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    * 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
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   * the names of its contributors may be used to endorse or promote
   * products derived from this software without specific prior written
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   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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  package com.jcabi.simpledb;
  
  import com.amazonaws.auth.AWSStaticCredentialsProvider;
  import com.amazonaws.auth.BasicAWSCredentials;
  import com.amazonaws.client.builder.AwsClientBuilder;
  import com.amazonaws.regions.Regions;
  import com.amazonaws.services.simpledb.AmazonSimpleDB;
  import com.amazonaws.services.simpledb.AmazonSimpleDBClientBuilder;
  import com.jcabi.aspects.Immutable;
  import com.jcabi.aspects.Loggable;
  import javax.validation.constraints.NotNull;
  import lombok.EqualsAndHashCode;
  import org.apache.commons.lang3.Validate;
  
  /**
   * Amazon SimpleDB credentials.
   *
   * <p>It is recommended to use {@link Credentials.Simple} in most cases.
   *
   * @since 0.1
   */
  @Immutable
  public interface Credentials {
  
      /**
       * Test credentials, for unit testing mostly.
       */
      Credentials TEST = new Credentials.Simple(
          "AAAAAAAAAAAAAAAAAAAA",
          "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
      );
  
      /**
       * Build AWS client.
       *
       * @return Amazon Dynamo DB client
       */
      @NotNull
      AmazonSimpleDB aws();
  
      /**
       * Simple implementation.
       *
       * @since 0.1
       */
      @Immutable
      @Loggable(Loggable.DEBUG)
      @EqualsAndHashCode(of = { "key", "secret", "region" })
      final class Simple implements Credentials {
          /**
           * AWS key.
           */
          private final transient String key;
  
          /**
           * AWS secret.
           */
          private final transient String secret;
  
          /**
           * Region name.
           */
          private final transient String region;
  
          /**
           * Public ctor, with "us-east-1" region.
           * @param akey AWS key
           * @param scrt Secret
           */
          public Simple(@NotNull final String akey, @NotNull final String scrt) {
             this(akey, scrt, Regions.US_EAST_1.getName());
         }
 
         /**
          * Public ctor.
          * @param akey AWS key
          * @param scrt Secret
          * @param reg Region
          */
         @SuppressWarnings("PMD.ConstructorOnlyInitializesOrCallOtherConstructors")
         public Simple(
             @NotNull(message = "AWS key can't be NULL") final String akey,
             @NotNull(message = "AWS secret can't be NULL") final String scrt,
             @NotNull(message = "AWS region can't be NULL") final String reg) {
             Validate.matchesPattern(
                 akey, "[A-Z0-9]{20}",
                 "Invalid AWS key '%s'", akey
             );
             this.key = akey;
             Validate.matchesPattern(
                 scrt, "[a-zA-Z0-9+/=]{40}",
                 "Invalid AWS secret key '%s'", scrt
             );
             this.secret = scrt;
             Validate.matchesPattern(
                 reg, "[-a-z0-9]+",
                 "Invalid AWS region name '%s'", reg
             );
             this.region = reg;
         }
 
         @Override
         public String toString() {
             return String.format("%s/%s", this.region, this.key);
         }
 
         @Override
         @NotNull
         public AmazonSimpleDB aws() {
             return AmazonSimpleDBClientBuilder.standard()
                 .withRegion(this.region)
                 .withCredentials(
                     new AWSStaticCredentialsProvider(
                         new BasicAWSCredentials(this.key, this.secret)
                     )
                 ).build();
         }
     }
 
     /**
      * Assumed AWS IAM role.
      *
      * @since 0.1
      * @see <a href="http://docs.aws.amazon.com/IAM/latest/UserGuide/role-usecase-ec2app.html">Granting Applications that Run on Amazon EC2 Instances Access to AWS Resources</a>
      */
     @Immutable
     @Loggable(Loggable.DEBUG)
     @EqualsAndHashCode(of = "region")
     final class Assumed implements Credentials {
         /**
          * Region name.
          */
         private final transient String region;
 
         /**
          * Public ctor.
          */
         public Assumed() {
             this(Regions.US_EAST_1.getName());
         }
 
         /**
          * Public ctor.
          * @param reg Region
          */
         @SuppressWarnings("PMD.ConstructorOnlyInitializesOrCallOtherConstructors")
         public Assumed(@NotNull(message = "SimpleDB region can't be NULL")
             final String reg) {
             Validate.matchesPattern(
                 reg, "[-0-9a-z]+",
                 "Invalid AWS region name: '%s'", reg
             );
             this.region = reg;
         }
 
         @Override
         public String toString() {
             return this.region;
         }
 
         @Override
         @NotNull
         public AmazonSimpleDB aws() {
             return AmazonSimpleDBClientBuilder.standard()
                 .withRegion(this.region)
                 .build();
         }
     }
 
     /**
      * With explicitly specified endpoint.
      *
      * @since 0.1
      */
     @Immutable
     @Loggable(Loggable.DEBUG)
     @EqualsAndHashCode(of = { "origin", "endpoint" })
     final class Direct implements Credentials {
         /**
          * Original credentials.
          */
         private final transient Credentials.Simple origin;
 
         /**
          * Endpoint.
          */
         private final transient String endpoint;
 
         /**
          * Public ctor.
          * @param creds Original credentials
          * @param pnt Endpoint
          */
         public Direct(
             @NotNull(message = "credentials is NULL") final Credentials.Simple creds,
             @NotNull(message = "end point can't be NULL") final String pnt) {
             this.origin = creds;
             this.endpoint = pnt;
         }
 
         /**
          * Public ctor.
          * @param creds Original credentials
          * @param port Port number for localhost
          */
         public Direct(@NotNull final Credentials.Simple creds, final int port) {
             this(creds, String.format("http://localhost:%d", port));
         }
 
         @Override
         public String toString() {
             return String.format("%s at %s", this.origin, this.endpoint);
         }
 
         @Override
         @NotNull
         public AmazonSimpleDB aws() {
             return AmazonSimpleDBClientBuilder.standard()
                 .withEndpointConfiguration(
                     new AwsClientBuilder.EndpointConfiguration(
                         this.endpoint, Regions.US_EAST_1.getName()
                     )
                 )
                 .withCredentials(
                     new AWSStaticCredentialsProvider(
                         new BasicAWSCredentials(
                             this.origin.key, this.origin.secret
                         )
                     )
                 )
                 .build();
         }
     }
 
 }