<?php

declare(strict_types=1);

require_once __DIR__ . '/helpers.php';

final class AirQualityService
{
    public function fetchGrouped(DateTimeImmutable $center, int $dayOffset): array
    {
        $pastDays = 4;
        $forecastDays = max(4, $dayOffset + 4);
        if ($forecastDays < 1) {
            $forecastDays = 7;
        }

        $url = sprintf(
            'https://air-quality-api.open-meteo.com/v1/air-quality?latitude=%s&longitude=%s&hourly=european_aqi,pm10,pm2_5,alder_pollen,birch_pollen,grass_pollen,mugwort_pollen,ragweed_pollen&timezone=%s&past_days=%d&forecast_days=%d',
            rawurlencode(LAT),
            rawurlencode(LON),
            rawurlencode(APP_TIMEZONE),
            $pastDays,
            $forecastDays
        );

        $data = fetchJson($url, 1800); // Cache air quality data for 30 minutes
        if (!is_array($data) || !isset($data['hourly']['time'])) {
            return ['hourly_by_date' => [], 'error' => 'Luftqualitätsdaten konnten nicht geladen werden.'];
        }

        return ['hourly_by_date' => $this->groupHourlyByDate($data['hourly']), 'error' => null];
    }

    private function groupHourlyByDate(array $hourly): array
    {
        $result = [];
        $count = count($hourly['time'] ?? []);
        for ($i = 0; $i < $count; $i++) {
            $timestamp = (string)$hourly['time'][$i];
            $date = substr($timestamp, 0, 10);
            $hour = (int)substr($timestamp, 11, 2);
            $result[$date][] = [
                'hour' => $hour,
                'aqi' => isset($hourly['european_aqi'][$i]) ? (float)$hourly['european_aqi'][$i] : null,
                'pm10' => isset($hourly['pm10'][$i]) ? (float)$hourly['pm10'][$i] : null,
                'pm25' => isset($hourly['pm2_5'][$i]) ? (float)$hourly['pm2_5'][$i] : null,
                'alder' => isset($hourly['alder_pollen'][$i]) ? (float)$hourly['alder_pollen'][$i] : null,
                'birch' => isset($hourly['birch_pollen'][$i]) ? (float)$hourly['birch_pollen'][$i] : null,
                'grass' => isset($hourly['grass_pollen'][$i]) ? (float)$hourly['grass_pollen'][$i] : null,
                'mugwort' => isset($hourly['mugwort_pollen'][$i]) ? (float)$hourly['mugwort_pollen'][$i] : null,
                'ragweed' => isset($hourly['ragweed_pollen'][$i]) ? (float)$hourly['ragweed_pollen'][$i] : null,
            ];
        }
        return $result;
    }

    public function summarizeDay(array $rows): array
    {
        if ($rows === []) {
            return [
                'has_data' => false,
                'aqi_max' => null,
                'aqi_avg' => null,
                'aqi_label' => 'keine Daten',
                'pm25_avg' => null,
                'pm10_avg' => null,
                'pollen_peak' => null,
                'pollen_label' => 'keine Daten',
                'pollen_level' => 'keine Daten',
            ];
        }

        $aqis = array_values(array_filter(array_column($rows, 'aqi'), static function($v) { return $v !== null; }));
        $pm25 = array_values(array_filter(array_column($rows, 'pm25'), static function($v) { return $v !== null; }));
        $pm10 = array_values(array_filter(array_column($rows, 'pm10'), static function($v) { return $v !== null; }));

        $pollenMax = [
            'Erle' => $this->maxNullable(array_column($rows, 'alder')),
            'Birke' => $this->maxNullable(array_column($rows, 'birch')),
            'Gräser' => $this->maxNullable(array_column($rows, 'grass')),
            'Beifuß' => $this->maxNullable(array_column($rows, 'mugwort')),
            'Ambrosia' => $this->maxNullable(array_column($rows, 'ragweed')),
        ];
        arsort($pollenMax);
        $peakName = (string)array_key_first($pollenMax);
        $peakValue = $pollenMax[$peakName] ?? null;

        return [
            'has_data' => $aqis !== [] || $pm25 !== [] || $pm10 !== [] || $peakValue !== null,
            'aqi_max' => $aqis !== [] ? max($aqis) : null,
            'aqi_avg' => $aqis !== [] ? array_sum($aqis) / count($aqis) : null,
            'aqi_label' => $aqis !== [] ? $this->aqiLabel((float)max($aqis)) : 'keine Daten',
            'pm25_avg' => $pm25 !== [] ? array_sum($pm25) / count($pm25) : null,
            'pm10_avg' => $pm10 !== [] ? array_sum($pm10) / count($pm10) : null,
            'pollen_peak' => $peakValue !== null ? ['name' => $peakName, 'value' => $peakValue] : null,
            'pollen_label' => $peakValue !== null ? $peakName . ' ' . number_format((float)$peakValue, 1, ',', '') : 'keine Daten',
            'pollen_level' => $peakValue !== null ? $this->pollenLevel((float)$peakValue) : 'keine Daten',
        ];
    }

    private function maxNullable(array $values): ?float
    {
        $values = array_values(array_filter($values, static function($v) { return $v !== null; }));
        return $values !== [] ? (float)max($values) : null;
    }

    private function aqiLabel(float $aqi): string
    {
        if ($aqi <= 20) {
            return 'sehr gut';
        } elseif ($aqi <= 40) {
            return 'gut';
        } elseif ($aqi <= 60) {
            return 'mäßig';
        } elseif ($aqi <= 80) {
            return 'schlecht';
        } elseif ($aqi <= 100) {
            return 'sehr schlecht';
        } else {
            return 'extrem schlecht';
        }
    }

    private function pollenLevel(float $value): string
    {
        if ($value < 1) {
            return 'kaum Belastung';
        } elseif ($value < 10) {
            return 'leicht';
        } elseif ($value < 50) {
            return 'mittel';
        } elseif ($value < 100) {
            return 'hoch';
        } else {
            return 'sehr hoch';
        }
    }
}