<?php

declare(strict_types=1);

// SPDX-FileCopyrightText: 2026 Dillard Blom
// SPDX-License-Identifier: AGPL-3.0-or-later

namespace OCA\NgBackup\Service;

use OCA\NgBackup\Backend\ExternalStorageFactory;
use OCA\NgBackup\Backend\IBackend;
use OCA\NgBackup\Backend\StorageBackend;
use OCA\NgBackup\Db\Snapshot;
use OCA\NgBackup\Db\SnapshotMapper;
use OCA\NgBackup\Db\Target;
use OCA\NgBackup\Db\TargetMapper;
use OCA\NgBackup\Repository\Repository;
use OCP\App\IAppManager;
use OCP\AppFramework\Db\DoesNotExistException;
use OCP\Files\Storage\IStorage;
use OCP\Security\ICrypto;
use OCP\Server;

/**
 * Backup targets: a files_external backend + auth mechanism + options + base path. The storage
 * object is built only while it is used; nothing is mounted. files_external is loaded for its
 * classes but its enabled/disabled state is left as the admin set it.
 */
final class TargetService {
	/** Deletion delay taken when a location's own cannot be read: nothing leaves the Bin sooner than on the old server. */
	public const LONGEST_DELETE_DELAY = 365;

	public function __construct(
		private TargetMapper $mapper,
		private KeyService $keys,
		private ICrypto $crypto,
		private IAppManager $appManager,
		private \OCA\NgBackup\Db\DbIndexCache $indexCache,
		private \OCA\NgBackup\Db\AppConfigCatalogAnchor $anchor,
		private SnapshotMapper $snapshots,
		private AlertService $alerts,
		private \OCA\NgBackup\Db\RunMapper $runs,
	) {
	}

	/** @return list<array{id:string, name:string, auth:list<array{id:string, name:string, parameters:array}>, parameters:array}> */
	public function availableBackends(): array {
		return $this->factory()->describeBackends();
	}

	/**
	 * Add a target: connect, create the repository there (or adopt an existing one made with this
	 * installation's key), then save it.
	 *
	 * @param array<string, mixed> $options
	 * @param ?callable(int, int): void $progress reading an existing repository's index: files done, and in all
	 * @return array{target: Target, created: bool}
	 */
	public function add(string $name, string $backend, string $auth, array $options, string $basePath, ?callable $progress = null, bool $repairConfig = false): array {
		$this->validateName($name);
		$this->requireUsableBackend($backend);
		$keys = $this->keys->keyRing();
		$storageBackend = $this->buildBackend($backend, $auth, $options, $basePath, !$repairConfig);
		try {
			if ($repairConfig) {
				Repository::repairConfig($storageBackend, $keys, $this->keys->wrappedKey());
			}
			if ($storageBackend->exists('config')) {
				$repo = Repository::openWithKey($storageBackend, $keys, $this->indexCache, $this->anchor, $progress);
				$created = false;
			} else {
				$repo = Repository::initWithKey($storageBackend, $keys, $this->keys->wrappedKey(), $this->anchor);
				$created = true;
			}
		} catch (\OCA\NgBackup\Repository\RepositoryException $e) {
			$otherKey = str_contains($e->getMessage(), 'different key') || str_contains($e->getMessage(), 'do not open with this key');
			if ($otherKey && $this->keyIsUnused()) {
				throw new \OCA\NgBackup\Repository\RepositoryException(rtrim($e->getMessage(), '.') . '. ' . self::UNUSED_KEY_HINT, 0, $e);
			}
			throw $e;
		}
		$this->keys->markUsed();
		$this->recordSettings($repo);

		foreach ($this->mapper->findAll() as $existing) {
			if ($existing->getRepositoryId() === $repo->id()) {
				throw new \InvalidArgumentException("This repository is already registered as '{$existing->getName()}'");
			}
		}

		$target = new Target();
		$target->setName($name);
		$target->setBackend($backend);
		$target->setAuth($auth);
		$target->setOptions($this->crypto->encrypt(json_encode($options, JSON_THROW_ON_ERROR)));
		$target->setBasePath(trim($basePath, '/'));
		$target->setRepositoryId($repo->id());
		$target->setCreatedAt(time());
		// Like the location before it: a backup scheme is usually one scheme.
		$first = $this->mapper->findAll()[0] ?? null;
		$target->setSchedule($first?->getSchedule() ?? '');
		$target->setScheduleZone($first?->getScheduleZone());
		$target->setScheduleSince(time());
		$target = $this->mapper->insert($target);
		if (!$created) {
			// Disaster recovery: occ backup:list reads this local cache, not the repository
			// directly, so a snapshot made by another installation must be backfilled here too.
			$this->adoptSnapshots($target, $repo);
		}
		return ['target' => $target, 'created' => $created];
	}

	public const UNUSED_KEY_HINT = 'The backup key of this server was never used (no location, no backup), so it can make way for the key of these backups: '
		. 'with the old server\'s recovery kit, occ backup:key:import <kit file> --replace-unused-key; without the kit, '
		. 'occ backup:target:add with the same details and --replace-unused-key (asks for a passphrase of the old server)';

	/**
	 * A key that never protected anything: no location was created or adopted with it, and the
	 * database has no location and no run (installations from before the flag existed). Only such
	 * a key may make way for the key of existing backups, e.g. after a new key was made by
	 * mistake on a server that is being restored.
	 */
	public function keyIsUnused(): bool {
		return $this->keys->isInitialized() && !$this->keys->wasUsed()
			&& $this->mapper->findAll() === [] && $this->runs->countAll() === 0;
	}

	/**
	 * occ backup:key:import on a server whose own key was never used: the kit's key takes its place.
	 *
	 * @param array<string, mixed> $kit
	 * @throws \OCA\NgBackup\Crypto\CryptoException wrong passphrase: nothing changed
	 */
	public function importKitReplacingUnusedKey(array $kit, #[\SensitiveParameter] string $passphrase): void {
		$old = $this->requireUnusedKey();
		$this->keys->importRecoveryKit($kit, $passphrase, true);
		$this->alerts->securityEvent('key_replaced', ['old' => $old, 'new' => $this->keys->fingerprint()]);
	}

	/** @return string the fingerprint of the unused key */
	private function requireUnusedKey(): string {
		if (!$this->keys->isInitialized()) {
			throw new \RuntimeException('There is no backup key here to replace');
		}
		if (!$this->keyIsUnused()) {
			throw new \RuntimeException('The backup key of this server (fingerprint ' . $this->keys->fingerprint() . ') has been used for a backup location: it is never replaced');
		}
		return $this->keys->fingerprint();
	}

	public const LOCATION_REPOSITORY = 'repository';
	public const LOCATION_DATA_WITHOUT_CONFIG = 'data-without-config';
	public const LOCATION_EMPTY = 'empty';

	/**
	 * What these settings lead to: a repository, backup data whose config is gone, or nothing
	 * of NG Backup. Creates nothing.
	 *
	 * @return self::LOCATION_*
	 */
	public function locationState(string $backend, string $auth, array $options, string $basePath): string {
		$this->requireUsableBackend($backend);
		$storage = $this->buildBackend($backend, $auth, $options, $basePath, false);
		if ($storage->exists('config')) {
			return self::LOCATION_REPOSITORY;
		}
		return Repository::holdsData($storage) ? self::LOCATION_DATA_WITHOUT_CONFIG : self::LOCATION_EMPTY;
	}

	/**
	 * Disaster recovery without the recovery kit, on an installation without a backup key: take
	 * the key from the location's config with one of its passphrases, then add the location as
	 * usual. The key is only kept when it really is the one the repository was made with.
	 * With $replaceUnusedKey, a key this server has but never used makes way (keyIsUnused()).
	 *
	 * @param array<string, mixed> $options
	 * @param ?callable(int, int): void $progress
	 * @return array{target: Target, created: bool, deleteDelayDays: ?int, settingsUnreadable: bool} the deletion delay the location had stored, if any, and whether its settings could not be read
	 * @throws \OCA\NgBackup\Crypto\CryptoException wrong passphrase
	 */
	public function addWithPassphrase(string $name, string $backend, string $auth, array $options, string $basePath,
		#[\SensitiveParameter] string $passphrase, ?callable $progress = null, bool $replaceUnusedKey = false): array {
		$old = null;
		if ($replaceUnusedKey) {
			$old = $this->requireUnusedKey();
		} elseif ($this->keys->isInitialized()) {
			throw new \RuntimeException('A backup key already exists here');
		}
		$this->validateName($name);
		$this->requireUsableBackend($backend);
		$storageBackend = $this->buildBackend($backend, $auth, $options, $basePath, false);
		if (!$storageBackend->exists('config')) {
			throw new \InvalidArgumentException("No NG Backup repository found in folder '" . trim($basePath, '/') . "'");
		}
		$wrapped = Repository::wrappedKeyAt($storageBackend);
		$keys = \OCA\NgBackup\Crypto\KeyRing::unwrapAny($wrapped, $passphrase);
		if (!Repository::madeWithKey($storageBackend, $keys)) {
			throw new \RuntimeException('The key in the config at this location does not open its backups: the config is damaged or was replaced. Only the recovery kit can help now: occ backup:key:import <kit file>, then this command again.');
		}
		$settings = Repository::settingsAt($storageBackend, $keys);
		$stored = $settings['delete_delay_days'] ?? null;
		$delay = is_int($stored) && $stored >= 1 && $stored <= 365 ? $stored : null;
		// Settings that are there but cannot be read, or hold no valid delay (also none at all): the old server's delay
		// is unknown, so take the longest one; a shorter guess could empty the Bin too soon.
		$unknown = ($settings['unreadable'] ?? false) === true || ($settings !== [] && $delay === null);
		$this->keys->adoptKey($keys, $wrapped, $delay ?? ($unknown ? self::LONGEST_DELETE_DELAY : null), $replaceUnusedKey);
		if ($old !== null) {
			$this->alerts->securityEvent('key_replaced', ['old' => $old, 'new' => $this->keys->fingerprint()]);
		}
		return $this->add($name, $backend, $auth, $options, $basePath, $progress) + ['deleteDelayDays' => $delay, 'settingsUnreadable' => $unknown];
	}

	/** A passphrase change that missed this location (offline at the time) reaches it now. A failure is tried again at the next backup. */
	public function catchUpWrappedKey(Target $target, Repository $repo): void {
		if (!$this->keys->wrappedKeyPending($target->getId())) {
			return;
		}
		try {
			$repo->updateWrappedKey($this->keys->wrappedKey());
			$this->keys->setWrappedKeyPending($target->getId(), false);
		} catch (\Throwable $e) {
			Server::get(\Psr\Log\LoggerInterface::class)->warning('NG Backup: the last passphrase change still does not reach ' . $target->getName()
				. ' (it keeps the previous passphrases); tried again at its next backup: ' . $e->getMessage(), ['exception' => $e]);
		}
	}

	/** Seal the settings fixed at installation on the location, once. A failure is tried again at the next backup. */
	public function recordSettings(Repository $repo): void {
		try {
			$repo->recordSettings(['delete_delay_days' => $this->keys->deleteDelayDays()]);
		} catch (\Throwable) {
		}
	}

	/**
	 * Change how an existing location is reached (credentials, host, folder, even the connection
	 * type) or its name. The new settings must lead to the same repository: the history stays
	 * and a typo cannot silently start a new, empty repository. A null option value keeps the
	 * stored one, so the web interface never has to send stored passwords back.
	 *
	 * @param array<string, mixed> $options
	 */
	public function update(Target $target, string $name, string $backend, string $auth, array $options, string $basePath): Target {
		$this->validateName($name, $target->getId());
		$this->requireUsableBackend($backend);
		$stored = $this->options($target);
		foreach ($options as $key => $value) {
			if ($value === null) {
				if (array_key_exists($key, $stored)) {
					$options[$key] = $stored[$key];
				} else {
					unset($options[$key]);
				}
			}
		}
		// Do not create the folder: a typo in the path must not leave an empty folder behind.
		$storageBackend = $this->buildBackend($backend, $auth, $options, $basePath, false);
		if (!$storageBackend->exists('config')) {
			if (!$storageBackend->canConnect()) {
				throw new \InvalidArgumentException('Cannot connect with these settings. Check the host, user name and password');
			}
			throw new \InvalidArgumentException("No NG Backup repository found in folder '" . trim($basePath, '/') . "'. To start an empty repository, add a new location instead");
		}
		$repo = Repository::openWithKey($storageBackend, $this->keys->keyRing(), $this->indexCache, $this->anchor);
		if ($target->getRepositoryId() !== null && $repo->id() !== $target->getRepositoryId()) {
			throw new \InvalidArgumentException('These settings lead to a different repository than the one of this location');
		}
		$target->setName($name);
		$target->setBackend($backend);
		$target->setAuth($auth);
		$target->setOptions($this->crypto->encrypt(json_encode($options, JSON_THROW_ON_ERROR)));
		$target->setBasePath(trim($basePath, '/'));
		return $this->mapper->update($target);
	}

	/**
	 * The stored options for an edit form: password-type values are replaced by null, which
	 * update() reads as "keep the stored value".
	 *
	 * @return array<string, mixed>
	 */
	public function editableOptions(Target $target): array {
		$secret = [];
		foreach ($this->availableBackends() as $b) {
			if ($b['id'] !== $target->getBackend()) {
				continue;
			}
			$params = $b['parameters'];
			foreach ($b['auth'] as $a) {
				if ($a['id'] === $target->getAuth()) {
					$params += $a['parameters'];
				}
			}
			foreach ($params as $key => $p) {
				if (($p['type'] ?? 0) === 2) {
					$secret[$key] = true;
				}
			}
		}
		$options = $this->options($target);
		foreach ($options as $key => $value) {
			if (isset($secret[$key])) {
				$options[$key] = null;
			}
		}
		return $options;
	}

	private function validateName(string $name, ?int $ownId = null): void {
		if (!preg_match('/^[A-Za-z0-9][A-Za-z0-9 _.-]{0,63}$/', $name)) {
			throw new \InvalidArgumentException('Name: letters, digits, space, _ . - (max 64)');
		}
		try {
			$other = $this->mapper->findByName($name);
		} catch (DoesNotExistException) {
			return;
		}
		if ($other->getId() !== $ownId) {
			throw new \InvalidArgumentException("A target named '$name' already exists");
		}
	}

	private function requireUsableBackend(string $backend): void {
		// Without the native extension files_external falls back to the smbclient binary, which
		// registers fine but cannot seek: the first backup then fails with "Seek failed". Refuse
		// up front instead of letting the admin find out from a failed run.
		if ($backend === 'smb' && !extension_loaded('smbclient')) {
			throw new \InvalidArgumentException('The SMB backend needs the PHP smbclient extension (pecl install smbclient); the smbclient binary alone cannot seek and every backup would fail');
		}
	}

	/**
	 * A target's options are encrypted with Nextcloud's own instance secret (ICrypto), not
	 * ng_backup's key, so changing that secret (occ backup:restore:full merging config.php)
	 * would otherwise leave every target permanently undecryptable. Call $applySecretChange
	 * (which must be the only thing that changes the secret) through here instead: every
	 * target's options are decrypted first, then re-encrypted under whatever secret is active
	 * once $applySecretChange returns.
	 */
	public function reencryptOptionsAround(callable $applySecretChange): mixed {
		$plain = [];
		foreach ($this->mapper->findAll() as $target) {
			$plain[$target->getId()] = $this->options($target);
		}
		$result = $applySecretChange();
		foreach ($this->mapper->findAll() as $target) {
			if (!isset($plain[$target->getId()])) {
				continue; // added by $applySecretChange itself; nothing to re-encrypt
			}
			$target->setOptions($this->crypto->encrypt(json_encode($plain[$target->getId()], JSON_THROW_ON_ERROR)));
			$this->mapper->update($target);
		}
		return $result;
	}

	/** Update the local copy of a snapshot's note or pin, if the snapshot is listed here at all. */
	public function syncSnapshot(Target $target, string $snapshotId, ?string $note = null, ?bool $pinned = null): void {
		try {
			$s = $this->snapshots->findOne($target->getId(), $snapshotId);
		} catch (DoesNotExistException) {
			return;
		}
		if ($note !== null) {
			$s->setNote($note !== '' ? $note : null);
		}
		if ($pinned !== null) {
			$s->setPinned($pinned);
		}
		$this->snapshots->update($s);
	}

	private function adoptSnapshots(Target $target, Repository $repo): void {
		$notes = $repo->snapshotNotes();
		$pinned = array_flip($repo->pinnedSnapshots());
		foreach ($repo->listSnapshots() as $snapshotId) {
			try {
				$this->snapshots->findOne($target->getId(), $snapshotId);
				continue; // already known locally
			} catch (DoesNotExistException) {
			}
			// One unreadable/corrupt snapshot must not stop the rest of the location's
			// snapshots from being backfilled, nor abort adding the target itself.
			try {
				$meta = $repo->snapshotMeta($snapshotId);
				$s = new Snapshot();
				$s->setTargetId($target->getId());
				$s->setSnapshotId($snapshotId);
				$s->setKind((string)($meta['kind'] ?? 'full'));
				$s->setLabel(($meta['label'] ?? '') !== '' ? $meta['label'] : null);
				$s->setCreatedAt((int)strtotime((string)($meta['time'] ?? 'now')));
				$s->setFiles((int)($meta['stats']['files'] ?? 0));
				$s->setBytes((int)($meta['stats']['bytes'] ?? 0));
				$s->setNote($notes[$snapshotId] ?? null);
				$s->setPinned(isset($pinned[$snapshotId]));
				$this->snapshots->insert($s);
			} catch (\Throwable $e) {
				Server::get(\Psr\Log\LoggerInterface::class)->warning('NG Backup: snapshot ' . $snapshotId . ' on ' . $target->getName() . ' not listed: ' . $e->getMessage(), ['exception' => $e]);
			}
		}
	}

	/** @return list<Target> */
	public function list(): array {
		return $this->mapper->findAll();
	}

	public function get(string $nameOrId): Target {
		try {
			return ctype_digit($nameOrId) ? $this->mapper->find((int)$nameOrId) : $this->mapper->findByName($nameOrId);
		} catch (DoesNotExistException) {
			throw new \InvalidArgumentException("No such location: $nameOrId");
		}
	}

	/** Size limit for the data stored on this location (null = none). */
	/**
	 * @param string $schedule see LocationSchedule
	 * @throws \InvalidArgumentException
	 */
	public function setSchedule(Target $target, string $schedule, string $zone): Target {
		if (!Schedule::validZone($zone)) {
			throw new \InvalidArgumentException('Unknown time zone: ' . $zone);
		}
		$new = LocationSchedule::normalize($schedule);
		$turnedOff = $new === '' && (string)$target->getSchedule() !== '';
		if ($new === (string)$target->getSchedule() && $zone === $target->getScheduleZone()) {
			// Saved again unchanged: a moment that already passed still gets its backup
			return $target;
		}
		$target->setSchedule($new);
		$target->setScheduleZone($zone);
		$target->setScheduleSince(time());
		$target = $this->mapper->update($target);
		if ($turnedOff) {
			$this->alerts->securityEvent('schedule_off', ['target' => $target->getName()]);
		}
		return $target;
	}

	public function setMaxBytes(Target $target, ?int $maxBytes): Target {
		$target->setMaxBytes($maxBytes);
		return $this->mapper->update($target);
	}

	public function setAppendOnly(Target $target, bool $appendOnly): Target {
		$target->setAppendOnly($appendOnly);
		return $this->mapper->update($target);
	}

	/** Remove the target from NG Backup. The backups on the target itself are not touched. */
	public function remove(Target $target): void {
		$this->mapper->delete($target);
		// The location is gone now: tidying up must not fail the removal, or the caller would skip
		// the removal event and a retry would no longer find the location
		$this->tidyUp($target, fn () => $this->keys->setWrappedKeyPending($target->getId(), false));
		// The cached index of its repository is only of use while a location points at it
		$this->tidyUp($target, function () use ($target): void {
			$repositoryId = $target->getRepositoryId();
			if ($repositoryId !== null && !array_filter($this->list(), fn (Target $t) => $t->getRepositoryId() === $repositoryId)) {
				$this->indexCache->forget($repositoryId);
			}
		});
	}

	/** One tidy-up step after a removal: a failure is logged (if even that works) and never thrown. */
	private function tidyUp(Target $target, callable $step): void {
		try {
			$step();
		} catch (\Throwable $e) {
			try {
				Server::get(\Psr\Log\LoggerInterface::class)->warning('NG Backup: location ' . $target->getName()
					. ' removed, tidying up after it failed: ' . $e->getMessage(), ['exception' => $e]);
			} catch (\Throwable) {
				// nothing left to tell it to
			}
		}
	}

	public function backend(Target $target): IBackend {
		return $this->buildBackend($target->getBackend(), $target->getAuth(), $this->options($target), $target->getBasePath());
	}

	public function repository(Target $target): Repository {
		$repo = Repository::openWithKey($this->backend($target), $this->keys->keyRing(), $this->indexCache, $this->anchor);
		if ($target->getRepositoryId() !== null && $repo->id() !== $target->getRepositoryId()) {
			throw new \RuntimeException('The target now contains a different repository than when it was added');
		}
		$repo->setMaxBytes($target->getMaxBytes());
		return $repo;
	}

	/** @return array<string, mixed> */
	public function options(Target $target): array {
		return json_decode($this->crypto->decrypt($target->getOptions()), true, 512, JSON_THROW_ON_ERROR);
	}

	private function buildBackend(string $backend, string $auth, array $options, string $basePath, bool $createBase = true): StorageBackend {
		$create = fn (): IStorage => $this->factory()->create($backend, $auth, $options);
		$storage = new StorageBackend($create(), $basePath, $createBase, $create);
		$storage->readAheadConnections = Server::get(\OCP\IAppConfig::class)
			->getValueInt('ng_backup', 'restore_sftp_connections', \OCA\NgBackup\Backend\SftpRangeFetcher::DEFAULT_CONNECTIONS);
		return $storage;
	}

	private ?ExternalStorageFactory $factory = null;

	/**
	 * files_external's connection code, without changing the app's state:
	 * - enabled: it is booted by Nextcloud; use its own BackendService;
	 * - disabled: do NOT boot it (booting registers its mount provider and listeners, which use
	 *   its database tables; on installations where it was never enabled those do not exist).
	 *   Only its classes are loaded, and a private BackendService gets its backends and auth
	 *   mechanisms from its Application class.
	 */
	private function factory(): ExternalStorageFactory {
		if ($this->factory !== null) {
			return $this->factory;
		}
		if ($this->appManager->isEnabledForAnyone('files_external')) {
			$this->appManager->loadApp('files_external');
			return $this->factory = new ExternalStorageFactory(Server::get(\OCA\Files_External\Service\BackendService::class));
		}
		if (!class_exists(\OCA\Files_External\AppInfo\Application::class)) {
			$path = $this->appManager->getAppPath('files_external');
			require_once $path . '/composer/autoload.php';
		}
		$service = new \OCA\Files_External\Service\BackendService(
			Server::get(\OCP\IAppConfig::class), Server::get(\Psr\Log\LoggerInterface::class));
		$app = new \OCA\Files_External\AppInfo\Application();
		$service->registerBackendProvider($app);
		$service->registerAuthMechanismProvider($app);
		return $this->factory = new ExternalStorageFactory($service);
	}
}