/**

  * Copyright (c) 2012-2016, jcabi.com

  * All rights reserved.

  *

  * Redistribution and use in source and binary forms, with or without

  * modification, are permitted provided that the following conditions

  * are met: 1) Redistributions of source code must retain the above

  * copyright notice, this list of conditions and the following

  * disclaimer. 2) Redistributions in binary form must reproduce the above

  * copyright notice, this list of conditions and the following

  * disclaimer in the documentation and/or other materials provided

  * with the distribution. 3) Neither the name of the jcabi.com nor

  * the names of its contributors may be used to endorse or promote

  * products derived from this software without specific prior written

  * permission.

  *

  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT

  * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND

  * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL

  * THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,

  * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR

  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,

  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED

  * OF THE POSSIBILITY OF SUCH DAMAGE.

  */

 package com.jcabi.dynamo;

 import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;

 import com.amazonaws.services.dynamodbv2.model.AttributeValue;

 import com.amazonaws.services.dynamodbv2.model.DeleteItemRequest;

 import com.amazonaws.services.dynamodbv2.model.DeleteItemResult;

 import com.amazonaws.services.dynamodbv2.model.ReturnConsumedCapacity;

 import com.jcabi.aspects.Immutable;

 import com.jcabi.aspects.Loggable;

 import com.jcabi.immutable.Array;

 import com.jcabi.log.Logger;

 import java.io.IOException;

 import java.util.ArrayList;

 import java.util.Collection;

 import java.util.Collections;

 import java.util.Iterator;

 import java.util.List;

 import java.util.Map;

 import java.util.NoSuchElementException;

 import java.util.concurrent.atomic.AtomicReference;

 import lombok.EqualsAndHashCode;

 import lombok.ToString;

 /**

  * Iterator of items in AWS SDK.

  *

  * <p>The class is mutable and thread-safe.

  *

  * @author Yegor Bugayenko (yegor@tpc2.com)

  * @version $Id: 16c947fa17d44229eadc7b833ef05559b1e7f89f $

  * @checkstyle ClassDataAbstractionCoupling (500 lines)

  * @since 0.1

  */

 @Loggable(Loggable.DEBUG)

 @ToString

 @EqualsAndHashCode

     (

         of = { "credentials", "conditions", "frame", "name", "keys", "valve" }

     )

 final class AwsIterator implements Iterator<Item> {

     /**

      * AWS credentials.

      */

     private final transient Credentials credentials;

     /**

      * Conditions.

      */

     private final transient Conditions conditions;

     /**

      * Frame.

      */

     private final transient AwsFrame frame;

     /**

      * Table name.

      */

     private final transient String name;

     /**

      * List of primary keys in the table.

      */

     private final transient Collection<String> keys;

     /**

      * Valve that loads dosages of items.

      */

     private final transient Valve valve;

     /**

      * Last scan result (mutable).

      */

     private final transient AtomicReference<Dosage> dosage;

     /**

      * Position inside the scan result, last seen, starts with -1 (mutable).

      */

     private transient int position;

     /**

      * Public ctor.

      * @param creds Credentials

      * @param frm Frame object

      * @param label Table name

      * @param conds Conditions

      * @param primary Primary keys of the table

      * @param vlv Valve with items

      * @checkstyle ParameterNumber (5 lines)

      */

     AwsIterator(final Credentials creds, final AwsFrame frm,

         final String label, final Conditions conds,

         final Collection<String> primary, final Valve vlv) {

         this.credentials = creds;

         this.frame = frm;

         this.name = label;

         this.conditions = conds;

         this.keys = primary;

         this.valve = vlv;

         this.dosage = new AtomicReference<Dosage>();

         this.position = -1;

     }

     @Override

     public boolean hasNext() {

         synchronized (this.dosage) {

             if (this.dosage.get() == null) {

                 try {

                     this.dosage.set(

                         this.valve.fetch(

                             this.credentials,

                             this.name,

                             this.conditions,

                             this.keys

                         )

                     );

                 } catch (final IOException ex) {

                     throw new IllegalStateException(ex);

                 }

                 this.position = -1;

             }

             if (this.dosage.get().hasNext()

                 && this.position + 1 >= this.dosage.get().items().size()) {

                 this.dosage.set(this.dosage.get().next());

                 this.position = -1;

             }

             return this.dosage.get().items().size() - this.position > 1;

         }

     }

     @Override

     public Item next() {

         synchronized (this.dosage) {

             if (!this.hasNext()) {

                 throw new NoSuchElementException(

                     String.format(

                         "no more items in the frame, position=%d",

                         this.position

                     )

                 );

             }

             ++this.position;

             return new AwsItem(

                 this.credentials,

                 this.frame,

                 this.name,

                 new Attributes(this.dosage.get().items().get(this.position)),

                 new Array<String>(this.keys)

             );

         }

     }

     @Override

     @SuppressWarnings("PMD.UseConcurrentHashMap")

     public void remove() {

         synchronized (this.dosage) {

             final AmazonDynamoDB aws = this.credentials.aws();

             try {

                 final Dosage prev = this.dosage.get();

                 final List<Map<String, AttributeValue>> items =

                     new ArrayList<Map<String, AttributeValue>>(prev.items());

                 final Map<String, AttributeValue> item =

                     items.remove(this.position);

                 final long start = System.currentTimeMillis();

                 final DeleteItemResult res = aws.deleteItem(

                     new DeleteItemRequest()

                         .withTableName(this.name)

                         .withKey(new Attributes(item).only(this.keys))

                         .withReturnConsumedCapacity(

                             ReturnConsumedCapacity.TOTAL

                         )

                         .withExpected(

                             new Attributes(item).only(this.keys).asKeys()

                         )

                 );

                 this.dosage.set(new AwsIterator.Fixed(prev, items));

                 --this.position;

                 Logger.info(

                     this,

                     "#remove(): item #%d removed from DynamoDB, %s, in %[ms]s",

                     this.position,

                     new PrintableConsumedCapacity(

                         res.getConsumedCapacity()

                     ).print(),

                     System.currentTimeMillis() - start

                 );

             } finally {

                 aws.shutdown();

             }

         }

     }

     /**

      * Dosage with fixed list of items.

      */

     @Immutable

     private static final class Fixed implements Dosage {

         /**

          * List of items.

          */

         private final transient Array<Map<String, AttributeValue>> list;

         /**

          * Previous dosage.

          */

         private final transient Dosage prev;

         /**

          * Ctor.

          * @param dsg Dosage

          * @param items Items

          */

         Fixed(final Dosage dsg, final List<Map<String, AttributeValue>> items) {

             this.prev = dsg;

             this.list = new Array<Map<String, AttributeValue>>(items);

         }

         @Override

         public List<Map<String, AttributeValue>> items() {

             return Collections.unmodifiableList(this.list);

         }

         @Override

         public Dosage next() {

             return this.prev.next();

         }

         @Override

         public boolean hasNext() {

             return this.prev.hasNext();

         }

     }

 }