<?php

declare(strict_types=1);

trait AbrechnungHelper {
    private function jsonDecodeProperty(string $name): array {
        $s = $this->ReadPropertyString($name);
        $a = json_decode($s, true);
        return is_array($a) ? $a : [];
    }

    private function saveTempFile(string $filename, string $content): string {
        $dir = IPS_GetKernelDir() . 'media' . DIRECTORY_SEPARATOR . 'Abrechnung';
        if (!is_dir($dir)) {
            @mkdir($dir, 0777, true);
        }
        $path = $dir . DIRECTORY_SEPARATOR . $filename;
        file_put_contents($path, $content);
        return $path;
    }

    private function formatCurrency(float $v): string {
        return number_format($v, 2, '.', '');
    }
}

class Abrechnung extends IPSModule
{
    use AbrechnungHelper;

    public function Create()
    {
        // Never delete this line!
        parent::Create();

        // Properties to store JSON arrays for Users and Meters
        $this->RegisterPropertyString('Users', json_encode([], JSON_THROW_ON_ERROR));
        $this->RegisterPropertyString('Meters', json_encode([], JSON_THROW_ON_ERROR));

        // This is used to return status message in the form
        $this->RegisterVariableString('LastPDF', 'Letztes PDF', '', 10);
    }

    public function ApplyChanges()
    {
        parent::ApplyChanges();
    }

    // Called by the button in form.json
    public function GenerateInvoices($data)
    {
        // $data contains the values from the form (from, to, work_price, fixed_fee)
        try {
            $from = isset($data['from']) ? strtotime($data['from']) : null;
            $to = isset($data['to']) ? strtotime($data['to']) : null;
            $workPrice = isset($data['work_price']) ? floatval($data['work_price']) : 0.0;
            $fixedFee = isset($data['fixed_fee']) ? floatval($data['fixed_fee']) : 0.0;

            if (!$from || !$to || $to <= $from) {
                return $this->ReturnResult(false, 'Ungültiger Zeitraum angegeben.');
            }

            $users = $this->jsonDecodeProperty('Users');
            $meters = $this->jsonDecodeProperty('Meters');

            // Map meters to users
            $userMeters = [];
            foreach ($meters as $m) {
                $uid = $m['user_id'] ?? null;
                if ($uid === null) continue;
                $userMeters[$uid][] = $m;
            }

            // Prepare per-user statements
            $invoiceData = [];
            foreach ($users as $u) {
                $uid = $u['id'] ?? null;
                if ($uid === null) continue;
                $name = $u['name'] ?? 'Unbenannt';
                $email = $u['email'] ?? '';
                $address = $u['address'] ?? '';

                $entries = [];
                $sumCost = 0.0;
                $sumConsumption = 0.0;

                $mList = $userMeters[$uid] ?? [];
                foreach ($mList as $m) {
                    $varId = intval($m['variableid']);
                    if ($varId <= 0) {
                        $entries[] = [
                            'name' => $m['name'],
                            'error' => 'keine gültige Variable'
                        ];
                        continue;
                    }
                    // We read the first value before period and last value at end period
                    // If counters are absolute cumulative, we look up the last value before period and last value at 'to'.
                    $fromValue = $this->GetVariableValueAt($varId, $from);
                    $toValue = $this->GetVariableValueAt($varId, $to);

                    if ($fromValue === null || $toValue === null) {
                        $entries[] = [
                            'name' => $m['name'],
                            'error' => 'keine historischen Werte gefunden'
                        ];
                        continue;
                    }

                    $consumption = $toValue - $fromValue;
                    if ($consumption < 0) {
                        // possibly rollover or wrong counter — keep absolute
                        $consumption = 0;
                    }
                    $cost = $consumption * $workPrice;
                    $sumConsumption += $consumption;
                    $sumCost += $cost;

                    $entries[] = [
                        'name' => $m['name'],
                        'variableid' => $varId,
                        'unit' => $m['unit'] ?? '',
                        'fromValue' => $fromValue,
                        'toValue' => $toValue,
                        'consumption' => $consumption,
                        'cost' => $cost
                    ];
                }

                // add fixed fee per user
                $sumCost += $fixedFee;

                $invoiceData[] = [
                    'user' => [
                        'id' => $uid,
                        'name' => $name,
                        'email' => $email,
                        'address' => $address
                    ],
                    'entries' => $entries,
                    'summary' => [
                        'consumption' => $sumConsumption,
                        'work_price' => $workPrice,
                        'fixed_fee' => $fixedFee,
                        'total' => $sumCost
                    ]
                ];
            }

            // generate PDF content
            $filename = $this->generatePdfFilename($from, $to);
            $path = $this->generatePdf($invoiceData, $from, $to, $filename);

            if ($path === false) {
                return $this->ReturnResult(false, 'PDF-Erzeugung fehlgeschlagen (TCPDF fehlt?).');
            }

            // Save path in a variable for easy retrieval
            SetValue($this->GetIDForIdent('LastPDF'), basename($path));

            $result = [
                'success' => true,
                'message' => 'PDF erstellt',
                'file' => $path
            ];
            return $result;
        } catch (Exception $e) {
            return $this->ReturnResult(false, 'Fehler: ' . $e->getMessage());
        }
    }

    private function ReturnResult(bool $ok, string $msg)
    {
        return ['success' => $ok, 'message' => $msg];
    }

    private function GetVariableValueAt(int $variableId, int $timestamp)
    {
        // Try to get the value at timestamp using IPS_GetVariableProfile or historic values
        // We use AC_GetLoggedValues if available (Symcon built-in)
        if (!function_exists('AC_GetLoggedValues')) {
            // fallback: try current value if historical not available
            return GetValue($variableId);
        }
        // get a single value at timestamp +/- 1 second
        $data = AC_GetLoggedValues($variableId, $timestamp - 60, $timestamp + 60, 1);
        if (!is_array($data) || count($data) === 0) {
            // no historical value -> try current value
            return GetValue($variableId);
        }
        // AC_GetLoggedValues returns an array of arrays with 'Value' => ...
        if (isset($data[0]['Value'])) {
            return floatval($data[0]['Value']);
        }
        return null;
    }

    private function generatePdfFilename(int $from, int $to): string {
        return 'Abrechnung_' . date('Ymd_His', $from) . '_' . date('Ymd_His', $to) . '.pdf';
    }

    private function generatePdf(array $invoiceData, int $from, int $to, string $filename)
    {
        // Try to include TCPDF
        if (!class_exists('\TCPDF')) {
            // Attempt to include from common locations (you might need to adjust)
            $possible = [
                IPS_GetKernelDir() . 'libs' . DIRECTORY_SEPARATOR . 'tcpdf' . DIRECTORY_SEPARATOR . 'tcpdf.php',
                IPS_GetKernelDir() . 'libs' . DIRECTORY_SEPARATOR . 'TCPDF' . DIRECTORY_SEPARATOR . 'tcpdf.php'
            ];
            $found = false;
            foreach ($possible as $p) {
                if (file_exists($p)) {
                    require_once $p;
                    $found = true;
                    break;
                }
            }
            if (!$found && !class_exists('\TCPDF')) {
                // TCPDF not available
                IPS_LogMessage('Abrechnung', 'TCPDF nicht gefunden. Bitte installiere tcpdf in ' . IPS_GetKernelDir() . 'libs/tcpdf. Composer: composer require tecnickcom/tcpdf');
                return false;
            }
        }

        // create new PDF document
        $pdf = new \TCPDF(PDF_PAGE_ORIENTATION, PDF_UNIT, PDF_PAGE_FORMAT, true, 'UTF-8', false);
        $pdf->SetCreator('IPSymcon Abrechnung');
        $pdf->SetAuthor('Abrechnung Modul');
        $pdf->SetTitle('Zählerabrechnung');
        $pdf->SetMargins(15, 20, 15);
        $pdf->SetHeaderMargin(5);
        $pdf->SetFooterMargin(10);
        $pdf->AddPage();

        // cover page
        $pdf->SetFont('helvetica', 'B', 16);
        $pdf->Cell(0, 10, 'Abrechnung', 0, 1, 'C');
        $pdf->SetFont('helvetica', '', 10);
        $pdf->Ln(2);
        $pdf->Cell(0, 6, 'Zeitraum: ' . date('Y-m-d H:i', $from) . ' - ' . date('Y-m-d H:i', $to), 0, 1);
        $pdf->Ln(6);

        foreach ($invoiceData as $inv) {
            $user = $inv['user'];
            $entries = $inv['entries'];
            $summary = $inv['summary'];

            $pdf->AddPage();

            $pdf->SetFont('helvetica', 'B', 12);
            $pdf->Cell(0, 8, $user['name'] . ' (ID: ' . $user['id'] . ')', 0, 1);
            $pdf->SetFont('helvetica', '', 10);
            if (!empty($user['address'])) {
                $pdf->MultiCell(0, 5, $user['address'], 0, 'L', 0, 1);
            }
            if (!empty($user['email'])) {
                $pdf->Cell(0, 5, 'E-Mail: ' . $user['email'], 0, 1);
            }
            $pdf->Ln(4);

            // Table header
            $pdf->SetFont('helvetica', 'B', 10);
            $pdf->Cell(60, 7, 'Zähler', 1);
            $pdf->Cell(30, 7, 'Von', 1);
            $pdf->Cell(30, 7, 'Bis', 1);
            $pdf->Cell(30, 7, 'Verbrauch', 1);
            $pdf->Cell(30, 7, 'Kosten', 1);
            $pdf->Ln();

            // Entries
            $pdf->SetFont('helvetica', '', 9);
            foreach ($entries as $e) {
                if (isset($e['error'])) {
                    $pdf->Cell(60, 6, $e['name'] . ' (' . $e['error'] . ')', 1);
                    $pdf->Cell(30, 6, '-', 1);
                    $pdf->Cell(30, 6, '-', 1);
                    $pdf->Cell(30, 6, '-', 1);
                    $pdf->Cell(30, 6, '-', 1);
                    $pdf->Ln();
                    continue;
                }
                $pdf->Cell(60, 6, ($e['name'] ?? 'Zähler'), 1);
                $pdf->Cell(30, 6, (string)round($e['fromValue'], 4) . ' ' . ($e['unit'] ?? ''), 1);
                $pdf->Cell(30, 6, (string)round($e['toValue'], 4) . ' ' . ($e['unit'] ?? ''), 1);
                $pdf->Cell(30, 6, (string)round($e['consumption'], 4), 1);
                $pdf->Cell(30, 6, $this->formatCurrency($e['cost']), 1);
                $pdf->Ln();
            }

            $pdf->Ln(4);
            $pdf->SetFont('helvetica', 'B', 10);
            $pdf->Cell(0, 6, 'Zusammenfassung', 0, 1);
            $pdf->SetFont('helvetica', '', 9);
            $pdf->Cell(80, 6, 'Gesamtverbrauch: ' . round($summary['consumption'], 4) . ' Einheiten', 0, 1);
            $pdf->Cell(80, 6, 'Arbeitspreis: ' . $this->formatCurrency($summary['work_price']) . ' / Einheit', 0, 1);
            $pdf->Cell(80, 6, 'Fixbetrag: ' . $this->formatCurrency($summary['fixed_fee']), 0, 1);
            $pdf->Ln(2);
            $pdf->SetFont('helvetica', 'B', 11);
            $pdf->Cell(80, 7, 'Gesamtbetrag: ' . $this->formatCurrency($summary['total']), 0, 1);
        }

        // output PDF to file
        $content = $pdf->Output('', 'S'); // return as string
        $path = $this->saveTempFile($filename, $content);
        return $path;
    }
}