AttributeValidationResult.java

/**
 * Copyright 2010 Google Inc.
 *
 * 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 org.waveprotocol.wave.model.experimental.schema;

/**
 * The result of the validation of attributes.
 *
 */
public abstract class AttributeValidationResult {

  /**
   * The type of the validation result.
   */
  public enum Type {
    VALID,
    ATTRIBUTE_NOT_ALLOWED,
    INVALID_ATTRIBUTE_VALUE,
    MISSING_REQUIRED_ATTRIBUTE,
    REMOVING_REQUIRED_ATTRIBUTE
  }

  /**
   * A result indicating the existence of an attribute that is not allowed.
   */
  public static final class AttributeNotAllowed extends AttributeValidationResult {

    private final String name;

    AttributeNotAllowed(String name) {
      this.name = name;
    }

    @Override
    public Type getType() {
      return Type.ATTRIBUTE_NOT_ALLOWED;
    }

    @Override
    public AttributeNotAllowed asAttributeNotAllowed() {
      return this;
    }

    /**
     * Returns the name of the disallowed attribute that was encountered.
     */
    public String getName() {
      return name;
    }

    @Override
    public String toString() {
      return "Attribute not allowed: " + name;
    }

  }

  /**
   * A result indicating that an attribute has an invalid value.
   */
  public static final class InvalidAttributeValue extends AttributeValidationResult {

    private final String name;
    private final String value;

    InvalidAttributeValue(String name, String value) {
      this.name = name;
      this.value = value;
    }

    @Override
    public Type getType() {
      return Type.INVALID_ATTRIBUTE_VALUE;
    }

    @Override
    public InvalidAttributeValue asInvalidAttributeValue() {
      return this;
    }

    /**
     * Returns the name of the attribute with the invalid value.
     */
    public String getName() {
      return name;
    }

    /**
     * Returns the invalid attribute value.
     */
    public String getValue() {
      return value;
    }

    @Override
    public String toString() {
      return "Invalid value for attribute " + name + ": " + value;
    }

  }

  /**
   * A result indicating that a required attribute is missing.
   */
  public static final class MissingRequiredAttribute extends AttributeValidationResult {

    private final String name;

    MissingRequiredAttribute(String name) {
      this.name = name;
    }

    @Override
    public Type getType() {
      return Type.MISSING_REQUIRED_ATTRIBUTE;
    }

    @Override
    public MissingRequiredAttribute asMissingRequiredAttribute() {
      return this;
    }

    /**
     * Returns the name of the missing required attribute.
     */
    public String getName() {
      return name;
    }

    @Override
    public String toString() {
      return "Required attribute missing: " + name;
    }

  }

  /**
   * A result indicating that an attribute update attempts to remove a required attribute.
   */
  public static final class RemovingRequiredAttribute extends AttributeValidationResult {

    private final String name;

    RemovingRequiredAttribute(String name) {
      this.name = name;
    }

    @Override
    public Type getType() {
      return Type.REMOVING_REQUIRED_ATTRIBUTE;
    }

    @Override
    public RemovingRequiredAttribute asRemovingRequiredAttribute() {
      return this;
    }

    /**
     * Returns the name the of required attribute whose removal was attempted.
     */
    public String getName() {
      return name;
    }

    @Override
    public String toString() {
      return "Attempt to remove required attribute: " + name;
    }

  }

  /**
   * A result indicating that nothing invalid was encountered.
   */
  public static final AttributeValidationResult VALID = new AttributeValidationResult() {

    @Override
    public Type getType() {
      return Type.VALID;
    }

    @Override
    public String toString() {
      return "Valid";
    }

  };

  private AttributeValidationResult() {}

  /**
   * Returns the type of the validation result.
   */
  public abstract Type getType();

  /**
   * Returns this object if it is an <code>AttributeNotAllowed</code>, or null
   * otherwise.
   */
  public AttributeNotAllowed asAttributeNotAllowed() {
    return null;
  }

  /**
   * Returns this object if it is an <code>InvalidAttributeValue</code>, or null
   * otherwise.
   */
  public InvalidAttributeValue asInvalidAttributeValue() {
    return null;
  }

  /**
   * Returns this object if it is an <code>MissingRequiredAttribute</code>, or
   * null otherwise.
   */
  public MissingRequiredAttribute asMissingRequiredAttribute() {
    return null;
  }

  /**
   * Returns this object if it is an <code>RemovingRequiredAttribute</code>, or
   * null otherwise.
   */
  public RemovingRequiredAttribute asRemovingRequiredAttribute() {
    return null;
  }

}