package com.nimbusds.infinispan.persistence.dynamodb;


import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.time.Instant;
import java.util.concurrent.Executor;
import java.util.function.Predicate;

import com.amazonaws.ClientConfiguration;
import com.amazonaws.auth.DefaultAWSCredentialsProviderChain;
import com.amazonaws.client.builder.AwsClientBuilder;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDB;
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder;
import com.amazonaws.services.dynamodbv2.document.DynamoDB;
import com.amazonaws.services.dynamodbv2.document.Index;
import com.amazonaws.services.dynamodbv2.document.Item;
import com.amazonaws.services.dynamodbv2.document.Table;
import com.amazonaws.services.dynamodbv2.document.spec.GetItemSpec;
import com.amazonaws.services.dynamodbv2.model.*;
import com.codahale.metrics.Timer;
import io.reactivex.Flowable;
import net.jcip.annotations.ThreadSafe;
import org.infinispan.commons.configuration.ConfiguredBy;
import org.infinispan.commons.persistence.Store;
import org.infinispan.marshall.core.MarshalledEntry;
import org.infinispan.marshall.core.MarshalledEntryFactory;
import org.infinispan.persistence.spi.InitializationContext;
import org.infinispan.persistence.spi.PersistenceException;
import org.kohsuke.MetaInfServices;
import org.reactivestreams.Publisher;

import com.nimbusds.infinispan.persistence.common.InfinispanEntry;
import com.nimbusds.infinispan.persistence.common.InfinispanStore;
import com.nimbusds.infinispan.persistence.common.query.QueryExecutor;
import com.nimbusds.infinispan.persistence.dynamodb.config.DynamoDBStoreConfiguration;
import com.nimbusds.infinispan.persistence.dynamodb.logging.Loggers;
import com.nimbusds.infinispan.persistence.dynamodb.query.DynamoDBQueryExecutor;
import com.nimbusds.infinispan.persistence.dynamodb.query.DynamoDBQueryExecutorInitContext;


/**
 * AWS DynamoDB store for Infinispan 9.3+ caches and maps.
 */
@ThreadSafe
@MetaInfServices
@ConfiguredBy(DynamoDBStoreConfiguration.class)
@Store(shared = true)
public class DynamoDBStore<K,V> extends InfinispanStore<K,V> {


        /**
         * The DynamoDB configuration.
         */
        private DynamoDBStoreConfiguration config;
        
        
        /**
         * The DynamoDB HTTP client.
         */
        private AmazonDynamoDB client;
        
        
        /**
         * The DynamoDB table API client.
         */
        private Table table;


        /**
         * The DynamoDB item transformer (to / from Infinispan entries).
         */
        private DynamoDBItemTransformer<K,V> itemTransformer;
        
        
        /**
         * The optional DynamoDB query executor.
         */
        private DynamoDBQueryExecutor<K,V> queryExecutor;
        
        
        /**
         * The DynamoDB request factory.
         */
        private RequestFactory<K,V> requestFactory;
        
        
        /**
         * Optional item HMAC SHA-256 security.
         */
        private ItemHMAC itemHMAC;


        /**
         * The marshalled Infinispan entry factory.
         */
        private MarshalledEntryFactory<K,V> marshalledEntryFactory;


        /**
         * Purges expired entries found in the DynamoDB store, as indicated by
         * their persisted metadata (optional, may be ignored / not stored).
         */
        private ExpiredEntryReaper<K,V> reaper;
        
        
        /**
         * DynamoDB meters.
         */
        private DynamoDBMeters meters;


        /**
         * Loads a DynamoDB item transformer with the specified class name.
         *
         * @param clazz The class. Must not be {@code null}.
         *
         * @return The DynamoDB entry transformer.
         */
        private DynamoDBItemTransformer<K,V> loadItemTransformerClass(final Class<?> clazz) {

                try {
                        @SuppressWarnings( "unchecked" )
                        Class<DynamoDBItemTransformer<K,V>> genClazz = (Class<DynamoDBItemTransformer<K,V>>)clazz;
                        return genClazz.newInstance();
                } catch (Exception e) {
                        throw new PersistenceException("Couldn't load DynamoDB item transformer class: " + e.getMessage(), e);
                }
        }
        
        
        /**
         * Loads a DynamoDB query executor with the specified class name.
         *
         * @param clazz The class. Must not be {@code null}.
         *
         * @return The DynamoDB query executor.
         */
        private DynamoDBQueryExecutor<K,V> loadQueryExecutorClass(final Class<?> clazz) {
                
                try {
                        @SuppressWarnings( "unchecked" )
                        Class<DynamoDBQueryExecutor<K,V>> genClazz = (Class<DynamoDBQueryExecutor<K,V>>)clazz;
                        return genClazz.newInstance();
                } catch (Exception e) {
                        throw new PersistenceException("Couldn't load DynamoDB query executor class: " + e.getMessage(), e);
                }
        }
        
        
        /**
         * Returns the DynamoDB store configuration.
         *
         * @return The DynamoDB store configuration, {@code null} if not
         *         initialised.
         */
        public DynamoDBStoreConfiguration getConfiguration() {
                return config;
        }
        
        
        /**
         * Returns the underlying DynamoDB table.
         *
         * @return The DynamoDB table, {@code null} if not initialised.
         */
        public Table getTable() {
                return table;
        }
        
        
        /**
         * Returns the configured DynamoDB item transformer.
         *
         * @return The DynamoDB item transformer, {@code null} if not
         *         initialised.
         */
        public DynamoDBItemTransformer<K, V> getItemTransformer() {
                return itemTransformer;
        }
        
        
        @Override
        public QueryExecutor<K, V> getQueryExecutor() {
                return queryExecutor;
        }
        
        
        /**
         * Returns the DynamoDB timers.
         *
         * @return The timers, {@code null} if not initialised.
         */
        public DynamoDBMeters getMeters() {
                return meters;
        }
        
        
        @Override
        @SuppressWarnings("unchecked")
        public void init(final InitializationContext ctx) {

                // This method will be invoked by the PersistenceManager during initialization. The InitializationContext
                // contains:
                // - this CacheLoader's configuration
                // - the cache to which this loader is applied. Your loader might want to use the cache's name to construct
                //   cache-specific identifiers
                // - the StreamingMarshaller that needs to be used to marshall/unmarshall the entries
                // - a TimeService which the loader can use to determine expired entries
                // - a ByteBufferFactory which needs to be used to construct ByteBuffers
                // - a MarshalledEntryFactory which needs to be used to construct entries from the data retrieved by the loader

                super.init(ctx);
                
                this.config = ctx.getConfiguration();
                
                // Log the configuration
                Loggers.MAIN_LOG.info("[DS0100] DynamoDB store: Infinispan cache store configuration for {}:", getCacheName());
                config.log();
                
                // Create a DynamoDB client
                AmazonDynamoDBClientBuilder builder = AmazonDynamoDBClientBuilder
                        .standard()
                        .withCredentials(DefaultAWSCredentialsProviderChain.getInstance());
                
                if (config.getEndpoint() != null && ! config.getEndpoint().trim().isEmpty()) {
                        // If endpoint is set, override region
                        builder = builder.withEndpointConfiguration(
                                new AwsClientBuilder.EndpointConfiguration(
                                        config.getEndpoint(),
                                        null // inferred from endpoint
                                )
                        );
                } else {
                        builder.withRegion(config.getRegion());
                }
                
                if (config.getHTTPProxyHost() != null) {
                        ClientConfiguration clientConfig = new ClientConfiguration().withProxyHost(config.getHTTPProxyHost());
                        if (config.getHTTPProxyPort() > -1) {
                                clientConfig.withProxyPort(config.getHTTPProxyPort());
                        }
                        builder = builder.withClientConfiguration(clientConfig);
                }
                
                try {
                        itemHMAC = new ItemHMAC(config.getHMACSHA256Key());
                } catch (InvalidKeyException e) {
                        throw new PersistenceException(e.getMessage(), e);
                }
                
                client = builder.build();
                
                Loggers.MAIN_LOG.info("[DS0140] DynamoDB store: Expiration thread wake up interval for cache {}: {}", getCacheName(),
                        ctx.getCache().getCacheConfiguration().expiration().wakeUpInterval());
                
                // Load and initialise the DynamoDB item transformer
                Loggers.MAIN_LOG.debug("[DS0101] Loading DynamoDB item transformer class {} for cache {}...",
                        config.getItemTransformerClass(),
                        getCacheName());
                
                itemTransformer = loadItemTransformerClass(config.getItemTransformerClass());
                itemTransformer.init(() -> config.isEnableTTL());
        
                requestFactory = new RequestFactory<>(
                        itemTransformer,
                        config.getIndexedAttributes(),
                        config.isConsistentReads(),
                        config.getProvisionedThroughput(),
                        config.isTableWithEncryptionAtRest(),
                        config.getTablePrefix(),
                        config.getApplyRangeKey(),
                        config.getRangeKeyValue(),
                        config.isEnableStream());
                
                table = new DynamoDB(client).getTable(requestFactory.getTableName());
                
                // Load and initialise the optional query executor
                if (config.getQueryExecutorClass() != null) {
                        Loggers.MAIN_LOG.debug("[DS0130] Loading optional DynamoDB query executor class {} for cache {}...",
                                config.getQueryExecutorClass(),
                                getCacheName());
                        
                        queryExecutor = loadQueryExecutorClass(config.getQueryExecutorClass());
                        
                        queryExecutor.init(new DynamoDBQueryExecutorInitContext<K, V>() {
                                @Override
                                public DynamoDBItemTransformer<K,V> getDynamoDBItemTransformer() {
                                        return itemTransformer;
                                }
                                
                                @Override
                                public Table getDynamoDBTable() {
                                        return table;
                                }
                                
                                @Override
                                public Index getDynamoDBIndex(final String attributeName) {
                                        if (config.getIndexedAttributes() != null && config.getIndexedAttributes().contains(attributeName)) {
                                                return table.getIndex(requestFactory.getGSIName(attributeName));
                                        } else {
                                                return null;
                                        }
                                }
                        });
                }

                marshalledEntryFactory = (MarshalledEntryFactory<K,V>)ctx.getMarshalledEntryFactory();

                final String metricsPrefix = ctx.getCache().getName() + ".";
                if (config.getMetricRegistry() == null)
                        meters = new DynamoDBMeters(metricsPrefix);
                else
                        meters = new DynamoDBMeters(metricsPrefix, config.getMetricRegistry());

                Loggers.MAIN_LOG.info("[DS0102] Initialized DynamoDB store for cache {} with table {}",
                        getCacheName(),
                        table.getTableName());
        }
        
        
        @Override
        public void start() {

                // This method will be invoked by the PersistenceManager to start the CacheLoader. At this stage configuration
                // is complete and the loader can perform operations such as opening a connection to the external storage,
                // initialize internal data structures, etc.
                
                CreateTableRequest ctr = requestFactory.resolveCreateTableRequest();
                
                try {
                        table = new DynamoDB(client)
                                .createTable(
                                        ctr.withProvisionedThroughput(config.getProvisionedThroughput())
                                );
                        
                        Loggers.MAIN_LOG.info("[DS0129] DynamoDB store: Created table {} for cache {}", table.getTableName(), getCacheName());
                        
                } catch (ResourceInUseException e) {
                        // table exists
                        Loggers.MAIN_LOG.info("[DS0133] DynamoDB store: Table {} for cache {} exists", table.getTableName(), getCacheName());
                } catch (Exception e) {
                        Loggers.MAIN_LOG.fatal("[DS0103] DynamoDB store: Couldn't create table {} with {}: {}: {}", table.getTableName(), ctr, e.getMessage(), e);
                        throw new PersistenceException(e.getMessage(), e);
                }
                
                try {
                        table.waitForActive();
                } catch (InterruptedException e) {
                        throw new PersistenceException("Interrupted while awaiting DynamoDB table " + table.getTableName() + " to become active: " + e.getMessage(), e);
                }
                
                Loggers.MAIN_LOG.info("[DS0141] DynamoDB store: Table properties: " + table.getDescription());
                
                
                ContinuousBackupsStatus contBackupStatus = null;
                
                try {
                        // Not available on localhost DynamoDB
                        DescribeContinuousBackupsResult result = client.describeContinuousBackups(new DescribeContinuousBackupsRequest().withTableName(table.getTableName()));
                        contBackupStatus = ContinuousBackupsStatus.fromValue(result.getContinuousBackupsDescription().getContinuousBackupsStatus());
                        Loggers.MAIN_LOG.info("[DS0143] DynamoDB store: Continuous backup status for table {}: {}", table.getTableName(), contBackupStatus);
                        Loggers.MAIN_LOG.info("[DS0144] DynamoDB store: Point in time recovery status for table {}: {}",
                                table.getTableName(),
                                result.getContinuousBackupsDescription().getPointInTimeRecoveryDescription().getPointInTimeRecoveryStatus());
                } catch (Exception e) {
                        Loggers.MAIN_LOG.error("[DS0145] DynamoDB store: Couldn't obtain continuous backup status for table {}: {}", table.getTableName(), e.getMessage());
                }
                
                if (ContinuousBackupsStatus.DISABLED.equals(contBackupStatus) && config.isEnableContinuousBackups()) {
                        
                        try {
                                client.updateContinuousBackups(
                                        new UpdateContinuousBackupsRequest()
                                                .withTableName(table.getTableName())
                                                .withPointInTimeRecoverySpecification(
                                                        new PointInTimeRecoverySpecification()
                                                                .withPointInTimeRecoveryEnabled(true)));
                                
                        } catch (Exception e) {
                                String msg = "Couldn't set up continuous backups for table " + table.getTableName() + ": " + e.getMessage();
                                Loggers.MAIN_LOG.fatal("[DS0104] DynamoDB store: {}", msg);
                                throw new PersistenceException(msg, e);
                        }
                }
                
                TimeToLiveStatus currentTTLStatus = null;
                
                try {
                        // Not available on localhost DynamoDB
                        DescribeTimeToLiveResult result = client.describeTimeToLive(new DescribeTimeToLiveRequest().withTableName(table.getTableName()));
                        currentTTLStatus = TimeToLiveStatus.fromValue(result.getTimeToLiveDescription().getTimeToLiveStatus());
                        Loggers.MAIN_LOG.info("[DS0161] DynamoDB store: TTL for table {}: status={} attribute={}",
                                table.getTableName(),
                                currentTTLStatus,
                                result.getTimeToLiveDescription().getAttributeName());
                } catch (Exception e) {
                        Loggers.MAIN_LOG.error("[DS0162] DynamoDB store: Couldn't obtain TTL status for table {}: {}", table.getTableName(), e.getMessage());
                }
                
                if (TimeToLiveStatus.DISABLED.equals(currentTTLStatus) && config.isEnableTTL() && requestFactory.getItemTransformer().getTTLAttributeName() != null) {
                        try {
                                client.updateTimeToLive(
                                        new UpdateTimeToLiveRequest()
                                                .withTableName(table.getTableName())
                                                .withTimeToLiveSpecification(
                                                        new TimeToLiveSpecification()
                                                                .withAttributeName(requestFactory.getItemTransformer().getTTLAttributeName())
                                                                .withEnabled(true)));
                        } catch (Exception e) {
                                String msg = "Couldn't set up TTL for table " + table.getTableName() + ": " + e.getMessage();
                                Loggers.MAIN_LOG.fatal("[DS0160] DynamoDB store: {}", msg);
                                throw new PersistenceException(msg, e);
                        }
                }
                
                reaper = new ExpiredEntryReaper<>(marshalledEntryFactory, table, requestFactory, config.getPurgeLimit(), meters.purgeTimer);
                
                Loggers.MAIN_LOG.info("[DS0104] Started DynamoDB external store connector for cache {} with table {}", getCacheName(), table.getTableName());
        }


        @Override
        public void stop() {

                super.stop();
                
                if (client != null) {
                        client.shutdown();
                }
                
                Loggers.MAIN_LOG.info("[DS0105] Stopped DynamoDB store connector for cache {}",  getCacheName());
        }


        @Override
        public boolean contains(final Object key) {

                // This method will be invoked by the PersistenceManager to determine if the loader contains the specified key.
                // The implementation should be as fast as possible, e.g. it should strive to transfer the least amount of data possible
                // from the external storage to perform the check. Also, if possible, make sure the field is indexed on the external storage
                // so that its existence can be determined as quickly as possible.
                //
                // Note that keys will be in the cache's native format, which means that if the cache is being used by a remoting protocol
                // such as HotRod or REST and compatibility mode has not been enabled, then they will be encoded in a byte[].

                Loggers.DYNAMODB_LOG.trace("[DS0106] DynamoDB store: Checking {} cache key {}", getCacheName(), key);
                
                Timer.Context timerCtx = meters.getTimer.time();
                
                try {
                        return table.getItem(requestFactory.resolveGetItemSpec(key)) != null;
                        
                } catch (Exception e) {
                        Loggers.DYNAMODB_LOG.error("[DS0107] {}: {}", e.getMessage(), e);
                        throw new PersistenceException(e.getMessage(), e);
                } finally {
                        timerCtx.stop();
                }
        }


        @Override
        public MarshalledEntry<K,V> load(final Object key) {

                // Fetches an entry from the storage using the specified key. The CacheLoader should retrieve from the external storage all
                // of the data that is needed to reconstruct the entry in memory, i.e. the value and optionally the metadata. This method
                // needs to return a MarshalledEntry which can be constructed as follows:
                //
                // ctx.getMarshalledEntryFactory().new MarshalledEntry(key, value, metadata);
                //
                // If the entry does not exist or has expired, this method should return null.
                // If an error occurs while retrieving data from the external storage, this method should throw a PersistenceException
                //
                // Note that keys and values will be in the cache's native format, which means that if the cache is being used by a remoting protocol
                // such as HotRod or REST and compatibility mode has not been enabled, then they will be encoded in a byte[].
                // If the loader needs to have knowledge of the key/value data beyond their binary representation, then it needs access to the key's and value's
                // classes and the marshaller used to encode them.

                Loggers.DYNAMODB_LOG.trace("[DS0108] DynamoDB store: Loading {} cache entry with key {}", getCacheName(), key);
                
                Item item;
                
                Timer.Context timerCtx = meters.getTimer.time();
                
                GetItemSpec getItemSpec = requestFactory.resolveGetItemSpec(key);
                
                try {
                        item = table.getItem(getItemSpec);
                        
                } catch (Exception e) {
                        Loggers.DYNAMODB_LOG.error("[DS0109] {}, {}", e.getMessage(), e);
                        throw new PersistenceException(e.getMessage(), e);
                } finally {
                        timerCtx.stop();
                }
                
                if (item == null) {
                        // Not found
                        Loggers.DYNAMODB_LOG.trace("[DS0110] DynamoDB store: Item with key {} not found", key);
                        return null;
                }
                
                Loggers.DYNAMODB_LOG.trace("[DS0111] DynamoDB store: Retrieved {} cache item: {}", getCacheName(), item);
                
                try {
                        item = itemHMAC.verify(item);
                } catch (InvalidHMACException e) {
                        meters.invalidItemHmacCounter.inc();
                        Loggers.DYNAMODB_LOG.error("[DS0131] DynamoDB store: Invalid item HMAC in {}: {}", getCacheName(), e.getMessage());
                        throw new PersistenceException(e.getMessage(), e);
                } catch (NoSuchAlgorithmException | InvalidKeyException e) {
                        throw new PersistenceException(e.getMessage(), e);
                }
                
                // Transform DynamoDB entry to Infinispan entry
                InfinispanEntry<K,V> infinispanEntry = itemTransformer.toInfinispanEntry(item);
                
                if (infinispanEntry.isExpired()) {
                        Loggers.DYNAMODB_LOG.trace("[DS0114] DynamoDB store: Item with key {} expired", key);
                        return null;
                }

                return marshalledEntryFactory.newMarshalledEntry(
                        infinispanEntry.getKey(),
                        infinispanEntry.getValue(),
                        infinispanEntry.getMetadata());
        }


        @Override
        public boolean delete(final Object key) {

                // The CacheWriter should remove from the external storage the entry identified by the specified key.
                // Note that keys will be in the cache's native format, which means that if the cache is being used by a remoting protocol
                // such as HotRod or REST and compatibility mode has not been enabled, then they will be encoded in a byte[].

                Loggers.DYNAMODB_LOG.trace("[DS0112] DynamoDB store: Deleting {} cache entry with key {}", getCacheName(), key);
                
                final boolean deleted;
                
                Timer.Context timerCtx = meters.deleteTimer.time();
                
                try {
                        deleted = table.deleteItem(requestFactory.resolveDeleteItemSpec(key)).getItem() != null;
                        
                } catch (Exception e) {
                        Loggers.DYNAMODB_LOG.error("[DS0113] {}, {}", e.getMessage(), e);
                        throw new PersistenceException(e.getMessage(), e);
                } finally {
                        timerCtx.stop();
                }
                
                if (deleted) {
                        Loggers.DYNAMODB_LOG.trace("[DS0116] DynamoDB store: Deleted {} cache item with key {}", getCacheName(), key);
                }
                
                return deleted;
        }


        @Override
        public void write(final MarshalledEntry<? extends K, ? extends V> marshalledEntry) {

                // The CacheWriter should write the specified entry to the external storage.
                //
                // The PersistenceManager uses MarshalledEntry as the default format so that CacheWriters can efficiently store data coming
                // from a remote node, thus avoiding any additional transformation steps.
                //
                // Note that keys and values will be in the cache's native format, which means that if the cache is being used by a remoting protocol
                // such as HotRod or REST and compatibility mode has not been enabled, then they will be encoded in a byte[].

                Loggers.DYNAMODB_LOG.trace("[DS0115] DynamoDB store: Writing {} cache entry {}", getCacheName(), marshalledEntry);
                
                Timer.Context timerCtx = meters.putTimer.time();
                
                try {
                        Item item = requestFactory.resolveItem(
                                new InfinispanEntry<>(
                                        marshalledEntry.getKey(),
                                        marshalledEntry.getValue(),
                                        marshalledEntry.getMetadata()));
                        
                        item = itemHMAC.apply(item);
                        
                        Loggers.DYNAMODB_LOG.trace("[DS0132] DynamoDB store: Writing {} cache item: {}", getCacheName(), item);
                        
                        table.putItem(item);
                        
                } catch (Exception e) {
                        Loggers.DYNAMODB_LOG.error("[DS0117] {}: {}", e.getMessage(), e);
                        throw new PersistenceException(e.getMessage(), e);
                } finally {
                        timerCtx.stop();
                }
        }

        @Override
        public Publisher<MarshalledEntry<K, V>> publishEntries(final Predicate<? super K> filter, final boolean fetchValue, final boolean fetchMetadata) {
                
                Loggers.DYNAMODB_LOG.trace("[DS0118] DynamoDB store: Processing key filter for {} cache: fetchValue={} fetchMetadata={}",
                                getCacheName(), fetchValue, fetchMetadata);
                
                final Instant now = Instant.now();
                
                return Flowable.using(meters.processTimer::time,
                                ignore -> Flowable.fromIterable(requestFactory.getAllItems(table))
                                                .map(itemTransformer::toInfinispanEntry)
                                                .filter(infinispanEntry -> filter == null || filter.test(infinispanEntry.getKey()))
                                                .filter(infinispanEntry -> ! infinispanEntry.isExpired(now))
                                                .map(infinispanEntry -> marshalledEntryFactory.newMarshalledEntry(
                                                                infinispanEntry.getKey(),
                                                                infinispanEntry.getValue(),
                                                                infinispanEntry.getMetadata()))
                                                .doOnError(e -> Loggers.DYNAMODB_LOG.error("[DS0119] {}: {}", e.getMessage(), e)),
                                Timer.Context::stop);
        }

        @Override
        public int size() {

                // Infinispan code analysis on 8.2 and 9.4.11 shows that this method is never called in practice, and
                // is not wired to the data / cache container API
                
                // TODO inaccurate when a range key is applied!

                Loggers.DYNAMODB_LOG.trace("[DS0120] DynamoDB store: Counting {} cache items", getCacheName());

                final int count;
                
                try {
                        count = table.describe().getItemCount().intValue();
                        
                } catch (Exception e) {
                        Loggers.DYNAMODB_LOG.error("[DS0121] {}: {}", e.getMessage(), e);
                        throw new PersistenceException(e.getMessage(), e);
                }

                Loggers.DYNAMODB_LOG.trace("[DS0122] DynamoDB store: Reported approximately {} {} items", count, getCacheName());

                return count;
        }


        @Override
        public void clear() {

                Loggers.DYNAMODB_LOG.trace("[DS0123] DynamoDB store: Clearing {} items", getCacheName());
                
                if (requestFactory.getRangeKeyResolvedName() != null) {
                        throw new PersistenceException("DynamoDB clear operation not supported with applied range key");
                }

                try {
                        DeleteTableResult result = table.delete();
                        
                        int numDeleted = result.getTableDescription().getItemCount().intValue();
                        
                        Loggers.DYNAMODB_LOG.info("[DS0125] DynamoDB store: Cleared {} {} items", numDeleted, table.getTableName());
                        
                        table.waitForDelete();
                        
                        client.createTable(requestFactory.resolveCreateTableRequest());
                        
                        table.waitForActive();
                        
                } catch (Exception e) {
                        Loggers.DYNAMODB_LOG.error("[DS0124] {}: {}", e.getMessage(), e);
                        throw new PersistenceException(e.getMessage(), e);
                }
        }


        @Override
        public void purge(final Executor executor, final PurgeListener<? super K> purgeListener) {

                Loggers.DYNAMODB_LOG.trace("[DS0126] DynamoDB store: Purging {} cache entries", getCacheName());
                
                try {
                        executor.execute(() -> reaper.purge(purgeListener));
                        
                } catch (Exception e) {
                        Loggers.DYNAMODB_LOG.error("[DS0127] {}: {}", e.getMessage(), e);
                        throw new PersistenceException("Purge exception: " + e.getMessage(), e);
                }
        }
        
        
        @Override
        public void purge(final Executor executor, final ExpirationPurgeListener<K,V> purgeListener) {
                
                Loggers.DYNAMODB_LOG.trace("[DS0150] DynamoDB store: Purging {} cache entries", getCacheName());
                
                try {
                        executor.execute(() -> reaper.purgeExtended(purgeListener));
                        
                } catch (Exception e) {
                        Loggers.DYNAMODB_LOG.error("[DS0151] {}: {}", e.getMessage(), e);
                        throw new PersistenceException("Purge exception: " + e.getMessage(), e);
                }
        }
}