/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.kafka.streams.kstream.internals.foreignkeyjoin;

import org.apache.kafka.common.metrics.Sensor;
import org.apache.kafka.common.utils.Bytes;
import org.apache.kafka.streams.KeyValue;
import org.apache.kafka.streams.errors.StreamsException;
import org.apache.kafka.streams.kstream.internals.Change;
import org.apache.kafka.streams.processor.AbstractProcessor;
import org.apache.kafka.streams.processor.Processor;
import org.apache.kafka.streams.processor.ProcessorContext;
import org.apache.kafka.streams.processor.ProcessorSupplier;
import org.apache.kafka.streams.processor.internals.InternalProcessorContext;
import org.apache.kafka.streams.processor.internals.metrics.ThreadMetrics;
import org.apache.kafka.streams.state.KeyValueIterator;
import org.apache.kafka.streams.state.StoreBuilder;
import org.apache.kafka.streams.state.TimestampedKeyValueStore;
import org.apache.kafka.streams.state.ValueAndTimestamp;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.nio.ByteBuffer;

public class ForeignJoinSubscriptionProcessorSupplier<K, KO, VO> implements ProcessorSupplier<KO, Change<VO>> {
    private static final Logger LOG = LoggerFactory.getLogger(ForeignJoinSubscriptionProcessorSupplier.class);
    private final StoreBuilder<TimestampedKeyValueStore<Bytes, SubscriptionWrapper<K>>> storeBuilder;
    private final CombinedKeySchema<KO, K> keySchema;

    public ForeignJoinSubscriptionProcessorSupplier(
        final StoreBuilder<TimestampedKeyValueStore<Bytes, SubscriptionWrapper<K>>> storeBuilder,
        final CombinedKeySchema<KO, K> keySchema) {

        this.storeBuilder = storeBuilder;
        this.keySchema = keySchema;
    }

    @Override
    public Processor<KO, Change<VO>> get() {
        return new KTableKTableJoinProcessor();
    }


    private final class KTableKTableJoinProcessor extends AbstractProcessor<KO, Change<VO>> {
        private Sensor skippedRecordsSensor;
        private TimestampedKeyValueStore<Bytes, SubscriptionWrapper<K>> store;

        @Override
        public void init(final ProcessorContext context) {
            super.init(context);
            final InternalProcessorContext internalProcessorContext = (InternalProcessorContext) context;
            skippedRecordsSensor =
                ThreadMetrics.skipRecordSensor(Thread.currentThread().getName(), internalProcessorContext.metrics());
            store = internalProcessorContext.getStateStore(storeBuilder);
        }

        /**
         * @throws StreamsException if key is null
         */
        @Override
        public void process(final KO key, final Change<VO> value) {
            // if the key is null, we do not need proceed aggregating
            // the record with the table
            if (key == null) {
                LOG.warn(
                    "Skipping record due to null key. value=[{}] topic=[{}] partition=[{}] offset=[{}]",
                    value, context().topic(), context().partition(), context().offset()
                );
                skippedRecordsSensor.record();
                return;
            }

            final Bytes prefixBytes = keySchema.prefixBytes(key);

            //Perform the prefixScan and propagate the results
            try (final KeyValueIterator<Bytes, ValueAndTimestamp<SubscriptionWrapper<K>>> prefixScanResults =
                     store.range(prefixBytes, Bytes.increment(prefixBytes))) {

                while (prefixScanResults.hasNext()) {
                    final KeyValue<Bytes, ValueAndTimestamp<SubscriptionWrapper<K>>> next = prefixScanResults.next();
                    // have to check the prefix because the range end is inclusive :(
                    if (prefixEquals(next.key.get(), prefixBytes.get())) {
                        final CombinedKey<KO, K> combinedKey = keySchema.fromBytes(next.key);
                        context().forward(
                            combinedKey.getPrimaryKey(),
                            new SubscriptionResponseWrapper<>(next.value.value().getHash(), value.newValue)
                        );
                    }
                }
            }
        }

        private boolean prefixEquals(final byte[] x, final byte[] y) {
            final int min = Math.min(x.length, y.length);
            final ByteBuffer xSlice = ByteBuffer.wrap(x, 0, min);
            final ByteBuffer ySlice = ByteBuffer.wrap(y, 0, min);
            return xSlice.equals(ySlice);
        }
    }
}
