/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project 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 io.netty.example.http.cors;

import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.http.HttpObjectAggregator;
import io.netty.handler.codec.http.HttpRequestDecoder;
import io.netty.handler.codec.http.HttpResponseEncoder;
import io.netty.handler.codec.http.cors.CorsConfig;
import io.netty.handler.codec.http.cors.CorsConfigBuilder;
import io.netty.handler.codec.http.cors.CorsHandler;
import io.netty.handler.ssl.SslContext;
import io.netty.handler.stream.ChunkedWriteHandler;

Please refer to the CorsConfig javadocs for information about all the configuration options available. Below are some of configuration discussed in this example: 
Support only a specific origin
To support a single origin instead of the wildcard use the following:
CorsConfig corsConfig = CorsConfig.withOrigin("http://domain1.com")

Enable loading from the file system
To enable the server to handle an origin specified as 'null', which happens
when a web browser loads a file from the local file system use the following:
corsConfig.isNullOriginAllowed()

Enable request headers
To enable additional request headers:
corsConfig.allowedRequestHeaders("custom-request-header")

Expose response headers
By default a browser only exposes the following simple header:

Cache-Control
Content-Language
Content-Type
Expires
Last-Modified
Pragma

Any of the above response headers can be retrieved by:
xhr.getResponseHeader("Content-Type");

If you need to get access to other headers this must be enabled by the server, for example:
corsConfig.exposedHeaders("custom-response-header");

/**
 * Please refer to the {@link CorsConfig} javadocs for information about all the
 * configuration options available.
 *
 * Below are some of configuration discussed in this example:
 * <h3>Support only a specific origin</h3>
 * To support a single origin instead of the wildcard use the following:
 * <pre>
 * CorsConfig corsConfig = CorsConfig.withOrigin("http://domain1.com")
 * </pre>
 *
 * <h3>Enable loading from the file system</h3>
 * To enable the server to handle an origin specified as 'null', which happens
 * when a web browser loads a file from the local file system use the following:
 * <pre>
 * corsConfig.isNullOriginAllowed()
 * </pre>
 *
 * <h3>Enable request headers</h3>
 * To enable additional request headers:
 * <pre>
 * corsConfig.allowedRequestHeaders("custom-request-header")
 * </pre>
 *
 * <h3>Expose response headers</h3>
 * By default a browser only exposes the following simple header:
 * <ul>
 * <li>Cache-Control</li>
 * <li>Content-Language</li>
 * <li>Content-Type</li>
 * <li>Expires</li>
 * <li>Last-Modified</li>
 * <li>Pragma</li>
 * </ul>
 * Any of the above response headers can be retrieved by:
 * <pre>
 * xhr.getResponseHeader("Content-Type");
 * </pre>
 * If you need to get access to other headers this must be enabled by the server, for example:
 * <pre>
 * corsConfig.exposedHeaders("custom-response-header");
 * </pre>
 */
public class HttpCorsServerInitializer extends ChannelInitializer<SocketChannel> {

    private final SslContext sslCtx;

    public HttpCorsServerInitializer(SslContext sslCtx) {
        this.sslCtx = sslCtx;
    }

    @Override
    public void initChannel(SocketChannel ch) {
        CorsConfig corsConfig = CorsConfigBuilder.forAnyOrigin().allowNullOrigin().allowCredentials().build();
        ChannelPipeline pipeline = ch.pipeline();
        if (sslCtx != null) {
            pipeline.addLast(sslCtx.newHandler(ch.alloc()));
        }
        pipeline.addLast(new HttpResponseEncoder());
        pipeline.addLast(new HttpRequestDecoder());
        pipeline.addLast(new HttpObjectAggregator(65536));
        pipeline.addLast(new ChunkedWriteHandler());
        pipeline.addLast(new CorsHandler(corsConfig));
        pipeline.addLast(new OkResponseHandler());
    }

}