/*
 * WorldEdit, a Minecraft world manipulation toolkit
 * Copyright (C) sk89q <http://www.sk89q.com>
 * Copyright (C) WorldEdit team and contributors
 *
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */

package com.sk89q.worldedit.registry;

import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

import javax.annotation.Nullable;

import static com.google.common.base.Preconditions.checkState;
import static java.util.Objects.requireNonNull;

public final class NamespacedRegistry<V> {
    private static final String MINECRAFT_NAMESPACE = "minecraft";
    private final Map<String, V> map = new HashMap<>();

    public @Nullable V get(final String key) {
        checkState(key.equals(key.toLowerCase()), "key must be lowercase");
        return this.map.get(this.orDefaultNamespace(key));
    }

    public V register(final String key, final V value) {
        requireNonNull(key, "key");
        requireNonNull(value, "value");
        checkState(key.indexOf(':') > -1, "key is not namespaced");
        checkState(key.equals(key.toLowerCase()), "key must be lowercase");
        checkState(!this.map.containsKey(key), "key %s already has an entry", key);
        this.map.put(key, value);
        return value;
    }

    public Set<String> keySet() {
        return Collections.unmodifiableSet(this.map.keySet());
    }

    public Collection<V> values() {
        return Collections.unmodifiableCollection(this.map.values());
    }

    private String orDefaultNamespace(final String key) {
        if (key.indexOf(':') == -1) {
            return MINECRAFT_NAMESPACE + ':' + key;
        }
        return key;
    }
}