[iOS] Crash when trying to navigate to locked content

Course/Course/Presentation/Unit/CourseNavigationView.swift

@@ -43,28 +43,18 @@ struct CourseNavigationView: View {
                         })
                     }
                     UnitButtonView(type: .last, action: {
-                        let sequentials = viewModel.chapters[viewModel.chapterIndex].childs
-                        let verticals = viewModel
-                            .chapters[viewModel.chapterIndex]
-                            .childs[viewModel.sequentialIndex]
-                            .childs
-                        let chapters = viewModel.chapters
                         let currentVertical = viewModel.verticals[viewModel.verticalIndex]
 
                         viewModel.router.presentAlert(
                             alertTitle: CourseLocalization.Courseware.goodWork,
                             alertMessage: (CourseLocalization.Courseware.section
                                            + currentVertical.displayName + CourseLocalization.Courseware.isFinished),
                             nextSectionName: {
-                                if viewModel.verticals.count > viewModel.verticalIndex + 1 {
-                                    return viewModel.verticals[viewModel.verticalIndex + 1].displayName
-                                } else if sequentials.count > viewModel.sequentialIndex + 1 {
-                                    return sequentials[viewModel.sequentialIndex + 1].childs.first?.displayName ?? ""
-                                } else if chapters.count > viewModel.chapterIndex + 1 {
-                                    return chapters[viewModel.chapterIndex + 1].childs.first?.childs.first?.displayName
-                                } else {
-                                    return nil
+                                if let data = viewModel.nextData,
+                                    let vertical = viewModel.vertical(for: data) {
+                                    return vertical.displayName
                                 }
+                                return nil
                             }(),
                             action: CourseLocalization.Courseware.backToOutline,
                             image: CoreAssets.goodWork.swiftUIImage,
@@ -82,44 +72,25 @@ struct CourseNavigationView: View {
                                 playerStateSubject.send(VideoPlayerState.kill)
                                 viewModel.router.dismiss(animated: false)
 
-                                let chapterIndex: Int
-                                let sequentialIndex: Int
-                                let verticalIndex: Int
-
-                                // Switch to the next Vertical
-                                if verticals.count - 1 > viewModel.verticalIndex {
-                                    chapterIndex = viewModel.chapterIndex
-                                    sequentialIndex = viewModel.sequentialIndex
-                                    verticalIndex = viewModel.verticalIndex + 1
-                                    // Switch to the next Sequential
-                                } else if sequentials.count - 1 > viewModel.sequentialIndex {
-                                    chapterIndex = viewModel.chapterIndex
-                                    sequentialIndex = viewModel.sequentialIndex + 1
-                                    verticalIndex = 0
-                                } else {
-                                    // Switch to the next Chapter
-                                    chapterIndex = viewModel.chapterIndex + 1
-                                    sequentialIndex = 0
-                                    verticalIndex = 0
-                                }
-
                                 viewModel.analytics
                                     .finishVerticalNextSectionClicked(
                                         courseId: viewModel.courseID,
                                         courseName: viewModel.courseName,
                                         blockId: viewModel.selectedLesson().blockId,
                                         blockName: viewModel.selectedLesson().displayName
                                     )
-
+
+                                guard let data = viewModel.nextData else { return }
                                 viewModel.router.replaceCourseUnit(
                                     courseName: viewModel.courseName,
                                     blockId: viewModel.lessonID,
                                     courseID: viewModel.courseID,
                                     sectionName: viewModel.selectedLesson().displayName,
-                                    verticalIndex: verticalIndex,
+                                    verticalIndex: data.verticalIndex,
                                     chapters: viewModel.chapters,
-                                    chapterIndex: chapterIndex,
-                                    sequentialIndex: sequentialIndex)
+                                    chapterIndex: data.chapterIndex,
+                                    sequentialIndex: data.sequentialIndex
+                                )
                             }
                         )
                         playerStateSubject.send(VideoPlayerState.pause)

Course/Course/Presentation/Unit/CourseUnitViewModel.swift

@@ -180,4 +180,58 @@ public class CourseUnitViewModel: ObservableObject {
     func trackFinishVerticalBackToOutlineClicked() {
         analytics.finishVerticalBackToOutlineClicked(courseId: courseID, courseName: courseName)
     }
+
+    //MARK: Navigation to next vertical
+    typealias VerticalData = (chapterIndex: Int, sequentialIndex: Int, verticalIndex: Int)
+    var nextData: VerticalData? {
+        nextData(from: (chapterIndex, sequentialIndex, verticalIndex))
+    }
+
+    private func chapter(for data: VerticalData) -> CourseChapter? {
+        guard data.chapterIndex >= 0 && data.chapterIndex < chapters.count else { return nil }
+        return chapters[data.chapterIndex]
+    }
+
+    private func sequential(for data: VerticalData) -> CourseSequential? {
+        guard let chapter = chapter(for: data),
+              data.sequentialIndex >= 0 && data.sequentialIndex < chapter.childs.count
+        else { return nil }
+        return chapter.childs[data.sequentialIndex]
+    }
+
+    func vertical(for data: VerticalData) -> CourseVertical? {
+        guard let sequential = sequential(for: data),
+            data.verticalIndex >= 0 && data.verticalIndex < sequential.childs.count
+        else { return nil }
+        return sequential.childs[data.verticalIndex]
+    }
+
+    private func sequentials(for data: VerticalData) -> [CourseSequential]? {
+        guard let chapter = chapter(for: data) else { return nil }
+        return chapter.childs
+    }
+
+    private func verticals(for data: VerticalData) -> [CourseVertical]? {
+        guard let sequential = sequential(for: data) else { return nil }
+        return sequential.childs
+    }
+
+    private func nextData(from data: VerticalData) -> VerticalData? {
+        var resultData: VerticalData = data
+        if let verticals = verticals(for: data), verticals.count > data.verticalIndex + 1 {
+            resultData = (data.chapterIndex, data.sequentialIndex, data.verticalIndex + 1)
+        } else if let sequentials = sequentials(for: data), sequentials.count > data.sequentialIndex + 1 {
+            resultData = (data.chapterIndex, data.sequentialIndex + 1, 0)
+        } else if chapters.count > data.chapterIndex + 1 {
+            resultData = (data.chapterIndex + 1, 0, 0)
+        } else {
+            return nil
+        }
+
+        if let vertical = vertical(for: resultData), vertical.childs.count > 0 {
+            return resultData
+        } else {
+            return nextData(from: resultData)
+        }
+    }
 }