<?php
declare(strict_types=1);

/**
 * Fachliche Hilfsfunktionen fuer T-CrB im Telegram-Cron.
 *
 * Diese Datei enthaelt Datenbankabfragen zu T-CrB-Beobachtungen, Aufbau der
 * Telegram-Nachricht, Diagramm-Erzeugung als SVG/PNG sowie kleine Farb- und
 * Formatierungshelfer, die speziell fuer den T-CrB-Versand gebraucht werden.
 */

function fetchLatestTcrbObservationByFilter(PDO $pdo, string $filterCode): ?array
{
    $stmt = $pdo->prepare("
        SELECT
            `id`,
            `observed_at_utc`,
            `jd`,
            `magnitude`,
            `magnitude_error`,
            `filter_code`,
            `observer_code`
        FROM `aavso_tcrb_observations`
        WHERE `filter_code` = :filter_code
        ORDER BY `observed_at_utc` DESC, `id` DESC
        LIMIT 1
    ");
    $stmt->execute([':filter_code' => $filterCode]);
    $row = $stmt->fetch();

    return is_array($row) ? $row : null;
}


function fetchRecentTcrbObservationsByFilterWindow(PDO $pdo, string $filterCode, string $windowSpec = '-2 months'): array
{
    $windowStartUtc = (new DateTimeImmutable('now', new DateTimeZone('UTC')))
        ->modify($windowSpec)
        ->format('Y-m-d H:i:s');

    $stmt = $pdo->prepare("
        SELECT
            `id`,
            `observed_at_utc`,
            `jd`,
            `magnitude`,
            `magnitude_error`,
            `filter_code`,
            `observer_code`
        FROM `aavso_tcrb_observations`
        WHERE `filter_code` = :filter_code
          AND `observed_at_utc` >= :window_start_utc
        ORDER BY `observed_at_utc` ASC, `id` ASC
    ");
    $stmt->execute([
        ':filter_code' => $filterCode,
        ':window_start_utc' => $windowStartUtc,
    ]);
    $rows = $stmt->fetchAll();

    if ($rows === []) {
        $fallbackStmt = $pdo->prepare("
            SELECT
                `id`,
                `observed_at_utc`,
                `jd`,
                `magnitude`,
                `magnitude_error`,
                `filter_code`,
                `observer_code`
            FROM `aavso_tcrb_observations`
            WHERE `filter_code` = :filter_code
            ORDER BY `observed_at_utc` DESC, `id` DESC
            LIMIT 30
        ");
        $fallbackStmt->execute([
            ':filter_code' => $filterCode,
        ]);
        $rows = $fallbackStmt->fetchAll();
        usort($rows, static function (array $a, array $b): int {
            return strcmp((string) ($a['observed_at_utc'] ?? ''), (string) ($b['observed_at_utc'] ?? ''));
        });
    }

    return $rows;
}


function fetchTelegramRecipients(PDO $pdo): array
{
    $stmt = $pdo->query("
        SELECT `id`, `telegram_chat_id`, `telegram_username`
        FROM `app_users`
        WHERE `telegram_chat_id` IS NOT NULL
          AND `telegram_chat_id` <> ''
          AND `telegram_tcrb_v_enabled` = 1
          AND `is_active` = 1
        ORDER BY `id` ASC
    ");

    return $stmt->fetchAll();
}


function buildTcrbLatestVMessage(array $observation, DateTimeImmutable $nowBerlin): string
{
    $observedUtc = trim((string) ($observation['observed_at_utc'] ?? ''));
    $observedText = formatGermanDateTime($observedUtc);
    $magnitude = formatDecimal($observation['magnitude'] ?? null, 3);
    $magnitudeError = $observation['magnitude_error'] !== null
        ? ' ± ' . formatDecimal($observation['magnitude_error'], 3)
        : '';
    $jd = formatDecimal($observation['jd'] ?? null, 6);
    $observerCode = trim((string) ($observation['observer_code'] ?? ''));
    $nextPossibleEruptionDate = calculateNextPossibleTcrbEruptionDate($nowBerlin);

    $lines = [
        'SkyViews TCrBotti mit dem Update',
        '',
        'Magnitude: ' . $magnitude . $magnitudeError,
        'Zeitpunkt: ' . $observedText,
        'JD: ' . $jd,
        'Nächster möglicher Ausbruch: ' . $nextPossibleEruptionDate,
    ];
    

    return implode("\n", $lines);
}


function calculateNextPossibleTcrbEruptionDate(DateTimeImmutable $referenceDate): string
{
    $eruptionIntervalDays = 227.5687;
    $lastEruptionUtc = new DateTimeImmutable('1946-02-09 00:00:00', new DateTimeZone('UTC'));
    $referenceUtc = $referenceDate->setTimezone(new DateTimeZone('UTC'));
    $secondsPerDay = 86400;
    $eruptionIntervalSeconds = (int) round($eruptionIntervalDays * $secondsPerDay);
    $elapsedSecondsSinceLastEruption = max(0, $referenceUtc->getTimestamp() - $lastEruptionUtc->getTimestamp());
    $elapsedIntervals = (int) floor($elapsedSecondsSinceLastEruption / $eruptionIntervalSeconds);
    $nextPossibleEruptionUtc = $lastEruptionUtc->modify('+' . (($elapsedIntervals + 1) * $eruptionIntervalSeconds) . ' seconds');

    return $nextPossibleEruptionUtc->format('d.m.Y');
}


function formatGermanDateTime(?string $value): string
{
    if ($value === null || trim($value) === '') {
        return 'unbekannt';
    }

    try {
        $date = new DateTimeImmutable($value, new DateTimeZone('UTC'));
    } catch (Exception) {
        return $value;
    }

    return $date->format('d.m.Y H:i:s') . ' UTC';
}


function buildTcrbVChartSvg(array $observations, array $latestObservation): string
{
    $filterColors = loadFilterColors();
    $vColor = (string) ($filterColors['V'] ?? '#92FF00');
    $vStrokeColor = darkenHexColor($vColor, 0.35);
    $vHighlightColor = '#FF5A5F';
    $vHighlightStrokeColor = '#FFD6D6';

    $width = 1200;
    $height = 700;
    $paddingLeft = 90;
    $paddingRight = 40;
    $paddingTop = 80;
    $paddingBottom = 90;
    $plotWidth = $width - $paddingLeft - $paddingRight;
    $plotHeight = $height - $paddingTop - $paddingBottom;
    $plotBottomY = $paddingTop + $plotHeight;
    $plotRightX = $paddingLeft + $plotWidth;

    if (count($observations) < 2) {
        $observations = [$latestObservation];
    }

    $timestamps = [];
    $magnitudes = [];
    foreach ($observations as $row) {
        $timestamps[] = strtotime((string) ($row['observed_at_utc'] ?? ''));
        $magnitudes[] = (float) ($row['magnitude'] ?? 0.0);
    }

    $timestamps = array_values(array_filter($timestamps, static fn ($value): bool => is_int($value) || is_float($value)));
    if ($timestamps === []) {
        $timestamps = [time() - 3600, time()];
    }

    $minX = (float) min($timestamps);
    $maxX = (float) max($timestamps);
    if ($maxX <= $minX) {
        $maxX = $minX + 3600.0;
    }

    $minY = min($magnitudes);
    $maxY = max($magnitudes);
    if ($maxY <= $minY) {
        $maxY = $minY + 0.5;
    }

    $paddingMag = max(0.06, ($maxY - $minY) * 0.10);
    $axisMinY = $minY - $paddingMag;
    $axisMaxY = $maxY + $paddingMag;

    $scaleX = static function (float $timestamp) use ($minX, $maxX, $paddingLeft, $plotWidth): float {
        return $paddingLeft + (($timestamp - $minX) / ($maxX - $minX)) * $plotWidth;
    };

    $scaleY = static function (float $magnitude) use ($axisMinY, $axisMaxY, $paddingTop, $plotHeight): float {
        $ratio = ($magnitude - $axisMinY) / ($axisMaxY - $axisMinY);
        return $paddingTop + $ratio * $plotHeight;
    };

    $gridLines = [];
    for ($i = 0; $i <= 4; $i++) {
        $gridMag = $axisMinY + (($axisMaxY - $axisMinY) / 4) * $i;
        $y = $scaleY($gridMag);
        $gridLines[] = sprintf(
            '<line x1="%1$.2f" y1="%2$.2f" x2="%3$.2f" y2="%2$.2f" stroke="#243445" stroke-width="1" stroke-dasharray="6 6" />',
            $paddingLeft,
            $y,
            $paddingLeft + $plotWidth
        );
        $gridLines[] = sprintf(
            '<text x="%1$.2f" y="%2$.2f" fill="#dbe7f2" font-size="20" text-anchor="end" dominant-baseline="middle">%3$s</text>',
            $paddingLeft - 14,
            $y,
            htmlspecialchars(number_format($gridMag, 2, '.', ''), ENT_QUOTES, 'UTF-8')
        );
    }

    $pathParts = [];
    $errorBars = [];
    $pointsSvg = [];

    foreach ($observations as $index => $row) {
        $timestamp = strtotime((string) ($row['observed_at_utc'] ?? ''));
        if ($timestamp === false) {
            continue;
        }

        $magnitude = (float) ($row['magnitude'] ?? 0.0);
        $x = $scaleX((float) $timestamp);
        $y = $scaleY($magnitude);
        $pathParts[] = sprintf('%s %.2f %.2f', $index === 0 ? 'M' : 'L', $x, $y);

        $error = isset($row['magnitude_error']) && $row['magnitude_error'] !== null
            ? (float) $row['magnitude_error']
            : 0.0;
        if ($error > 0) {
            $yTop = $scaleY($magnitude - $error);
            $yBottom = $scaleY($magnitude + $error);
            $errorBars[] = sprintf(
                '<line x1="%1$.2f" y1="%2$.2f" x2="%1$.2f" y2="%3$.2f" stroke="%6$s" stroke-width="2" opacity="0.9" />' .
                '<line x1="%4$.2f" y1="%2$.2f" x2="%5$.2f" y2="%2$.2f" stroke="%6$s" stroke-width="2" opacity="0.9" />' .
                '<line x1="%4$.2f" y1="%3$.2f" x2="%5$.2f" y2="%3$.2f" stroke="%6$s" stroke-width="2" opacity="0.9" />',
                $x,
                $yTop,
                $yBottom,
                $x - 7,
                $x + 7,
                htmlspecialchars($vHighlightColor, ENT_QUOTES, 'UTF-8')
            );
        }

        $isLatest = (string) ($row['observed_at_utc'] ?? '') === (string) ($latestObservation['observed_at_utc'] ?? '')
            && (string) ($row['jd'] ?? '') === (string) ($latestObservation['jd'] ?? '');

        $pointsSvg[] = sprintf(
            '<circle cx="%1$.2f" cy="%2$.2f" r="%3$.2f" fill="%4$s" stroke="%5$s" stroke-width="%6$.2f" />',
            $x,
            $y,
            $isLatest ? 5.8 : 3.0,
            $isLatest ? $vHighlightColor : $vColor,
            $isLatest ? $vHighlightStrokeColor : $vHighlightColor,
            $isLatest ? 2.2 : 1.0
        );
    }

    $firstLabel = date('d.m.Y H:i', (int) $minX) . ' UTC';
    $lastLabel = date('d.m.Y H:i', (int) $maxX) . ' UTC';
    $latestMagnitude = number_format((float) ($latestObservation['magnitude'] ?? 0.0), 3, '.', '');
    $latestError = isset($latestObservation['magnitude_error']) && $latestObservation['magnitude_error'] !== null
        ? ' +/- ' . number_format((float) $latestObservation['magnitude_error'], 3, '.', '')
        : '';
    $latestUtc = htmlspecialchars((string) ($latestObservation['observed_at_utc'] ?? ''), ENT_QUOTES, 'UTF-8');
    $gridSvg = implode("\n  ", $gridLines);
    $errorBarsSvg = implode("\n  ", $errorBars);
    $pathSvg = implode(' ', $pathParts);
    $pointsSvgMarkup = implode("\n  ", $pointsSvg);

    return sprintf(
        <<<'SVG'
<svg xmlns="http://www.w3.org/2000/svg" width="%d" height="%d" viewBox="0 0 %d %d">
  <defs>
    <linearGradient id="bg" x1="0%%" y1="0%%" x2="0%%" y2="100%%">
      <stop offset="0%%" stop-color="#07111d"/>
      <stop offset="100%%" stop-color="#0f2133"/>
    </linearGradient>
  </defs>
  <rect width="%d" height="%d" fill="url(#bg)"/>
  <rect x="%d" y="%d" width="%d" height="%d" rx="16" fill="#11263b" stroke="#2f4d68" stroke-width="1.5"/>
  <text x="%d" y="44" fill="#f8fafc" font-size="30" font-weight="700">T CrB Lichtkurve - Filter V</text>
  <text x="%d" y="70" fill="#cbd5e1" font-size="19">letzte 2 Monate - Astronomiemuseum der Sternwarte Sonneberg</text>
  <text x="%d" y="%d" fill="#cbd5e1" font-size="18">%s</text>
  <text x="%d" y="%d" fill="#cbd5e1" font-size="18" text-anchor="end">%s</text>
  <text x="%d" y="48" fill="%s" font-size="22" text-anchor="end">Aktuell: %s%s</text>
  <text x="%d" y="74" fill="#cbd5e1" font-size="18" text-anchor="end">%s UTC</text>
  %s
  <line x1="%d" y1="%d" x2="%d" y2="%d" stroke="#88a4bf" stroke-width="1.6"/>
  <line x1="%d" y1="%d" x2="%d" y2="%d" stroke="#88a4bf" stroke-width="1.6"/>
  %s
  <path d="%s" fill="none" stroke="%s" stroke-width="3" stroke-linejoin="round" stroke-linecap="round"/>
  %s
</svg>
SVG,
        $width,
        $height,
        $width,
        $height,
        $width,
        $height,
        $paddingLeft,
        $paddingTop,
        $plotWidth,
        $plotHeight,
        $paddingLeft,
        $paddingLeft,
        $paddingLeft,
        $height - 28,
        htmlspecialchars($firstLabel, ENT_QUOTES, 'UTF-8'),
        $width - $paddingRight,
        $height - 28,
        htmlspecialchars($lastLabel, ENT_QUOTES, 'UTF-8'),
        $width - $paddingRight,
        htmlspecialchars($vHighlightColor, ENT_QUOTES, 'UTF-8'),
        htmlspecialchars($latestMagnitude, ENT_QUOTES, 'UTF-8'),
        htmlspecialchars($latestError, ENT_QUOTES, 'UTF-8'),
        $width - $paddingRight,
        $latestUtc,
        $gridSvg,
        $paddingLeft,
        $paddingTop,
        $paddingLeft,
        $plotBottomY,
        $paddingLeft,
        $plotBottomY,
        $plotRightX,
        $plotBottomY,
        $errorBarsSvg,
        $pathSvg,
        htmlspecialchars($vStrokeColor, ENT_QUOTES, 'UTF-8'),
        $pointsSvgMarkup
    );
}


function loadFilterColors(): array
{
    static $colors = null;
    global $filterColorConfigPath;

    if (is_array($colors)) {
        return $colors;
    }

    $colors = [];
    if (!is_string($filterColorConfigPath) || !is_file($filterColorConfigPath)) {
        return $colors;
    }

    $raw = file_get_contents($filterColorConfigPath);
    $decoded = is_string($raw) ? json_decode($raw, true) : null;
    if (!is_array($decoded)) {
        return $colors;
    }

    foreach ($decoded as $filterCode => $config) {
        if (is_array($config) && !empty($config['color'])) {
            $colors[(string) $filterCode] = (string) $config['color'];
        }
    }

    return $colors;
}


function darkenHexColor(string $hexColor, float $amount): string
{
    return adjustHexColor($hexColor, -abs($amount));
}


function lightenHexColor(string $hexColor, float $amount): string
{
    return adjustHexColor($hexColor, abs($amount));
}


function adjustHexColor(string $hexColor, float $amount): string
{
    $hex = ltrim(trim($hexColor), '#');
    if (!preg_match('/^[0-9a-fA-F]{6}$/', $hex)) {
        return '#92FF00';
    }

    $channels = [
        hexdec(substr($hex, 0, 2)),
        hexdec(substr($hex, 2, 2)),
        hexdec(substr($hex, 4, 2)),
    ];

    foreach ($channels as $index => $value) {
        if ($amount >= 0) {
            $channels[$index] = (int) round($value + ((255 - $value) * $amount));
        } else {
            $channels[$index] = (int) round($value * (1 + $amount));
        }
        $channels[$index] = max(0, min(255, $channels[$index]));
    }

    return sprintf('#%02X%02X%02X', $channels[0], $channels[1], $channels[2]);
}


function buildTcrbObservationSignature(array $observation): string
{
    return implode('|', [
        (string) ($observation['observed_at_utc'] ?? ''),
        (string) ($observation['jd'] ?? ''),
        (string) ($observation['magnitude'] ?? ''),
        (string) ($observation['magnitude_error'] ?? ''),
        (string) ($observation['filter_code'] ?? ''),
        (string) ($observation['observer_code'] ?? ''),
    ]);
}


function createTelegramChartPackage(string $svgContent): array
{
    $directory = sys_get_temp_dir() . DIRECTORY_SEPARATOR . 'skyview_telegram_charts';
    if (!is_dir($directory) && !mkdir($directory, 0775, true) && !is_dir($directory)) {
        throw new RuntimeException('Temp-Verzeichnis fuer Telegram-Diagramme konnte nicht erstellt werden.');
    }

    $baseName = 'tcrb_v_latest_chart_' . date('Ymd_His') . '_' . bin2hex(random_bytes(4));
    $svgPath = $directory . DIRECTORY_SEPARATOR . $baseName . '.svg';
    if (@file_put_contents($svgPath, $svgContent) === false) {
        throw new RuntimeException('Diagrammdatei konnte nicht geschrieben werden: ' . $svgPath);
    }

    $pngPath = $directory . DIRECTORY_SEPARATOR . $baseName . '.png';
    if (convertSvgToPng($svgPath, $pngPath)) {
        return [
            'kind' => 'photo',
            'path' => $pngPath,
            'cleanup' => [$svgPath, $pngPath],
        ];
    }

    return [
        'kind' => 'document',
        'path' => $svgPath,
        'cleanup' => [$svgPath],
    ];
}


function cleanupTelegramChartPackage(array $chartPackage): void
{
    $files = is_array($chartPackage['cleanup'] ?? null) ? $chartPackage['cleanup'] : [];
    foreach ($files as $file) {
        if (is_string($file) && $file !== '') {
            @unlink($file);
        }
    }
}


function convertSvgToPng(string $svgPath, string $pngPath): bool
{
    if (!is_file($svgPath)) {
        return false;
    }

    $commands = [
        sprintf('rsvg-convert -o %s %s', escapeshellarg($pngPath), escapeshellarg($svgPath)),
        sprintf('magick %s %s', escapeshellarg($svgPath), escapeshellarg($pngPath)),
        sprintf('convert %s %s', escapeshellarg($svgPath), escapeshellarg($pngPath)),
    ];

    foreach ($commands as $command) {
        if (!function_exists('shell_exec')) {
            continue;
        }

        @shell_exec($command . ' 2>&1');
        if (is_file($pngPath) && filesize($pngPath) > 0) {
            return true;
        }
    }

    return false;
}