Prevent corner-case where link previews were generated for SMS.

Also added some hardening to make sure that it's impossible for any link
previews to be fetched if the setting is disabled (this was already the
case in practice, we just have some assertions in there now).

Fixes #9956

app/src/main/java/org/thoughtcrime/securesms/conversation/ConversationActivity.java

@@ -1840,6 +1840,7 @@ public class ConversationActivity extends PassphraseRequiredActivity
     sendButton.addOnTransportChangedListener((newTransport, manuallySelected) -> {
       calculateCharactersRemaining();
       updateLinkPreviewState();
+      linkPreviewViewModel.onTransportChanged(newTransport.isSms());
       composeText.setTransport(newTransport);
 
       buttonToggle.getBackground().setColorFilter(newTransport.getBackgroundColor(), PorterDuff.Mode.MULTIPLY);
@@ -2692,7 +2693,7 @@ public class ConversationActivity extends PassphraseRequiredActivity
   }
 
   private void updateLinkPreviewState() {
-    if (SignalStore.settings().isLinkPreviewsEnabled() && !sendButton.getSelectedTransport().isSms() && !attachmentManager.isAttachmentPresent()) {
+    if (SignalStore.settings().isLinkPreviewsEnabled() && isSecureText && !sendButton.getSelectedTransport().isSms() && !attachmentManager.isAttachmentPresent()) {
       linkPreviewViewModel.onEnabled();
       linkPreviewViewModel.onTextChanged(this, composeText.getTextTrimmed().toString(), composeText.getSelectionStart(), composeText.getSelectionEnd());
     } else {

app/src/main/java/org/thoughtcrime/securesms/linkpreview/LinkPreviewViewModel.java

@@ -7,9 +7,11 @@ import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.lifecycle.LiveData;
 import androidx.lifecycle.MutableLiveData;
+import androidx.lifecycle.Transformations;
 import androidx.lifecycle.ViewModel;
 import androidx.lifecycle.ViewModelProvider;
 
+import org.thoughtcrime.securesms.keyvalue.SignalStore;
 import org.thoughtcrime.securesms.net.RequestController;
 import org.thoughtcrime.securesms.util.Debouncer;
 import org.thoughtcrime.securesms.util.Util;
@@ -23,32 +25,36 @@ public class LinkPreviewViewModel extends ViewModel {
 
   private final LinkPreviewRepository             repository;
   private final MutableLiveData<LinkPreviewState> linkPreviewState;
+  private final LiveData<LinkPreviewState>        linkPreviewSafeState;
 
   private String            activeUrl;
   private RequestController activeRequest;
   private boolean           userCanceled;
   private Debouncer         debouncer;
+  private boolean           enabled;
 
   private LinkPreviewViewModel(@NonNull LinkPreviewRepository repository) {
-    this.repository       = repository;
+    this.repository           = repository;
-    this.linkPreviewState = new MutableLiveData<>();
+    this.linkPreviewState     = new MutableLiveData<>();
-    this.debouncer        = new Debouncer(250);
+    this.debouncer            = new Debouncer(250);
+    this.enabled              = SignalStore.settings().isLinkPreviewsEnabled();
+    this.linkPreviewSafeState = Transformations.map(linkPreviewState, state -> enabled ? state : LinkPreviewState.forNoLinks());
   }
 
   public LiveData<LinkPreviewState> getLinkPreviewState() {
-    return linkPreviewState;
+    return linkPreviewSafeState;
   }
 
   public boolean hasLinkPreview() {
-    return linkPreviewState.getValue() != null && linkPreviewState.getValue().getLinkPreview().isPresent();
+    return linkPreviewSafeState.getValue() != null && linkPreviewSafeState.getValue().getLinkPreview().isPresent();
   }
 
   public boolean hasLinkPreviewUi() {
-    return linkPreviewState.getValue() != null && linkPreviewState.getValue().hasContent();
+    return linkPreviewSafeState.getValue() != null && linkPreviewSafeState.getValue().hasContent();
   }
 
   public @NonNull List<LinkPreview> getActiveLinkPreviews() {
-    final LinkPreviewState state = linkPreviewState.getValue();
+    final LinkPreviewState state = linkPreviewSafeState.getValue();
 
     if (state == null || !state.getLinkPreview().isPresent()) {
       return Collections.emptyList();
@@ -58,6 +64,8 @@ public class LinkPreviewViewModel extends ViewModel {
   }
 
   public void onTextChanged(@NonNull Context context, @NonNull String text, int cursorStart, int cursorEnd) {
+    if (!enabled) return;
+
     debouncer.publish(() -> {
       if (TextUtils.isEmpty(text)) {
         userCanceled = false;
@@ -129,6 +137,14 @@ public class LinkPreviewViewModel extends ViewModel {
     linkPreviewState.setValue(LinkPreviewState.forNoLinks());
   }
 
+  public void onTransportChanged(boolean isSms) {
+    enabled = !isSms;
+
+    if (isSms) {
+      onUserCancel();
+    }
+  }
+
   public void onSend() {
     if (activeRequest != null) {
       activeRequest.cancel();
@@ -143,7 +159,12 @@ public class LinkPreviewViewModel extends ViewModel {
   }
 
   public void onEnabled() {
+    if (!SignalStore.settings().isLinkPreviewsEnabled()) {
+      throw new AssertionError();
+    }
+
     userCanceled = false;
+    enabled      = true;
   }
 
   @Override