package com.ruoyi.system.service.impl;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Comparator;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;

/** 按单个接收区间检查历史序号；暂停和区间边界由调用方分组后自然排除。 */
final class IntervalIntegrityChecker
{
    record Gap(long from, long to) { }

    private IntervalIntegrityChecker() { }

    static List<Gap> gaps(Collection<Long> sequenceIds)
    {
        if (sequenceIds == null || sequenceIds.isEmpty()) return List.of();
        Set<Long> unique = new LinkedHashSet<>();
        sequenceIds.stream().filter(value -> value != null && value > 0).forEach(unique::add);
        List<Long> ordered = new ArrayList<>(unique);
        ordered.sort(Comparator.naturalOrder());
        List<Gap> result = new ArrayList<>();
        for (int index = 1; index < ordered.size(); index++)
        {
            long previous = ordered.get(index - 1);
            long current = ordered.get(index);
            if (current > previous + 1) result.add(new Gap(previous + 1, current - 1));
        }
        return List.copyOf(result);
    }
}