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Hyperledger Fabric Java Chaincode Shim
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/*
Copyright IBM Corp. All Rights Reserved.

SPDX-License-Identifier: Apache-2.0
*/

package org.hyperledger.fabric.shim.impl;

import static org.hyperledger.fabric.protos.peer.ChaincodeShim.ChaincodeMessage.Type.QUERY_STATE_CLOSE;
import static org.hyperledger.fabric.protos.peer.ChaincodeShim.ChaincodeMessage.Type.QUERY_STATE_NEXT;

import java.util.Collections;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.function.Function;

import org.hyperledger.fabric.protos.peer.ChaincodeShim.ChaincodeMessage;
import org.hyperledger.fabric.protos.peer.ChaincodeShim.QueryResponse;
import org.hyperledger.fabric.protos.peer.ChaincodeShim.QueryResultBytes;
import org.hyperledger.fabric.protos.peer.ChaincodeShim.QueryStateClose;
import org.hyperledger.fabric.protos.peer.ChaincodeShim.QueryStateNext;
import org.hyperledger.fabric.shim.ledger.QueryResultsIterator;

import com.google.protobuf.ByteString;
import com.google.protobuf.InvalidProtocolBufferException;

/**
 * This class provides an ITERABLE object of query results; NOTE the class name
 * is misleading - as this class is not an iterator itself, rather it implements
 * java.lang.Iterable via the QueryResultsIterator
 *
 * public interface QueryResultsIterator extends Iterable, AutoCloseable
 *
 * @param 
 */
class QueryResultsIteratorImpl implements QueryResultsIterator {

	private final ChaincodeInnvocationTask handler;
	private final String channelId;
	private final String txId;
	private Iterator currentIterator;
	private QueryResponse currentQueryResponse;
	private Function mapper;

	public QueryResultsIteratorImpl(final ChaincodeInnvocationTask handler,
			final String channelId, final String txId, final ByteString responseBuffer,
			Function mapper) {

		try {
			this.handler = handler;
			this.channelId = channelId;
			this.txId = txId;
			this.currentQueryResponse = QueryResponse.parseFrom(responseBuffer);
			this.currentIterator = currentQueryResponse.getResultsList().iterator();
			this.mapper = mapper;
		} catch (InvalidProtocolBufferException e) {
			throw new RuntimeException(e);
		}
	}



	@Override
	public Iterator iterator() {
		return new Iterator() {

			@Override
			public boolean hasNext() {
				return currentIterator.hasNext() || currentQueryResponse.getHasMore();
			}

			@Override
			public T next() {

				// return next fetched result, if any
				if (currentIterator.hasNext())
					return mapper.apply(currentIterator.next());

				// throw exception if there are no more expected results
				if (!currentQueryResponse.getHasMore())
					throw new NoSuchElementException();

				// get more results from peer

				ByteString requestPayload = QueryStateNext.newBuilder().setId(currentQueryResponse.getId()).build()
						.toByteString();
				ChaincodeMessage requestNextMessage = ChaincodeMessageFactory.newEventMessage(QUERY_STATE_NEXT, channelId, txId, requestPayload);

				ByteString responseMessage = QueryResultsIteratorImpl.this.handler.invoke(requestNextMessage);
				try {
					currentQueryResponse = QueryResponse.parseFrom(responseMessage);
				} catch (InvalidProtocolBufferException e) {
					throw new RuntimeException(e);
				}
				currentIterator = currentQueryResponse.getResultsList().iterator();

				// return next fetched result
				return mapper.apply(currentIterator.next());

			}

		};
	}

	@Override
	public void close() throws Exception {

		ByteString requestPayload = QueryStateClose.newBuilder()
        .setId(currentQueryResponse.getId())
        .build().toByteString();

		ChaincodeMessage requestNextMessage = ChaincodeMessageFactory.newEventMessage(QUERY_STATE_CLOSE, channelId, txId, requestPayload);
        this.handler.invoke(requestNextMessage);

		this.currentIterator = Collections.emptyIterator();
		this.currentQueryResponse = QueryResponse.newBuilder().setHasMore(false).build();
	}

}