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

/**
 * A closure that outputs HTML rooted at a single element.
 *
 */
public interface UiBuilder extends HtmlClosure {

  /**
   * {@inheritDoc}
   *
   * The output HTML has a single top-level element.
   */
  @Override
  void outputHtml(SafeHtmlBuilder out);

  /** An empty UI builder that outputs nothing. */
  UiBuilder EMPTY = new UiBuilder() {
    @Override
    public void outputHtml(SafeHtmlBuilder out) {
    }
  };

  /**
   * A UI builder that outputs a constant html string.
   */
  final class Constant {

    // Utility class
    private Constant() {
    }

    public static UiBuilder of(final SafeHtml html) {
      return new UiBuilder() {
        @Override
        public void outputHtml(SafeHtmlBuilder out) {
          out.append(html);
        }
      };
    }
  }
}