Add an IDN helper (#2217)

* Add an IDN helper

Add a helper that checks the validity of labels in IDNs.
All organizes TLDs according to the IDNs they support.

core/src/main/java/google/registry/bsa/IdnChecker.java

@@ -0,0 +1,108 @@
+// Copyright 2023 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.bsa;
+
+import static com.google.common.collect.ImmutableSet.toImmutableSet;
+import static com.google.common.collect.Maps.transformValues;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableMultimap;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Sets;
+import com.google.common.collect.Sets.SetView;
+import google.registry.model.tld.Tld;
+import google.registry.model.tld.Tld.TldType;
+import google.registry.model.tld.Tlds;
+import google.registry.tldconfig.idn.IdnLabelValidator;
+import google.registry.tldconfig.idn.IdnTableEnum;
+import google.registry.util.Clock;
+import javax.inject.Inject;
+import org.joda.time.DateTime;
+
+/**
+ * Checks labels' validity wrt Idns in TLDs enrolled with BSA.
+ *
+ * <p>Each instance takes a snapshot of the TLDs at instantiation time, and should be limited to the
+ * Request scope.
+ */
+public class IdnChecker {
+  private static final IdnLabelValidator IDN_LABEL_VALIDATOR = new IdnLabelValidator();
+
+  private final ImmutableMap<IdnTableEnum, ImmutableSet<Tld>> idnToTlds;
+  private final ImmutableSet<Tld> allTlds;
+
+  @Inject
+  IdnChecker(Clock clock) {
+    this.idnToTlds = getIdnToTldMap(clock.nowUtc());
+    allTlds = idnToTlds.values().stream().flatMap(ImmutableSet::stream).collect(toImmutableSet());
+  }
+
+  // TODO(11/30/2023): Remove below when new Tld schema is deployed and the `getBsaEnrollStartTime`
+  // method is no longer hardcoded.
+  @VisibleForTesting
+  IdnChecker(ImmutableMap<IdnTableEnum, ImmutableSet<Tld>> idnToTlds) {
+    this.idnToTlds = idnToTlds;
+    allTlds = idnToTlds.values().stream().flatMap(ImmutableSet::stream).collect(toImmutableSet());
+  }
+
+  /** Returns all IDNs in which the {@code label} is valid. */
+  ImmutableSet<IdnTableEnum> getAllValidIdns(String label) {
+    return idnToTlds.keySet().stream()
+        .filter(idnTable -> idnTable.getTable().isValidLabel(label))
+        .collect(toImmutableSet());
+  }
+
+  /**
+   * Returns the TLDs that support at least one IDN in the {@code idnTables}.
+   *
+   * @param idnTables String names of {@link IdnTableEnum} values
+   */
+  public ImmutableSet<Tld> getSupportingTlds(ImmutableSet<String> idnTables) {
+    return idnTables.stream()
+        .map(IdnTableEnum::valueOf)
+        .filter(idnToTlds::containsKey)
+        .map(idnToTlds::get)
+        .flatMap(ImmutableSet::stream)
+        .collect(toImmutableSet());
+  }
+
+  /**
+   * Returns the TLDs that do not support any IDN in the {@code idnTables}.
+   *
+   * @param idnTables String names of {@link IdnTableEnum} values
+   */
+  public SetView<Tld> getForbiddingTlds(ImmutableSet<String> idnTables) {
+    return Sets.difference(allTlds, getSupportingTlds(idnTables));
+  }
+
+  private static boolean isEnrolledWithBsa(Tld tld, DateTime now) {
+    DateTime enrollTime = tld.getBsaEnrollStartTime();
+    return enrollTime != null && enrollTime.isBefore(now);
+  }
+
+  private static ImmutableMap<IdnTableEnum, ImmutableSet<Tld>> getIdnToTldMap(DateTime now) {
+    ImmutableMultimap.Builder<IdnTableEnum, Tld> idnToTldMap = new ImmutableMultimap.Builder();
+    Tlds.getTldEntitiesOfType(TldType.REAL).stream()
+        .filter(tld -> isEnrolledWithBsa(tld, now))
+        .forEach(
+            tld -> {
+              for (IdnTableEnum idn : IDN_LABEL_VALIDATOR.getIdnTablesForTld(tld)) {
+                idnToTldMap.put(idn, tld);
+              }
+            });
+    return ImmutableMap.copyOf(transformValues(idnToTldMap.build().asMap(), ImmutableSet::copyOf));
+  }
+}

core/src/main/java/google/registry/tldconfig/idn/IdnLabelValidator.java

@@ -38,9 +38,7 @@ public final class IdnLabelValidator {
   public Optional<String> findValidIdnTableForTld(String label, String tldStr) {
     String unicodeString = Idn.toUnicode(label);
     Tld tld = Tld.get(tldStr); // uses the cache
-    ImmutableSet<IdnTableEnum> idnTablesForTld = tld.getIdnTables();
-    ImmutableSet<IdnTableEnum> idnTables =
-        idnTablesForTld.isEmpty() ? DEFAULT_IDN_TABLES : idnTablesForTld;
+    ImmutableSet<IdnTableEnum> idnTables = getIdnTablesForTld(tld);
     for (IdnTableEnum idnTable : idnTables) {
       if (idnTable.getTable().isValidLabel(unicodeString)) {
         return Optional.of(idnTable.getTable().getName());
@@ -48,4 +46,10 @@ public final class IdnLabelValidator {
     }
     return Optional.empty();
   }
+
+  /** Returns the names of the IDN tables supported by a {@code tld}. */
+  public ImmutableSet<IdnTableEnum> getIdnTablesForTld(Tld tld) {
+    ImmutableSet<IdnTableEnum> idnTablesForTld = tld.getIdnTables();
+    return idnTablesForTld.isEmpty() ? DEFAULT_IDN_TABLES : idnTablesForTld;
+  }
 }

core/src/main/java/google/registry/tldconfig/idn/IdnTable.java

@@ -84,7 +84,7 @@ public final class IdnTable {
    * Returns true if the given label is valid for this IDN table. A label is considered valid if all
    * of its codepoints are in the IDN table.
    */
-  boolean isValidLabel(String label) {
+  public boolean isValidLabel(String label) {
     final int length = label.length();
     for (int i = 0; i < length; ) {
       int codepoint = label.codePointAt(i);