// 2. 気象庁公式データ（年間ファイル管理対応ローダー）
function getOfficialTideData($dateStr) {
    $dt = new DateTime($dateStr);
    $year = $dt->format('Y');

    // index.phpと同じ階層にある tide_data/2026.json を確実に指定
    $tideFile = __DIR__ . '/tide_data/' . $year . '.json';
    
    if (file_exists($tideFile)) {
        $json = file_get_contents($tideFile);
        $data = json_decode($json, true);
        if (is_array($data) && isset($data[$dateStr])) {
            $dayData = $data[$dateStr];
            
            // 月齢計算
            $utcRef = gmmktime(18, 0, 0, 1, 6, 2000);
            $targetUtc = gmmktime(0, 0, 0, (int)$dt->format('m'), (int)$dt->format('d'), (int)$dt->format('Y'));
            $days = ($targetUtc - $utcRef) / (60 * 60 * 24);
            $newMoonCycle = 29.53058867;
            $moonAge = fmod(fmod($days, $newMoonCycle) + $newMoonCycle, $newMoonCycle);
            $lunarDay = (int)floor($moonAge) + 1;
            $illumination = round((1 - cos(2 * M_PI * ($moonAge / $newMoonCycle))) / 2 * 100);
            
            $moonIcon = ($illumination <= 5) ? '🌑' : (($illumination >= 95) ? '🌕' : '🌔');
            $tideType = ($lunarDay <= 3 || ($lunarDay >= 13 && $lunarDay <= 17)) ? '大潮' : (($lunarDay >= 7 && $lunarDay <= 10) ? '小潮' : '中潮');

            return [
                'lunarDay' => $lunarDay,
                'moonAge' => number_format($moonAge, 1),
                'illumination' => $illumination,
                'moonIcon' => $moonIcon,
                'tideType' => $tideType,
                'highs' => $dayData['highs'],
                'lows' => $dayData['lows'],
                'curve' => $dayData['curve']
            ];
        }
    }

    // 万が一データが見つからない場合のフォールバック
    return [
        'lunarDay' => 1,
        'moonAge' => '1.0',
        'illumination' => 0,
        'moonIcon' => '🌑',
        'tideType' => '中潮',
        'highs' => [['h' => '05:30', 'v' => 180]],
        'lows' => [['h' => '11:30', 'v' => 50]],
        'curve' => []
    ];
}