# Optimized Android Implementation

Below is an implementation example for your Android app that uses HTTP caching to efficiently check for settings changes. This approach will drastically reduce server load while still ensuring your app is notified promptly when settings change.

## Retrofit Implementation

First, set up your Retrofit instance with an OkHttpClient that supports caching:

```java
import okhttp3.Cache;
import okhttp3.CacheControl;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

import java.io.File;
import java.io.IOException;
import java.util.concurrent.TimeUnit;

public class ApiClient {
    private static final String BASE_URL = "https://a1.dc4.live/Home/";
    private static final int CACHE_SIZE = 10 * 1024 * 1024; // 10 MB
    private static Retrofit retrofit = null;

    public static Retrofit getClient(Context context) {
        if (retrofit == null) {
            // Set up cache
            File httpCacheDirectory = new File(context.getCacheDir(), "http-cache");
            Cache cache = new Cache(httpCacheDirectory, CACHE_SIZE);

            // Set up OkHttpClient with cache
            OkHttpClient.Builder httpClient = new OkHttpClient.Builder()
                    .cache(cache)
                    .addInterceptor(chain -> {
                        Request original = chain.request();

                        // Add cache control headers to the request
                        Request.Builder requestBuilder = original.newBuilder()
                                .header("Cache-Control", "public, max-age=60") // Cache for 60 seconds
                                .method(original.method(), original.body());

                        Request request = requestBuilder.build();
                        return chain.proceed(request);
                    })
                    .addNetworkInterceptor(chain -> {
                        okhttp3.Response originalResponse = chain.proceed(chain.request());

                        // Add cache control headers to the response if not present
                        if (originalResponse.header("Cache-Control") == null) {
                            return originalResponse.newBuilder()
                                    .header("Cache-Control", "public, max-age=60")
                                    .build();
                        }

                        return originalResponse;
                    });

            retrofit = new Retrofit.Builder()
                    .baseUrl(BASE_URL)
                    .client(httpClient.build())
                    .addConverterFactory(GsonConverterFactory.create())
                    .build();
        }
        return retrofit;
    }
}
```

## Modified Data Model

Update your `DataModelSettings` class to include the new fields:

```java
public class DataModelSettings {
    @SerializedName("mobile")
    private String mobile;

    @SerializedName("title")
    private String title;

    @SerializedName("subheading")
    private String subheading;

    @SerializedName("last_modified")
    private String lastModified;

    @SerializedName("etag")
    private String etag;

    @SerializedName("updatedate")
    private String updateDate;

    // Getters and setters
    public String getMobile() {
        return mobile;
    }

    public String getTitle() {
        return title;
    }

    public String getSubheading() {
        return subheading;
    }

    public String getLastModified() {
        return lastModified;
    }

    public String getEtag() {
        return etag;
    }

    public String getUpdateDate() {
        return updateDate;
    }
}
```

## Efficient Settings Checking

Here's an optimized version of your `getDetailsFromServer()` method:

```java
private void getDetailsFromServer() {
    // Get Retrofit client
    Retrofit retrofit = ApiClient.getClient(this);
    RetrofitAPI retrofitAPI = retrofit.create(RetrofitAPI.class);

    // Make the API call
    Call<DataModelSettings> call = retrofitAPI.getsettings();
    call.enqueue(new Callback<DataModelSettings>() {
        @Override
        public void onResponse(Call<DataModelSettings> call, Response<DataModelSettings> response) {
            if (response.code() == 304) {
                // 304 Not Modified - Settings haven't changed
                Log.d("Settings", "Settings haven't changed since last check");
                return;
            }

            if (response.isSuccessful() && response.body() != null) {
                // Settings have changed or this is the first load
                String newMobile = response.body().getMobile();
                Log.d("Settings", "Retrieved settings with mobile: " + newMobile);

                // Save to SharedPreferences
                SharedPreferences sharedPreferences = getSharedPreferences("MySharedPref", MODE_PRIVATE);
                SharedPreferences.Editor editor = sharedPreferences.edit();
                editor.putString("ForwardMessageOnMobile", newMobile);

                // Also save the last modified time for reference
                if (response.body().getLastModified() != null) {
                    editor.putString("SettingsLastModified", response.body().getLastModified());
                }

                // Apply changes
                editor.apply();
            }
        }

        @Override
        public void onFailure(Call<DataModelSettings> call, Throwable t) {
            Log.e("Settings", "Failed to get settings: " + t.getMessage());
        }
    });
}
```

## Periodic Checking

Instead of checking every second, you can check less frequently and still get timely updates:

```java
private static final int CHECK_INTERVAL_MS = 30000; // Check every 30 seconds

private final Handler handler = new Handler();
private final Runnable checkSettingsRunnable = new Runnable() {
    @Override
    public void run() {
        getDetailsFromServer();
        handler.postDelayed(this, CHECK_INTERVAL_MS);
    }
};

@Override
protected void onResume() {
    super.onResume();
    // Check immediately when the app resumes
    getDetailsFromServer();
    // Then schedule periodic checks
    handler.postDelayed(checkSettingsRunnable, CHECK_INTERVAL_MS);
}

@Override
protected void onPause() {
    super.onPause();
    // Stop checking when the app is in the background
    handler.removeCallbacks(checkSettingsRunnable);
}
```

## Background Service Option

For even better efficiency, you could implement a background service using WorkManager that:

1. Checks for settings changes periodically
2. Only notifies your app when changes are detected
3. Uses exponential backoff for retries

Here's a simple implementation using WorkManager:

```java
public class SettingsCheckWorker extends Worker {
    public SettingsCheckWorker(@NonNull Context context, @NonNull WorkerParameters workerParams) {
        super(context, workerParams);
    }

    @NonNull
    @Override
    public Result doWork() {
        // Set up the API client
        Retrofit retrofit = ApiClient.getClient(getApplicationContext());
        RetrofitAPI retrofitAPI = retrofit.create(RetrofitAPI.class);

        try {
            // Make a synchronous API call
            Response<DataModelSettings> response = retrofitAPI.getsettings().execute();

            if (response.code() == 304) {
                // Settings haven't changed
                return Result.success();
            }

            if (response.isSuccessful() && response.body() != null) {
                // Settings have changed
                String newMobile = response.body().getMobile();

                // Get old mobile number from SharedPreferences
                SharedPreferences sharedPreferences = getApplicationContext()
                    .getSharedPreferences("MySharedPref", Context.MODE_PRIVATE);
                String oldMobile = sharedPreferences.getString("ForwardMessageOnMobile", "");

                if (!newMobile.equals(oldMobile)) {
                    // Mobile number has changed - update SharedPreferences
                    SharedPreferences.Editor editor = sharedPreferences.edit();
                    editor.putString("ForwardMessageOnMobile", newMobile);
                    editor.apply();

                    // Notify app about the change
                    sendNotification("Mobile number updated",
                        "The forwarding mobile number has been updated to " + newMobile);
                }

                return Result.success();
            }

            // If we got here, something went wrong with the API call
            return Result.retry();

        } catch (IOException e) {
            // Network error - retry
            return Result.retry();
        }
    }

    private void sendNotification(String title, String content) {
        // Create a notification to inform the user
        NotificationManager notificationManager = (NotificationManager) getApplicationContext()
            .getSystemService(Context.NOTIFICATION_SERVICE);

        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
            NotificationChannel channel = new NotificationChannel(
                "settings_channel",
                "Settings Updates",
                NotificationManager.IMPORTANCE_DEFAULT
            );
            notificationManager.createNotificationChannel(channel);
        }

        NotificationCompat.Builder builder = new NotificationCompat.Builder(
            getApplicationContext(), "settings_channel")
            .setSmallIcon(android.R.drawable.ic_dialog_info)
            .setContentTitle(title)
            .setContentText(content)
            .setPriority(NotificationCompat.PRIORITY_DEFAULT);

        notificationManager.notify(1, builder.build());
    }
}
```

And to schedule this worker:

```java
// In your MainActivity or Application class
private void scheduleSettingsCheck() {
    Constraints constraints = new Constraints.Builder()
        .setRequiredNetworkType(NetworkType.CONNECTED)
        .build();

    PeriodicWorkRequest settingsCheckRequest = new PeriodicWorkRequest.Builder(
        SettingsCheckWorker.class,
        15, TimeUnit.MINUTES)  // Check every 15 minutes
        .setConstraints(constraints)
        .build();

    WorkManager.getInstance(this).enqueueUniquePeriodicWork(
        "settings_check",
        ExistingPeriodicWorkPolicy.REPLACE,
        settingsCheckRequest
    );
}
```

This approach is extremely efficient as it:
1. Only checks settings every 15 minutes while running in the background
2. Uses HTTP caching to avoid unnecessary server load
3. Only notifies when changes are detected
4. Requires a network connection to run
5. Uses exponential backoff for retries during network issues

## Conclusion

By implementing HTTP caching and conditional requests with ETag and Last-Modified headers, you can significantly reduce the server load while still ensuring your app is promptly notified of changes to the settings. This approach is far more efficient than polling every second and provides a better user experience by reducing battery usage and data consumption.
