Fixes #4934. Enforces Wikimedia character blocklisting on media titles. (#4955)

app/src/main/java/fr/free/nrw/commons/upload/UploadMediaDetailAdapter.java

@@ -3,6 +3,7 @@ package fr.free.nrw.commons.upload;
 import android.app.Dialog;
 import android.content.Intent;
 import android.text.Editable;
+import android.text.InputFilter;
 import android.text.TextUtils;
 import android.text.TextWatcher;
 import android.view.LayoutInflater;
@@ -165,6 +166,9 @@ public class UploadMediaDetailAdapter extends RecyclerView.Adapter<UploadMediaDe
                 captionInputLayout.setEndIconDrawable(R.drawable.mapbox_info_icon_default);
                 captionInputLayout.setEndIconOnClickListener(v ->
                     callback.showAlert(R.string.media_detail_caption, R.string.caption_info));
+                Objects.requireNonNull(captionInputLayout.getEditText()).setFilters(new InputFilter[] {
+                    new UploadMediaDetailInputFilter()
+                });
 
                 descInputLayout.setEndIconMode(TextInputLayout.END_ICON_CUSTOM);
                 descInputLayout.setEndIconDrawable(R.drawable.mapbox_info_icon_default);

app/src/main/java/fr/free/nrw/commons/upload/UploadMediaDetailInputFilter.java

@@ -0,0 +1,80 @@
+package fr.free.nrw.commons.upload;
+
+import android.text.InputFilter;
+import android.text.Spanned;
+import java.util.regex.Pattern;
+
+/**
+ * An {@link InputFilter} class that removes characters blocklisted in Wikimedia titles. The list
+ * of blocklisted characters is linked below.
+ * @see <a href="https://commons.wikimedia.org/wiki/MediaWiki:Titleblacklist"></a>wikimedia.org</a>
+ */
+public class UploadMediaDetailInputFilter implements InputFilter {
+    private final Pattern[] patterns;
+
+    /**
+     * Initializes the blocklisted patterns.
+     */
+    public UploadMediaDetailInputFilter() {
+        patterns = new Pattern[]{
+            Pattern.compile("[\\x{00A0}\\x{1680}\\x{180E}\\x{2000}-\\x{200B}\\x{2028}\\x{2029}\\x{202F}\\x{205F}\\x{3000}]"),
+            Pattern.compile("[\\x{202A}-\\x{202E}]"),
+            Pattern.compile("\\p{Cc}"),
+            Pattern.compile("\\x{FEFF}"),
+            Pattern.compile("\\x{00AD}"),
+            Pattern.compile("[\\x{E000}-\\x{F8FF}\\x{FFF0}-\\x{FFFF}]"),
+            Pattern.compile("[^\\x{0000}-\\x{FFFF}\\p{sc=Han}]")
+        };
+    }
+
+    /**
+     * Checks if the source text contains any blocklisted characters.
+     * @param source input text
+     * @return contains a blocklisted character
+     */
+    private Boolean checkBlocklisted(final CharSequence source) {
+        for (final Pattern pattern: patterns) {
+            if (pattern.matcher(source).find()) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * Removes any blocklisted characters from the source text.
+     * @param source input text
+     * @return a cleaned character sequence
+     */
+    private CharSequence removeBlocklisted(CharSequence source) {
+        for (final Pattern pattern: patterns) {
+            source = pattern.matcher(source).replaceAll("");
+        }
+
+        return source;
+    }
+
+    /**
+     * Filters out any blocklisted characters.
+     * @param source {@inheritDoc}
+     * @param start {@inheritDoc}
+     * @param end {@inheritDoc}
+     * @param dest {@inheritDoc}
+     * @param dstart {@inheritDoc}
+     * @param dend {@inheritDoc}
+     * @return {@inheritDoc}
+     */
+    @Override
+    public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart,
+        int dend) {
+        if (checkBlocklisted(source)) {
+            if (start == dstart) {
+                return dest;
+            }
+
+            return removeBlocklisted(source);
+        }
+        return null;
+    }
+}