EmploymentGaps.java

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.ObjectMapper;

import java.time.Duration;
import java.time.LocalDate;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

/**
 * EmploymentGaps.
 *
 * @author evgeni.gordeev
 * @since 4/17/21
 */
public class EmploymentGaps {

    static class Employment {
        String type;
        String start_date;
        String end_date;

        public String getType() {
            return type;
        }

        public void setType(String type) {
            this.type = type;
        }

        public String getStart_date() {
            return start_date;
        }

        public void setStart_date(String start_date) {
            this.start_date = start_date;
        }

        public String getEnd_date() {
            return end_date;
        }

        public void setEnd_date(String end_date) {
            this.end_date = end_date;
        }
    }

    public List<Employment> findGaps(List<Employment> employments) {
        if (employments == null || employments.isEmpty()) {
            return Collections.emptyList();
        }
        employments.sort(Comparator.comparing(Employment::getStart_date));
        Employment prev = employments.get(0);
        LocalDate maxEndDate = LocalDate.parse(prev.end_date);
        for (int i = 1; i < employments.size(); i++) {
            Employment curr = employments.get(i);
            LocalDate date1 = LocalDate.parse(prev.end_date);
            if (date1.isAfter(maxEndDate)) {
                maxEndDate = date1;
            }
            LocalDate date2 = LocalDate.parse(curr.start_date);
            if (date2.isAfter(maxEndDate) && Duration.between(date1.atStartOfDay(), date2.atStartOfDay()).toDays() > 30) {
                Employment gap = new Employment();
                gap.setType("employment_gap");
                gap.setStart_date(prev.end_date);
                gap.setEnd_date(curr.start_date);
                employments.add(i, gap);
                i++;
            }
            prev = curr;
        }
        return employments;
    }

    static void test(String input, String expected) throws JsonProcessingException {
        // GIVEN
        ObjectMapper objectMapper = new ObjectMapper();
        List<Employment> employments = objectMapper.readValue(input, new TypeReference<>() {
        });
        // WHEN
        EmploymentGaps eg = new EmploymentGaps();
        List<Employment> employmentsWithGaps = eg.findGaps(employments);
        // THEN
        String output = objectMapper.writeValueAsString(employmentsWithGaps);
        if (!objectMapper.readTree(output).equals(objectMapper.readTree(expected))) {
            throw new RuntimeException("Output doesn't equal expected");
        }
    }

    public static void main(String[] args) throws JsonProcessingException {
        String input = "[ \n" +
            "  { \"type\": \"employment\", \"start_date\": \"2010-01-01\", \"end_date\": \"2012-02-13\" },\n" +
            "  { \"type\": \"employment\", \"start_date\": \"2013-05-01\", \"end_date\": \"2015-03-13\" },\n" +
            "  { \"type\": \"employment\", \"start_date\": \"2012-03-01\", \"end_date\": \"2013-03-13\" }\n" +
            "]";
        String output = "[ \n" +
            "  { \"type\": \"employment\", \"start_date\": \"2010-01-01\", \"end_date\": \"2012-02-13\" },\n" +
            "  { \"type\": \"employment\", \"start_date\": \"2012-03-01\", \"end_date\": \"2013-03-13\" },\n" +
            "  { \"type\": \"employment_gap\", \"start_date\": \"2013-03-13\", \"end_date\": \"2013-05-01\" },\n" +
            "  { \"type\": \"employment\", \"start_date\": \"2013-05-01\", \"end_date\": \"2015-03-13\" }\n" +
            "]";
        test(input, output);
        // another test to verify if end date lasts more than 2 next employments
        input = "[ \n" +
            "  { \"type\": \"employment\", \"start_date\": \"2011-01-01\", \"end_date\": \"2015-02-13\" },\n" +
            "  { \"type\": \"employment\", \"start_date\": \"2010-01-01\", \"end_date\": \"2012-02-13\" },\n" +
            "  { \"type\": \"employment\", \"start_date\": \"2013-05-01\", \"end_date\": \"2015-03-13\" },\n" +
            "  { \"type\": \"employment\", \"start_date\": \"2012-03-01\", \"end_date\": \"2013-03-13\" }\n" +
            "]";
        output = "[" +
            "{\"type\":\"employment\",\"start_date\":\"2010-01-01\",\"end_date\":\"2012-02-13\"}," +
            "{\"type\":\"employment\",\"start_date\":\"2011-01-01\",\"end_date\":\"2015-02-13\"}," +
            "{\"type\":\"employment\",\"start_date\":\"2012-03-01\",\"end_date\":\"2013-03-13\"}," +
            "{\"type\":\"employment\",\"start_date\":\"2013-05-01\",\"end_date\":\"2015-03-13\"}" +
            "]";
        test(input, output);
    }
}