add TodoItemStorage class

app/src/main/java/org/cutem/cutecalendar/model/TodoItemManager.java

@@ -1,13 +1,11 @@
 package org.cutem.cutecalendar.model;
 
-import com.google.gson.GsonBuilder;
 import org.cutem.cutecalendar.util.CalendarUtil;
 import org.jetbrains.annotations.NotNull;
 
 import java.util.*;
 
 public class TodoItemManager {
-    private static final String TODO_LIST_SAVE_NAME = "todo-list.json";
 
 
     private static TodoItemManager ourInstance;
@@ -51,6 +49,10 @@ public class TodoItemManager {
         addDateCache(item);
     }
 
+    public void add(@NotNull Collection<TodoItem> items) {
+        items.forEach(this::add);
+    }
+
     public void remove(@NotNull TodoItem item) {
         remove(item.getId());
     }
@@ -129,11 +131,32 @@ public class TodoItemManager {
 
 
 
+
     String toJson() {
-        GsonBuilder gson = new GsonBuilder();
-        gson.registerTypeAdapter(TodoItem.class, new TodoItemSerializer());
-        return gson.create().toJson(items);
+        return TodoItemsStorage.toJson(items);
+    }
+
+    boolean save(String filename) {
+        return TodoItemsStorage.save(filename, items);
+    }
+
+    public boolean save() {
+        return save(TodoItemsStorage.TODO_LIST_SAVE_NAME);
+    }
+
+    void load(String filename) {
+        add(TodoItemsStorage.load(filename));
+    }
+
+    public void load() {
+        load(TodoItemsStorage.TODO_LIST_SAVE_NAME);
     }
 
 
+    public TodoItem get(long id) {
+        return idCache.getOrDefault(id, null);
+    }
+
+
+
 }

app/src/main/java/org/cutem/cutecalendar/model/TodoItemsStorage.java

@@ -0,0 +1,63 @@
+package org.cutem.cutecalendar.model;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonParser;
+import org.jetbrains.annotations.NotNull;
+
+import java.io.*;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+public class TodoItemsStorage {
+    public static final String TODO_LIST_SAVE_NAME = "todo-list.json";
+
+    public static String toJson(Collection<TodoItem> items) {
+        GsonBuilder gsonBuilder = new GsonBuilder();
+        gsonBuilder.registerTypeAdapter(TodoItem.class, new TodoItemSerializer());
+        return gsonBuilder.create().toJson(items);
+    }
+
+    public static boolean save(@NotNull String filename, Collection<TodoItem> items) {
+        GsonBuilder gsonBuilder = new GsonBuilder();
+        gsonBuilder.registerTypeAdapter(TodoItem.class, new TodoItemSerializer());
+        Gson gson = gsonBuilder.create();
+
+        try (
+                OutputStream out = new BufferedOutputStream(new FileOutputStream(filename))
+        ) {
+            OutputStreamWriter writer = new OutputStreamWriter(out);
+            gson.toJson(items, writer);
+            writer.flush();
+        } catch (IOException ex) {
+            return false;
+        }
+
+        return true;
+    }
+
+    public static List<TodoItem> load(@NotNull String filename) {
+        ArrayList<TodoItem> items = new ArrayList<>();
+
+        try (
+                InputStream in = new BufferedInputStream(new FileInputStream(filename))
+        ) {
+            JsonParser parser = new JsonParser();
+            JsonArray ele = parser.parse(new InputStreamReader(in)).getAsJsonArray();
+
+            GsonBuilder gsonBuilder = new GsonBuilder();
+            gsonBuilder.registerTypeAdapter(TodoItem.class, new TodoItemDeserializer());
+            Gson gson = gsonBuilder.create();
+
+            ele.forEach(o -> items.add(gson.fromJson(o, TodoItem.class)));
+
+        } catch (IOException ex) {
+            // do nothing
+        }
+
+        return items;
+    }
+
+}

app/src/test/java/org/cutem/cutecalendar/model/TodoItemManagerTest.java

@@ -6,16 +6,19 @@ import org.junit.Test;
 
 import java.util.Calendar;
 
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotEquals;
 
 public class TodoItemManagerTest {
 
     @Before
     public void setUp() {
+        System.out.println("##### TodoItemManagerTest *bgn* #####");
     }
 
     @After
     public void tearDown() {
+        System.out.println("##### TodoItemManagerTest *end* #####");
     }
 
     @Test
@@ -45,17 +48,32 @@ public class TodoItemManagerTest {
 
         assertNotEquals(item1, item2);
 
+        String oldJson = manager.toJson();
         System.out.println(
-                manager.toJson()
+                oldJson
         );
 
         manager.remove(item1);
-
         System.out.println(
                 manager.toJson()
         );
 
+        String filename = "build/" + TodoItemsStorage.TODO_LIST_SAVE_NAME;
+        manager.remove(item1);
+        manager.remove(item2);
+        manager.add(item1);
+        manager.add(item2);
+        System.out.println(manager.toJson());
+        System.out.println(manager.save(filename));
+        manager.remove(item1);
+        manager.remove(item2);
+        manager.load(filename);
 
+        String newJson = manager.toJson();
+        System.out.println(
+                newJson
+        );
+        assertEquals(oldJson, newJson);
     }