<?php

declare(strict_types=1);

namespace OCA\WorkflowDeckAutomation\Service;

use OCA\Deck\Db\Card;
use OCA\WorkflowDeckAutomation\Db\Workflow;
use OCP\IL10N;
use OCP\IURLGenerator;
use OCP\IUser;
use OCP\L10N\IFactory;
use OCP\Mail\IEMailTemplate;
use OCP\Mail\IMailer;
use OCP\Util;
use Psr\Log\LoggerInterface;
use Throwable;

class NotificationMailer {
	private const APP_ID = 'workflow_deck_automation';

	/**
	 * Descriptions are unbounded in Deck; keep the mail readable and well
	 * clear of any MTA size limits.
	 */
	private const MAX_DESCRIPTION_LENGTH = 2000;

	public function __construct(
		private IMailer $mailer,
		private IURLGenerator $urlGenerator,
		private IFactory $l10nFactory,
		private LoggerInterface $logger,
	) {
	}

	/**
	 * One mail listing every card moved for $recipient in this run — they
	 * may come from several workflows and boards.
	 *
	 * @param non-empty-list<array{workflow: Workflow, card: Card, targets: array{board: string, sourceStack: string, targetStack: string}}> $entries
	 *        targets are the titles resolved by DeckIntegrationService::describeTargets()
	 */
	public function sendCardsMovedNotification(IUser $recipient, array $entries): void {
		$email = $recipient->getEMailAddress();
		if ($email === null || $email === '') {
			$this->logger->info('Skipping moved-cards mail: user ' . $recipient->getUID() . ' has no email address', [
				'app' => self::APP_ID,
			]);
			return;
		}

		$count = count($entries);
		$l10n = $this->l10nFor($recipient);

		try {
			$template = $this->mailer->createEMailTemplate(self::APP_ID . '.CardsMoved', [
				'count' => $count,
				'cardTitles' => array_map(static fn (array $entry) => $entry['card']->getTitle(), $entries),
			]);
			$template->setSubject($count === 1
				? $l10n->t('Deck card moved: %s', [$entries[0]['card']->getTitle()])
				: $l10n->n('%n Deck card moved', '%n Deck cards moved', $count));
			$template->addHeader();
			$template->addHeading($l10n->n('A card was moved automatically', '%n cards were moved automatically', $count), false);

			foreach ($entries as $entry) {
				$this->addCard($template, $l10n, $entry['workflow'], $entry['card'], $entry['targets']);
			}

			$template->addFooter();

			$message = $this->mailer->createMessage();
			$message->setTo([$email => $recipient->getDisplayName()]);
			$message->setFrom([Util::getDefaultEmailAddress('noreply') => $l10n->t('Deck Workflow Automation')]);
			$message->useTemplate($template);

			$failedRecipients = $this->mailer->send($message);
			if (!empty($failedRecipients)) {
				$this->logger->error('Moved-cards mail failed for: ' . implode(', ', $failedRecipients), [
					'app' => self::APP_ID,
				]);
			}
		} catch (Throwable $e) {
			$this->logger->error('Could not send moved-cards mail to ' . $recipient->getUID() . ': ' . $e->getMessage(), [
				'app' => self::APP_ID,
				'exception' => $e,
			]);
		}
	}

	/**
	 * @param array{board: string, sourceStack: string, targetStack: string} $targets
	 */
	private function addCard(IEMailTemplate $template, IL10N $l10n, Workflow $workflow, Card $card, array $targets): void {
		$template->addBodyText($l10n->t(
			'The card "%1$s" was moved because it is overdue (workflow "%2$s").',
			[$card->getTitle(), $workflow->getTitle()],
		));
		// Single-argument addBodyText() runs htmlspecialchars() itself, so
		// these board- and stack-titles (user input) are safe as-is —
		// unlike the description below, which passes both parts.
		$template->addBodyText($l10n->t(
			'Board "%1$s": moved from "%2$s" to "%3$s".',
			[$targets['board'], $targets['sourceStack'], $targets['targetStack']],
		));
		$this->addCardDescription($template, $l10n, $card);
		$template->addBodyButton(
			$l10n->t('Open card'),
			$this->urlGenerator->getAbsoluteURL('/apps/deck/board/' . $workflow->getBoardId() . '/card/' . $card->getId()),
		);
	}

	/**
	 * One-off notice that a workflow was switched off because the board or
	 * stack it points at is gone.
	 *
	 * @param WorkflowRunner::TARGET_* $brokenTarget
	 */
	public function sendWorkflowDisabledNotification(IUser $user, Workflow $workflow, string $brokenTarget): void {
		$email = $user->getEMailAddress();
		if ($email === null || $email === '') {
			$this->logger->info('Cannot notify about disabled workflow ' . $workflow->getId() . ': user ' . $user->getUID() . ' has no email address', [
				'app' => self::APP_ID,
			]);
			return;
		}

		$l10n = $this->l10nFor($user);
		$reason = match ($brokenTarget) {
			WorkflowRunner::TARGET_SOURCE_STACK => $l10n->t('its source stack no longer exists'),
			WorkflowRunner::TARGET_TARGET_STACK => $l10n->t('its target stack no longer exists'),
			default => $l10n->t('its board no longer exists or is no longer available to you'),
		};

		try {
			$settingsLink = $this->urlGenerator->getAbsoluteURL('/settings/user/' . self::APP_ID);

			$template = $this->mailer->createEMailTemplate(self::APP_ID . '.WorkflowDisabled', [
				'workflowTitle' => $workflow->getTitle(),
			]);
			$template->setSubject($l10n->t('Deck workflow deactivated: %s', [$workflow->getTitle()]));
			$template->addHeader();
			$template->addHeading($l10n->t('A workflow was deactivated'), false);
			$template->addBodyText($l10n->t(
				'The workflow "%1$s" was switched off automatically because %2$s. No cards are being moved by it any more.',
				[$workflow->getTitle(), $reason],
			));
			$template->addBodyText($l10n->t(
				'Delete the workflow or point it at an existing board and stack to reactivate it. You will not be reminded about this workflow again.',
			));
			$template->addBodyButton($l10n->t('Open settings'), $settingsLink);
			$template->addFooter();

			$message = $this->mailer->createMessage();
			$message->setTo([$email => $user->getDisplayName()]);
			$message->setFrom([Util::getDefaultEmailAddress('noreply') => $l10n->t('Deck Workflow Automation')]);
			$message->useTemplate($template);

			$failedRecipients = $this->mailer->send($message);
			if (!empty($failedRecipients)) {
				$this->logger->error('Deactivation mail for workflow ' . $workflow->getId() . ' failed for: ' . implode(', ', $failedRecipients), [
					'app' => self::APP_ID,
				]);
			}
		} catch (Throwable $e) {
			$this->logger->error('Could not send deactivation mail for workflow ' . $workflow->getId() . ': ' . $e->getMessage(), [
				'app' => self::APP_ID,
				'exception' => $e,
			]);
		}
	}

	/**
	 * The recipient's own language. Cron has no request to take one from, so
	 * an injected IL10N would always speak the instance default — wrong as
	 * soon as a mail goes to someone other than whoever set that default.
	 */
	private function l10nFor(IUser $user): IL10N {
		return $this->l10nFactory->get(self::APP_ID, $this->l10nFactory->getUserLanguage($user));
	}

	/**
	 * Appends the card's description, if it has one.
	 *
	 * Deck stores the description as Markdown. It is sent as-is rather than
	 * rendered: pulling a Markdown parser in just for the mail would be a
	 * lot of machinery, and unrendered Markdown still reads fine.
	 */
	private function addCardDescription(IEMailTemplate $template, IL10N $l10n, Card $card): void {
		$description = trim((string)$card->getDescription());
		if ($description === '') {
			return;
		}

		if (mb_strlen($description) > self::MAX_DESCRIPTION_LENGTH) {
			$description = mb_substr($description, 0, self::MAX_DESCRIPTION_LENGTH) . ' […]';
		}

		$template->addBodyText($l10n->t('Card content:'));

		// addBodyText() only runs htmlspecialchars() when it has to build the
		// plain-text part itself. Passing both parts means escaping is on us
		// -- and it has to be, because a card description is user input that
		// would otherwise land unescaped in the HTML mail.
		$template->addBodyText(
			nl2br(htmlspecialchars($description, ENT_QUOTES, 'UTF-8'), false),
			$description,
		);
	}
}