/*
 * 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.flink.connector.jdbc.split;

import org.apache.flink.util.Preconditions;

import java.io.Serializable;

/**
 * This query parameters generator is an helper class to parameterize from/to queries on a numeric
 * column. The generated array of from/to values will be equally sized to fetchSize (apart from the
 * last one), ranging from minVal up to maxVal.
 *
 * <p>For example, if there's a table <CODE>BOOKS</CODE> with a numeric PK <CODE>id</CODE>, using a
 * query like:
 *
 * <PRE>
 * SELECT * FROM BOOKS WHERE id BETWEEN ? AND ?
 * </PRE>
 *
 * <p>You can take advantage of this class to automatically generate the parameters of the BETWEEN
 * clause, based on the passed constructor parameters.
 */
public class JdbcNumericBetweenParametersProvider implements JdbcParameterValuesProvider {

    private final long minVal;
    private final long maxVal;

    private long batchSize;
    private int batchNum;

    /**
     * NumericBetweenParametersProviderJdbc constructor.
     *
     * @param minVal the lower bound of the produced "from" values
     * @param maxVal the upper bound of the produced "to" values
     */
    public JdbcNumericBetweenParametersProvider(long minVal, long maxVal) {
        Preconditions.checkArgument(minVal <= maxVal, "minVal must not be larger than maxVal");
        this.minVal = minVal;
        this.maxVal = maxVal;
    }

    /**
     * NumericBetweenParametersProviderJdbc constructor.
     *
     * @param fetchSize the max distance between the produced from/to pairs
     * @param minVal the lower bound of the produced "from" values
     * @param maxVal the upper bound of the produced "to" values
     */
    public JdbcNumericBetweenParametersProvider(long fetchSize, long minVal, long maxVal) {
        Preconditions.checkArgument(minVal <= maxVal, "minVal must not be larger than maxVal");
        this.minVal = minVal;
        this.maxVal = maxVal;
        ofBatchSize(fetchSize);
    }

    public JdbcNumericBetweenParametersProvider ofBatchSize(long batchSize) {
        Preconditions.checkArgument(batchSize > 0, "Batch size must be positive");

        long maxElemCount = (maxVal - minVal) + 1;
        if (batchSize > maxElemCount) {
            batchSize = maxElemCount;
        }
        this.batchSize = batchSize;
        this.batchNum = new Double(Math.ceil((double) maxElemCount / batchSize)).intValue();
        return this;
    }

    public JdbcNumericBetweenParametersProvider ofBatchNum(int batchNum) {
        Preconditions.checkArgument(batchNum > 0, "Batch number must be positive");

        long maxElemCount = (maxVal - minVal) + 1;
        if (batchNum > maxElemCount) {
            batchNum = (int) maxElemCount;
        }
        this.batchNum = batchNum;
        this.batchSize = new Double(Math.ceil((double) maxElemCount / batchNum)).longValue();
        return this;
    }

    @Override
    public Serializable[][] getParameterValues() {
        Preconditions.checkState(
                batchSize > 0,
                "Batch size and batch number must be positive. Have you called `ofBatchSize` or `ofBatchNum`?");

        long maxElemCount = (maxVal - minVal) + 1;
        long bigBatchNum = maxElemCount - (batchSize - 1) * batchNum;

        Serializable[][] parameters = new Serializable[batchNum][2];
        long start = minVal;
        for (int i = 0; i < batchNum - 1; i++) {
            long end = start + batchSize - 1 - (i >= bigBatchNum ? 1 : 0);
            parameters[i] = new Long[] {start, end};
            start = end + 1;
        }
        parameters[batchNum - 1] = new Long[] {start, maxVal};
        return parameters;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        JdbcNumericBetweenParametersProvider that = (JdbcNumericBetweenParametersProvider) o;
        return minVal == that.minVal
                && maxVal == that.maxVal
                && batchSize == that.batchSize
                && batchNum == that.batchNum;
    }
}
