/*
 * Copyright (c) 2016—2021 Andrei Tomashpolskiy and individual contributors.
 *
 * Licensed 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.
 */

package bt.metainfo;

import bt.BtException;
import bt.protocol.Protocols;

import java.util.Arrays;
import java.util.Objects;

/**
 * Object wrapper for binary torrent identifiers.
 *
 * @since 1.0
 */
public class TorrentId {

    private static final int TORRENT_ID_LENGTH = 20;

    /**
     * @return Length in bytes
     * @since 1.0
     */
    public static int length() {
        return TORRENT_ID_LENGTH;
    }

    /**
     * Create a TorrentId instance from a binary representation.
     *
     * @param bytes Binary representation of torrent's ID
     * @since 1.0
     */
    public static TorrentId fromBytes(byte[] bytes) {
        return new TorrentId(bytes);
    }

    private final byte[] torrentId;

    private TorrentId(byte[] torrentId) {
        Objects.requireNonNull(torrentId);
        if (torrentId.length != TORRENT_ID_LENGTH) {
            throw new BtException("Illegal torrent ID length: " + torrentId.length);
        }
        this.torrentId = torrentId;
    }

    /**
     * @return Binary representation of torrent's ID
     * @since 1.0
     */
    public byte[] getBytes() {
        return torrentId;
    }

    @Override
    public int hashCode() {
        return Arrays.hashCode(torrentId);
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        if (obj == null || !TorrentId.class.isAssignableFrom(obj.getClass())) {
            return false;
        }
        return Arrays.equals(torrentId, ((TorrentId) obj).getBytes());
    }

    @Override
    public String toString() {
        return Protocols.toHex(torrentId);
    }
}
