/*

 * Copyright (c) 2015, 2016, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package jdk.incubator.http;

import java.util.ArrayList;

import java.util.List;

import java.util.Map;

import java.util.Optional;

import java.util.OptionalLong;

import java.util.TreeMap;

import java.util.function.Predicate;

import static java.util.Collections.emptyList;

import static java.util.Collections.emptyMap;

import static java.util.Collections.unmodifiableList;

import static java.util.Collections.unmodifiableMap;

import static java.util.Objects.requireNonNull;

final class ImmutableHeaders implements HttpHeaders {

    private final Map<String, List<String>> map;

    public static ImmutableHeaders empty() {

        return of(emptyMap());

    }

    public static ImmutableHeaders of(Map<String, List<String>> src) {

        return of(src, x -> true);

    }

    public static ImmutableHeaders of(Map<String, List<String>> src,

                                      Predicate<? super String> keyAllowed) {

        requireNonNull(src, "src");

        requireNonNull(keyAllowed, "keyAllowed");

        return new ImmutableHeaders(src, keyAllowed);

    }

    private ImmutableHeaders(Map<String, List<String>> src,

                             Predicate<? super String> keyAllowed) {

        Map<String, List<String>> m = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);

        src.entrySet().stream()

                .filter(e -> keyAllowed.test(e.getKey()))

                .forEach(e ->

                        {

                            List<String> values = new ArrayList<>(e.getValue());

                            m.put(e.getKey(), unmodifiableList(values));

                        }

                );

        this.map = unmodifiableMap(m);

    }

    @Override

    public Optional<String> firstValue(String name) {

        return allValues(name).stream().findFirst();

    }

    @Override

    public OptionalLong firstValueAsLong(String name) {

        return allValues(name).stream().mapToLong(Long::valueOf).findFirst();

    }

    @Override

    public List<String> allValues(String name) {

        requireNonNull(name);

        List<String> values = map.get(name);

        // Making unmodifiable list out of empty in order to make a list which

        // throws UOE unconditionally

        return values != null ? values : unmodifiableList(emptyList());

    }

    @Override

    public Map<String, List<String>> map() {

        return map;

    }

}