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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                                                                             *
// *                                                                                                                         *
// * 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.apache.juneau.http;

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

import java.io.*;
import java.nio.*;
import java.util.*;

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

/**
 * Represents the contents of a byte stream file with convenience methods for adding HTTP response headers.
 *
 * <p>
 * <br>These objects can to be returned as responses by REST methods.
 *
 * <p>
 * <l>StreamResources</l> are meant to be thread-safe and reusable objects.
 * <br>The contents of the request passed into the constructor are immediately converted to read-only byte arrays.
 *
 * <p>
 * Instances of this class can be built using {@link Builder}.
 *
 * <ul class='seealso'>
 *    <li class='link'>{@doc juneau-rest-server.RestMethod.StreamResource}
 * </ul>
 */
@Response
public class StreamResource implements Streamable {

   private final MediaType mediaType;
   private final Object[] contents;
   private final Map<String,Object> headers;

   StreamResource(Builder b) throws IOException {
      this(b.mediaType, b.headers, b.cached, b.contents.toArray());
   }

   /**
    * Constructor.
    *
    * @param mediaType The resource media type.
    * @param headers The HTTP response headers for this streamed resource.
    * @param cached
    *    Identifies if this stream resource is cached in memory.
    *    <br>If <jk>true</jk>, the contents will be loaded into a byte array 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><code><jk>byte</jk>[]</code>
    *       <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 StreamResource(MediaType mediaType, Map<String,Object> headers, boolean cached, Object...contents) throws IOException {
      this.mediaType = mediaType;
      this.headers = immutableMap(headers);
      this.contents = cached ? new Object[]{readBytes(contents)} : contents;
   }

   //-----------------------------------------------------------------------------------------------------------------
   // 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 StreamResource} objects.
    *
    * <ul class='seealso'>
    *    <li class='link'>{@doc juneau-rest-server.RestMethod.StreamResource}
    * </ul>
    */
   public static class Builder {
      ArrayList<Object> contents = new ArrayList<>();
      MediaType mediaType;
      Map<String,Object> headers = new LinkedHashMap<>();
      boolean cached;

      /**
       * Specifies the resource media type string.
       *
       * @param mediaType The resource media type string.
       * @return This object (for method chaining).
       */
      public Builder mediaType(String mediaType) {
         this.mediaType = MediaType.forString(mediaType);
         return this;
      }

      /**
       * Specifies the resource media type string.
       *
       * @param mediaType The resource media type string.
       * @return This object (for method chaining).
       */
      public Builder mediaType(MediaType mediaType) {
         this.mediaType = mediaType;
         return this;
      }

      /**
       * Specifies the contents for this resource.
       *
       * <p>
       * This method can be called multiple times to add more content.
       *
       * @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><code><jk>byte</jk>[]</code>
       *       <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>
       * @return This object (for method chaining).
       */
      public Builder contents(Object...contents) {
         this.contents.addAll(Arrays.asList(contents));
         return this;
      }

      /**
       * Specifies an HTTP response header value.
       *
       * @param name The HTTP header name.
       * @param value
       *    The HTTP header value.
       *    <br>Will be converted to a <c>String</c> using {@link Object#toString()}.
       * @return This object (for method chaining).
       */
      public Builder header(String name, Object value) {
         this.headers.put(name, value);
         return this;
      }

      /**
       * Specifies HTTP response header values.
       *
       * @param headers
       *    The HTTP headers.
       *    <br>Values will be converted to <c>Strings</c> using {@link Object#toString()}.
       * @return This object (for method chaining).
       */
      public Builder headers(Map<String,Object> headers) {
         this.headers.putAll(headers);
         return this;
      }

      /**
       * Specifies that this resource is intended to be cached.
       *
       * <p>
       * This will trigger the contents to be loaded into a byte array for fast serializing.
       *
       * @return This object (for method chaining).
       */
      public Builder cached() {
         this.cached = true;
         return this;
      }

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

   /**
    * Get the HTTP response headers.
    *
    * @return
    *    The HTTP response headers.
    *    <br>An unmodifiable map.
    *    <br>Never <jk>null</jk>.
    */
   @ResponseHeader("*")
   public Map<String,Object> getHeaders() {
      return headers;
   }

   @ResponseBody
   @Override /* Streamable */
   public void streamTo(OutputStream os) throws IOException {
      for (Object c : contents)
         pipe(c, os);
      os.flush();
   }

   @ResponseHeader("Content-Type")
   @Override /* Streamable */
   public MediaType getMediaType() {
      return mediaType;
   }

   /**
    * Returns the contents of this stream resource.
    *
    * @return The contents of this stream resource.
    * @throws IOException Thrown by underlying stream.
    */
   public InputStream getContents() throws IOException {
      if (contents.length == 1) {
         Object c = contents[0];
         if (c != null) {
            if (c instanceof byte[])
               return new ByteArrayInputStream((byte[])c);
            else if (c instanceof InputStream)
               return (InputStream)c;
            else if (c instanceof File)
               return new FileInputStream((File)c);
            else if (c instanceof CharSequence)
               return new ByteArrayInputStream((((CharSequence)c).toString().getBytes(UTF8)));
         }
      }
      byte[][] bc = new byte[contents.length][];
      int c = 0;
      for (int i = 0; i < contents.length; i++) {
         Object o = contents[i];
         if (o == null)
            bc[i] = new byte[0];
         else if (o instanceof byte[])
            bc[i] = (byte[])o;
         else if (o instanceof InputStream)
            bc[i] = readBytes((InputStream)o, 1024);
         else if (o instanceof Reader)
            bc[i] = read((Reader)o).getBytes(UTF8);
         else if (o instanceof File)
            bc[i] = readBytes((File)o);
         else if (o instanceof CharSequence)
            bc[i] = ((CharSequence)o).toString().getBytes(UTF8);
         c += bc[i].length;
      }
      ByteBuffer bb = ByteBuffer.allocate(c);
      for (byte[] b : bc)
         bb.put(b);
      return new ByteArrayInputStream(bb.array());
   }
}