Managing Favorites sections

Model/FavoritesModel.swift

@@ -0,0 +1,77 @@
+import Defaults
+import Foundation
+
+struct FavoritesModel {
+    static let shared = FavoritesModel()
+
+    @Default(.favorites) var all
+
+    func contains(_ item: FavoriteItem) -> Bool {
+        all.contains { $0 == item }
+    }
+
+    func toggle(_ item: FavoriteItem) {
+        contains(item) ? remove(item) : add(item)
+    }
+
+    func add(_ item: FavoriteItem) {
+        all.append(item)
+    }
+
+    func remove(_ item: FavoriteItem) {
+        if let index = all.firstIndex(where: { $0 == item }) {
+            all.remove(at: index)
+        }
+    }
+
+    func canMoveUp(_ item: FavoriteItem) -> Bool {
+        if let index = all.firstIndex(where: { $0 == item }) {
+            return index > all.startIndex
+        }
+
+        return false
+    }
+
+    func canMoveDown(_ item: FavoriteItem) -> Bool {
+        if let index = all.firstIndex(where: { $0 == item }) {
+            return index < all.endIndex - 1
+        }
+
+        return false
+    }
+
+    func moveUp(_ item: FavoriteItem) {
+        guard canMoveUp(item) else {
+            return
+        }
+
+        if let from = all.firstIndex(where: { $0 == item }) {
+            all.move(
+                fromOffsets: IndexSet(integer: from),
+                toOffset: from - 1
+            )
+        }
+    }
+
+    func moveDown(_ item: FavoriteItem) {
+        guard canMoveDown(item) else {
+            return
+        }
+
+        if let from = all.firstIndex(where: { $0 == item }) {
+            all.move(
+                fromOffsets: IndexSet(integer: from),
+                toOffset: from + 2
+            )
+        }
+    }
+
+    func addableItems() -> [FavoriteItem] {
+        let allItems = [
+            FavoriteItem(section: .subscriptions),
+            FavoriteItem(section: .popular)
+        ]
+
+        return allItems.filter { item in !all.contains { $0.section == item.section } }
+    }
+}