Clear formatting when pasting text.

Fixes #8058
Closes #12614

app/src/main/java/org/thoughtcrime/securesms/components/emoji/EmojiEditText.java

@@ -4,7 +4,12 @@ import android.content.Context;
 import android.content.res.TypedArray;
 import android.graphics.drawable.Drawable;
 import android.text.InputFilter;
+import android.text.Spannable;
+import android.text.SpannableString;
 import android.util.AttributeSet;
+import android.content.ClipData;
+import android.content.ClipboardManager;
+import android.text.Spanned;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
@@ -12,11 +17,15 @@ import androidx.appcompat.widget.AppCompatEditText;
 
 import org.thoughtcrime.securesms.R;
 import org.thoughtcrime.securesms.components.emoji.EmojiProvider.EmojiDrawable;
+import org.thoughtcrime.securesms.components.mention.MentionAnnotation;
+import org.thoughtcrime.securesms.database.model.Mention;
 import org.thoughtcrime.securesms.keyvalue.SignalStore;
 import org.thoughtcrime.securesms.util.EditTextExtensionsKt;
+import org.thoughtcrime.securesms.util.ServiceUtil;
 import org.thoughtcrime.securesms.util.TextSecurePreferences;
 
 import java.util.HashSet;
+import java.util.List;
 import java.util.Set;
 
 
@@ -95,4 +104,44 @@ public class EmojiEditText extends AppCompatEditText {
 
     return result;
   }
+
+  @Override
+  public boolean onTextContextMenuItem(int id) {
+    if (id == android.R.id.paste) {
+      ClipboardManager clipboardManager = ServiceUtil.getClipboardManager(getContext());
+      ClipData         originalClipData = clipboardManager.getPrimaryClip();
+      CharSequence     pendingPaste     = getTextFromClipData(originalClipData);
+
+      if (pendingPaste == null) {
+        return super.onTextContextMenuItem(id);
+      }
+
+      CharSequence sanitizedText = (pendingPaste instanceof Spanned) ? clearFormattingFromText(pendingPaste)
+                                                                     : pendingPaste;
+
+      clipboardManager.setPrimaryClip(ClipData.newPlainText("signal_sanitized", sanitizedText));
+      boolean performedAction = super.onTextContextMenuItem(id);
+
+      clipboardManager.setPrimaryClip(originalClipData);
+      return performedAction;
+    }
+    return super.onTextContextMenuItem(id);
+  }
+
+  private CharSequence clearFormattingFromText(CharSequence text) {
+    List<Mention> mentions          = MentionAnnotation.getMentionsFromAnnotations(text);
+    Spannable     withoutFormatting = new SpannableString(text.toString());
+
+    MentionAnnotation.setMentionAnnotations(withoutFormatting, mentions);
+
+    return withoutFormatting;
+  }
+
+  private @Nullable CharSequence getTextFromClipData(ClipData data) {
+    if (data != null && data.getItemCount() > 0) {
+      return data.getItemAt(0).coerceToText(getContext());
+    } else {
+      return null;
+    }
+  }
 }