Implement iOS progress view #2162

Multiplatform/Shared/Sidebar/RefreshProgressModel.swift

@@ -0,0 +1,101 @@
+//
+//  RefreshProgressModel.swift
+//  NetNewsWire
+//
+//  Created by Phil Viso on 7/2/20.
+//  Copyright © 2020 Ranchero Software. All rights reserved.
+//
+
+import Account
+import Combine
+import Foundation
+import SwiftUI
+
+class RefreshProgressModel: ObservableObject {
+	
+	enum State {
+		case refreshProgress(Float)
+		case lastRefreshDateText(String)
+		case none
+	}
+		
+	@Published var state = State.none
+	
+	private static var dateFormatter: RelativeDateTimeFormatter = {
+		let formatter = RelativeDateTimeFormatter()
+		formatter.dateTimeStyle = .named
+		
+		return formatter
+	}()
+		
+	private let lastRefreshDate: () -> Date?
+	private let combinedRefreshProgress: () -> CombinedRefreshProgress
+	
+	private static let lastRefreshDateTextUpdateInterval = 60
+	private static let lastRefreshDateTextRelativeDateFormattingThreshold = 60.0
+	
+	init(lastRefreshDateProvider: @escaping () -> Date?,
+		 combinedRefreshProgressProvider: @escaping () -> CombinedRefreshProgress) {
+		self.lastRefreshDate = lastRefreshDateProvider
+		self.combinedRefreshProgress = combinedRefreshProgressProvider
+		
+		updateState()
+		
+		observeRefreshProgress()
+		scheduleLastRefreshDateTextUpdate()
+	}
+	
+	// MARK: Observing account changes
+	
+	private func observeRefreshProgress() {
+		NotificationCenter.default.addObserver(self, selector: #selector(updateState), name: .AccountRefreshProgressDidChange, object: nil)
+	}
+	
+	// MARK: Refreshing state
+	
+	@objc private func updateState() {
+		let progress = combinedRefreshProgress()
+		
+		if !progress.isComplete {
+			let fractionCompleted = Float(progress.numberCompleted) / Float(progress.numberOfTasks)
+			self.state = .refreshProgress(fractionCompleted)
+		} else if let lastRefreshDate = self.lastRefreshDate() {
+			let text = localizedLastRefreshText(lastRefreshDate: lastRefreshDate)
+			self.state = .lastRefreshDateText(text)
+		} else {
+			self.state = .none
+		}
+	}
+	
+	private func scheduleLastRefreshDateTextUpdate() {
+		DispatchQueue.main.asyncAfter(deadline: .now() + .seconds(Self.lastRefreshDateTextUpdateInterval)) {
+			self.updateState()
+			self.scheduleLastRefreshDateTextUpdate()
+		}
+	}
+	
+	private func localizedLastRefreshText(lastRefreshDate: Date) -> String {
+		let now = Date()
+		
+		if now > lastRefreshDate.addingTimeInterval(Self.lastRefreshDateTextRelativeDateFormattingThreshold) {
+			let localizedDate = Self.dateFormatter.localizedString(for: lastRefreshDate, relativeTo: now)
+			let formatString = NSLocalizedString("Updated %@", comment: "Updated") as NSString
+			
+			return NSString.localizedStringWithFormat(formatString, localizedDate) as String
+		} else {
+			return NSLocalizedString("Updated Just Now", comment: "Updated Just Now")
+		}
+	}
+		
+}
+
+extension RefreshProgressModel {
+	
+	convenience init() {
+		self.init(
+			lastRefreshDateProvider: { AccountManager.shared.lastArticleFetchEndTime },
+			combinedRefreshProgressProvider: { AccountManager.shared.combinedRefreshProgress }
+		)
+	}
+		
+}