<?php
/**
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 */
namespace MediaWiki\Extension\AbuseFilter;

use MediaWiki\Api\ApiRawMessage;
use MediaWiki\CommentStore\CommentStoreComment;
use MediaWiki\Content\JsonContent;
use MediaWiki\Json\FormatJson;
use MediaWiki\Message\Message;
use MediaWiki\Page\WikiPageFactory;
use MediaWiki\Permissions\Authority;
use MediaWiki\Revision\RevisionLookup;
use MediaWiki\Revision\RevisionRecord;
use MediaWiki\Revision\SlotRecord;
use MediaWiki\Title\TitleValue;
use MediaWiki\User\UserFactory;
use MediaWiki\User\UserIdentity;
use MediaWiki\Utils\UrlUtils;
use RecentChange;
use StatusValue;
use Wikimedia\ObjectCache\BagOStuff;
use Wikimedia\Rdbms\DBAccessObjectUtils;
use Wikimedia\Rdbms\IDBAccessObject;

/**
 * Hold and update information about blocked external domains
 *
 * @ingroup SpecialPage
 */
class BlockedDomainStorage implements IDBAccessObject {
	public const SERVICE_NAME = 'AbuseFilterBlockedDomainStorage';
	public const TARGET_PAGE = 'BlockedExternalDomains.json';

	private RevisionLookup $revisionLookup;
	private BagOStuff $cache;
	private UserFactory $userFactory;
	private WikiPageFactory $wikiPageFactory;
	private UrlUtils $urlUtils;

	/**
	 * @param BagOStuff $cache Local-server caching
	 * @param RevisionLookup $revisionLookup
	 * @param UserFactory $userFactory
	 * @param WikiPageFactory $wikiPageFactory
	 * @param UrlUtils $urlUtils
	 */
	public function __construct(
		BagOStuff $cache,
		RevisionLookup $revisionLookup,
		UserFactory $userFactory,
		WikiPageFactory $wikiPageFactory,
		UrlUtils $urlUtils
	) {
		$this->cache = $cache;
		$this->revisionLookup = $revisionLookup;
		$this->userFactory = $userFactory;
		$this->wikiPageFactory = $wikiPageFactory;
		$this->urlUtils = $urlUtils;
	}

	/**
	 * @return string
	 */
	private function makeCacheKey() {
		return $this->cache->makeKey( 'abusefilter-blocked-domains' );
	}

	/**
	 * Load the configuration page, with optional local-server caching.
	 *
	 * @param int $flags bit field, see IDBAccessObject::READ_XXX
	 * @return StatusValue The content of the configuration page (as JSON
	 *   data in PHP-native format), or a StatusValue on error.
	 */
	public function loadConfig( int $flags = 0 ): StatusValue {
		if ( DBAccessObjectUtils::hasFlags( $flags, IDBAccessObject::READ_LATEST ) ) {
			return $this->fetchConfig( $flags );
		}

		// Load configuration from APCU
		return $this->cache->getWithSetCallback(
			$this->makeCacheKey(),
			BagOStuff::TTL_MINUTE * 5,
			function ( &$ttl ) use ( $flags ) {
				$result = $this->fetchConfig( $flags );
				if ( !$result->isGood() ) {
					// error should not be cached
					$ttl = BagOStuff::TTL_UNCACHEABLE;
				}
				return $result;
			}
		);
	}

	/**
	 * Load the computed domain blocklist
	 *
	 * @return array<string,true> Flipped for performance reasons
	 */
	public function loadComputed(): array {
		return $this->cache->getWithSetCallback(
			$this->cache->makeKey( 'abusefilter-blocked-domains-computed' ),
			BagOStuff::TTL_MINUTE * 5,
			function () {
				$status = $this->loadConfig();
				if ( !$status->isGood() ) {
					return [];
				}
				$computedDomains = [];
				foreach ( $status->getValue() as $domain ) {
					if ( !( $domain['domain'] ?? null ) ) {
						continue;
					}
					$validatedDomain = $this->validateDomain( $domain['domain'] );
					if ( $validatedDomain ) {
						// It should be a map, benchmark at https://phabricator.wikimedia.org/P48956
						$computedDomains[$validatedDomain] = true;
					}
				}
				return $computedDomains;
			}
		);
	}

	/**
	 * Validate an input domain
	 *
	 * @param string|null $domain Domain such as foo.wikipedia.org
	 * @return string|false Parsed domain, or false otherwise
	 */
	public function validateDomain( $domain ) {
		if ( !$domain ) {
			return false;
		}

		$domain = trim( $domain );
		if ( !str_contains( $domain, '//' ) ) {
			$domain = 'https://' . $domain;
		}

		$parsedUrl = $this->urlUtils->parse( $domain );
		// Parse url returns a valid URL for "foo"
		if ( !$parsedUrl || !str_contains( $parsedUrl['host'], '.' ) ) {
			return false;
		}
		return $parsedUrl['host'];
	}

	/**
	 * Fetch the contents of the configuration page, without caching.
	 *
	 * The result is not validated with a config validator.
	 *
	 * @param int $flags bit field, see IDBAccessObject::READ_XXX; do NOT pass READ_UNCACHED
	 * @return StatusValue Status object, with the configuration (as JSON data) on success.
	 */
	private function fetchConfig( int $flags ): StatusValue {
		$revision = $this->revisionLookup->getRevisionByTitle( $this->getBlockedDomainPage(), 0, $flags );
		if ( !$revision ) {
			// The configuration page does not exist. Pretend it does not configure anything
			// specific (failure mode and empty-page behaviors are equal).
			return StatusValue::newGood( [] );
		}
		$content = $revision->getContent( SlotRecord::MAIN );
		if ( !$content instanceof JsonContent ) {
			return StatusValue::newFatal( new ApiRawMessage(
				'The configuration title has no content or is not JSON content.',
				'newcomer-tasks-configuration-loader-content-error' ) );
		}

		return FormatJson::parse( $content->getText(), FormatJson::FORCE_ASSOC );
	}

	/**
	 * This doesn't do validation.
	 *
	 * @param string $domain domain to be blocked
	 * @param string $notes User provided notes
	 * @param Authority|UserIdentity $user Performer
	 *
	 * @return RevisionRecord|null Null on failure
	 */
	public function addDomain( string $domain, string $notes, $user ): ?RevisionRecord {
		$content = $this->fetchLatestConfig();
		if ( $content === null ) {
			return null;
		}
		$content[] = [ 'domain' => $domain, 'notes' => $notes, 'addedBy' => $user->getName() ];
		$comment = Message::newFromSpecifier( 'abusefilter-blocked-domains-domain-added-comment' )
			->params( $domain, $notes )
			->plain();
		return $this->saveContent( $content, $user, $comment );
	}

	/**
	 * This doesn't do validation
	 *
	 * @param string $domain domain to be removed from the blocked list
	 * @param string $notes User provided notes
	 * @param Authority|UserIdentity $user Performer
	 *
	 * @return RevisionRecord|null Null on failure
	 */
	public function removeDomain( string $domain, string $notes, $user ): ?RevisionRecord {
		$content = $this->fetchLatestConfig();
		if ( $content === null ) {
			return null;
		}
		foreach ( $content as $key => $value ) {
			if ( ( $value['domain'] ?? '' ) == $domain ) {
				unset( $content[$key] );
			}
		}
		$comment = Message::newFromSpecifier( 'abusefilter-blocked-domains-domain-removed-comment' )
			->params( $domain, $notes )
			->plain();
		return $this->saveContent( array_values( $content ), $user, $comment );
	}

	/**
	 * @return array[]|null Empty array when the page doesn't exist, null on failure
	 */
	private function fetchLatestConfig(): ?array {
		$configPage = $this->getBlockedDomainPage();
		$revision = $this->revisionLookup->getRevisionByTitle( $configPage, 0, IDBAccessObject::READ_LATEST );
		if ( !$revision ) {
			return [];
		}

		$revContent = $revision->getContent( SlotRecord::MAIN );
		if ( $revContent instanceof JsonContent ) {
			$status = FormatJson::parse( $revContent->getText(), FormatJson::FORCE_ASSOC );
			if ( $status->isOK() ) {
				return $status->getValue();
			}
		}

		return null;
	}

	/**
	 * Save the provided content into the page
	 *
	 * @param array[] $content To be turned into JSON
	 * @param Authority|UserIdentity $user Performer
	 * @param string $comment Save comment
	 *
	 * @return RevisionRecord|null
	 */
	private function saveContent( array $content, $user, string $comment ): ?RevisionRecord {
		$configPage = $this->getBlockedDomainPage();
		$page = $this->wikiPageFactory->newFromLinkTarget( $configPage );
		$updater = $page->newPageUpdater( $user );
		$updater->setContent( SlotRecord::MAIN, new JsonContent( FormatJson::encode( $content ) ) );

		if ( $this->userFactory->newFromUserIdentity( $user )->isAllowed( 'autopatrol' ) ) {
			$updater->setRcPatrolStatus( RecentChange::PRC_AUTOPATROLLED );
		}

		return $updater->saveRevision(
			CommentStoreComment::newUnsavedComment( $comment )
		);
	}

	/**
	 * @return TitleValue TitleValue of the config JSON page
	 */
	private function getBlockedDomainPage(): TitleValue {
		return new TitleValue( NS_MEDIAWIKI, self::TARGET_PAGE );
	}
}