<?php

namespace App\Support\Pdf;

use App\Services\FontService;
use App\Support\Net\BlockedUrlException;
use App\Support\Net\PrivateNetworkGuard;
use Gotenberg\Gotenberg;
use Gotenberg\Stream;
use Illuminate\Support\Facades\View;
use Psr\Http\Message\RequestInterface;

class GotenbergPdfDriver implements PdfDriver
{
    public function loadView(string $template, array $metadata = []): ResponseStream
    {
        return new GotenbergPdfResponse(Gotenberg::send($this->buildRequest($template, $metadata)));
    }

    /**
     * Assemble the Chromium request without sending it.
     *
     * Split out so the option wiring can actually be asserted on. Everything
     * below this line used to be inlined into loadView(), which meant the only
     * way to check that an option was set was to run a Gotenberg service.
     */
    public function buildRequest(string $template, array $metadata = []): RequestInterface
    {
        $page = PdfPageSetup::fromConfig();
        [$width, $height] = $page->gotenbergPaper();
        [$marginTop, $marginBottom, $marginLeft, $marginRight] = $page->gotenbergMargins();

        $host = config('pdf.connections.gotenberg.host');

        // SSRF guard: gotenberg_host is an admin-supplied URL the server POSTs
        // the rendered HTML to, and whose response is streamed back as the PDF.
        // Block private/reserved/link-local targets even if set via env/seed/stale
        // config or reachable through DNS rebinding. The single exception is the
        // host the operator declared in GOTENBERG_ALLOWED_PRIVATE_HOST, which is
        // how a sidecar deployment is supported — see GotenbergHostPolicy.
        if (! GotenbergHostPolicy::isExemptFromPrivateNetworkGuard((string) $host)) {
            try {
                PrivateNetworkGuard::assertAllowed((string) $host);
            } catch (BlockedUrlException $e) {
                throw new \InvalidArgumentException('Invalid Gotenberg host: '.$e->getMessage());
            }
        }

        $chromium = Gotenberg::chromium($host)
            ->pdf()
            // Only affects the root (body/html) background: Chromium paints
            // element backgrounds either way, verified against gotenberg:8, so
            // no stock template changes. dompdf does paint the body background,
            // so this is here to stop a custom template that sets one from
            // rendering differently depending on the selected driver.
            ->printBackground()
            // config/dompdf.php renders as `screen`; Chromium defaults to `print`.
            // Align them so a template with media queries behaves the same either
            // way rather than depending on which driver is selected.
            ->emulateScreenMediaType()
            ->margins($marginTop, $marginBottom, $marginLeft, $marginRight)
            ->paperSize($width, $height);

        // landscape() swaps the axes itself, so paperSize() above is always given
        // the portrait pair — the same convention dompdf's setPaper() follows.
        if ($page->isLandscape()) {
            $chromium->landscape();
        }

        // Archival conformance, converted by LibreOffice inside the Gotenberg
        // image. PDF/A-3 is what the EU e-invoicing formats ask for. The value is
        // passed through unvalidated by the SDK, so an unsupported one surfaces
        // as an HTTP error from the service; the setting is a fixed list for
        // that reason.
        if ($pdfa = config('pdf.connections.gotenberg.pdfa')) {
            $chromium->pdfa($pdfa);
        }

        if ($metadata !== []) {
            $chromium->metadata($metadata);
        }

        // Must be attached before html(), which is terminal: it returns the built
        // request rather than the builder.
        if ($header = $this->companion($template, '_header')) {
            $chromium->header(Stream::string('header.html', $header));
        }

        if ($footer = $this->companion($template, '_footer') ?? $this->defaultFooter()) {
            $chromium->footer(Stream::string('footer.html', $footer));
        }

        $html = view($template)->render();

        // Fonts must travel with the document; see attachFonts().
        [$html, $fonts] = $this->attachFonts($html);

        if ($fonts !== []) {
            $chromium->assets(...$fonts);
        }

        return $chromium->html(
            // The SDK renames this to index.html regardless of what we pass
            // (ChromiumPdf::html()), so name it that way rather than implying
            // a choice we do not have.
            Stream::string('index.html', $html)
        );
    }

    /**
     * Send the installed font files alongside the document, and point the
     * font-face rules at them.
     *
     * FontService emits `src: url("/var/www/html/storage/fonts/...")` — an
     * absolute path on this container's filesystem. dompdf shares that
     * filesystem so it resolves; Chromium runs inside the Gotenberg container
     * and cannot see any of it, so every package silently failed to load and
     * documents fell back to whatever fonts that image happens to ship. The
     * docs recommend Gotenberg precisely for mixed-script documents, which made
     * this the wrong way round.
     *
     * Gotenberg unpacks assets next to index.html, so a bare filename resolves.
     * Only fonts actually referenced by the markup are sent, to keep a CJK
     * package off every request that does not use it.
     *
     * @return array{0: string, 1: list<Stream>}
     */
    private function attachFonts(string $html): array
    {
        $streams = [];

        foreach (app(FontService::class)->getInstalledFontFilePaths() as $filename => $path) {
            if (! str_contains($html, $path) || ! is_readable($path)) {
                continue;
            }

            $html = str_replace($path, $filename, $html);
            $streams[] = Stream::path($path, $filename);
        }

        return [$html, $streams];
    }

    /**
     * A `{template}_header` or `{template}_footer` view rendered alongside the
     * document, repeated by Chromium on every page.
     *
     * The suffix resolves through the `pdf_templates::` namespace too, so a
     * custom template gets this without any extra wiring. PdfTemplateUtils hides
     * the suffixed views from the template picker, which would otherwise list
     * them as separately selectable templates.
     */
    private function companion(string $template, string $suffix): ?string
    {
        $view = $template.$suffix;

        return View::exists($view) ? View::make($view)->render() : null;
    }

    /**
     * Page numbers, when no template supplies a footer of its own.
     *
     * Gotenberg is the only driver that can do this: Chromium repeats a footer
     * template on every page and substitutes the pageNumber/totalPages spans.
     * dompdf has no equivalent, so the setting is presented under Gotenberg.
     *
     * Note the footer draws inside the bottom margin, so it is invisible when
     * that margin is zero. The default of 1.2cm leaves room.
     */
    private function defaultFooter(): ?string
    {
        if (! config('pdf.page.page_numbers')) {
            return null;
        }

        return View::make('app.pdf.partials.page-footer')->render();
    }
}