/*
 * ====================================================================
 * 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 org.apache.hc.core5.http.protocol;

import java.io.IOException;
import java.net.URISyntaxException;

import org.apache.hc.core5.annotation.Contract;
import org.apache.hc.core5.annotation.ThreadingBehavior;
import org.apache.hc.core5.http.EntityDetails;
import org.apache.hc.core5.http.Header;
import org.apache.hc.core5.http.HttpException;
import org.apache.hc.core5.http.HttpHeaders;
import org.apache.hc.core5.http.HttpRequest;
import org.apache.hc.core5.http.HttpRequestInterceptor;
import org.apache.hc.core5.http.HttpVersion;
import org.apache.hc.core5.http.ProtocolException;
import org.apache.hc.core5.http.ProtocolVersion;
import org.apache.hc.core5.net.URIAuthority;
import org.apache.hc.core5.util.Args;

/**
 * This request interceptor is responsible for copying {@code Host} header value to
 * {@link HttpRequest#setAuthority(URIAuthority)} of incoming request messages.
 * <p>
 * This interceptor is essential for the HTTP protocol conformance and
 * the correct operation of the server-side message processing pipeline.
 * </p>
 *
 * @since 5.0
 */
@Contract(threading = ThreadingBehavior.IMMUTABLE)
public class RequestValidateHost implements HttpRequestInterceptor {

    public static final RequestValidateHost INSTANCE = new RequestValidateHost();

    public RequestValidateHost() {
        super();
    }

    @Override
    public void process(final HttpRequest request, final EntityDetails entity, final HttpContext context)
            throws HttpException, IOException {
        Args.notNull(request, "HTTP request");

        // Request authority already specified (likely in an absolute request URI)
        if (request.getAuthority() != null) {
            return;
        }

        final Header header = request.getHeader(HttpHeaders.HOST);
        if (header != null) {
            final URIAuthority authority;
            try {
                authority = URIAuthority.create(header.getValue());
            } catch (final URISyntaxException ex) {
                throw new ProtocolException(ex.getMessage(), ex);
            }
            request.setAuthority(authority);
        } else {
            final ProtocolVersion version = request.getVersion() != null ? request.getVersion() : HttpVersion.HTTP_1_1;
            if (version.greaterEquals(HttpVersion.HTTP_1_1)) {
                throw new ProtocolException("Host header is absent");
            }
        }
    }

}
