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/*
 * 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.data;

import bt.event.EventSource;
import bt.metainfo.Torrent;
import bt.metainfo.TorrentId;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Note that this class is not a part of the public API and is a subject to change.
 */
public class DataReaderFactory {

    private Map> channelsByTorrentId;

    public DataReaderFactory(EventSource eventSource) {
        this.channelsByTorrentId = new HashMap<>();

        eventSource.onPieceVerified(null, e -> onPieceVerified(e.getTorrentId(), e.getPieceIndex()));
    }

    public DataReader createReader(Torrent torrent, DataDescriptor dataDescriptor) {
        return () -> {
            DataReaderChannel channel = new DataReaderChannel(dataDescriptor, torrent.getChunkSize());
            register(torrent.getTorrentId(), channel);
            return channel;
        };
    }

    private synchronized void onPieceVerified(TorrentId torrentId, int pieceIndex) {
        List channels = channelsByTorrentId.get(torrentId);
        if (channels != null) {
            channels.forEach(channel -> channel.onPieceVerified(pieceIndex));
        }
    }

    private synchronized void register(TorrentId torrentId, DataReaderChannel channel) {
        channel.init();
        channelsByTorrentId.computeIfAbsent(torrentId, it -> new ArrayList<>())
                .add(channel);
    }
}