From 4a63b28c73c11c9d6cc7b380f638b56a40b7fd14 Mon Sep 17 00:00:00 2001
From: Maurice Parker <mo@vincode.io>
Date: Sun, 26 Jan 2020 14:21:04 -0700
Subject: [PATCH] Change how next and previous articles are selected so that
 animation timings can't impact them.  Issue #1707

---
 iOS/Article/ArticleViewController.swift |  8 ++++++--
 iOS/SceneCoordinator.swift              | 14 ++++++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/iOS/Article/ArticleViewController.swift b/iOS/Article/ArticleViewController.swift
index 38c51c74f..0599c7d14 100644
--- a/iOS/Article/ArticleViewController.swift
+++ b/iOS/Article/ArticleViewController.swift
@@ -268,14 +268,18 @@ extension ArticleViewController: WebViewControllerDelegate {
 extension ArticleViewController: UIPageViewControllerDataSource {
 	
 	func pageViewController(_ pageViewController: UIPageViewController, viewControllerBefore viewController: UIViewController) -> UIViewController? {
-		guard let article = coordinator.prevArticle else {
+		guard let webViewController = viewController as? WebViewController,
+			let currentArticle = webViewController.article,
+			let article = coordinator.findPrevArticle(currentArticle) else {
 			return nil
 		}
 		return createWebViewController(article)
 	}
 	
 	func pageViewController(_ pageViewController: UIPageViewController, viewControllerAfter viewController: UIViewController) -> UIViewController? {
-		guard let article = coordinator.nextArticle else {
+		guard let webViewController = viewController as? WebViewController,
+			let currentArticle = webViewController.article,
+			let article = coordinator.findNextArticle(currentArticle) else {
 			return nil
 		}
 		return createWebViewController(article)
diff --git a/iOS/SceneCoordinator.swift b/iOS/SceneCoordinator.swift
index 249ed48d0..5d737cbfd 100644
--- a/iOS/SceneCoordinator.swift
+++ b/iOS/SceneCoordinator.swift
@@ -825,6 +825,20 @@ class SceneCoordinator: NSObject, UndoableCommandRunner, UnreadCountProvider {
 		
 	}
 	
+	func findPrevArticle(_ article: Article) -> Article? {
+		guard let index = articles.firstIndex(of: article), index > 0 else {
+			return nil
+		}
+		return articles[index - 1]
+	}
+	
+	func findNextArticle(_ article: Article) -> Article? {
+		guard let index = articles.firstIndex(of: article), index + 1 != articles.count else {
+			return nil
+		}
+		return articles[index + 1]
+	}
+	
 	func selectPrevArticle() {
 		if let article = prevArticle {
 			selectArticle(article)