Review comments: split up/document into smaller functions

Author: jpelgrom

app/src/main/kotlin/io/homeassistant/companion/android/webview/WebViewPresenterImpl.kt

@@ -507,42 +507,7 @@ class WebViewPresenterImpl @Inject constructor(
             mainScope.launch {
                 if (tlv != null && borderAgentId != null) {
                     Timber.d("Matter commissioning payload has preferred Thread dataset, comparing")
-                    val isPreferred = threadUseCase.isPreferredDatasetByDevice(context, tlv)
-
-                    if (isPreferred) {
-                        Timber.d("Device prefers core preferred dataset, starting commissioning")
-                        startMatterCommissioningFlow(context)
-                    } else if (!threadUseCase.hasSyncedPreferredDataset(serverId)) {
-                        // We only sync if the server has never synced, as a full sync can be slow
-                        Timber.d("Device doesn't prefer core preferred dataset, starting first sync")
-                        val deviceThreadIntent = try {
-                            val result = threadUseCase.syncPreferredDataset(
-                                context = context,
-                                serverId = serverId,
-                                exportOnly = false,
-                                scope = CoroutineScope(mainScope.coroutineContext + SupervisorJob()),
-                            )
-                            when (result) {
-                                is ThreadManager.SyncResult.OnlyOnDevice -> result.exportIntent
-                                is ThreadManager.SyncResult.AllHaveCredentials -> result.exportIntent
-                                else -> null
-                            }
-                        } catch (e: Exception) {
-                            Timber.w(e, "Unable to sync preferred Thread dataset, continuing")
-                            null
-                        }
-                        if (deviceThreadIntent != null) {
-                            matterThreadIntentSender = deviceThreadIntent
-                            mutableMatterThreadStep.tryEmit(MatterThreadStep.THREAD_EXPORT_TO_SERVER_MATTER)
-                        } else {
-                            startMatterCommissioningFlow(context)
-                        }
-                    } else {
-                        Timber.d(
-                            "Device doesn't prefer core preferred dataset but has previously synced, starting commissioning",
-                        )
-                        startMatterCommissioningFlow(context)
-                    }
+                    compareThreadCredentialsForCommissioning(context, tlv)
                 } else {
                     Timber.d("Matter commissioning payload doesn't have Thread, starting commissioning")
                     startMatterCommissioningFlow(context)
@@ -551,6 +516,67 @@ class WebViewPresenterImpl @Inject constructor(
         } // else already waiting for a result, don't send another request
     }
 
+    /**
+     * Compare Thread credentials supplied for Matter commissioning, and take action depending on the device state:
+     * - Device prefers credentials: start (external) Matter commissioning flow
+     * - Device doesn't prefer credentials:
+     *    - Has never synced Thread for the server: do a full Thread credentials sync (this will usually result in the
+     *    credentials becoming preferred)
+     *    - Has previously synced Thread for the server: start (external) Matter commissioning flow (the app is
+     *    expected to be unable to change the preferred state by syncing)
+     */
+    private suspend fun compareThreadCredentialsForCommissioning(context: Context, tlv: String) {
+        val isPreferred = threadUseCase.isPreferredDatasetByDevice(context, tlv)
+
+        if (isPreferred) {
+            Timber.d("Device prefers core preferred dataset, starting commissioning")
+            startMatterCommissioningFlow(context)
+        } else if (!threadUseCase.hasSyncedPreferredDataset(serverId)) {
+            // We only sync if the server has never synced, as a full sync can be slow
+            Timber.d("Device doesn't prefer core preferred dataset, starting first sync")
+            val syncExportIntent = syncThreadDataset(context)
+
+            if (syncExportIntent != null) {
+                matterThreadIntentSender = syncExportIntent
+                mutableMatterThreadStep.tryEmit(MatterThreadStep.THREAD_EXPORT_TO_SERVER_MATTER)
+            } else {
+                startMatterCommissioningFlow(context)
+            }
+        } else {
+            Timber.d(
+                "Device doesn't prefer core preferred dataset, has previously synced, starting commissioning",
+            )
+            startMatterCommissioningFlow(context)
+        }
+    }
+
+    /**
+     * Try to sync the preferred Thread dataset between the server and the device.
+     * @return [IntentSender] if syncing requires starting an intent to complete (export to server), otherwise `null`
+     */
+    private suspend fun syncThreadDataset(context: Context): IntentSender? {
+        return try {
+            val result = threadUseCase.syncPreferredDataset(
+                context = context,
+                serverId = serverId,
+                exportOnly = false,
+                scope = CoroutineScope(mainScope.coroutineContext + SupervisorJob()),
+            )
+            when (result) {
+                is ThreadManager.SyncResult.OnlyOnDevice -> result.exportIntent
+                is ThreadManager.SyncResult.AllHaveCredentials -> result.exportIntent
+                else -> null
+            }
+        } catch (e: Exception) {
+            Timber.w(e, "Unable to sync preferred Thread dataset, continuing")
+            null
+        }
+    }
+
+    /**
+     * Start the (external) Matter commissioning flow. Depending on the result, this will emit a new step with the
+     * intent to open the activity, or a new step for an error.
+     * */
     private fun startMatterCommissioningFlow(context: Context) {
         matterUseCase.startNewCommissioningFlow(
             context,