Search Console APIで急上昇・急落キーワードを検出する方法

function nines_detect_keyword_changes(array $current, array $previous): array
{
    $previous_by_query = [];
    foreach ($previous as $row) {
        $previous_by_query[$row['query']] = $row;
    }

    $changes = [];

    foreach ($current as $row) {
        $query = $row['query'];
        $old = $previous_by_query[$query] ?? [
            'clicks' => 0,
            'impressions' => 0,
            'position' => null,
        ];

        $click_diff = $row['clicks'] - $old['clicks'];
        $impression_diff = $row['impressions'] - $old['impressions'];
        $position_diff = is_null($old['position']) ? null : $old['position'] - $row['position'];

        $changes[] = [
            'query' => $query,
            'click_diff' => $click_diff,
            'impression_diff' => $impression_diff,
            'position_diff' => $position_diff,
            'status' => $click_diff >= 5 || $impression_diff >= 100 ? '急上昇' : '通常',
        ];
    }

    usort($changes, fn($a, $b) => $b['impression_diff'] <=> $a['impression_diff']);

    return $changes;
}