<?php

namespace App\Email;

use App\Config\EmailTextCatalog;
use App\Config\EmailTextKey;
use App\Model\RenderedEmailTextDto;
use App\Repository\EmailTextRepository;

/**
 * Turns the text an admin wrote into the HTML of a transactional mail.
 *
 * Admins write Markdown with {placeholder} tokens - never markup, never Twig. The body is
 * handed to App\Email\MailBodyRenderer, which is where the escaping that makes
 * email/generic.html.twig's |raw safe happens; subject and headline are plain text and
 * are dealt with here.
 */
class EmailTextRenderer
{
    /**
     * Printed for a placeholder that has no value, so a mail never shows a stray label
     * with nothing behind it (a teamer's disposition usually has no special agreements).
     */
    private const EMPTY_VALUE = '-';

    /**
     * Text only ever lands in element content here, never in an attribute, so single
     * quotes stay readable instead of turning into &#039; in the middle of a sentence.
     */
    private const ESCAPE_FLAGS = ENT_COMPAT | ENT_SUBSTITUTE;

    /**
     * The token for the booking link, and why it is not handled like the other placeholders:
     * a placeholder value is substituted into the *rendered HTML* and escaped there, which is
     * what makes a teamer's own words harmless - but it also means such a value can never be a
     * link target, because CommonMark has already percent-encoded the braces by then
     * ("%7BbookingUrl%7D"). This one is substituted into the Markdown *before* parsing instead,
     * so the admin can write it as a proper link and CommonMark still gets to vet the URL
     * through allow_unsafe_links. That is only defensible because the value comes from the
     * deployment's own environment, exactly like the wording it is substituted into - never
     * from a teamer or an applicant. Do not extend this to anything a user can influence.
     */
    private const BOOKING_URL_TOKEN = '{bookingUrl}';

    public function __construct(
        private readonly EmailTextCatalog $catalog,
        private readonly EmailTextRepository $emailTextRepository,
        private readonly MailBodyRenderer $mailBodyRenderer,
        private readonly string $bookingUrl = '',
    ) {
    }

    /**
     * @param array<string, string|int|null> $placeholders
     */
    public function render(EmailTextKey $key, array $placeholders): RenderedEmailTextDto
    {
        $definition = $this->catalog->get($key);
        $emailText = $this->emailTextRepository->findByKey($key);

        return $this->renderValues(
            $key,
            $emailText?->getSubject() ?: $definition->defaultSubject,
            $emailText?->getHeadline() ?? $definition->defaultHeadline,
            $emailText?->getBody() ?: $definition->defaultBody,
            $placeholders
        );
    }

    /**
     * Renders wording that is not (or not yet) the saved one - the admin preview shows
     * what is currently in the form, which is the whole point of previewing before saving.
     * The values come straight from a half-filled form, so all three may be null.
     *
     * @param array<string, string|int|null> $placeholders
     */
    public function renderValues(
        EmailTextKey $key,
        ?string $subject,
        ?string $headline,
        ?string $body,
        array $placeholders,
    ): RenderedEmailTextDto {
        $definition = $this->catalog->get($key);

        // Three token maps from the same values, because the three parts of a mail are not
        // the same kind of text: the subject is a plain header, the headline is escaped
        // plain text, and the body is Markdown the renderer escapes for us.
        $rawTokens = [];
        $htmlTokens = [];

        foreach ($definition->getPlaceholderNames() as $name) {
            $value = (string) ($placeholders[$name] ?? '');
            $value = '' === trim($value) ? self::EMPTY_VALUE : $value;

            $rawTokens['{'.$name.'}'] = $value;
            $htmlTokens['{'.$name.'}'] = htmlspecialchars($value, self::ESCAPE_FLAGS, 'UTF-8');
        }

        return new RenderedEmailTextDto(
            strtr($subject ?? '', $rawTokens),
            $this->renderHeadline($headline ?? '', $htmlTokens),
            $this->mailBodyRenderer->render($this->insertBookingUrl($body ?? ''), $rawTokens),
        );
    }

    /**
     * Refuses rather than sending a broken link: an unconfigured APPLICATION_FORM_BOOKING_URL
     * would otherwise render as <a href=""> and invite an applicant to book a call they cannot
     * reach. The caller decides what that means - the endpoint logs it and answers the
     * submission anyway, a reviewer sending by hand gets to see it.
     */
    private function insertBookingUrl(string $body): string
    {
        if (false === str_contains($body, self::BOOKING_URL_TOKEN)) {
            return $body;
        }

        if ('' === trim($this->bookingUrl)) {
            throw new \RuntimeException('The mail wording uses {bookingUrl}, but APPLICATION_FORM_BOOKING_URL is not configured.');
        }

        return str_replace(self::BOOKING_URL_TOKEN, trim($this->bookingUrl), $body);
    }

    /**
     * The headline is set as the mail's own <h1>, so it deliberately takes no Markdown:
     * emphasis inside an already bold heading says nothing, and a stray "-" or "#" at the
     * start of one should stay the character it is.
     *
     * @param array<string, string> $tokens
     */
    private function renderHeadline(string $headline, array $tokens): string
    {
        return strtr(
            htmlspecialchars(trim($headline), self::ESCAPE_FLAGS, 'UTF-8'),
            $tokens
        );
    }
}