type: .oauthAccessToken, username: username, secret: oauthToken)
-		try CredentialsManager.storeCredentials(tokenCredentials, server: Self.server)
-		let tokenSecretCredentials = Credentials(type: .oauthRefreshToken, username: username, secret: oauthRefreshToken)
-		try CredentialsManager.storeCredentials(tokenSecretCredentials, server: Self.server)
-	}
-	
 }

Account/Sources/Account/FeedProvider/Reddit/RedditFeedProviderTokenRefreshOperation.swift

@@ -0,0 +1,78 @@
+//
+//  RedditFeedProviderTokenRefreshOperation.swift
+//  
+//
+//  Created by Maurice Parker on 8/12/20.
+//
+
+import Foundation
+import os.log
+import RSCore
+import OAuthSwift
+import Secrets
+
+protocol RedditFeedProviderTokenRefreshOperationDelegate: class {
+	var username: String? { get }
+	var oauthTokenLastRefresh: Date? { get set }
+	var oauthToken: String { get set }
+	var oauthRefreshToken: String { get set }
+	var oauthSwift: OAuth2Swift? { get }
+}
+
+class RedditFeedProviderTokenRefreshOperation: MainThreadOperation {
+
+	var log = OSLog(subsystem: Bundle.main.bundleIdentifier!, category: "RedditFeedProvider")
+
+	public var isCanceled = false
+	public var id: Int?
+	public weak var operationDelegate: MainThreadOperationDelegate?
+	public var name: String? = "WebViewProviderReplenishQueueOperation"
+	public var completionBlock: MainThreadOperation.MainThreadOperationCompletionBlock?
+
+	private weak var delegate: RedditFeedProviderTokenRefreshOperationDelegate?
+	
+	var error: Error?
+	
+	init(delegate: RedditFeedProviderTokenRefreshOperationDelegate) {
+		self.delegate = delegate
+	}
+	
+	func run() {
+		guard let delegate = delegate, let username = delegate.username else {
+			self.operationDelegate?.operationDidComplete(self)
+			return
+		}
+
+		// If another operation has recently refreshed the token, we don't need to do it again
+		if let lastRefresh = delegate.oauthTokenLastRefresh, Date().timeIntervalSince(lastRefresh) < 120 {
+			self.operationDelegate?.operationDidComplete(self)
+			return
+		}
+
+		os_log(.debug, log: self.log, "Access token expired, attempting to renew...")
+
+		delegate.oauthSwift?.renewAccessToken(withRefreshToken: delegate.oauthRefreshToken) { [weak self] result in
+			guard let self = self else { return }
+			
+			switch result {
+			case .success(let tokenSuccess):
+				delegate.oauthToken = tokenSuccess.credential.oauthToken
+				delegate.oauthRefreshToken = tokenSuccess.credential.oauthRefreshToken
+				do {
+					try RedditFeedProvider.storeCredentials(username: username, oauthToken: delegate.oauthToken, oauthRefreshToken: delegate.oauthRefreshToken)
+					delegate.oauthTokenLastRefresh = Date()
+					os_log(.debug, log: self.log, "Access token renewed.")
+				} catch {
+					self.error = error
+					self.operationDelegate?.operationDidComplete(self)
+				}
+				self.operationDelegate?.operationDidComplete(self)
+			case .failure(let oathError):
+				self.error = oathError
+				self.operationDelegate?.operationDidComplete(self)
+			}
+		}
+
+	}
+	
+}