io.virtdata.libbasics.shared.from_long.to_string.ModuloCSVLineToString Maven / Gradle / Ivy

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With inspiration from other libraries

There is a newer version: 2.12.15

/*
 *
 *       Copyright 2015 Jonathan Shook
 *
 *   Licensed 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 io.virtdata.libbasics.shared.from_long.to_string;

import io.virtdata.annotations.Example;
import io.virtdata.annotations.ThreadSafeMapper;
import io.virtdata.util.VirtDataResources;
import org.apache.commons.csv.CSVParser;
import org.apache.commons.csv.CSVRecord;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.ArrayList;
import java.util.List;
import java.util.function.LongFunction;

/**
 * Select a value from a CSV file line by modulo division against the number
 * of lines in the file. The second parameter is the field name, and this must
 * be provided in the CSV header line as written.
 */
@ThreadSafeMapper
public class ModuloCSVLineToString implements LongFunction {
    private final static Logger logger = LoggerFactory.getLogger(ModuloLineToString.class);

    private List lines = new ArrayList<>();

    private String filename;

    @Example({"ModuloCSVLineToString('data/myfile.csv','lat')","load values for 'lat' from the CSV file myfile.csv."})
    public ModuloCSVLineToString(String filename, String fieldname) {
        this.filename = filename;
        CSVParser csvp = VirtDataResources.readFileCSV(filename);
        int column = csvp.getHeaderMap().get(fieldname);
        for (CSVRecord strings : csvp) {
            lines.add(strings.get(column));
        }
    }

    @Override
    public String apply(long input) {
        int itemIdx = (int) (input % lines.size()) % Integer.MAX_VALUE;
        String item = lines.get(itemIdx);
        return item;
    }

    public String toString() {
        return getClass().getSimpleName() + ":" + filename;
    }


}