<?php

declare(strict_types=1);

namespace OCA\WorkflowDeckAutomation\Controller;

use OCA\WorkflowDeckAutomation\Db\Workflow;
use OCA\WorkflowDeckAutomation\Db\WorkflowMapper;
use OCA\WorkflowDeckAutomation\Service\DeckIntegrationService;
use OCA\WorkflowDeckAutomation\Service\DeckUnavailableException;
use OCA\WorkflowDeckAutomation\Service\LoopDetector;
use OCA\WorkflowDeckAutomation\Service\NotificationPolicy;
use OCA\WorkflowDeckAutomation\Service\TriggerDate;
use OCP\AppFramework\Db\DoesNotExistException;
use OCP\AppFramework\Http;
use OCP\AppFramework\Http\Attribute\NoAdminRequired;
use OCP\AppFramework\Http\DataResponse;
use OCP\AppFramework\OCS\OCSBadRequestException;
use OCP\AppFramework\OCS\OCSNotFoundException;
use OCP\AppFramework\OCS\OCSPreconditionFailedException;
use OCP\AppFramework\OCSController;
use OCP\IRequest;
use OCP\IUserSession;

class WorkflowController extends OCSController {
	public function __construct(
		string $appName,
		IRequest $request,
		private WorkflowMapper $workflowMapper,
		private DeckIntegrationService $deckService,
		private IUserSession $userSession,
	) {
		parent::__construct($appName, $request);
	}

	private function currentUserId(): string {
		$user = $this->userSession->getUser();
		if ($user === null) {
			throw new OCSPreconditionFailedException('Nicht angemeldet');
		}
		return $user->getUID();
	}

	/**
	 * Every workflow on a board the user owns, no matter who created it: a
	 * workflow belongs to its board's owner, and follows the board when
	 * Deck transfers it.
	 */
	#[NoAdminRequired]
	public function index(): DataResponse {
		$workflows = $this->workflowMapper->findAllForBoards($this->ownedBoardIds());

		// validate() keeps new loops out, but workflows stored before that
		// check can still form one; the runner skips them, the list says why.
		$looping = LoopDetector::findLoopingWorkflows(LoopDetector::edgesOf(
			array_filter($workflows, static fn (Workflow $w) => (bool)$w->getEnabled()),
		));

		return new DataResponse(array_map(
			static fn (Workflow $w) => $w->jsonSerialize() + ['loop' => in_array((int)$w->getId(), $looping, true)],
			$workflows,
		));
	}

	#[NoAdminRequired]
	public function create(
		string $title,
		int $boardId,
		int $sourceStackId,
		int $targetStackId,
		string $triggerDate = TriggerDate::DUE,
		string $notifyMode = NotificationPolicy::MODE_OFF,
		string $notifyChannel = NotificationPolicy::CHANNEL_MAIL,
		bool $enabled = true,
	): DataResponse {
		$this->validate(null, $title, $boardId, $sourceStackId, $targetStackId, $triggerDate, $notifyMode, $notifyChannel, $enabled);

		$workflow = new Workflow();
		$workflow->setUserId($this->currentUserId());
		$this->applyFields($workflow, $title, $boardId, $sourceStackId, $targetStackId, $triggerDate, $notifyMode, $notifyChannel, $enabled);

		$workflow = $this->workflowMapper->insert($workflow);
		return new DataResponse($workflow->jsonSerialize(), Http::STATUS_CREATED);
	}

	#[NoAdminRequired]
	public function update(
		int $id,
		string $title,
		int $boardId,
		int $sourceStackId,
		int $targetStackId,
		string $triggerDate = TriggerDate::DUE,
		string $notifyMode = NotificationPolicy::MODE_OFF,
		string $notifyChannel = NotificationPolicy::CHANNEL_MAIL,
		bool $enabled = true,
	): DataResponse {
		$workflow = $this->findOwnWorkflow($id);
		$this->validate($id, $title, $boardId, $sourceStackId, $targetStackId, $triggerDate, $notifyMode, $notifyChannel, $enabled);

		// Kept in step with the board owner so the job runs as, and mails,
		// the right user; validate() made sure the editor owns the board.
		$workflow->setUserId($this->currentUserId());
		$this->applyFields($workflow, $title, $boardId, $sourceStackId, $targetStackId, $triggerDate, $notifyMode, $notifyChannel, $enabled);
		$workflow = $this->workflowMapper->update($workflow);

		return new DataResponse($workflow->jsonSerialize());
	}

	#[NoAdminRequired]
	public function destroy(int $id): DataResponse {
		$workflow = $this->findOwnWorkflow($id);
		$this->workflowMapper->delete($workflow);
		return new DataResponse([]);
	}

	#[NoAdminRequired]
	public function boards(): DataResponse {
		$this->assertDeck();
		return new DataResponse($this->ownedBoards());
	}

	#[NoAdminRequired]
	public function stacks(int $boardId): DataResponse {
		$this->assertDeck();
		return new DataResponse($this->deckService->listStacks($boardId));
	}

	private function findOwnWorkflow(int $id): Workflow {
		try {
			$workflow = $this->workflowMapper->findById($id);
		} catch (DoesNotExistException $e) {
			throw new OCSNotFoundException('Workflow nicht gefunden');
		}

		if (!in_array($workflow->getBoardId(), $this->ownedBoardIds(), true)) {
			// Same answer as for a missing id: don't reveal other users' workflows.
			throw new OCSNotFoundException('Workflow nicht gefunden');
		}
		return $workflow;
	}

	/**
	 * @return array<int, array{id: int, title: string, archived: bool}>
	 */
	private function ownedBoards(): array {
		$userId = $this->currentUserId();
		$this->assertDeck();
		try {
			return $this->deckService->listOwnedBoards($userId);
		} catch (DeckUnavailableException $e) {
			throw new OCSPreconditionFailedException('Deine Deck-Boards konnten nicht geladen werden: ' . $e->getMessage());
		}
	}

	/**
	 * @return int[]
	 */
	private function ownedBoardIds(): array {
		return array_map(static fn (array $board) => $board['id'], $this->ownedBoards());
	}

	private function assertDeck(): void {
		$user = $this->userSession->getUser();
		if ($user === null) {
			throw new OCSPreconditionFailedException('Nicht angemeldet');
		}
		try {
			$this->deckService->assertDeckAvailable($user);
		} catch (DeckUnavailableException $e) {
			throw new OCSPreconditionFailedException('Deck ist nicht verfügbar: ' . $e->getMessage());
		}
	}

	/**
	 * @param ?int $id the workflow being changed, `null` for a new one
	 */
	private function validate(?int $id, string $title, int $boardId, int $sourceStackId, int $targetStackId, string $triggerDate, string $notifyMode, string $notifyChannel, bool $enabled): void {
		if (trim($title) === '') {
			throw new OCSBadRequestException('Bitte einen Titel angeben.');
		}
		if ($sourceStackId === $targetStackId) {
			throw new OCSBadRequestException('Quell- und Ziel-Stapel müssen sich unterscheiden.');
		}
		if (!TriggerDate::isValid($triggerDate)) {
			throw new OCSBadRequestException('Ungültiges Datum für die Verschiebung, erlaubt sind: ' . implode(', ', TriggerDate::ALL));
		}
		if (!NotificationPolicy::isValidMode($notifyMode)) {
			throw new OCSBadRequestException('Ungültige Benachrichtigungs-Einstellung, erlaubt sind: ' . implode(', ', NotificationPolicy::MODES));
		}
		if (!NotificationPolicy::isValidChannel($notifyChannel)) {
			throw new OCSBadRequestException('Ungültiger Benachrichtigungsweg, erlaubt sind: ' . implode(', ', NotificationPolicy::CHANNELS));
		}

		// Reject references to boards or stacks that are gone (or were never
		// the user's) instead of storing a workflow that can only fail later.
		// assertDeck() ran first, so an empty list here means "not there",
		// not "Deck is unreachable".
		$this->assertDeck();
		if ($triggerDate === TriggerDate::START && !$this->deckService->supportsStartdate()) {
			throw new OCSBadRequestException('Die installierte Deck-Version kennt kein Startdatum.');
		}

		// Only boards the user owns are listed, so this also enforces the
		// owner rule. Archived boards stay listed (their workflows must stay
		// visible) but are no target for a new or changed workflow.
		$board = null;
		foreach ($this->ownedBoards() as $candidate) {
			if ($candidate['id'] === $boardId) {
				$board = $candidate;
				break;
			}
		}
		if ($board === null || $board['archived']) {
			throw new OCSBadRequestException('Das gewählte Board existiert nicht, ist archiviert oder gehört dir nicht.');
		}

		$stackIds = array_map(
			static fn (array $stack) => (int)$stack['id'],
			$this->deckService->listStacks($boardId),
		);
		if (!in_array($sourceStackId, $stackIds, true) || !in_array($targetStackId, $stackIds, true)) {
			throw new OCSBadRequestException('Der gewählte Stapel existiert auf diesem Board nicht.');
		}

		// A disabled workflow moves nothing and can close no loop; it is
		// checked again when it gets switched on, which also goes through here.
		if ($enabled) {
			$this->assertNoLoop($id, $boardId, $sourceStackId, $targetStackId);
		}
	}

	/**
	 * Rejects a workflow whose target stack leads back to its source through
	 * the board's other enabled workflows — cards would circle forever. See
	 * LoopDetector.
	 */
	private function assertNoLoop(?int $id, int $boardId, int $sourceStackId, int $targetStackId): void {
		$others = [];
		foreach ($this->workflowMapper->findAllForBoards([$boardId]) as $other) {
			if ($other->getId() !== $id && $other->getEnabled()) {
				$others[(int)$other->getId()] = $other;
			}
		}

		$path = LoopDetector::findPath(LoopDetector::edgesOf($others), $targetStackId, $sourceStackId);
		if ($path === null) {
			return;
		}

		$titles = array_map(static fn (int $otherId) => '„' . $others[$otherId]->getTitle() . '“', $path);
		throw new OCSBadRequestException(sprintf(
			'Zusammen mit %s würde dieser Workflow eine Schleife bilden, in der Karten immer wieder hin- und hergeschoben werden. Wähle einen anderen Ziel-Stapel oder deaktiviere einen der Workflows.',
			implode(', ', $titles),
		));
	}

	private function applyFields(
		Workflow $workflow,
		string $title,
		int $boardId,
		int $sourceStackId,
		int $targetStackId,
		string $triggerDate,
		string $notifyMode,
		string $notifyChannel,
		bool $enabled,
	): void {
		$workflow->setTitle($title);
		$workflow->setBoardId($boardId);
		$workflow->setSourceStackId($sourceStackId);
		$workflow->setTargetStackId($targetStackId);
		$workflow->setTriggerDate($triggerDate);
		$workflow->setNotifyMode($notifyMode);
		$workflow->setNotifyChannel($notifyChannel);
		$workflow->setEnabled($enabled);
	}
}