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/*
 * The MIT License
 *
 * Copyright 2015 Tim Boudreau.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package com.mastfrog.giulius.mongodb.async;

import com.mastfrog.settings.Settings;
import com.mastfrog.util.preconditions.Exceptions;
import com.mongodb.async.AsyncBatchCursor;
import com.mongodb.async.SingleResultCallback;
import com.mongodb.async.client.MongoDatabase;
import com.mongodb.async.client.MongoIterable;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import javax.inject.Inject;
import javax.inject.Provider;
import javax.inject.Singleton;

/**
 *
 * @author Tim Boudreau
 */
@Singleton
class KnownCollections implements Iterable {

    private Set knownCollections;
    private final Provider dbProvider;
    public static final String SETTINGS_KEY_MAX_WAIT_SECONDS = "mongo.list.collections.max.wait.seconds";
    private final long maxWaitSeconds;

    // PENDING: AsyncMongoClientProvider should create the set maintained
    // here, and let initializers augment it, so there is no need for the
    // blocking / locking done here
    @Inject
    KnownCollections(Provider dbProvider, Settings settings) {
        this.dbProvider = dbProvider;
        maxWaitSeconds = settings.getInt(SETTINGS_KEY_MAX_WAIT_SECONDS, 30);
    }
    
    synchronized void add(String created) {
        knownCollections().add(created);
    }

    public boolean exists(String collection) {
        return knownCollections().contains(collection);
    }

    private synchronized Set knownCollections() {
        if (knownCollections == null) {
            MongoDatabase db = dbProvider.get();
            MongoIterable iter = db.listCollectionNames();
            CollectionListReceiver recv = new CollectionListReceiver(maxWaitSeconds);
            iter.batchCursor(recv);
            knownCollections = recv.await();
        }
        return knownCollections;
    }

    @Override
    public Iterator iterator() {
        return knownCollections().iterator();
    }

    static class CollectionListReceiver implements SingleResultCallback> {

        private final SRC src = new SRC();
        private final Set allCollections = Collections.synchronizedSet(new HashSet());
        private volatile Throwable toThrow;
        private volatile AsyncBatchCursor cursor;
        private final CountDownLatch latch = new CountDownLatch(1);
        private final long maxWaitSeconds;

        private CollectionListReceiver(long maxWaitSeconds) {
            this.maxWaitSeconds = maxWaitSeconds;
        }

        @Override
        public void onResult(AsyncBatchCursor t, Throwable thrwbl) {
            cursor = t;
            if (cursor != null) {
                cursor.setBatchSize(200);
                t.next(src);
            }
        }

        Set await() {
            try {
                latch.await(maxWaitSeconds, TimeUnit.SECONDS);
                if (toThrow != null) {
                    return Exceptions.chuck(toThrow);
                }
                return allCollections;
            } catch (InterruptedException ex) {
                return Exceptions.chuck(ex);
            }
        }

        class SRC implements SingleResultCallback> {

            @Override
            public void onResult(List t, Throwable thrwbl) {
                if (thrwbl != null && toThrow == null) {
                    toThrow = thrwbl;
                }
                if (t != null) {
                    allCollections.addAll(t);
                    cursor.next(this);
                } else {
                    cursor.close();
                    latch.countDown();
                }
            }
        }
    }
}