/**
 * The MIT License (MIT)
 *
 * Copyright (c) 2014-2017 Yegor Bugayenko
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package org.takes.facets.fork;

import java.io.IOException;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.regex.Pattern;
import lombok.EqualsAndHashCode;
import org.takes.Request;
import org.takes.Response;
import org.takes.misc.EnglishLowerCase;
import org.takes.misc.Opt;
import org.takes.rq.RqHeaders;

/**
 * Fork by encoding accepted by "Accept-Encoding" HTTP header.
 *
 * <p>Use this fork in order to deliver responses with different
 * encoding, depending on user preferences. For example, you want
 * to deliver GZIP-compressed response when "Accept-Encoding" request
 * header contains "gzip". Here is how:
 *
 * <pre> new TkFork(
 *   new FkEncoding("gzip", new RsGzip(response)),
 *   new FkEncoding("", response)
 * )</pre>
 *
 * <p>Empty string as an encoding means that the fork should match
 * in any case.
 *
 * <p>The class is immutable and thread-safe.
 * @author Yegor Bugayenko (yegor256@gmail.com)
 * @version $Id: fbe1a97f7cc1379bff24b6819a848cc0a48269dd $
 * @see org.takes.facets.fork.RsFork
 * @since 0.10
 */
@EqualsAndHashCode
public final class FkEncoding implements Fork {

    /**
     * Accept-Encoding separator.
     */
    private static final Pattern ENCODING_SEP = Pattern.compile("\\s*,\\s*");

    /**
     * Encoding we can deliver (or empty string).
     */
    private final String encoding;

    /**
     * Response to return.
     */
    private final Response origin;

    /**
     * Ctor.
     * @param enc Encoding we accept
     * @param response Response to return
     */
    public FkEncoding(final String enc, final Response response) {
        this.encoding = new EnglishLowerCase(enc.trim()).string();
        this.origin = response;
    }

    @Override
    public Opt<Response> route(final Request req) throws IOException {
        final Iterator<String> headers =
            new RqHeaders.Base(req).header("Accept-Encoding").iterator();
        final Opt<Response> resp;
        if (this.encoding.isEmpty()) {
            resp = new Opt.Single<Response>(this.origin);
        } else if (headers.hasNext()) {
            final Collection<String> items = Arrays.asList(
                ENCODING_SEP.split(
                    new EnglishLowerCase(headers.next().trim())
                        .string()
                )
            );
            if (items.contains(this.encoding)) {
                resp = new Opt.Single<Response>(this.origin);
            } else {
                resp = new Opt.Empty<Response>();
            }
        } else {
            resp = new Opt.Empty<Response>();
        }
        return resp;
    }

}