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pedi-foods/Sources/PediFoods/ViewModel.swift

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+import Foundation
+import Observation
+import SkipFuse
+
+/// The Observable ViewModel used by the application.
+@Observable public class ViewModel {
+    var items: [Item] = loadItems() {
+        didSet { saveItems() }
+    }
+
+    init() {
+    }
+
+    func clear() {
+        items.removeAll()
+    }
+
+    func isUpdated(_ item: Item) -> Bool {
+        item != items.first { i in
+            i.id == item.id
+        }
+    }
+
+    func save(item: Item) {
+        items = items.map { i in
+            i.id == item.id ? item : i
+        }
+    }
+}
+
+/// An individual item held by the ViewModel
+struct Item : Identifiable, Hashable, Codable {
+    let id: UUID
+    var date: Date
+    var favorite: Bool
+    var title: String
+    var notes: String
+
+    init(id: UUID = UUID(), date: Date = .now, favorite: Bool = false, title: String = "", notes: String = "") {
+        self.id = id
+        self.date = date
+        self.favorite = favorite
+        self.title = title
+        self.notes = notes
+    }
+
+    var itemTitle: String {
+        !title.isEmpty ? title : dateString
+    }
+
+    var dateString: String {
+        date.formatted(date: .complete, time: .omitted)
+    }
+
+    var dateTimeString: String {
+        date.formatted(date: .abbreviated, time: .shortened)
+    }
+}
+
+/// Utilities for defaulting and persising the items in the list
+extension ViewModel {
+    private static let savePath = URL.applicationSupportDirectory.appendingPathComponent("appdata.json")
+
+    fileprivate static func loadItems() -> [Item] {
+        do {
+            let start = Date.now
+            let data = try Data(contentsOf: savePath)
+            defer {
+                let end = Date.now
+                logger.info("loaded \(data.count) bytes from \(Self.savePath.path) in \(end.timeIntervalSince(start)) seconds")
+            }
+            return try JSONDecoder().decode([Item].self, from: data)
+        } catch {
+            // perhaps the first launch, or the data could not be read
+            logger.warning("failed to load data from \(Self.savePath), using defaultItems: \(error)")
+            let defaultItems = (1...365).map { Date(timeIntervalSinceNow: Double($0 * 60 * 60 * 24 * -1)) }
+            return defaultItems.map({ Item(date: $0) })
+        }
+    }
+
+    fileprivate func saveItems() {
+        do {
+            let start = Date.now
+            let data = try JSONEncoder().encode(items)
+            try FileManager.default.createDirectory(at: URL.applicationSupportDirectory, withIntermediateDirectories: true)
+            try data.write(to: Self.savePath)
+            let end = Date.now
+            logger.info("saved \(data.count) bytes to \(Self.savePath.path) in \(end.timeIntervalSince(start)) seconds")
+        } catch {
+            logger.error("error saving data: \(error)")
+        }
+    }
+}