NetNewsWire/Frameworks/Account/Feedly/FeedlyAccountDelegate.swift

//
//  FeedlyAccountDelegate.swift
//  Account
//
//  Created by Kiel Gillard on 3/9/19.
//  Copyright © 2019 Ranchero Software, LLC. All rights reserved.
//

import Articles
import RSCore
import RSParser
import RSWeb
import SyncDatabase
import os.log

final class FeedlyAccountDelegate: AccountDelegate {

	// TODO: Kiel, if you decide not to support OPML import you will have to disallow it in the behaviors
	// See https://developer.feedly.com/v3/opml/
	var behaviors: AccountBehaviors = [.disallowFeedInRootFolder]
	
	let isOPMLImportSupported = false
	
	var isOPMLImportInProgress = false
	
	var server: String? {
		return caller.server
	}
	
	var credentials: Credentials? {
		didSet {
			// https://developer.feedly.com/v3/developer/
			if let devToken = ProcessInfo.processInfo.environment["FEEDLY_DEV_ACCESS_TOKEN"], !devToken.isEmpty {
				caller.credentials = Credentials(type: .oauthAccessToken, username: "Developer", secret: devToken)
			} else {
				caller.credentials = credentials
			}
		}
	}
	
	var accountMetadata: AccountMetadata?
	
	var refreshProgress = DownloadProgress(numberOfTasks: 0)
	
	private let caller: FeedlyAPICaller
	private let log = OSLog(subsystem: Bundle.main.bundleIdentifier!, category: "Feedly")
	private let articleStatusCoodinator: FeedlyArticleStatusCoordinator
	
	init(dataFolder: String, transport: Transport?, api: FeedlyAPICaller.API = .default) {
		
		if let transport = transport {
			caller = FeedlyAPICaller(transport: transport, api: api)
			
		} else {
			
			let sessionConfiguration = URLSessionConfiguration.default
			sessionConfiguration.requestCachePolicy = .reloadIgnoringLocalCacheData
			sessionConfiguration.timeoutIntervalForRequest = 60.0
			sessionConfiguration.httpShouldSetCookies = false
			sessionConfiguration.httpCookieAcceptPolicy = .never
			sessionConfiguration.httpMaximumConnectionsPerHost = 1
			sessionConfiguration.httpCookieStorage = nil
			sessionConfiguration.urlCache = nil
			
			if let userAgentHeaders = UserAgent.headers() {
				sessionConfiguration.httpAdditionalHeaders = userAgentHeaders
			}
			
			let session = URLSession(configuration: sessionConfiguration)
			caller = FeedlyAPICaller(transport: session, api: api)
		}
		
		articleStatusCoodinator = FeedlyArticleStatusCoordinator(dataFolderPath: dataFolder,
																 caller: caller,
																 log: log)
	}
	
	// MARK: Account API
	
	private var syncStrategy: FeedlySyncStrategy?
	
	func refreshAll(for account: Account, completion: @escaping (Result<Void, Error>) -> Void) {
		let date = Date()
		let log = self.log
		let progress = refreshProgress
		progress.addToNumberOfTasksAndRemaining(1)
		syncStrategy?.startSync { result in
			os_log(.debug, log: log, "Sync took %.3f seconds", -date.timeIntervalSinceNow)
			progress.completeTask()
			completion(result)
		}
	}
	
	func sendArticleStatus(for account: Account, completion: @escaping (() -> Void)) {
		// Ensure remote articles have the same status as they do locally.
		articleStatusCoodinator.sendArticleStatus(for: account, completion: completion)
	}
	
	/// Attempts to ensure local articles have the same status as they do remotely.
	/// So if the user is using another client roughly simultaneously with this app,
	/// this app does its part to ensure the articles have a consistent status between both.
	///
	/// Feedly has no API that allows the app to fetch the identifiers of unread articles only.
	/// The only way to identify unread articles is to pull all of the article data,
	/// which is effectively equivalent of a full refresh.
	///
	/// - Parameter account: The account whose articles have a remote status.
	/// - Parameter completion: Call on the main queue.
	func refreshArticleStatus(for account: Account, completion: @escaping (() -> Void)) {
		refreshAll(for: account) { _ in
			completion()
		}
	}
	
	func importOPML(for account: Account, opmlFile: URL, completion: @escaping (Result<Void, Error>) -> Void) {
		let data: Data
		
		do {
			data = try Data(contentsOf: opmlFile)
		} catch {
			completion(.failure(error))
			return
		}
		
		os_log(.debug, log: log, "Begin importing OPML...")
		isOPMLImportInProgress = true
		refreshProgress.addToNumberOfTasksAndRemaining(1)
		
		caller.importOpml(data) { result in
			switch result {
			case .success:
				os_log(.debug, log: self.log, "Import OPML done.")
				self.refreshProgress.completeTask()
				self.isOPMLImportInProgress = false
				DispatchQueue.main.async {
					completion(.success(()))
				}
			case .failure(let error):
				os_log(.debug, log: self.log, "Import OPML failed.")
				self.refreshProgress.completeTask()
				self.isOPMLImportInProgress = false
				DispatchQueue.main.async {
					let wrappedError = AccountError.wrappedError(error: error, account: account)
					completion(.failure(wrappedError))
				}
			}
		}
	}
	
	func addFolder(for account: Account, name: String, completion: @escaping (Result<Folder, Error>) -> Void) {
		
		let progress = refreshProgress
		progress.addToNumberOfTasksAndRemaining(1)
		
		caller.createCollection(named: name) { result in
			progress.completeTask()
			
			switch result {
			case .success(let collection):
				if let folder = account.ensureFolder(with: collection.label) {
					folder.externalID = collection.id
					completion(.success(folder))
				} else {
					// Is the name empty? Or one of the global resource names?
					completion(.failure(FeedlyAccountDelegateError.unableToAddFolder(name)))
				}
			case .failure(let error):
				completion(.failure(error))
			}
		}
	}
	
	func renameFolder(for account: Account, with folder: Folder, to name: String, completion: @escaping (Result<Void, Error>) -> Void) {
		guard let id = folder.externalID else {
			return DispatchQueue.main.async {
				completion(.failure(FeedlyAccountDelegateError.unableToRenameFolder(folder.nameForDisplay, name)))
			}
		}
		
		let nameBefore = folder.name
		
		caller.renameCollection(with: id, to: name) { result in
			switch result {
			case .success(let collection):
				folder.name = collection.label
				completion(.success(()))
			case .failure(let error):
				folder.name = nameBefore
				completion(.failure(error))
			}
		}
		
		folder.name = name
	}
	
	func removeFolder(for account: Account, with folder: Folder, completion: @escaping (Result<Void, Error>) -> Void) {
		guard let id = folder.externalID else {
			return DispatchQueue.main.async {
				completion(.failure(FeedlyAccountDelegateError.unableToRemoveFolder(folder.nameForDisplay)))
			}
		}
		
		let progress = refreshProgress
		progress.addToNumberOfTasksAndRemaining(1)
		
		caller.deleteCollection(with: id) { result in
			progress.completeTask()
			
			switch result {
			case .success:
				account.removeFolder(folder)
				completion(.success(()))
			case .failure(let error):
				completion(.failure(error))
			}
		}
	}
	
	private func isValidContainer(for account: Account, container: Container) throws -> (Folder, String) {
		guard let folder = container as? Folder else {
			throw FeedlyAccountDelegateError.addFeedChooseFolder
		}
		
		guard let collectionId = folder.externalID else {
			throw FeedlyAccountDelegateError.addFeedInvalidFolder(folder)
		}
		
		guard let userId = credentials?.username else {
			throw FeedlyAccountDelegateError.notLoggedIn
		}
		
		let uncategorized = FeedlyCategoryResourceId.uncategorized(for: userId)
		
		guard collectionId != uncategorized.id else {
			throw FeedlyAccountDelegateError.addFeedInvalidFolder(folder)
		}
		
		return (folder, collectionId)
	}
	
	func createFeed(for account: Account, url: String, name: String?, container: Container, completion: @escaping (Result<Feed, Error>) -> Void) {
		let (folder, collectionId): (Folder, String)
		do {
			(folder, collectionId) = try isValidContainer(for: account, container: container)
		} catch {
			return DispatchQueue.main.async {
				completion(.failure(error))
			}
		}
		
		let resourceId = FeedlyFeedResourceId(url: url)
		
		let progress = refreshProgress
		progress.addToNumberOfTasksAndRemaining(1)
		
		caller.addFeed(with: resourceId, title: name, toCollectionWith: collectionId) { [weak self] result in
			defer { progress.completeTask() }
			
			switch result {
			case .success(let feedlyFeeds):
				let feedsBefore = folder.flattenedFeeds()
				for feedlyFeed in feedlyFeeds where !account.hasFeed(with: feedlyFeed.feedId) {
					let resourceId = FeedlyFeedResourceId(id: feedlyFeed.id)
					let feed = account.createFeed(with: feedlyFeed.title,
												  url: resourceId.url,
												  feedID: feedlyFeed.id,
												  homePageURL: feedlyFeed.website)
					folder.addFeed(feed)
				}
				
				let feedsAfter = folder.flattenedFeeds()
				let added = feedsAfter.subtracting(feedsBefore)
				
				guard let first = added.first else {
					return completion(.failure(AccountError.createErrorNotFound))
				}
				
				let group = DispatchGroup()
				progress.addToNumberOfTasksAndRemaining(1)
				
				if let self = self {
					for feed in added {
						group.enter()
						let resourceId = FeedlyFeedResourceId(id: feed.feedID)
						self.caller.getStream(for: resourceId, newerThan: nil, unreadOnly: nil) { result in
							switch result {
							case .success(let stream):
								let items = Set(stream.items.map { FeedlyEntryParser(entry: $0).parsedItemRepresentation })
								
								account.update(feed, parsedItems: items, defaultRead: false) {
									group.leave()
								}
								
							case .failure:
								// Feed will remain empty until new articles appear.
								group.leave()
							}
						}
					}
				}
				
				group.notify(queue: .main) {
					progress.completeTask()
					completion(.success(first))
				}
				
			case .failure(let error):
				completion(.failure(error))
			}
		}
	}
	
	func renameFeed(for account: Account, with feed: Feed, to name: String, completion: @escaping (Result<Void, Error>) -> Void) {
		let folderCollectionIds = account.folders?.filter { $0.has(feed) }.compactMap { $0.externalID }
		guard let collectionIds = folderCollectionIds, let collectionId = collectionIds.first else {
			completion(.failure(FeedbinAccountDelegateError.invalidParameter))
			return
		}
		
		let feedId = FeedlyFeedResourceId(id: feed.feedID)
		let editedNameBefore = feed.editedName
		
		// Adding an existing feed updates it.
		// Updating feed name in one folder/collection updates it for all folders/collections.
		caller.addFeed(with: feedId, title: name, toCollectionWith: collectionId) { result in
			switch result {
			case .success:
				completion(.success(()))
				
			case .failure(let error):
				feed.editedName = editedNameBefore
				completion(.failure(error))
			}
		}
		
		// optimistically set the name
		feed.editedName = name
	}
	
	func addFeed(for account: Account, with: Feed, to container: Container, completion: @escaping (Result<Void, Error>) -> Void) {
		let (folder, collectionId): (Folder, String)
		do {
			(folder, collectionId) = try isValidContainer(for: account, container: container)
		} catch {
			return DispatchQueue.main.async {
				completion(.failure(error))
			}
		}
		
		let feedId = FeedlyFeedResourceId(id: with.feedID)
		
		caller.addFeed(with: feedId, toCollectionWith: collectionId) { result in
			switch result {
			case .success(let feedlyFeeds):
				for feedlyFeed in feedlyFeeds where !folder.hasFeed(with: feedlyFeed.feedId) {
					let feed: Feed = {
						if with.url == FeedlyFeedResourceId(id: feedlyFeed.id).url {
							with.metadata.feedID = feedlyFeed.id
							with.name = feedlyFeed.title
							with.homePageURL = feedlyFeed.website
							return with
						} else {
							let resourceId = FeedlyFeedResourceId(id: feedlyFeed.id)
							return account.createFeed(with: feedlyFeed.title,
													  url: resourceId.url,
													  feedID: feedlyFeed.id,
													  homePageURL: feedlyFeed.website)
						}
					}()
					folder.addFeed(feed)
				}
				
				completion(.success(()))
				
			case .failure(let error):
				completion(.failure(error))
			}
		}
	}
	
	func removeFeed(for account: Account, with feed: Feed, from container: Container, completion: @escaping (Result<Void, Error>) -> Void) {
		guard let folder = container as? Folder, let collectionId = folder.externalID else {
			return DispatchQueue.main.async {
				completion(.failure(FeedlyAccountDelegateError.unableToRemoveFeed(feed)))
			}
		}
		
		caller.removeFeed(feed.feedID, fromCollectionWith: collectionId) { result in
			switch result {
			case .success:
				completion(.success(()))
			case .failure(let error):
				folder.addFeed(feed)
				completion(.failure(error))
			}
		}
		
		folder.removeFeed(feed)
	}
	
	func moveFeed(for account: Account, with feed: Feed, from: Container, to: Container, completion: @escaping (Result<Void, Error>) -> Void) {
		guard let from = from as? Folder, let to = to as? Folder else {
			return DispatchQueue.main.async {
				completion(.failure(FeedlyAccountDelegateError.addFeedChooseFolder))
			}
		}
		
		addFeed(for: account, with: feed, to: to) { [weak self] addResult in
			switch addResult {
				// now that we have added the feed, remove it from the other collection
			case .success:
				self?.removeFeed(for: account, with: feed, from: from) { removeResult in
					switch removeResult {
					case .success:
						completion(.success(()))
					case .failure:
						from.addFeed(feed)
						completion(.failure(FeedlyAccountDelegateError.unableToMoveFeedBetweenFolders(feed, from, to)))
					}
				}
			case .failure(let error):
				from.addFeed(feed)
				to.removeFeed(feed)
				completion(.failure(error))
			}
			
		}
		
		// optimistically move the feed, undoing as appropriate to the failure
		from.removeFeed(feed)
		to.addFeed(feed)
	}
	
	func restoreFeed(for account: Account, feed: Feed, container: Container, completion: @escaping (Result<Void, Error>) -> Void) {
		if let existingFeed = account.existingFeed(withURL: feed.url) {
			account.addFeed(existingFeed, to: container) { result in
				switch result {
				case .success:
					completion(.success(()))
				case .failure(let error):
					completion(.failure(error))
				}
			}
		} else {
			createFeed(for: account, url: feed.url, name: feed.editedName, container: container) { result in
				switch result {
				case .success:
					completion(.success(()))
				case .failure(let error):
					completion(.failure(error))
				}
			}
		}
	}
	
	func restoreFolder(for account: Account, folder: Folder, completion: @escaping (Result<Void, Error>) -> Void) {
		let group = DispatchGroup()
		
		for feed in folder.topLevelFeeds {
			
			folder.topLevelFeeds.remove(feed)
			
			group.enter()
			restoreFeed(for: account, feed: feed, container: folder) { result in
				group.leave()
				switch result {
				case .success:
					break
				case .failure(let error):
					os_log(.error, log: self.log, "Restore folder feed error: %@.", error.localizedDescription)
				}
			}
			
		}
		
		group.notify(queue: .main) {
			account.addFolder(folder)
			completion(.success(()))
		}
	}
	
	func markArticles(for account: Account, articles: Set<Article>, statusKey: ArticleStatus.Key, flag: Bool) -> Set<Article>? {
		
		let acceptedStatuses = articleStatusCoodinator.articles(articles,
																for: account,
																didChangeStatus: statusKey,
																flag: flag)
		
		return acceptedStatuses
	}
	
	func accountDidInitialize(_ account: Account) {
		credentials = try? account.retrieveCredentials(type: .oauthAccessToken)
		
		syncStrategy = FeedlySyncStrategy(account: account,
										  caller: caller,
										  articleStatusCoordinator: articleStatusCoodinator,
										  log: log)
	}
	
	static func validateCredentials(transport: Transport, credentials: Credentials, endpoint: URL?, completion: @escaping (Result<Credentials?, Error>) -> Void) {
		fatalError()
	}
}