/*
 * Copyright 2002-2019 the original author or authors.
 *
 * 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.springframework.http.converter;

import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import javax.imageio.IIOImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageReadParam;
import javax.imageio.ImageReader;
import javax.imageio.ImageWriteParam;
import javax.imageio.ImageWriter;
import javax.imageio.stream.FileCacheImageInputStream;
import javax.imageio.stream.FileCacheImageOutputStream;
import javax.imageio.stream.ImageInputStream;
import javax.imageio.stream.ImageOutputStream;
import javax.imageio.stream.MemoryCacheImageInputStream;
import javax.imageio.stream.MemoryCacheImageOutputStream;

import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.StreamingHttpOutputMessage;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

Implementation of HttpMessageConverter that can read and write BufferedImages. 
By default, this converter can read all media types that are supported by the registered image readers, and writes using the media type of the first available registered image writer. The latter can be overridden by setting the defaultContentType property. 
If the cacheDir property is set, this converter will cache image data. 
The process(ImageReadParam) and process(ImageWriteParam) template methods allow subclasses to override Image I/O parameters. 
Author:
Arjen Poutsma
Since:
3.0/**
 * Implementation of {@link HttpMessageConverter} that can read and write
 * {@link BufferedImage BufferedImages}.
 *
 * <p>By default, this converter can read all media types that are supported
 * by the {@linkplain ImageIO#getReaderMIMETypes() registered image readers},
 * and writes using the media type of the first available
 * {@linkplain javax.imageio.ImageIO#getWriterMIMETypes() registered image writer}.
 * The latter can be overridden by setting the
 * {@link #setDefaultContentType defaultContentType} property.
 *
 * <p>If the {@link #setCacheDir cacheDir} property is set, this converter
 * will cache image data.
 *
 * <p>The {@link #process(ImageReadParam)} and {@link #process(ImageWriteParam)}
 * template methods allow subclasses to override Image I/O parameters.
 *
 * @author Arjen Poutsma
 * @since 3.0
 */
public class BufferedImageHttpMessageConverter implements HttpMessageConverter<BufferedImage> {

	private final List<MediaType> readableMediaTypes = new ArrayList<>();

	@Nullable
	private MediaType defaultContentType;

	@Nullable
	private File cacheDir;


	public BufferedImageHttpMessageConverter() {
		String[] readerMediaTypes = ImageIO.getReaderMIMETypes();
		for (String mediaType : readerMediaTypes) {
			if (StringUtils.hasText(mediaType)) {
				this.readableMediaTypes.add(MediaType.parseMediaType(mediaType));
			}
		}

		String[] writerMediaTypes = ImageIO.getWriterMIMETypes();
		for (String mediaType : writerMediaTypes) {
			if (StringUtils.hasText(mediaType)) {
				this.defaultContentType = MediaType.parseMediaType(mediaType);
				break;
			}
		}
	}


	
Sets the default Content-Type to be used for writing. 
Throws:
IllegalArgumentException – if the given content type is not supported by the Java Image I/O API/**
	 * Sets the default {@code Content-Type} to be used for writing.
	 * @throws IllegalArgumentException if the given content type is not supported by the Java Image I/O API
	 */
	public void setDefaultContentType(@Nullable MediaType defaultContentType) {
		if (defaultContentType != null) {
			Iterator<ImageWriter> imageWriters = ImageIO.getImageWritersByMIMEType(defaultContentType.toString());
			if (!imageWriters.hasNext()) {
				throw new IllegalArgumentException(
						"Content-Type [" + defaultContentType + "] is not supported by the Java Image I/O API");
			}
		}

		this.defaultContentType = defaultContentType;
	}

	
Returns the default Content-Type to be used for writing. Called when write is invoked without a specified content type parameter. /**
	 * Returns the default {@code Content-Type} to be used for writing.
	 * Called when {@link #write} is invoked without a specified content type parameter.
	 */
	@Nullable
	public MediaType getDefaultContentType() {
		return this.defaultContentType;
	}

	
Sets the cache directory. If this property is set to an existing directory,
this converter will cache image data.
/**
	 * Sets the cache directory. If this property is set to an existing directory,
	 * this converter will cache image data.
	 */
	public void setCacheDir(File cacheDir) {
		Assert.notNull(cacheDir, "'cacheDir' must not be null");
		Assert.isTrue(cacheDir.isDirectory(), "'cacheDir' is not a directory");
		this.cacheDir = cacheDir;
	}


	@Override
	public boolean canRead(Class<?> clazz, @Nullable MediaType mediaType) {
		return (BufferedImage.class == clazz && isReadable(mediaType));
	}

	private boolean isReadable(@Nullable MediaType mediaType) {
		if (mediaType == null) {
			return true;
		}
		Iterator<ImageReader> imageReaders = ImageIO.getImageReadersByMIMEType(mediaType.toString());
		return imageReaders.hasNext();
	}

	@Override
	public boolean canWrite(Class<?> clazz, @Nullable MediaType mediaType) {
		return (BufferedImage.class == clazz && isWritable(mediaType));
	}

	private boolean isWritable(@Nullable MediaType mediaType) {
		if (mediaType == null || MediaType.ALL.equalsTypeAndSubtype(mediaType)) {
			return true;
		}
		Iterator<ImageWriter> imageWriters = ImageIO.getImageWritersByMIMEType(mediaType.toString());
		return imageWriters.hasNext();
	}

	@Override
	public List<MediaType> getSupportedMediaTypes() {
		return Collections.unmodifiableList(this.readableMediaTypes);
	}

	@Override
	public BufferedImage read(@Nullable Class<? extends BufferedImage> clazz, HttpInputMessage inputMessage)
			throws IOException, HttpMessageNotReadableException {

		ImageInputStream imageInputStream = null;
		ImageReader imageReader = null;
		try {
			imageInputStream = createImageInputStream(inputMessage.getBody());
			MediaType contentType = inputMessage.getHeaders().getContentType();
			if (contentType == null) {
				throw new HttpMessageNotReadableException("No Content-Type header", inputMessage);
			}
			Iterator<ImageReader> imageReaders = ImageIO.getImageReadersByMIMEType(contentType.toString());
			if (imageReaders.hasNext()) {
				imageReader = imageReaders.next();
				ImageReadParam irp = imageReader.getDefaultReadParam();
				process(irp);
				imageReader.setInput(imageInputStream, true);
				return imageReader.read(0, irp);
			}
			else {
				throw new HttpMessageNotReadableException(
						"Could not find javax.imageio.ImageReader for Content-Type [" + contentType + "]",
						inputMessage);
			}
		}
		finally {
			if (imageReader != null) {
				imageReader.dispose();
			}
			if (imageInputStream != null) {
				try {
					imageInputStream.close();
				}
				catch (IOException ex) {
					// ignore
				}
			}
		}
	}

	private ImageInputStream createImageInputStream(InputStream is) throws IOException {
		if (this.cacheDir != null) {
			return new FileCacheImageInputStream(is, this.cacheDir);
		}
		else {
			return new MemoryCacheImageInputStream(is);
		}
	}

	@Override
	public void write(final BufferedImage image, @Nullable final MediaType contentType,
			final HttpOutputMessage outputMessage)
			throws IOException, HttpMessageNotWritableException {

		final MediaType selectedContentType = getContentType(contentType);
		outputMessage.getHeaders().setContentType(selectedContentType);

		if (outputMessage instanceof StreamingHttpOutputMessage) {
			StreamingHttpOutputMessage streamingOutputMessage = (StreamingHttpOutputMessage) outputMessage;
			streamingOutputMessage.setBody(outputStream -> writeInternal(image, selectedContentType, outputStream));
		}
		else {
			writeInternal(image, selectedContentType, outputMessage.getBody());
		}
	}

	private MediaType getContentType(@Nullable MediaType contentType) {
		if (contentType == null || contentType.isWildcardType() || contentType.isWildcardSubtype()) {
			contentType = getDefaultContentType();
		}
		Assert.notNull(contentType, "Could not select Content-Type. " +
				"Please specify one through the 'defaultContentType' property.");
		return contentType;
	}

	private void writeInternal(BufferedImage image, MediaType contentType, OutputStream body)
			throws IOException, HttpMessageNotWritableException {

		ImageOutputStream imageOutputStream = null;
		ImageWriter imageWriter = null;
		try {
			Iterator<ImageWriter> imageWriters = ImageIO.getImageWritersByMIMEType(contentType.toString());
			if (imageWriters.hasNext()) {
				imageWriter = imageWriters.next();
				ImageWriteParam iwp = imageWriter.getDefaultWriteParam();
				process(iwp);
				imageOutputStream = createImageOutputStream(body);
				imageWriter.setOutput(imageOutputStream);
				imageWriter.write(null, new IIOImage(image, null, null), iwp);
			}
			else {
				throw new HttpMessageNotWritableException(
						"Could not find javax.imageio.ImageWriter for Content-Type [" + contentType + "]");
			}
		}
		finally {
			if (imageWriter != null) {
				imageWriter.dispose();
			}
			if (imageOutputStream != null) {
				try {
					imageOutputStream.close();
				}
				catch (IOException ex) {
					// ignore
				}
			}
		}
	}

	private ImageOutputStream createImageOutputStream(OutputStream os) throws IOException {
		if (this.cacheDir != null) {
			return new FileCacheImageOutputStream(os, this.cacheDir);
		}
		else {
			return new MemoryCacheImageOutputStream(os);
		}
	}


	
Template method that allows for manipulating the ImageReadParam before it is used to read an image. 
The default implementation is empty.
/**
	 * Template method that allows for manipulating the {@link ImageReadParam}
	 * before it is used to read an image.
	 * <p>The default implementation is empty.
	 */
	protected void process(ImageReadParam irp) {
	}

	
Template method that allows for manipulating the ImageWriteParam before it is used to write an image. 
The default implementation is empty.
/**
	 * Template method that allows for manipulating the {@link ImageWriteParam}
	 * before it is used to write an image.
	 * <p>The default implementation is empty.
	 */
	protected void process(ImageWriteParam iwp) {
	}

}