/*
    * ====================================================================
    * 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.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package com.foxinmy.weixin4j.http.apache.mime;
  
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.nio.charset.Charset;
  import java.util.Random;
  
  import com.foxinmy.weixin4j.http.ContentType;
  import com.foxinmy.weixin4j.http.apache.content.ContentBody;
  import com.foxinmy.weixin4j.http.entity.HttpEntity;
  
  /**
   * Multipart/form coded HTTP entity consisting of multiple body parts.
   *
   * @since 4.0
   *
   */
  public class MultipartEntity implements HttpEntity {
  
      /**
       * The pool of ASCII chars to be used for generating a multipart boundary.
       */
      private final static char[] MULTIPART_CHARS =
          "-_1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
              .toCharArray();
  
      private final MultipartEntityBuilder builder;
      private volatile MultipartFormEntity entity;
  
      /**
       * Creates an instance using the specified parameters
       * @param mode the mode to use, may be {@code null}, in which case {@link HttpMultipartMode#STRICT} is used
       * @param boundary the boundary string, may be {@code null}, in which case {@link #generateBoundary()} is invoked to create the string
       * @param charset the character set to use, may be {@code null}, in which case {@link MIME#DEFAULT_CHARSET} - i.e. US-ASCII - is used.
       */
      public MultipartEntity(
              final HttpMultipartMode mode,
              final String boundary,
              final Charset charset) {
          super();
          this.builder = new MultipartEntityBuilder()
                  .setMode(mode)
                  .setCharset(charset != null ? charset : MIME.DEFAULT_CHARSET)
                  .setBoundary(boundary);
          this.entity = null;
      }
  
      /**
       * Creates an instance using the specified {@link HttpMultipartMode} mode.
       * Boundary and charset are set to {@code null}.
       * @param mode the desired mode
       */
      public MultipartEntity(final HttpMultipartMode mode) {
          this(mode, null, null);
      }
  
      /**
       * Creates an instance using mode {@link HttpMultipartMode#STRICT}
       */
      public MultipartEntity() {
          this(HttpMultipartMode.STRICT, null, null);
      }
  
      protected String generateContentType(
              final String boundary,
              final Charset charset) {
          final StringBuilder buffer = new StringBuilder();
          buffer.append("multipart/form-data; boundary=");
          buffer.append(boundary);
          if (charset != null) {
              buffer.append("; charset=");
             buffer.append(charset.name());
         }
         return buffer.toString();
     }
 
     protected String generateBoundary() {
         final StringBuilder buffer = new StringBuilder();
         final Random rand = new Random();
         final int count = rand.nextInt(11) + 30; // a random size from 30 to 40
         for (int i = 0; i < count; i++) {
             buffer.append(MULTIPART_CHARS[rand.nextInt(MULTIPART_CHARS.length)]);
         }
         return buffer.toString();
     }
 
     private MultipartFormEntity getEntity() {
         if (this.entity == null) {
             this.entity = this.builder.buildEntity();
         }
         return this.entity;
     }
 
     public void addPart(final FormBodyPart bodyPart) {
         this.builder.addPart(bodyPart);
         this.entity = null;
     }
 
     public void addPart(final String name, final ContentBody contentBody) {
         addPart(new FormBodyPart(name, contentBody));
     }
 
     public boolean isRepeatable() {
         return getEntity().isRepeatable();
     }
 
     public boolean isChunked() {
         return getEntity().isChunked();
     }
 
     public boolean isStreaming() {
         return getEntity().isStreaming();
     }
 
     @Override
     public long getContentLength() {
         return getEntity().getContentLength();
     }
 
     @Override
     public ContentType getContentType() {
         return getEntity().getContentType();
     }
 
     @Override
     public InputStream getContent() throws IOException, UnsupportedOperationException {
         throw new UnsupportedOperationException(
                     "Multipart form entity does not implement #getContent()");
     }
 
     @Override
     public void writeTo(final OutputStream outstream) throws IOException {
         getEntity().writeTo(outstream);
     }
 }