GroupChainGenerator.java

/*
 * Copyright 2012 Google Inc. Copyright 2016 Manfred Tremmel
 *
 * 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 de.knightsoftnet.validators.client.impl;

import de.knightsoftnet.validators.client.impl.metadata.ValidationGroupsMetadata;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import javax.validation.GroupDefinitionException;
import javax.validation.ValidationException;

/**
 * Helper class used to resolve groups and sequences into a single chain of groups which can then be
 * validated.
 * <p>
 * Modified from the Hibernate validator for use with GWT.
 * </p>
 */
public class GroupChainGenerator {
  private final ValidationGroupsMetadata validationGroupsMetadata;

  private final Map<Class<?>, List<Group>> resolvedSequences = new HashMap<Class<?>, List<Group>>();

  public GroupChainGenerator(final ValidationGroupsMetadata validationGroupsMetadata) {
    this.validationGroupsMetadata = validationGroupsMetadata;
  }

  /**
   * Generates a chain of groups to be validated given the specified validation groups.
   *
   * @param groups The groups specified at the validation call.
   *
   * @return an instance of {@code GroupChain} defining the order in which validation has to occur.
   */
  public GroupChain getGroupChainFor(final Collection<Class<?>> groups) {
    if (groups == null || groups.isEmpty()) {
      throw new IllegalArgumentException("At least one group has to be specified.");
    }

    for (final Class<?> clazz : groups) {
      if (!this.validationGroupsMetadata.containsGroup(clazz)
          && !this.validationGroupsMetadata.isSeqeuence(clazz)) {
        throw new ValidationException("The class " + clazz + " is not a valid group or sequence.");
      }
    }

    final GroupChain chain = new GroupChain();
    for (final Class<?> clazz : groups) {
      if (this.isGroupSequence(clazz)) {
        this.insertSequence(clazz, chain);
      } else {
        final Group group = new Group(clazz);
        chain.insertGroup(group);
        this.insertInheritedGroups(clazz, chain);
      }
    }

    return chain;
  }

  @Override
  public String toString() {
    final StringBuilder sb = new StringBuilder(64);
    sb.append("GroupChainGenerator");
    sb.append("{resolvedSequences=").append(this.resolvedSequences);
    sb.append('}');
    return sb.toString();
  }

  private void addGroups(final List<Group> resolvedGroupSequence, final List<Group> groups) {
    for (final Group tmpGroup : groups) {
      if (resolvedGroupSequence.contains(tmpGroup)
          && resolvedGroupSequence.indexOf(tmpGroup) < resolvedGroupSequence.size() - 1) {
        throw new GroupDefinitionException("Unable to expand group sequence.");
      }
      resolvedGroupSequence.add(tmpGroup);
    }
  }

  private void addInheritedGroups(final Group group, final List<Group> expandedGroups) {
    final Set<Class<?>> inheritedGroups =
        this.validationGroupsMetadata.getParentsOfGroup(group.getGroup());
    if (inheritedGroups != null) {
      for (final Class<?> inheritedGroup : inheritedGroups) {
        if (this.isGroupSequence(inheritedGroup)) {
          throw new GroupDefinitionException(
              "Sequence definitions are not allowed as composing " + "parts of a sequence.");
        }
        final Group g = new Group(inheritedGroup, group.getSequence());
        expandedGroups.add(g);
        this.addInheritedGroups(g, expandedGroups);
      }
    }
  }

  private List<Group> expandInhertitedGroups(final List<Group> sequence) {
    final List<Group> expandedGroup = new ArrayList<Group>();
    for (final Group group : sequence) {
      expandedGroup.add(group);
      this.addInheritedGroups(group, expandedGroup);
    }
    return expandedGroup;
  }

  /**
   * Recursively add inherited groups into the group chain.
   *
   * @param clazz The group interface
   * @param chain The group chain we are currently building.
   */
  private void insertInheritedGroups(final Class<?> clazz, final GroupChain chain) {
    for (final Class<?> inheritedGroup : this.validationGroupsMetadata.getParentsOfGroup(clazz)) {
      final Group group = new Group(inheritedGroup);
      chain.insertGroup(group);
      this.insertInheritedGroups(inheritedGroup, chain);
    }
  }

  private void insertSequence(final Class<?> clazz, final GroupChain chain) {
    List<Group> sequence;
    if (this.resolvedSequences.containsKey(clazz)) {
      sequence = this.resolvedSequences.get(clazz);
    } else {
      sequence = this.resolveSequence(clazz, new ArrayList<Class<?>>());
      // we expand the inherited groups only after we determined whether the sequence is expandable
      sequence = this.expandInhertitedGroups(sequence);
    }
    chain.insertSequence(sequence);
  }

  private boolean isGroupSequence(final Class<?> clazz) {
    return this.validationGroupsMetadata.isSeqeuence(clazz);
  }

  private List<Group> resolveSequence(final Class<?> group,
      final List<Class<?>> processedSequences) {
    if (processedSequences.contains(group)) {
      throw new GroupDefinitionException("Cyclic dependency in groups definition");
    } else {
      processedSequences.add(group);
    }
    final List<Group> resolvedGroupSequence = new ArrayList<Group>();
    final List<Class<?>> sequenceList = this.validationGroupsMetadata.getSequenceList(group);
    for (final Class<?> clazz : sequenceList) {
      if (this.isGroupSequence(clazz)) {
        final List<Group> tmpSequence = this.resolveSequence(clazz, processedSequences);
        this.addGroups(resolvedGroupSequence, tmpSequence);
      } else {
        final List<Group> list = new ArrayList<Group>();
        list.add(new Group(clazz, group));
        this.addGroups(resolvedGroupSequence, list);
      }
    }
    this.resolvedSequences.put(group, resolvedGroupSequence);
    return resolvedGroupSequence;
  }
}