/**
    * Copyright (c) 2014, stateful.co
    * 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 stateful.co 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 co.stateful.core;
  
  import co.stateful.spi.Locks;
  import com.amazonaws.AmazonClientException;
  import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
  import com.amazonaws.services.dynamodbv2.model.ConditionalCheckFailedException;
  import com.amazonaws.services.dynamodbv2.model.ExpectedAttributeValue;
  import com.amazonaws.services.dynamodbv2.model.PutItemRequest;
  import com.google.common.base.Predicate;
  import com.google.common.base.Predicates;
  import com.google.common.collect.ImmutableMap;
  import com.google.common.collect.Iterables;
  import com.jcabi.aspects.Immutable;
  import com.jcabi.aspects.Loggable;
  import com.jcabi.dynamo.Attributes;
  import com.jcabi.dynamo.Conditions;
  import com.jcabi.dynamo.Item;
  import com.jcabi.dynamo.QueryValve;
  import com.jcabi.dynamo.Table;
  import com.jcabi.urn.URN;
  import java.io.IOException;
  import java.util.Iterator;
  import java.util.Map;
  import lombok.EqualsAndHashCode;
  import lombok.ToString;
  
  /**
   * Locks in DynamoDB.
   *
   * @author Yegor Bugayenko (yegor@tpc2.com)
   * @version $Id$
   * @since 1.1
   */
  @Immutable
  @ToString
  @EqualsAndHashCode(of = "owner")
  @Loggable(Loggable.DEBUG)
  final class DyLocks implements Locks {
  
      /**
       * Table name.
       */
      public static final String TBL = "locks";
  
      /**
       * Hash.
       */
      public static final String HASH = "urn";
  
      /**
       * Range.
       */
      public static final String RANGE = "name";
  
      /**
       * Label.
       */
      public static final String ATTR_LABEL = "label";
  
      /**
       * Dynamo table.
       */
      private final transient Table table;
  
      /**
       * Name of the user.
       */
      private final transient URN owner;
  
      /**
      * Ctor.
      * @param tbl Dynamo table
      * @param urn Owner of them
      */
     DyLocks(final Table tbl, final URN urn) {
         this.table = tbl;
         this.owner = urn;
     }
 
     @Override
     public Map<String, String> names() {
         final ImmutableMap.Builder<String, String> map =
             new ImmutableMap.Builder<String, String>();
         Iterables.all(
             this.table.frame().through(
                 new QueryValve().withAttributesToGet(
                     DyLocks.ATTR_LABEL
                 )
             ).where(DyLocks.HASH, Conditions.equalTo(this.owner)),
             new Predicate<Item>() {
                 @Override
                 public boolean apply(final Item item) {
                     try {
                         map.put(
                             item.get(DyLocks.RANGE).getS(),
                             item.get(DyLocks.ATTR_LABEL).getS()
                         );
                     } catch (final IOException ex) {
                         throw new IllegalStateException(ex);
                     }
                     return true;
                 }
             }
         );
         return map.build();
     }
 
     @Override
     public String lock(final String name, final String label)
         throws IOException {
         final AmazonDynamoDB aws = this.table.region().aws();
         String msg = "";
         try {
             final PutItemRequest request = new PutItemRequest();
             request.setTableName(this.table.name());
             request.setItem(
                 new Attributes()
                     .with(DyLocks.HASH, this.owner)
                     .with(DyLocks.RANGE, name)
                     .with(DyLocks.ATTR_LABEL, label)
             );
             request.setExpected(
                 new ImmutableMap.Builder<String, ExpectedAttributeValue>().put(
                     DyLocks.ATTR_LABEL,
                     new ExpectedAttributeValue().withExists(false)
                 ).build()
             );
             aws.putItem(request);
         } catch (final ConditionalCheckFailedException ex) {
             msg = ex.getLocalizedMessage();
         } catch (final AmazonClientException ex) {
             throw new IOException(ex);
         } finally {
             aws.shutdown();
         }
         return msg;
     }
 
     @Override
     public void unlock(final String name) {
         Iterables.removeIf(
             this.table.frame()
                 .through(new QueryValve())
                 .where(DyLocks.HASH, this.owner.toString())
                 .where(DyLocks.RANGE, name),
             Predicates.alwaysTrue()
         );
     }
 
     @Override
     public String unlock(final String name, final String label)
         throws IOException {
         final Iterator<Item> items = this.table.frame()
             .through(new QueryValve())
             .where(DyLocks.HASH, this.owner.toString())
             .where(DyLocks.RANGE, name)
             .iterator();
         String msg = "";
         if (items.hasNext()) {
             final String required = items.next().get(DyLocks.ATTR_LABEL).getS();
             if (required.equals(label)) {
                 this.unlock(name);
             } else {
                 msg = required;
             }
         }
         return msg;
     }
 }