import com.sun.istack.internal.Nullable;

import java.io.*;
import java.lang.reflect.Field;

public class MySerializer {

    private MySerializer() {}

    public static void saveToFile(String filePath, MySerializable mySerializable) throws IOException {
        FileOutputStream fileOutputStream = new FileOutputStream(new File(filePath));
        fileOutputStream.write(mySerializable.getBytes());
        fileOutputStream.flush();
        fileOutputStream.close();
    }

    public
    @Nullable
    static <T> T restoreFromFile(String filepath, Class<T> cls) throws IOException {
        try (FileInputStream fis = new FileInputStream(filepath);
             DataInputStream dataInputStream = new DataInputStream(fis)) {
            T object = cls.newInstance();
            for (Field field : cls.getDeclaredFields()) {
                if (field.isAnnotationPresent(Save.class)) {
                    byte type = dataInputStream.readByte();
                    // TODO if type != -1
                    MySerializable.Primitive primitive = MySerializable.Primitive.values()[type];
                    Object value;
                    switch (primitive) {
                        case INT:
                            value = dataInputStream.readInt();
                            break;
                        case CHAR:
                            value = dataInputStream.readChar();
                            break;
                        // TODO complete switch for all primitive types
                        default:
                            value = null;
                    }
                    field.set(object, value);
                }
            }
            return object;
        } catch (IOException e) {
            throw e;
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }
}