compose: Minor improvements for download/install

Make purchase action noncancellable to allow it to happen even if user navigates
away from the screen after requesting it.

Also, don't allow expanding at all if no files are available as both actions at the
moment requires files to be available.

Signed-off-by: Aayush Gupta <aayushgupta219@gmail.com>

app/src/main/java/com/aurora/store/compose/composables/DownloadComposable.kt

@@ -137,7 +137,8 @@ fun DownloadComposable(
                 trailingButton = {
                     SplitButtonDefaults.TrailingButton(
                         checked = isExpanded,
-                        onCheckedChange = { isExpanded = it }
+                        onCheckedChange = { isExpanded = it },
+                        enabled = download.canInstall(context)
                     ) {
                         Icon(
                             painter = when {

app/src/main/java/com/aurora/store/viewmodel/details/AppDetailsViewModel.kt

@@ -40,6 +40,7 @@ import com.aurora.store.util.Preferences.PREFERENCE_UPDATES_EXTENDED
 import dagger.hilt.android.lifecycle.HiltViewModel
 import dagger.hilt.android.qualifiers.ApplicationContext
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.NonCancellable
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.SharingStarted
@@ -219,7 +220,7 @@ class AppDetailsViewModel @Inject constructor(
     }
 
     fun purchase(app: App) {
-        viewModelScope.launch(Dispatchers.IO) {
+        viewModelScope.launch(NonCancellable + Dispatchers.IO) {
             try {
                 _state.value = AppState.Downloading(0F, 0 ,0)
                 val files = purchaseHelper.purchase(app.packageName, app.versionCode, app.offerType)