Rename DetailViewController to ArticleViewController to fix name collision

iOS/Article/ArticleViewControllerWebViewProvider.swift

@@ -0,0 +1,93 @@
+//
+//  ArticleViewControllerWebViewProvider.swift
+//  NetNewsWire-iOS
+//
+//  Created by Maurice Parker on 9/21/19.
+//  Copyright © 2019 Ranchero Software. All rights reserved.
+//
+
+import Foundation
+import WebKit
+
+/// WKWebView has an awful behavior of a flash to white on first load when in dark mode.
+/// Keep a queue of WebViews where we've already done a trivial load so that by the time we need them in the UI, they're past the flash-to-shite part of their lifecycle.
+class ArticleViewControllerWebViewProvider: NSObject, WKNavigationDelegate {
+	
+	static let shared = ArticleViewControllerWebViewProvider()
+	
+	private let minimumQueueDepth = 3
+	private let maximumQueueDepth = 6
+	private var queue: [WKWebView] = []
+	
+	private var waitingForFirstLoad = true
+	private var waitingCompletionHandler: ((WKWebView) -> ())?
+
+	func dequeueWebView(completion: @escaping (WKWebView) -> ()) {
+		if waitingForFirstLoad {
+			waitingCompletionHandler = completion
+		} else {
+			completeRequest(completion: completion)
+		}
+	}
+	
+	func enqueueWebView(_ webView: WKWebView) {
+		guard queue.count < maximumQueueDepth else {
+			return
+		}
+
+		webView.navigationDelegate = self
+		queue.insert(webView, at: 0)
+
+		webView.loadHTMLString(ArticleRenderer.page.html, baseURL: ArticleRenderer.page.baseURL)
+
+	}
+
+	// MARK: WKNavigationDelegate
+	
+	func webView(_ webView: WKWebView, didFinish navigation: WKNavigation!) {
+		if waitingForFirstLoad {
+			waitingForFirstLoad = false
+			if let completion = waitingCompletionHandler {
+				completeRequest(completion: completion)
+				waitingCompletionHandler = nil
+			}
+		}
+	}
+	
+	// MARK: Private
+
+	private override init() {
+		super.init()
+		replenishQueueIfNeeded()
+	}
+
+	private func replenishQueueIfNeeded() {
+		while queue.count < minimumQueueDepth {
+			let preferences = WKPreferences()
+			preferences.javaScriptCanOpenWindowsAutomatically = false
+			preferences.javaScriptEnabled = true
+
+			let configuration = WKWebViewConfiguration()
+			configuration.preferences = preferences
+			configuration.allowsInlineMediaPlayback = true
+			configuration.mediaTypesRequiringUserActionForPlayback = .video
+			
+			let webView = WKWebView(frame: .zero, configuration: configuration)
+			enqueueWebView(webView)
+		}
+	}
+	
+	private func completeRequest(completion: @escaping (WKWebView) -> ()) {
+		if let webView = queue.popLast() {
+			webView.navigationDelegate = nil
+			replenishQueueIfNeeded()
+			completion(webView)
+			return
+		}
+
+		assertionFailure("Creating WKWebView in \(#function); queue has run dry.")
+		let webView = WKWebView(frame: .zero)
+		completion(webView)
+	}
+	
+}