feat: support add=true in QR codes (#1151)

app/src/main/java/com/geeksville/mesh/MainActivity.kt

@@ -35,6 +35,7 @@ import com.geeksville.mesh.model.BluetoothViewModel
 import com.geeksville.mesh.model.DeviceVersion
 import com.geeksville.mesh.model.UIViewModel
 import com.geeksville.mesh.model.primaryChannel
+import com.geeksville.mesh.model.shouldAddChannels
 import com.geeksville.mesh.model.toChannelSet
 import com.geeksville.mesh.repository.radio.BluetoothInterface
 import com.geeksville.mesh.service.*
@@ -399,27 +400,37 @@ class MainActivity : AppCompatActivity(), Logging {
         }
     }
 
+    @Suppress("NestedBlockDepth")
     private fun perhapsChangeChannel(url: Uri? = requestedChannelUrl) {
         // if the device is connected already, process it now
         if (url != null && model.isConnected()) {
             requestedChannelUrl = null
             try {
                 val channels = url.toChannelSet()
+                val shouldAdd = url.shouldAddChannels()
                 val primary = channels.primaryChannel
                 if (primary == null)
                     showSnackbar(R.string.channel_invalid)
                 else {
-
+                    val dialogMessage = if (!shouldAdd) {
+                        getString(R.string.do_you_want_switch).format(primary.name)
+                    } else {
+                        resources.getQuantityString(
+                            R.plurals.add_channel_from_qr,
+                            channels.settingsCount,
+                            channels.settingsCount
+                        )
+                    }
                     MaterialAlertDialogBuilder(this)
                         .setTitle(R.string.new_channel_rcvd)
-                        .setMessage(getString(R.string.do_you_want_switch).format(primary.name))
+                        .setMessage(dialogMessage)
                         .setNeutralButton(R.string.cancel) { _, _ ->
                             // Do nothing
                         }
                         .setPositiveButton(R.string.accept) { _, _ ->
                             debug("Setting channel from URL")
                             try {
-                                model.setChannels(channels)
+                                model.setChannels(channels, !shouldAdd)
                             } catch (ex: RemoteException) {
                                 errormsg("Couldn't change channel ${ex.message}")
                                 showSnackbar(R.string.cant_change_no_radio)

app/src/main/java/com/geeksville/mesh/model/ChannelSet.kt

@@ -12,22 +12,48 @@ import java.net.MalformedURLException
 import kotlin.jvm.Throws
 
 internal const val URL_PREFIX = "https://meshtastic.org/e/#"
+private const val MESHTASTIC_DOMAIN = "meshtastic.org"
+private const val MESHTASTIC_CHANNEL_CONFIG_PATH = "/e/"
 private const val BASE64FLAGS = Base64.URL_SAFE + Base64.NO_WRAP + Base64.NO_PADDING
 
 /**
- * Return a [ChannelSet] that represents the URL
+ * Return a [ChannelSet] that represents the ChannelSet encoded by the URL.
  * @throws MalformedURLException when not recognized as a valid Meshtastic URL
  */
 @Throws(MalformedURLException::class)
 fun Uri.toChannelSet(): ChannelSet {
-    val urlStr = this.toString()
+    if (fragment.isNullOrBlank() ||
+        !host.equals(MESHTASTIC_DOMAIN, true) ||
+        !path.equals(MESHTASTIC_CHANNEL_CONFIG_PATH, true)
+    ) {
+        throw MalformedURLException("Not a valid Meshtastic URL: ${toString().take(40)}")
+    }
 
-    val pathRegex = Regex("$URL_PREFIX(.*)", RegexOption.IGNORE_CASE)
-    val (base64) = pathRegex.find(urlStr)?.destructured
-        ?: throw MalformedURLException("Not a Meshtastic URL: ${urlStr.take(40)}")
-    val bytes = Base64.decode(base64, BASE64FLAGS)
+    // Older versions of Meshtastic clients (Apple/web) included `?add=true` within the URL fragment.
+    // This gracefully handles those cases until the newer version are generally available/used.
+    return ChannelSet.parseFrom(Base64.decode(fragment!!.substringBefore('?'), BASE64FLAGS))
+}
 
-    return ChannelSet.parseFrom(bytes)
+/**
+ * Return a [Boolean] if the URL indicates the associated [ChannelSet] should be added to the
+ * existing configuration.
+ * @throws MalformedURLException when not recognized as a valid Meshtastic URL
+ */
+@Throws(MalformedURLException::class)
+fun Uri.shouldAddChannels(): Boolean {
+    if (fragment.isNullOrBlank() ||
+        !host.equals(MESHTASTIC_DOMAIN, true) ||
+        !path.equals(MESHTASTIC_CHANNEL_CONFIG_PATH, true)
+    ) {
+        throw MalformedURLException("Not a valid Meshtastic URL: ${toString().take(40)}")
+    }
+
+    // Older versions of Meshtastic clients (Apple/web) included `?add=true` within the URL fragment.
+    // This gracefully handles those cases until the newer version are generally available/used.
+    return fragment?.substringAfter('?', "")
+        ?.takeUnless { it.isBlank() }
+        ?.equals("add=true")
+        ?: getBooleanQueryParameter("add", false)
 }
 
 /**

app/src/main/java/com/geeksville/mesh/model/UIState.kt

@@ -78,7 +78,7 @@ fun getInitials(nameIn: String): String {
  * Only changes are included in the resulting list.
  *
  * @param new The updated [ChannelSettings] list.
- * @param old The current [ChannelSettings] list (required to disable unused channels).
+ * @param old The current [ChannelSettings] list (required when disabling unused channels).
  * @return A [Channel] list containing only the modified channels.
  */
 internal fun getChannelList(
@@ -394,13 +394,25 @@ class UIViewModel @Inject constructor(
         meshService?.setChannel(channel.toByteArray())
     }
 
-    // Set the radio config (also updates our saved copy in preferences)
-    fun setChannels(channelSet: AppOnlyProtos.ChannelSet) = viewModelScope.launch {
-        getChannelList(channelSet.settingsList, channels.value.settingsList).forEach(::setChannel)
-        radioConfigRepository.replaceAllSettings(channelSet.settingsList)
+    /**
+     * Set the radio config (also updates our saved copy in preferences). By default, this will replace
+     * all channels in the existing radio config. Otherwise, it will append all [ChannelSettings] that
+     * are unique in [channelSet] to the existing radio config.
+     */
+    fun setChannels(channelSet: AppOnlyProtos.ChannelSet, overwrite: Boolean = true) = viewModelScope.launch {
+        val newRadioSettings: List<ChannelSettings> = if (overwrite) {
+            channelSet.settingsList
+        }  else {
+            // To guarantee consistent ordering, using a LinkedHashSet which iterates through it's
+            // entries according to the order an item was *first* inserted.
+            // https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.collections/-linked-hash-set/
+            LinkedHashSet(channels.value.settingsList + channelSet.settingsList).toList()
+        }
 
+        getChannelList(newRadioSettings, channels.value.settingsList).forEach(::setChannel)
+        radioConfigRepository.replaceAllSettings(newRadioSettings)
         val newConfig = config { lora = channelSet.loraConfig }
-        if (config.lora != newConfig.lora) setConfig(newConfig)
+        if (overwrite && config.lora != newConfig.lora) setConfig(newConfig)
     }
 
     val provideLocation = object : MutableLiveData<Boolean>(preferences.getBoolean("provide-location", false)) {