/*
 * 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.phoenix.iterate;

import static org.apache.phoenix.monitoring.GlobalClientMetrics.GLOBAL_SCAN_BYTES;

import java.io.IOException;
import java.sql.SQLException;
import java.util.List;

import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.KeyValue;
import org.apache.hadoop.hbase.KeyValueUtil;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.client.ResultScanner;
import org.apache.phoenix.monitoring.CombinableMetric;
import org.apache.phoenix.monitoring.CombinableMetric.NoOpRequestMetric;
import org.apache.phoenix.monitoring.GlobalClientMetrics;
import org.apache.phoenix.schema.tuple.ResultTuple;
import org.apache.phoenix.schema.tuple.Tuple;
import org.apache.phoenix.util.ServerUtil;

public class ScanningResultIterator implements ResultIterator {
    private final ResultScanner scanner;
    private final CombinableMetric scanMetrics;

    public ScanningResultIterator(ResultScanner scanner, CombinableMetric scanMetrics) {
        this.scanner = scanner;
        this.scanMetrics = scanMetrics;
    }

    @Override
    public void close() throws SQLException {
        scanner.close();
    }

    @Override
    public Tuple next() throws SQLException {
        try {
            Result result = scanner.next();
            if (result == null) {
                close(); // Free up resources early
                return null;
            }
            calculateScanSize(result);
            // TODO: use ResultTuple.setResult(result)?
            // Need to create a new one if holding on to it (i.e. OrderedResultIterator)
            return new ResultTuple(result);
        } catch (IOException e) {
            throw ServerUtil.parseServerException(e);
        }
    }

    @Override
    public void explain(List<String> planSteps) {
    }

    @Override
    public String toString() {
        return "ScanningResultIterator [scanner=" + scanner + "]";
    }

    private void calculateScanSize(Result result) {
        if (GlobalClientMetrics.isMetricsEnabled() || scanMetrics != NoOpRequestMetric.INSTANCE) {
            if (result != null) {
                Cell[] cells = result.rawCells();
                long scanResultSize = 0;
                for (Cell cell : cells) {
                    KeyValue kv = KeyValueUtil.ensureKeyValue(cell);
                    scanResultSize += kv.heapSize();
                }
                scanMetrics.change(scanResultSize);
                GLOBAL_SCAN_BYTES.update(scanResultSize);
            }
        }
    }


    public ResultScanner getScanner() {
        return scanner;
    }
}