/* 
    * 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.esigate.parser.future;
  
  import java.io.IOException;
  import java.util.concurrent.ExecutionException;
  import java.util.concurrent.Future;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.TimeoutException;
  
  import org.esigate.HttpErrorPage;
  import org.esigate.Parameters;
  
  /**
   * This is an implementation of StringBuilder which can append Future<CharSequence> and is a
   * Future<CharSequence> itself.
   * <p>
   * It is intended for temporary buffers when implementing nested tags.
   * 
   * 
   * @author Nicolas Richeton
   * 
   */
  public class StringBuilderFutureAppendable implements FutureAppendable, Future<CharSequence> {
      private final StringBuilder builder;
      private final FutureAppendableAdapter futureBuilder;
  
      /**
       * Create a new builder with a default capacity of 1024.
       */
      public StringBuilderFutureAppendable() {
          this(Parameters.DEFAULT_BUFFER_SIZE);
      }
  
      /**
       * Create a new builder with a custom capacity.
       * 
       * @param capacity
       *            Capacity of the builder.
       */
      private StringBuilderFutureAppendable(int capacity) {
          this.builder = new StringBuilder(capacity);
          this.futureBuilder = new FutureAppendableAdapter(this.builder);
      }
  
      @Override
      public FutureAppendable enqueueAppend(Future<CharSequence> csq) {
          return this.futureBuilder.enqueueAppend(csq);
      }
  
      @Override
      public FutureAppendable performAppends() throws IOException, HttpErrorPage {
          return this.futureBuilder.performAppends();
      }
  
      @Override
      public boolean cancel(boolean mayInterruptIfRunning) {
          return false;
      }
  
      @Override
      public boolean isCancelled() {
          return false;
      }
  
      @Override
      public boolean isDone() {
          return this.futureBuilder.hasPending();
      }
  
      /*
       * (non-Javadoc)
       * 
       * @see java.util.concurrent.Future#get()
       */
      @Override
      public CharSequence get() throws ExecutionException {
          try {
              this.futureBuilder.performAppends();
          } catch (IOException | HttpErrorPage e) {
              throw new ExecutionException(e);
          }
          return this.builder.toString();
      }
  
      /*
      * (non-Javadoc)
      * 
      * @see java.util.concurrent.Future#get(long, java.util.concurrent.TimeUnit)
      */
     @Override
     public CharSequence get(long timeout, TimeUnit unit) throws ExecutionException {
         try {
             this.futureBuilder.performAppends();
         } catch (IOException | HttpErrorPage e) {
             throw new ExecutionException(e);
         }
         return this.builder.toString();
     }
 
     /*
      * (non-Javadoc)
      * 
      * @see org.esigate.parser.future.FutureAppendable#hasPending()
      */
     @Override
     public boolean hasPending() {
         return this.futureBuilder.hasPending();
     }
 
     /*
      * (non-Javadoc)
      * 
      * @see org.esigate.parser.future.FutureAppendable#performAppends(int, java.util.concurrent.TimeUnit)
      */
     @Override
     public FutureAppendable performAppends(int timeout, TimeUnit unit) throws IOException, HttpErrorPage,
             TimeoutException {
         return this.futureBuilder.performAppends(timeout, unit);
     }
 
 }