/*
 * 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.entity;

import static org.apache.juneau.common.utils.IOUtils.*;

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

import org.apache.http.*;
import org.apache.juneau.annotation.*;
import org.apache.juneau.assertions.*;
import org.apache.juneau.common.utils.*;
import org.apache.juneau.http.header.*;
import org.apache.juneau.internal.*;

/**
 * A basic {@link org.apache.http.HttpEntity} implementation with additional features.
 *
 * Provides the following features:
 * <ul class='spaced-list'>
 *    <li>
 *       Caching.
 *    <li>
 *       Fluent setters.
 *    <li>
 *       Fluent assertions.
 *    <li>
 *       Externally-supplied/dynamic content.
 * </ul>
 *
 * <h5 class='section'>See Also:</h5><ul>
 *    <li class='link'><a class="doclink" href="https://juneau.apache.org/docs/topics/JuneauRestCommonBasics">juneau-rest-common Basics</a>
 * </ul>
 */
@BeanIgnore
public class BasicHttpEntity implements HttpEntity {

   //-----------------------------------------------------------------------------------------------------------------
   // Static
   //-----------------------------------------------------------------------------------------------------------------

   /**
    * An empty HttpEntity.
    */
   public static final BasicHttpEntity EMPTY = new BasicHttpEntity().setUnmodifiable();

   //-----------------------------------------------------------------------------------------------------------------
   // Instance
   //-----------------------------------------------------------------------------------------------------------------

   private boolean cached, chunked, unmodifiable;
   private Object content;
   private Supplier<?> contentSupplier;
   private ContentType contentType;
   private ContentEncoding contentEncoding;
   private Charset charset;
   private long contentLength = -1;
   private int maxLength = -1;

   /**
    * Constructor.
    */
   public BasicHttpEntity() {
   }

   /**
    * Constructor.
    *
    * @param contentType The entity content type.
    * @param content The entity content.
    */
   public BasicHttpEntity(ContentType contentType, Object content) {
      this.contentType = contentType;
      this.content = content;
   }

   /**
    * Copy constructor.
    *
    * @param copyFrom The bean being copied.
    */
   public BasicHttpEntity(BasicHttpEntity copyFrom) {
      this.cached = copyFrom.cached;
      this.chunked = copyFrom.chunked;
      this.content = copyFrom.content;
      this.contentSupplier = copyFrom.contentSupplier;
      this.contentType = copyFrom.contentType;
      this.contentEncoding = copyFrom.contentEncoding;
      this.contentLength = copyFrom.contentLength;
      this.charset = copyFrom.charset;
      this.maxLength = copyFrom.maxLength;
      this.unmodifiable = false;
   }

   /**
    * Creates a builder for this class initialized with the contents of this bean.
    *
    * <p>
    * Allows you to create a modifiable copy of this bean.
    *
    * @return A new builder bean.
    */
   public BasicHttpEntity copy() {
      return new BasicHttpEntity(this);
   }

   //-----------------------------------------------------------------------------------------------------------------
   // Properties
   //-----------------------------------------------------------------------------------------------------------------

   /**
    * Specifies whether this bean should be unmodifiable.
    * <p>
    * When enabled, attempting to set any properties on this bean will cause an {@link UnsupportedOperationException}.
    *
    * @return This object.
    */
   public BasicHttpEntity setUnmodifiable() {
      unmodifiable = true;
      return this;
   }

   /**
    * Returns <jk>true</jk> if this bean is unmodifiable.
    *
    * @return <jk>true</jk> if this bean is unmodifiable.
    */
   public boolean isUnmodifiable() {
      return unmodifiable;
   }

   /**
    * Throws an {@link UnsupportedOperationException} if the unmodifiable flag is set on this bean.
    */
   protected final void assertModifiable() {
      if (unmodifiable)
         throw new UnsupportedOperationException("Bean is read-only");
   }

   /**
    * Sets the content on this entity bean.
    *
    * @param value The entity content, can be <jk>null</jk>.
    * @return This object.
    */
   public BasicHttpEntity setContent(Object value) {
      assertModifiable();
      this.content = value;
      return this;
   }

   /**
    * Sets the content on this entity bean from a supplier.
    *
    * <p>
    * Repeatable entities such as {@link StringEntity} use this to allow the entity content to be resolved at
    * serialization time.
    *
    * @param value The entity content, can be <jk>null</jk>.
    * @return This object.
    */
   public BasicHttpEntity setContent(Supplier<?> value) {
      assertModifiable();
      this.contentSupplier = value == null ? ()->null : value;
      return this;
   }

   /**
    * Sets the content type on this entity bean.
    *
    * @param value The new <c>Content-Type</c> header, or <jk>null</jk> to unset.
    * @return This object.
    */
   public BasicHttpEntity setContentType(String value) {
      return setContentType(ContentType.of(value));
   }

   /**
    * Sets the content type on this entity bean.
    *
    * @param value The new <c>Content-Type</c> header, or <jk>null</jk> to unset.
    * @return This object.
    */
   public BasicHttpEntity setContentType(ContentType value) {
      assertModifiable();
      contentType = value;
      return this;
   }

   /**
    * Sets the content length on this entity bean.
    *
    * @param value The new <c>Content-Length</c> header value, or <c>-1</c> to unset.
    * @return This object.
    */
   public BasicHttpEntity setContentLength(long value) {
      assertModifiable();
      contentLength = value;
      return this;
   }

   /**
    * Sets the content encoding header on this entity bean.
    *
    * @param value The new <c>Content-Encoding</c> header, or <jk>null</jk> to unset.
    * @return This object.
    */
   public BasicHttpEntity setContentEncoding(String value) {
      return setContentEncoding(ContentEncoding.of(value));
   }

   /**
    * Sets the content encoding header on this entity bean.
    *
    * @param value The new <c>Content-Encoding</c> header, or <jk>null</jk> to unset.
    * @return This object.
    */
   public BasicHttpEntity setContentEncoding(ContentEncoding value) {
      assertModifiable();
      contentEncoding = value;
      return this;
   }

   /**
    * Sets the 'chunked' flag value to <jk>true</jk>.
    *
    * <h5 class='section'>Notes:</h5><ul>
    *    <li class='note'>If the {@link HttpEntity#getContentLength()} method returns a negative value, the HttpClient code will always
    *       use chunked encoding.
    * </ul>
    *
    * @return This object.
    */
   public BasicHttpEntity setChunked() {
      return setChunked(true);
   }

   /**
    * Sets the 'chunked' flag value.
    *
    * <h5 class='section'>Notes:</h5><ul>
    *    <li class='note'>If the {@link HttpEntity#getContentLength()} method returns a negative value, the HttpClient code will always
    *       use chunked encoding.
    * </ul>
    *
    * @param value The new value for this flag.
    * @return This object.
    */
   public BasicHttpEntity setChunked(boolean value) {
      assertModifiable();
      chunked = value;
      return this;
   }

   /**
    * Specifies that the contents of this resource should be cached into an internal byte array so that it can
    * be read multiple times.
    *
    * @return This object.
    * @throws IOException If entity could not be read into memory.
    */
   public BasicHttpEntity setCached() throws IOException {
      assertModifiable();
      cached = true;
      return this;
   }

   /**
    * Returns <jk>true</jk> if this entity is cached in-memory.
    *
    * @return <jk>true</jk> if this entity is cached in-memory.
    */
   public boolean isCached() {
      return cached;
   }

   /**
    * Specifies the charset to use when converting to and from stream-based resources.
    *
    * @param value The new value.  If <jk>null</jk>, <c>UTF-8</c> is assumed.
    * @return This object.
    */
   public BasicHttpEntity setCharset(Charset value) {
      assertModifiable();
      this.charset = value;
      return this;
   }

   /**
    * Returns the charset to use when converting to and from stream-based resources.
    *
    * @return The charset to use when converting to and from stream-based resources.
    */
   public Charset getCharset() {
      return charset == null ? UTF8 : charset;
   }

   /**
    * Specifies the maximum number of bytes to read or write to and from stream-based resources.
    *
    * <p>
    * Implementation is not universal.
    *
    * @param value The new value.  The default is <c>-1</c> which means read everything.
    * @return This object.
    */
   public BasicHttpEntity setMaxLength(int value) {
      assertModifiable();
      this.maxLength = value;
      return this;
   }

   /**
    * Returns the maximum number of bytes to read or write to and from stream-based resources.
    *
    * @return The maximum number of bytes to read or write to and from stream-based resources.
    */
   public int getMaxLength() {
      return maxLength;
   }

   //-----------------------------------------------------------------------------------------------------------------
   // Other methods
   //-----------------------------------------------------------------------------------------------------------------

   /**
    * Converts the contents of this entity as a string.
    *
    * <p>
    * Note that this may exhaust the content on non-repeatable, non-cached entities.
    *
    * @return The contents of this entity as a string.
    * @throws IOException If a problem occurred while trying to read the content.
    */
   public String asString() throws IOException {
      return read(getContent());
   }

   /**
    * Converts the contents of this entity as a byte array.
    *
    * <p>
    * Note that this may exhaust the content on non-repeatable, non-cached entities.
    *
    * @return The contents of this entity as a byte array.
    * @throws IOException If a problem occurred while trying to read the content.
    */
   public byte[] asBytes() throws IOException {
      return readBytes(getContent());
   }

   /**
    * Same as {@link #asBytes()} but wraps {@link IOException IOExceptions} inside a {@link RuntimeException}.
    *
    * @return The contents of this entity as a byte array.
    */
   protected byte[] asSafeBytes() {
      try {
         return asBytes();
      } catch (IOException e) {
         throw new UncheckedIOException(e);
      }
   }

   /**
    * Returns an assertion on the contents of this entity.
    *
    * <p>
    * Note that this may exhaust the content on non-repeatable, non-cached entities.
    *
    * @return A new fluent assertion.
    * @throws IOException If a problem occurred while trying to read the byte array.
    */
   public FluentStringAssertion<BasicHttpEntity> assertString() throws IOException {
      return new FluentStringAssertion<>(asString(), this);
   }

   /**
    * Returns an assertion on the contents of this entity.
    *
    * <p>
    * Note that this may exhaust the content on non-repeatable, non-cached entities.
    *
    * @return A new fluent assertion.
    * @throws IOException If a problem occurred while trying to read the byte array.
    */
   public FluentByteArrayAssertion<BasicHttpEntity> assertBytes() throws IOException {
      return new FluentByteArrayAssertion<>(asBytes(), this);
   }

   /**
    * Returns the content of this entity.
    *
    * @param <T> The value type.
    * @param def The default value if <jk>null</jk>.
    * @return The content object.
    */
   @SuppressWarnings("unchecked")
   protected <T> T contentOrElse(T def) {
      Object o = content;
      if (o == null && contentSupplier != null)
         o = contentSupplier.get();
      return (o == null ? def : (T)o);
   }

   /**
    * Returns <jk>true</jk> if the contents of this entity are provided through an external supplier.
    *
    * <p>
    * Externally supplied content generally means the content length cannot be reliably determined
    * based on the content.
    *
    * @return <jk>true</jk> if the contents of this entity are provided through an external supplier.
    */
   protected boolean isSupplied() {
      return contentSupplier != null;
   }

   @Override /* HttpEntity */
   public long getContentLength() {
      return contentLength;
   }

   @Override /* HttpEntity */
   public boolean isRepeatable() {
      return false;
   }

   @Override /* HttpEntity */
   public boolean isChunked() {
      return chunked;
   }

   @Override /* HttpEntity */
   public Header getContentType() {
      return contentType;
   }

   @Override /* HttpEntity */
   public Header getContentEncoding() {
      return contentEncoding;
   }

   @Override /* HttpEntity */
   public boolean isStreaming() {
      return false;
   }

   @Override /* HttpEntity */
   public void consumeContent() throws IOException {}

   @Override /* HttpEntity */
   public InputStream getContent() throws IOException, UnsupportedOperationException {
      return IOUtils.EMPTY_INPUT_STREAM;
   }

   @Override /* HttpEntity */
   public void writeTo(OutputStream outStream) throws IOException {}
}