<?php

/* Icinga PDF Export | (c) 2018 Icinga GmbH | GPLv2 */

namespace Icinga\Module\Pdfexport\ProvidedHook;

use Exception;
use Icinga\Application\Config;
use Icinga\Application\Hook;
use Icinga\Application\Hook\PdfexportHook;
use Icinga\Application\Icinga;
use Icinga\Application\Web;
use Icinga\File\Storage\TemporaryLocalFileStorage;
use Icinga\Module\Pdfexport\HeadlessChrome;
use Icinga\Module\Pdfexport\PrintableHtmlDocument;
use Karriere\PdfMerge\PdfMerge;
use React\Promise\ExtendedPromiseInterface;

class Pdfexport extends PdfexportHook
{
    public static function first()
    {
        $pdfexport = null;

        if (Hook::has('Pdfexport')) {
            $pdfexport = Hook::first('Pdfexport');

            if (! $pdfexport->isSupported()) {
                throw new Exception(
                    sprintf("Can't export: %s does not support exporting PDFs", get_class($pdfexport))
                );
            }
        }

        if (! $pdfexport) {
            throw new Exception("Can't export: No module found which provides PDF export");
        }

        return $pdfexport;
    }

    public static function getBinary()
    {
        return Config::module('pdfexport')->get('chrome', 'binary', '/usr/bin/google-chrome');
    }

    public static function getForceTempStorage()
    {
        return (bool) Config::module('pdfexport')->get('chrome', 'force_temp_storage', '0');
    }

    public static function getHost()
    {
        return Config::module('pdfexport')->get('chrome', 'host');
    }

    public static function getPort()
    {
        return Config::module('pdfexport')->get('chrome', 'port', 9222);
    }

    public function isSupported()
    {
        try {
            return $this->chrome()->getVersion() >= 59;
        } catch (Exception $e) {
            return false;
        }
    }

    public function htmlToPdf($html)
    {
        // Keep reference to the chrome object because it is using temp files which are automatically removed when
        // the object is destructed
        $chrome = $this->chrome();

        $pdf = $chrome->fromHtml($html, static::getForceTempStorage())->toPdf();

        if ($html instanceof PrintableHtmlDocument && ($coverPage = $html->getCoverPage()) !== null) {
            $coverPagePdf = $chrome
                ->fromHtml(
                    (new PrintableHtmlDocument())
                        ->add($coverPage)
                        ->addAttributes($html->getAttributes())
                        ->removeMargins(),
                    static::getForceTempStorage()
                )
                ->toPdf();

            $pdf = $this->mergePdfs($coverPagePdf, $pdf);
        }

        return $pdf;
    }

    /**
     * Transforms the given printable html document/string asynchronously to PDF.
     *
     * @param PrintableHtmlDocument|string $html
     *
     * @return ExtendedPromiseInterface
     */
    public function asyncHtmlToPdf($html): ExtendedPromiseInterface
    {
        // Keep reference to the chrome object because it is using temp files which are automatically removed when
        // the object is destructed
        $chrome = $this->chrome();

        $pdfPromise = $chrome->fromHtml($html, static::getForceTempStorage())->asyncToPdf();

        if ($html instanceof PrintableHtmlDocument && ($coverPage = $html->getCoverPage()) !== null) {
            /** @var ExtendedPromiseInterface $pdfPromise */
            $pdfPromise = $pdfPromise->then(function (string $pdf) use ($chrome, $html, $coverPage) {
                return $chrome->fromHtml(
                    (new PrintableHtmlDocument())
                        ->add($coverPage)
                        ->addAttributes($html->getAttributes())
                        ->removeMargins(),
                    static::getForceTempStorage()
                )->asyncToPdf()->then(
                    function (string $coverPagePdf) use ($pdf) {
                        return $this->mergePdfs($coverPagePdf, $pdf);
                    }
                );
            });
        }

        return $pdfPromise;
    }

    public function streamPdfFromHtml($html, $filename)
    {
        $filename = basename($filename, '.pdf') . '.pdf';

        // Generate the PDF before changing the response headers to properly handle and display errors in the UI.
        $pdf = $this->htmlToPdf($html);

        /** @var Web $app */
        $app = Icinga::app();
        $app->getResponse()
            ->setHeader('Content-Type', 'application/pdf', true)
            ->setHeader('Content-Disposition', "inline; filename=\"$filename\"", true)
            ->setBody($pdf)
            ->sendResponse();

        exit;
    }

    /**
     * Create an instance of HeadlessChrome from configuration
     *
     * @return HeadlessChrome
     */
    protected function chrome()
    {
        $chrome = new HeadlessChrome();
        $chrome->setBinary(static::getBinary());

        if (($host = static::getHost()) !== null) {
            $chrome->setRemote($host, static::getPort());
        }

        return $chrome;
    }

    protected function mergePdfs(string ...$pdfs): string
    {
        $merger = new PdfMerge();
        $storage = new TemporaryLocalFileStorage();

        try {
            foreach ($pdfs as $i => $pdf) {
                $storage->create($i, $pdf);
                $merger->add($storage->resolvePath($i));
            }

            return $merger->merge('', 'S');
        } finally {
            foreach ($pdfs as $i => $_) {
                $storage->delete($i);
            }
        }
    }
}
