feat:Android notification

apps/frontend/android/app/build.gradle

@@ -1,5 +1,10 @@
+import groovy.json.JsonOutput
+
 apply plugin: 'com.android.application'
 
+def apiBaseUrl = project.hasProperty("API_BASE_URL") ? project.property("API_BASE_URL") : "http://10.0.2.2:4000/api"
+def notificationSecret = project.hasProperty("NOTIFICATION_WEBHOOK_SECRET") ? project.property("NOTIFICATION_WEBHOOK_SECRET") : "CHANGE_ME"
+
 android {
     namespace "com.bill.ai"
     compileSdk rootProject.ext.compileSdkVersion
@@ -15,6 +20,11 @@ android {
              // Default: https://android.googlesource.com/platform/frameworks/base/+/282e181b58cf72b6ca770dc7ca5f91f135444502/tools/aapt/AaptAssets.cpp#61
             ignoreAssetsPattern '!.svn:!.git:!.ds_store:!*.scc:.*:!CVS:!thumbs.db:!picasa.ini:!*~'
         }
+        buildConfigField "String", "API_BASE_URL", JsonOutput.toJson(apiBaseUrl)
+        buildConfigField "String", "NOTIFICATION_WEBHOOK_SECRET", JsonOutput.toJson(notificationSecret)
+    }
+    buildFeatures {
+        buildConfig true
     }
     buildTypes {
         release {
@@ -36,6 +46,7 @@ dependencies {
     implementation "androidx.coordinatorlayout:coordinatorlayout:$androidxCoordinatorLayoutVersion"
     implementation "androidx.core:core-splashscreen:$coreSplashScreenVersion"
     implementation project(':capacitor-android')
+    implementation "com.squareup.okhttp3:okhttp:4.12.0"
     testImplementation "junit:junit:$junitVersion"
     androidTestImplementation "androidx.test.ext:junit:$androidxJunitVersion"
     androidTestImplementation "androidx.test.espresso:espresso-core:$androidxEspressoCoreVersion"

apps/frontend/android/app/src/main/AndroidManifest.xml

@@ -33,9 +33,20 @@
                 android:name="android.support.FILE_PROVIDER_PATHS"
                 android:resource="@xml/file_paths"></meta-data>
         </provider>
+
+        <service
+            android:name=".notification.AiBillNotificationListenerService"
+            android:exported="true"
+            android:label="@string/app_name"
+            android:permission="android.permission.BIND_NOTIFICATION_LISTENER_SERVICE">
+            <intent-filter>
+                <action android:name="android.service.notification.NotificationListenerService" />
+            </intent-filter>
+        </service>
     </application>
 
     <!-- Permissions -->
 
     <uses-permission android:name="android.permission.INTERNET" />
+    <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
 </manifest>

apps/frontend/android/app/src/main/java/com/bill/ai/notification/AiBillNotificationListenerService.java

@@ -0,0 +1,141 @@
+package com.bill.ai.notification;
+
+import android.app.Notification;
+import android.os.Bundle;
+import android.service.notification.NotificationListenerService;
+import android.service.notification.StatusBarNotification;
+import android.text.TextUtils;
+import android.util.Log;
+
+import androidx.annotation.NonNull;
+
+import com.bill.ai.BuildConfig;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.util.Locale;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+import javax.crypto.Mac;
+import javax.crypto.spec.SecretKeySpec;
+
+import okhttp3.MediaType;
+import okhttp3.OkHttpClient;
+import okhttp3.Request;
+import okhttp3.RequestBody;
+import okhttp3.Response;
+
+/**
+ * Listens for system notifications and forwards selected ones to the AI Bill backend.
+ * Ensure the user has granted notification access permission to this app.
+ */
+public class AiBillNotificationListenerService extends NotificationListenerService {
+
+    private static final String TAG = "AiBillNotification";
+    private static final MediaType JSON = MediaType.get("application/json; charset=utf-8");
+
+    private final OkHttpClient httpClient = new OkHttpClient();
+    private final ExecutorService executor = Executors.newSingleThreadExecutor();
+
+    @Override
+    public void onNotificationPosted(StatusBarNotification sbn) {
+        if (sbn == null) {
+            return;
+        }
+
+        Notification notification = sbn.getNotification();
+        if (notification == null) {
+            return;
+        }
+
+        Bundle extras = notification.extras;
+        CharSequence titleCs = extras != null ? extras.getCharSequence(Notification.EXTRA_TITLE) : null;
+        CharSequence textCs = extras != null ? extras.getCharSequence(Notification.EXTRA_TEXT) : null;
+
+        final String packageName = sbn.getPackageName();
+        final String title = titleCs != null ? titleCs.toString() : "";
+        final String body = textCs != null ? textCs.toString() : "";
+        final long timestamp = sbn.getPostTime();
+
+        if (TextUtils.isEmpty(packageName) || (TextUtils.isEmpty(title) && TextUtils.isEmpty(body))) {
+            return;
+        }
+
+        executor.execute(() -> sendToBackend(packageName, title, body, timestamp));
+    }
+
+    private void sendToBackend(@NonNull String packageName,
+                               @NonNull String title,
+                               @NonNull String body,
+                               long timestamp) {
+        String baseUrl = BuildConfig.API_BASE_URL != null ? BuildConfig.API_BASE_URL : "";
+        if (TextUtils.isEmpty(baseUrl)) {
+            Log.w(TAG, "API base URL is empty, skip notification upload");
+            return;
+        }
+
+        String endpoint = baseUrl.endsWith("/") ? baseUrl + "transactions/notification" : baseUrl + "/transactions/notification";
+        String payloadToSign = String.format(Locale.US, "%s|%s|%s|%d", packageName, title, body, timestamp);
+        String signature = computeSignature(payloadToSign, BuildConfig.NOTIFICATION_WEBHOOK_SECRET);
+
+        if (signature == null) {
+            Log.w(TAG, "Failed to compute signature, abort upload");
+            return;
+        }
+
+        String json = String.format(Locale.US,
+                "{\"packageName\":\"%s\",\"title\":\"%s\",\"body\":\"%s\",\"receivedAt\":%d,\"signature\":\"%s\"}",
+                escapeJson(packageName), escapeJson(title), escapeJson(body), timestamp, signature);
+
+        Request request = new Request.Builder()
+                .url(endpoint)
+                .post(RequestBody.create(json, JSON))
+                .build();
+
+        try (Response response = httpClient.newCall(request).execute()) {
+            if (!response.isSuccessful()) {
+                Log.w(TAG, "Notification upload failed: " + response.code() + " - " + response.message());
+            } else {
+                Log.d(TAG, "Notification uploaded successfully");
+            }
+        } catch (IOException e) {
+            Log.e(TAG, "Notification upload error", e);
+        }
+    }
+
+    private String computeSignature(String payload, String secret) {
+        if (TextUtils.isEmpty(secret)) {
+            Log.w(TAG, "Webhook secret not configured");
+            return null;
+        }
+        try {
+            Mac mac = Mac.getInstance("HmacSHA256");
+            SecretKeySpec keySpec = new SecretKeySpec(secret.getBytes(StandardCharsets.UTF_8), "HmacSHA256");
+            mac.init(keySpec);
+            byte[] digest = mac.doFinal(payload.getBytes(StandardCharsets.UTF_8));
+            return bytesToHex(digest);
+        } catch (Exception e) {
+            Log.e(TAG, "Failed to compute signature", e);
+            return null;
+        }
+    }
+
+    private String bytesToHex(byte[] bytes) {
+        StringBuilder sb = new StringBuilder(bytes.length * 2);
+        for (byte b : bytes) {
+            sb.append(String.format(Locale.US, "%02x", b));
+        }
+        return sb.toString();
+    }
+
+    private String escapeJson(String value) {
+        return value.replace("\\", "\\\\").replace("\"", "\\\"");
+    }
+
+    @Override
+    public void onDestroy() {
+        super.onDestroy();
+        executor.shutdownNow();
+    }
+}