Design and stub out FeedProvider protocol

Frameworks/FeedProvider/FeedProvider.swift

@@ -8,7 +8,26 @@
 
 import Foundation
 import RSCore
+import RSParser
+
+public enum FeedProviderAbility {
+	case owner
+	case available
+	case none
+}
 
 public protocol FeedProvider  {
 	
+	/// Informs the caller of the ability for this feed provider to service the given URL
+	func ability(_ url: URLComponents, forUsername: String?) -> FeedProviderAbility
+	
+	/// Provide the iconURL of the given URL
+	func iconURL(_ url: URLComponents, completion: @escaping (Result<String, Error>) -> Void)
+	
+	/// Construct a ParsedFeed that can be used to create and store a new Feed
+	func provide(_ url: URLComponents, completion: @escaping (Result<ParsedFeed, Error>) -> Void)
+	
+	/// Refresh all the article entries (ParsedItems)
+	func refresh(_ url: URLComponents, completion: @escaping (Result<Set<ParsedItem>, Error>) -> Void)
+	
 }

Frameworks/FeedProvider/Twitter/TwitterFeedProvider.swift

@@ -9,9 +9,10 @@
 import Foundation
 import Secrets
 import OAuthSwift
+import RSParser
+
+public struct TwitterFeedProvider: FeedProvider {
 
-public struct TwitterFeedProvider {
-	
 	private static let server = "api.twitter.com"
 	
 	public var userID: String
@@ -50,9 +51,34 @@ public struct TwitterFeedProvider {
 		self.oauthToken = tokenCredentials.secret
 		self.oauthTokenSecret = tokenSecretCredentials.secret
 	}
+
+	public func ability(_ urlComponents: URLComponents, forUsername username: String?) -> FeedProviderAbility {
+		guard urlComponents.host?.hasSuffix("twitter.com") ?? false else {
+			return .none
+		}
+		
+		if let username = username, username == userID {
+			return .owner
+		}
+		
+		return .available
+	}
+
+	public func iconURL(_ url: URLComponents, completion: @escaping (Result<String, Error>) -> Void) {
+		// TODO: Finish implementation
+	}
+
+	public func provide(_ url: URLComponents, completion: @escaping (Result<ParsedFeed, Error>) -> Void) {
+		// TODO: Finish implementation
+	}
 	
+	public func refresh(_ url: URLComponents, completion: @escaping (Result<Set<ParsedItem>, Error>) -> Void) {
+		// TODO: Finish implementation
+	}
+
 }
 
+// MARK: OAuth1SwiftProvider
 
 extension TwitterFeedProvider: OAuth1SwiftProvider {
 	
@@ -67,9 +93,3 @@ extension TwitterFeedProvider: OAuth1SwiftProvider {
 	}
 	
 }
-
-// MARK: FeedProvider
-
-extension TwitterFeedProvider: FeedProvider {
-	
-}

Shared/ExtensionPoints/ExtensionPointManager.swift

@@ -75,6 +75,13 @@ final class ExtensionPointManager {
 		saveExtensionPointIDs()
 	}
 	
+	func bestFeedProvider(for offered: URLComponents, with username: String?) -> FeedProvider? {
+		if let owner = feedProviderMatching(offered, forUsername: username, ability: .owner) {
+			return owner
+		}
+		return feedProviderMatching(offered, forUsername: username, ability: .available)
+	}
+	
 }
 
 private extension ExtensionPointManager {
@@ -123,4 +130,13 @@ private extension ExtensionPointManager {
 		}
 	}
 	
+	func feedProviderMatching(_ offered: URLComponents, forUsername username: String?, ability: FeedProviderAbility) -> FeedProvider? {
+		for extensionPoint in activeExtensionPoints.values {
+			if let feedProvider = extensionPoint as? FeedProvider, feedProvider.ability(offered, forUsername: username) == ability {
+				return feedProvider
+			}
+		}
+		return nil
+	}
+
 }