BuilderHelper.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.box.server.rpc.render.uibuilder;

import org.waveprotocol.box.server.rpc.render.common.safehtml.SafeHtmlBuilder;

/**
 * Helper methods for UI builders.
 *
 */
public final class BuilderHelper {

  public static final String KIND_ATTRIBUTE = "kind";

  public interface Component {
    /**
     * @param baseId
     * @return the dom id to use for the given component.
     */
    String getDomId(String baseId);
  }

  // No instances - this is a container of static helpers.
  private BuilderHelper() {
  }

  /** @return a non-null equivalent of a nullable ui. */
  public static UiBuilder nonNull(UiBuilder ui) {
    return ui != null ? ui : UiBuilder.EMPTY;
  }

  /** @return a non-null equivalent of a nullable ui. */
  public static HtmlClosure nonNull(HtmlClosure ui) {
    return ui != null ? ui : HtmlClosureCollection.EMPTY;
  }

  /** @return a builder composed of a sequence of builders. */
  public static HtmlClosure compose(final UiBuilder... uis) {
    return new HtmlClosure() {
      @Override
      public void outputHtml(SafeHtmlBuilder out) {
        for (UiBuilder ui : uis) {
          nonNull(ui).outputHtml(out);
        }
      }
    };
  }
}