/*
 * Copyright 2002-2009 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.ide.eclipse.boot.wizard.util;

import java.io.IOException;
import java.nio.charset.Charset;
import java.util.List;

import org.codehaus.jackson.JsonEncoding;
import org.codehaus.jackson.JsonGenerator;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.type.TypeFactory;
import org.codehaus.jackson.type.JavaType;
import org.springframework.http.HttpInputMessage;
import org.springframework.http.HttpOutputMessage;
import org.springframework.http.MediaType;
import org.springframework.http.converter.AbstractHttpMessageConverter;
import org.springframework.http.converter.HttpMessageNotReadableException;
import org.springframework.http.converter.HttpMessageNotWritableException;
import org.springframework.util.Assert;

//This is copy of MappingJacksonHttpMessageConverter from Spring 3. Slightly modified to compile
// in spring 4 and being compatible with old Jackson 1.6 library. The new version in spring 4
// requires more recent Jackons that do not ship with Eclipse.

/**
 * Implementation of {@link org.springframework.http.converter.HttpMessageConverter HttpMessageConverter} that can read
 * and write JSON using <a href="http://jackson.codehaus.org/">Jackson's</a> {@link ObjectMapper}.
 *
 * <p>This converter can be used to bind to typed beans, or untyped {@link java.util.HashMap HashMap} instances.
 *
 * <p>By default, this converter supports {@code application/json}. This can be overridden by setting the {@link
 * #setSupportedMediaTypes(List) supportedMediaTypes} property.
 * method.
 *
 * @author Arjen Poutsma
 * @see org.springframework.web.servlet.view.json.BindingJacksonJsonView
 * @since 3.0
 */
public class Spring3MappingJacksonHttpMessageConverter extends AbstractHttpMessageConverter<Object> {

	public static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");

	private ObjectMapper objectMapper = new ObjectMapper();

	private boolean prefixJson = false;

	/** Construct a new {@code BindingJacksonHttpMessageConverter}, */
	public Spring3MappingJacksonHttpMessageConverter() {
		super(
				new MediaType("application", "json", DEFAULT_CHARSET),
				new MediaType("text", "plain", DEFAULT_CHARSET) // download raw github url will give this even if file has json extension.
		);
	}

	/**
	 * Sets the {@code ObjectMapper} for this view. If not set, a default {@link ObjectMapper#ObjectMapper() ObjectMapper}
	 * is used.
	 *
	 * <p>Setting a custom-configured {@code ObjectMapper} is one way to take further control of the JSON serialization
	 * process. For example, an extended {@link org.codehaus.jackson.map.SerializerFactory} can be configured that provides
	 * custom serializers for specific types. The other option for refining the serialization process is to use Jackson's
	 * provided annotations on the types to be serialized, in which case a custom-configured ObjectMapper is unnecessary.
	 */
	public void setObjectMapper(ObjectMapper objectMapper) {
		Assert.notNull(objectMapper, "'objectMapper' must not be null");
		this.objectMapper = objectMapper;
	}

	/**
	 * Indicates whether the JSON output by this view should be prefixed with "{} &&". Default is false.
	 *
	 * <p> Prefixing the JSON string in this manner is used to help prevent JSON Hijacking. The prefix renders the string
	 * syntactically invalid as a script so that it cannot be hijacked. This prefix does not affect the evaluation of JSON,
	 * but if JSON validation is performed on the string, the prefix would need to be ignored.
	 */
	public void setPrefixJson(boolean prefixJson) {
		this.prefixJson = prefixJson;
	}

	@Override
	public boolean canRead(Class<?> clazz, MediaType mediaType) {
		JavaType javaType = TypeFactory.fromClass(clazz);
		return objectMapper.canDeserialize(javaType) && isSupported(mediaType);
	}

	private boolean isSupported(MediaType mediaType) {
		List<MediaType> supported = getSupportedMediaTypes();
		for (MediaType s : supported) {
			if (s.includes(mediaType)) {
				return true;
			}
		}
		return false;
	}

	@Override
	public boolean canWrite(Class<?> clazz, MediaType mediaType) {
		return objectMapper.canSerialize(clazz) && isSupported(mediaType);
	}

	@Override
	protected boolean supports(Class<?> clazz) {
		// should not be called, since we override canRead/Write
		throw new UnsupportedOperationException();
	}

	@Override
	protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage)
			throws IOException, HttpMessageNotReadableException, HttpMessageNotReadableException {
		return objectMapper.readValue(inputMessage.getBody(), clazz);
	}
	
	@Override
	protected void writeInternal(Object o, HttpOutputMessage outputMessage)
			throws IOException, HttpMessageNotWritableException {
		JsonEncoding encoding = getEncoding(outputMessage.getHeaders().getContentType());
		JsonGenerator jsonGenerator =
				objectMapper.getJsonFactory().createJsonGenerator(outputMessage.getBody(), encoding);
		if (prefixJson) {
			jsonGenerator.writeRaw("{} && ");
		}
		objectMapper.writeValue(jsonGenerator, o);
	}

	private JsonEncoding getEncoding(MediaType contentType) {
		if (contentType != null && contentType.getCharSet() != null) {
			Charset charset = contentType.getCharSet();
			for (JsonEncoding encoding : JsonEncoding.values()) {
				if (charset.name().equals(encoding.getJavaName())) {
					return encoding;
				}
			}
		}
		return JsonEncoding.UTF8;
	}

}