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

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

class QueryResultsIteratorImpl implements QueryResultsIterator {

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

    public QueryResultsIteratorImpl(final Handler handler, final String channelId, final String txId, final QueryResponse queryResponse, Function mapper) {
        this.handler = handler;
        this.channelId = channelId;
        this.txId = txId;
        this.currentQueryResponse = queryResponse;
        this.currentIterator = currentQueryResponse.getResultsList().iterator();
        this.mapper = mapper;
    }

    @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
                currentQueryResponse = handler.queryStateNext(channelId, txId, currentQueryResponse.getId());
                currentIterator = currentQueryResponse.getResultsList().iterator();

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

            }

        };
    }

    @Override
    public void close() throws Exception {
        this.handler.queryStateClose(channelId, txId, currentQueryResponse.getId());
        this.currentIterator = Collections.emptyIterator();
        this.currentQueryResponse = QueryResponse.newBuilder().setHasMore(false).build();
    }

}