feat: only allow sending SMS messages once per second to prevent incurring significant charges

Author: sds100

base/src/main/java/io/github/sds100/keymapper/base/utils/ErrorUtils.kt

@@ -249,6 +249,7 @@ fun KMError.getFullMessage(resourceProvider: ResourceProvider): String {
         PurchasingError.PurchasingNotImplemented -> resourceProvider.getString(R.string.purchasing_error_not_implemented)
 
         is KMError.KeyEventActionError -> resourceProvider.getString(R.string.error_fix_key_event_action)
+        is KMError.KeyMapperSmsRateLimit -> resourceProvider.getString(R.string.error_sms_rate_limit)
 
         else -> this.toString()
     }

base/src/main/res/values/strings.xml

@@ -866,6 +866,7 @@
     <string name="error_ui_element_not_found">UI element not found!</string>
     <string name="error_shell_command_timeout">Command timed out after %1$d seconds</string>
     <string name="error_system_bridge_disconnected">PRO Mode needs starting</string>
+    <string name="error_sms_rate_limit">Rate limit reached. You can only send once per second.</string>
     <!-- Error messages -->
 
     <!-- action labels -->

common/src/main/java/io/github/sds100/keymapper/common/utils/KMResult.kt

@@ -60,6 +60,7 @@ abstract class KMError : KMResult<Nothing>() {
     data object NoAppToPhoneCall : KMError()
     data object NoAppToSendSms : KMError()
     data class SendSmsError(val resultCode: Int) : KMError()
+    data object KeyMapperSmsRateLimit : KMError()
 
     data class NotAFile(val uri: String) : KMError()
     data class NotADirectory(val uri: String) : KMError()

system/src/main/java/io/github/sds100/keymapper/system/phone/AndroidPhoneAdapter.kt

@@ -11,6 +11,7 @@ import android.content.Intent
 import android.content.IntentFilter
 import android.content.pm.PackageManager
 import android.os.Build
+import android.os.SystemClock
 import android.telecom.TelecomManager
 import android.telephony.PhoneStateListener
 import android.telephony.SmsManager
@@ -29,6 +30,7 @@ import kotlinx.coroutines.channels.Channel
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withTimeout
+import timber.log.Timber
 import javax.inject.Inject
 import javax.inject.Singleton
 
@@ -39,6 +41,11 @@ class AndroidPhoneAdapter @Inject constructor(
 ) : PhoneAdapter {
     companion object {
         private const val ACTION_SMS_SENT_RESULT = "io.github.sds100.keymapper.SMS_SENT_RESULT"
+
+        /**
+         * The minimum frequency that SMS messages can be sent.
+         */
+        private const val SMS_MIN_RATE_MILLIS = 1000L
     }
 
     private val ctx: Context = context.applicationContext
@@ -57,9 +64,17 @@ class AndroidPhoneAdapter @Inject constructor(
 
     override val callStateFlow: MutableSharedFlow<CallState> = MutableSharedFlow()
 
-    // Emits the result code in SmsManager
+    /**
+     * Emits the result code in SmsManager
+     */
     private val smsSentResultFlow = Channel<Int>()
 
+    /**
+     * The time the last SMS was sent. This is used to prevent someone accidentally incurring
+     * significant charges.
+     */
+    private var lastSmsTime: Long = -1
+
     private val broadcastReceiver: BroadcastReceiver = object : BroadcastReceiver() {
         override fun onReceive(context: Context?, intent: Intent?) {
             context ?: return
@@ -170,7 +185,13 @@ class AndroidPhoneAdapter @Inject constructor(
             )
 
         try {
+            if (SystemClock.uptimeMillis() - lastSmsTime < SMS_MIN_RATE_MILLIS) {
+                Timber.d("SMS rate limit exceeded to protect against significant costs")
+                return KMError.KeyMapperSmsRateLimit
+            }
+
             smsManager.sendTextMessage(number, null, message, sentPendingIntent, null)
+            lastSmsTime = SystemClock.uptimeMillis()
         } catch (e: IllegalArgumentException) {
             return KMError.Exception(e)
         }