feat(view, model): 增加自动保存功能

增加自动保存功能

Signed-off-by: Ching <loooching@gmail.com>

EmojiArt/Constants.swift

@@ -11,4 +11,5 @@ import SwiftUI
 
 struct const {
     static let defaultEmojiFontSize: CGFloat = 40
+    static let coalescingInterval = 5.0
 }

EmojiArt/EmojiArtDocument.swift

@@ -10,15 +10,56 @@ import SwiftUI
 class EmojiArtDocument: ObservableObject {
     @Published private(set) var emojiArt: EmojiArtModel {
         didSet {
+            scheduleAutosave()
             if emojiArt.background != oldValue.background {
                 fetchBackgoundImageDataIfNecessary()
             }
         }
     }
     
+    private var autosaveTimer: Timer?
+
+    private func scheduleAutosave() {
+        autosaveTimer?.invalidate()
+        autosaveTimer = Timer.scheduledTimer(withTimeInterval: const.coalescingInterval, repeats: false) { _ in
+            self.autoSave()
+        }
+    }
+
+    private enum Autosave {
+        static let filename = "Autosaved.emojiart"
+        static var url: URL? {
+            let documentDirectory = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first
+            return documentDirectory?.appendingPathComponent(filename)
+        }
+    }
+
+    private func autoSave() {
+        if let url = Autosave.url {
+            save(to: url)
+        }
+    }
+
+    private func save(to url: URL) {
+        let thisFunction = "\(String(describing: self)).\(#function)"
+        do {
+            let data: Data = try emojiArt.json()
+            print("\(thisFunction) json = \(String(data: data, encoding: .utf8) ?? "nil")")
+            try data.write(to: url)
+            print("\(thisFunction) success")
+        } catch {
+            print("\(thisFunction) error = \(error)")
+        }
+    }
+
     init() {
+        if let url = Autosave.url, let autosavedEmojiArt = try? EmojiArtModel(url: url) {
+            emojiArt = autosavedEmojiArt
+            fetchBackgoundImageDataIfNecessary()
+        } else {
             emojiArt = EmojiArtModel()
         }
+    }
 
     var emojis: [EmojiArtModel.Emoji] { emojiArt.emojis }
     var background: EmojiArtModel.Background { emojiArt.background }

EmojiArt/EmojiArtModel.Background.swift

@@ -8,11 +8,36 @@
 import Foundation
 
 extension EmojiArtModel {
-    enum Background: Equatable {
+    enum Background: Equatable, Codable {
         case blank
         case url(URL)
         case imageData(Data)
         
+        init(from decoder: Decoder) throws {
+            let container = try decoder.container(keyedBy: CodingKeys.self)
+            if let url = try? container.decode(URL.self, forKey: .url) {
+                self = .url(url)
+            } else if let imageData = try? container.decode(Data.self, forKey: .imageData) {
+                self = .imageData(imageData)
+            } else {
+                self = .blank
+            }
+        }
+        
+        enum CodingKeys: String, CodingKey {
+            case url = "theURL"
+            case imageData
+        }
+        
+        func encode(to encoder: Encoder) throws {
+            var container = encoder.container(keyedBy: CodingKeys.self)
+            switch self {
+            case .url(let url): try container.encode(url, forKey: .url)
+            case .imageData(let data): try container.encode(data, forKey: .imageData)
+            case .blank: break
+            }
+        }
+        
         var url: URL? {
             switch self {
             case .url(let url): return url

EmojiArt/EmojiArtModel.swift

@@ -7,11 +7,11 @@
 
 import Foundation
 
-struct EmojiArtModel {
+struct EmojiArtModel: Codable {
     var background: Background = EmojiArtModel.Background.blank
     var emojis = [Emoji]()
 
-    struct Emoji: Identifiable {
+    struct Emoji: Identifiable, Hashable, Codable {
         let text: String
         var x: Int
         var y: Int
@@ -27,14 +27,25 @@ struct EmojiArtModel {
         }
     }
 
-    init() {
+    func json() throws -> Data {
-        
+        return try JSONEncoder().encode(self)
     }
 
+    
+    init(json: Data) throws {
+        self = try JSONDecoder().decode(EmojiArtModel.self, from: json)
+    }
+    
+    init(url: URL) throws {
+        let data = try Data(contentsOf: url)
+        self = try EmojiArtModel.init(json: data)
+    }
+    
+    init() {}
+
     private var uniqueEmojiId = 0
     mutating func addEmoji(_ text: String, at location: (x: Int, y: Int), size: Int) {
         uniqueEmojiId += 1
         emojis.append(Emoji(text: text, x: location.x, y: location.y, size: size, id: uniqueEmojiId))
     }
-
 }