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// * Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements.  See the NOTICE file *
// * distributed with this work for additional information regarding copyright ownership.  The ASF licenses this file        *
// * to you 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                                                                             *
// *                                                                                                                         *
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// * "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.apache.juneau.rest.helper;

import static org.apache.juneau.internal.IOUtils.*;

import org.apache.juneau.http.ReaderResource;
import java.io.*;
import java.util.*;

import org.apache.juneau.http.*;
import org.apache.juneau.http.annotation.*;
import org.apache.juneau.svl.*;

/**
 * An extension of {@link ReaderResource} that allows automatic resolution of SVL variables.
 */
public class ResolvingReaderResource extends ReaderResource {

   private final VarResolverSession varSession;

   /**
    * Constructor.
    *
    * @param b Builder containing values to initialize this object with.
    * @throws IOException Thrown by underlying stream.
    */
   protected ResolvingReaderResource(Builder b) throws IOException {
      this(b.mediaType, b.headers, b.cached, b.varResolver, b.contents.toArray());
   }

   /**
    * Constructor.
    *
    * @param mediaType The resource media type.
    * @param headers The HTTP response headers for this streamed resource.
    * @param varSession Optional variable resolver for resolving variables in the string.
    * @param cached
    *    Identifies if this resource is cached in memory.
    *    <br>If <jk>true</jk>, the contents will be loaded into a String for fast retrieval.
    * @param contents
    *    The resource contents.
    *    <br>If multiple contents are specified, the results will be concatenated.
    *    <br>Contents can be any of the following:
    *    <ul>
    *       <li><c>InputStream</c>
    *       <li><c>Reader</c> - Converted to UTF-8 bytes.
    *       <li><c>File</c>
    *       <li><c>CharSequence</c> - Converted to UTF-8 bytes.
    *    </ul>
    * @throws IOException Thrown by underlying stream.
    */
   public ResolvingReaderResource(MediaType mediaType, Map<String,Object> headers, boolean cached, VarResolverSession varSession, Object...contents) throws IOException {
      super(mediaType, headers, cached, contents);
      this.varSession = varSession;
   }

   //-----------------------------------------------------------------------------------------------------------------
   // Builder
   //-----------------------------------------------------------------------------------------------------------------

   /**
    * Creates a new instance of a {@link Builder} for this class.
    *
    * @return A new instance of a {@link Builder}.
    */
   public static Builder create() {
      return new Builder();
   }

   /**
    * Builder class for constructing {@link ResolvingReaderResource} objects.
    *
    * <ul class='seealso'>
    *    <li class='link'>{@doc juneau-rest-server.RestMethod.ReaderResource}
    * </ul>
    */
   public static class Builder extends ReaderResource.Builder {
      VarResolverSession varResolver;

      /**
       * Specifies the variable resolver to use for this resource.
       *
       * @param varResolver The variable resolver.
       * @return This object (for method chaining).
       */
      public Builder varResolver(VarResolverSession varResolver) {
         this.varResolver = varResolver;
         return this;
      }

      @Override
      public Builder mediaType(String mediaType) {
         super.mediaType(mediaType);
         return this;
      }

      @Override
      public Builder mediaType(MediaType mediaType) {
         super.mediaType(mediaType);
         return this;
      }

      @Override
      public Builder contents(Object...contents) {
         super.contents(contents);
         return this;
      }

      @Override
      public Builder header(String name, Object value) {
         super.header(name, value);
         return this;
      }

      @Override
      public Builder headers(Map<String,Object> headers) {
         super.headers(headers);
         return this;
      }

      @Override
      public Builder cached() {
         super.cached();
         return this;
      }

      /**
       * Create a new {@link ResolvingReaderResource} using values in this builder.
       *
       * @return A new immutable {@link ResolvingReaderResource} object.
       * @throws IOException Thrown by underlying stream.
       */
      @Override
      public ResolvingReaderResource build() throws IOException {
         return new ResolvingReaderResource(this);
      }
   }

   @ResponseBody
   @Override /* Writeable */
   public Writer writeTo(Writer w) throws IOException {
      for (Object o : contents) {
         if (o != null) {
            if (varSession == null)
               pipe(o, w);
            else
               varSession.resolveTo(read(o), w);
         }
      }
      return w;
   }
}