/*
 * Copyright (c) 2015, 2018, 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.internal.net.http;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.TreeMap;
import java.util.function.BiPredicate;
import java.util.function.Predicate;
import java.net.http.HttpHeaders;
import jdk.internal.net.http.common.HttpHeadersImpl;
import jdk.internal.net.http.common.Utils;
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 extends 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(HttpHeaders headers) {
        return (headers instanceof ImmutableHeaders)
                ? (ImmutableHeaders)headers
                : of(headers.map());
    }

    static ImmutableHeaders validate(HttpHeaders headers) {
        if (headers instanceof ImmutableHeaders) {
            return of(headers);
        }
        if (headers instanceof HttpHeadersImpl) {
            return of(headers);
        }
        Map<String, List<String>> map = headers.map();
        return new ImmutableHeaders(map, Utils.VALIDATE_USER_HEADER);
    }

    public static ImmutableHeaders of(Map<String, List<String>> src,
                                      Predicate<? super String> keyAllowed) {
        requireNonNull(src, "src");
        requireNonNull(keyAllowed, "keyAllowed");
        return new ImmutableHeaders(src, headerAllowed(keyAllowed));
    }

    public static ImmutableHeaders of(Map<String, List<String>> src,
                                      BiPredicate<? super String, ? super List<String>> headerAllowed) {
        requireNonNull(src, "src");
        requireNonNull(headerAllowed, "headerAllowed");
        return new ImmutableHeaders(src, headerAllowed);
    }

    private ImmutableHeaders(Map<String, List<String>> src,
                             BiPredicate<? super String, ? super List<String>> headerAllowed) {
        Map<String, List<String>> m = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
        src.entrySet().stream()
                .forEach(e -> addIfAllowed(e, headerAllowed, m));
        this.map = unmodifiableMap(m);
    }

    private static void addIfAllowed(Map.Entry<String, List<String>> e,
                                     BiPredicate<? super String, ? super List<String>> headerAllowed,
                                     Map<String, List<String>> map) {
        String key = e.getKey();
        List<String> values = unmodifiableValues(e.getValue());
        if (headerAllowed.test(key, values)) {
            map.put(key, values);
        }
    }

    private static List<String> unmodifiableValues(List<String> values) {
        return unmodifiableList(new ArrayList<>(Objects.requireNonNull(values)));
    }

    private static BiPredicate<String, List<String>> headerAllowed(Predicate<? super String> keyAllowed) {
        return (n,v) -> keyAllowed.test(n);
    }

    @Override
    public Map<String, List<String>> map() {
        return map;
    }
}