<?php

namespace MediaWiki\Extension\OAuth;

use Exception;
use GuzzleHttp\Psr7\ServerRequest;
use InvalidArgumentException;
use MediaWiki\Api\ApiBase;
use MediaWiki\Api\ApiMessage;
use MediaWiki\Api\Hook\ApiCheckCanExecuteHook;
use MediaWiki\Context\RequestContext;
use MediaWiki\Extension\OAuth\Backend\Consumer;
use MediaWiki\Extension\OAuth\Backend\ConsumerAcceptance;
use MediaWiki\Extension\OAuth\Backend\MWOAuthException;
use MediaWiki\Extension\OAuth\Backend\MWOAuthRequest;
use MediaWiki\Extension\OAuth\Backend\Utils;
use MediaWiki\Extension\OAuth\Repository\AccessTokenRepository;
use MediaWiki\Hook\MarkPatrolledHook;
use MediaWiki\Hook\RecentChange_saveHook;
use MediaWiki\Linker\Linker;
use MediaWiki\MediaWikiServices;
use MediaWiki\Message\Message;
use MediaWiki\RecentChanges\RecentChange;
use MediaWiki\Request\WebRequest;
use MediaWiki\Session\ImmutableSessionProviderWithCookie;
use MediaWiki\Session\SessionBackend;
use MediaWiki\Session\SessionInfo;
use MediaWiki\Session\SessionManager;
use MediaWiki\Session\UserInfo;
use MediaWiki\Title\Title;
use MediaWiki\User\User;
use MediaWiki\User\UserIdentity;
use MediaWiki\WikiMap\WikiMap;
use MWRestrictions;
use Wikimedia\Rdbms\DBError;

/**
 * Session provider for OAuth
 *
 * This is a fairly standard ImmutableSessionProviderWithCookie implementation:
 * the user identity is determined by the OAuth headers included in the
 * request. But since we want to make sure to fail the request when OAuth
 * headers are present but invalid, this takes the somewhat unusual step of
 * returning a bogus SessionInfo and then hooking ApiBeforeMain to throw a
 * fatal exception after MediaWiki is ready to handle it.
 *
 * It also takes advantage of the getAllowedUserRights() method for authz
 * purposes (limiting the rights to those included in the grant), and
 * registers some hooks to tag actions made via the provider.
 */
class SessionProvider
	extends ImmutableSessionProviderWithCookie
	implements ApiCheckCanExecuteHook, RecentChange_saveHook, MarkPatrolledHook
{

	public function __construct( array $params = [] ) {
		parent::__construct( $params );
	}

	protected function postInitSetup() {
		$hookContainer = MediaWikiServices::getInstance()->getHookContainer();

		$hookContainer->register( 'ApiCheckCanExecute', $this );
		$hookContainer->register( 'RecentChange_save', $this );
		$hookContainer->register( 'MarkPatrolled', $this );
	}

	/** @inheritDoc */
	public function provideSessionInfo( WebRequest $request ) {
		$oauthVersion = $this->getOAuthVersionFromRequest( $request );
		if ( $oauthVersion === null ) {
			// Not an OAuth request
			return null;
		}

		// OAuth is restricted to be API-only.
		if ( !defined( 'MW_API' ) && !defined( 'MW_REST_API' ) ) {
			$globalRequest = RequestContext::getMain()->getRequest();
			if ( $request !== $globalRequest ) {
				// We are looking at something other than the global request. No easy way to
				// find out the title, and showing an error should be handled in the global
				// request anyway. Bail out.
				return null;
			}
			// The global Title object is not set up yet.
			$title = Title::newFromText( $request->getText( 'title' ) );
			if ( $title && $title->isSpecial( 'OAuth' ) ) {
				// Some Special:OAuth subpages expect an OAuth request header, but process it
				// manually, not via SessionManager. We mustn't break those.
				// TODO: this can probably be limited to /token and /identify
				return null;
			}

			return $this->makeException( 'mwoauth-not-api' );
		}

		$logData = [
			'clientip' => $request->getIP(),
			'user' => false,
			'consumer' => '',
			'result' => 'fail',
		];

		$dbr = Utils::getCentralDB( DB_REPLICA );
		$access = null;
		try {
			if ( $oauthVersion === Consumer::OAUTH_VERSION_2 ) {
				$resourceServer = ResourceServer::factory();
				$accessTokenKey = $this->verifyOAuth2Request( $resourceServer, $request );
				$accessTokenRepo = new AccessTokenRepository( $this->config->get( 'CanonicalServer' ) );
				$accessId = $accessTokenRepo->getApprovalId( $accessTokenKey );
				if ( $accessId === 0 ) {
					if (
						$resourceServer->getUser()->getId() === 0 &&
						$resourceServer->getClient()->getOwnerOnly() === false
					) {
						// This tell us, with good degree of certainty, that the AT
						// was issued to a machine and represents no particular user
						$access = ConsumerAcceptance::newFromArray( [
							'id'           => null,
							'wiki'         => $resourceServer->getClient()->getWiki(),
							'userId'       => 0,
							'consumerId'   => $resourceServer->getClient()->getId(),
							'accessToken'  => '',
							'accessSecret' => '',
							'grants'       => $resourceServer->getClient()->getGrants(),
							'accepted'     => wfTimestampNow(),
							'oauth_version' => Consumer::OAUTH_VERSION_2
						] );
					}
				} else {
					$access = ConsumerAcceptance::newFromId(
						Utils::getCentralDB( DB_REPLICA ), $accessId
					);
				}
				if ( !$access ) {
					$logData['consumer'] = $resourceServer->getClient()->getConsumerKey();
					throw new MWOAuthException( 'mwoauth-oauth2-error-create-at-no-user-approval' );
				}

				// Set the scopes that are verified for this request
				$access->setField( 'grants', array_keys( $resourceServer->getScopes() ) );
			} else {
				$server = Utils::newMWOAuthServer();
				$oauthRequest = MWOAuthRequest::fromRequest( $request );
				$logData['consumer'] = $oauthRequest->getConsumerKey();
				[ , $accessToken ] = $server->verify_request( $oauthRequest );
				$accessTokenKey = $accessToken->key;
				$access = ConsumerAcceptance::newFromToken( $dbr, $accessTokenKey );
			}
		} catch ( Exception $ex ) {
			$this->logger->info( 'Bad OAuth request from {ip}', $logData + [ 'exception' => $ex ] );
			return $this->makeException( 'mwoauth-invalid-authorization', $ex->getMessage() );
		}

		$logData['user'] = Utils::getCentralUserNameFromId( $access->getUserId(), 'raw' );

		$wiki = WikiMap::getCurrentWikiId();
		// Access token is for this wiki
		if ( $access->getWiki() !== '*' && $access->getWiki() !== $wiki ) {
			$this->logger->debug( 'OAuth request for wrong wiki from user {user}', $logData );
			return $this->makeException( 'mwoauth-invalid-authorization-wrong-wiki', $wiki );
		}

		// There exists a local user
		$localUser = Utils::getLocalUserFromCentralId( $access->getUserId() );
		if ( !$localUser ) {
			$localUser = User::newFromId( 0 );
		}
		// If there is an actual approval, but user bound to it does not exist
		if ( $access->getId() > 0 && $localUser->getId() === 0 ) {
			$this->logger->debug( 'OAuth request for invalid or non-local user {user}', $logData );
			return $this->makeException( 'mwoauth-invalid-authorization-invalid-user',
				Message::rawParam( Linker::makeExternalLink(
					'https://www.mediawiki.org/wiki/Help:OAuth/Errors#E008',
					'E008',
					true
				) )
			);
		}
		if ( $localUser->isLocked() ) {
			$this->logger->debug( 'OAuth request for locked user {user}', $logData );
			return $this->makeException( 'mwoauth-invalid-authorization-blocked-user' );
		}
		if ( $this->config->get( 'BlockDisablesLogin' ) ) {
			$block = MediaWikiServices::getInstance()->getBlockManager()
				->getBlock( $localUser, null );
			if ( $block && $block->isSitewide() ) {
				$this->logger->debug( 'OAuth request for blocked user {user}', $logData );
				return $this->makeException( 'mwoauth-invalid-authorization-blocked-user' );
			}
		}

		// The consumer is approved or owned by $localUser, and is for this wiki.
		$consumer = Consumer::newFromId( $dbr, $access->getConsumerId() );
		if ( !$consumer->isUsableBy( $localUser ) ) {
			$this->logger->debug(
				'OAuth request for consumer {consumer} not approved by user {user}', $logData
			);
			return $this->makeException( 'mwoauth-invalid-authorization-not-approved',
				$consumer->getName() );
		} elseif ( $consumer->getWiki() !== '*' && $consumer->getWiki() !== $wiki ) {
			$this->logger->debug( 'OAuth request for consumer {consumer} to incorrect wiki', $logData );
			return $this->makeException( 'mwoauth-invalid-authorization-wrong-wiki', $wiki );
		}

		// Ok, use this user!
		if ( $this->sessionCookieName === null ) {
			// We're not configured to use cookies, so concatenate some of the
			// internal consumer-acceptance state to generate an ID.
			$id = $this->hashToSessionId( implode( "\n", [
				$access->getId(),
				$access->getWiki(),
				$access->getUserId(),
				$access->getConsumerId(),
				$access->getAccepted(),
				$wiki,
			] ) );
			$persisted = false;
			$forceUse = true;
		} else {
			$id = $this->getSessionIdFromCookie( $request );
			$persisted = $id !== null;
			$forceUse = false;
		}

		$logData['result'] = 'success';
		$this->logger->debug( 'OAuth request for consumer {consumer} by user {user}', $logData );

		return new SessionInfo( SessionInfo::MAX_PRIORITY, [
			'provider' => $this,
			'id' => $id,
			'userInfo' => UserInfo::newFromUser( $localUser, true ),
			'persisted' => $persisted,
			'forceUse' => $forceUse,
			'metadata' => [
				'oauthVersion' => $oauthVersion,
				'consumerId' => $consumer->getOwnerOnly() ? null : $consumer->getId(),
				'key' => $accessTokenKey,
				'rights' => MediaWikiServices::getInstance()
					->getGrantsInfo()
					->getGrantRights( $access->getGrants() ),
				'restrictions' => $consumer->getRestrictions()->toJson(),
			],
		] );
	}

	/**
	 * Determine OAuth version of the request
	 *
	 * @param WebRequest $request
	 * @return int|null if request is not using OAuth header
	 */
	private function getOAuthVersionFromRequest( WebRequest $request ) {
		if ( Utils::hasOAuthHeaders( $request ) ) {
			return Consumer::OAUTH_VERSION_1;
		}
		if ( ResourceServer::isOAuth2Request( $request ) ) {
			return Consumer::OAUTH_VERSION_2;
		}

		return null;
	}

	/**
	 * @param ResourceServer &$resourceServer
	 * @param WebRequest $request
	 * @return string
	 * @throws MWOAuthException
	 */
	private function verifyOAuth2Request( ResourceServer &$resourceServer, WebRequest $request ) {
		$request = ServerRequest::fromGlobals()->withHeader(
			'authorization',
			$request->getHeader( 'authorization' )
		);

		$response = new Response();
		$valid = false;
		$resourceServer->verify(
			$request,
			$response,
			static function ( $request, $response ) use ( &$valid ) {
				$valid = true;
			}
		);

		if ( $valid ) {
			return $resourceServer->getAccessTokenId();
		}

		throw new MWOAuthException( 'mwoauth-oauth2-invalid-access-token' );
	}

	/** @inheritDoc */
	public function preventSessionsForUser( $username ) {
		$id = Utils::getCentralIdFromUserName( $username );
		$dbw = Utils::getCentralDB( DB_PRIMARY );

		$dbw->startAtomic( __METHOD__ );
		try {
			// Remove any approvals for the user's consumers before deleting them
			$dbw->deleteJoin(
				'oauth_accepted_consumer',
				'oauth_registered_consumer',
				'oaac_consumer_id',
				'oarc_id',
				[ 'oarc_user_id' => $id ],
				__METHOD__
			);
			$dbw->newDeleteQueryBuilder()
				->deleteFrom( 'oauth_registered_consumer' )
				->where( [ 'oarc_user_id' => $id ] )
				->caller( __METHOD__ )
				->execute();

			// Remove any approvals by this user, too
			$dbw->newDeleteQueryBuilder()
				->deleteFrom( 'oauth_accepted_consumer' )
				->where( [ 'oaac_user_id' => $id ] )
				->caller( __METHOD__ )
				->execute();
		} catch ( DBError $e ) {
			$dbw->rollback( __METHOD__ );
			throw $e;
		}
		$dbw->endAtomic( __METHOD__ );
	}

	/** @inheritDoc */
	public function getVaryHeaders() {
		return [
			'Authorization' => null,
		];
	}

	/**
	 * Fetch the access data, if any, for this user-session
	 * @param UserIdentity|null $userIdentity
	 * @return array|null
	 */
	private function getSessionData( ?UserIdentity $userIdentity = null ) {
		if ( $userIdentity ) {
			$user = User::newFromIdentity( $userIdentity );
			$session = $user->getRequest()->getSession();
			if ( $session->getProvider() === $this &&
				$user->equals( $session->getUser() )
			) {
				return $session->getProviderMetadata();
			}
		} else {
			$session = SessionManager::getGlobalSession();
			if ( $session->getProvider() === $this ) {
				return $session->getProviderMetadata();
			}
		}

		return null;
	}

	/** @inheritDoc */
	public function getAllowedUserRights( SessionBackend $backend ) {
		if ( $backend->getProvider() !== $this ) {
			throw new InvalidArgumentException( 'Backend\'s provider isn\'t $this' );
		}
		$data = $backend->getProviderMetadata();
		if ( $data ) {
			return $data['rights'];
		}

		// Should never happen
		$this->logger->debug( __METHOD__ . ': No provider metadata, returning no rights allowed' );
		return [];
	}

	public function getRestrictions( ?array $data ): ?MWRestrictions {
		if ( $data && isset( $data['restrictions'] ) && is_string( $data['restrictions'] ) ) {
			try {
				return MWRestrictions::newFromJson( $data['restrictions'] );
			} catch ( \InvalidArgumentException $e ) {
				$this->logger->warning( __METHOD__ . ': Failed to parse restrictions: {restrictions}', [
					'restrictions' => $data['restrictions']
				] );
				return null;
			}
		}
		return null;
	}

	/**
	 * Disable certain API modules when used with OAuth
	 *
	 * @param ApiBase $module
	 * @param UserIdentity $userIdentity
	 * @param string|array &$message
	 * @return bool
	 */
	public function onApiCheckCanExecute( $module, $userIdentity, &$message ) {
		global $wgMWOauthDisabledApiModules;
		if ( !$this->getSessionData( $userIdentity ) ) {
			return true;
		}

		foreach ( $wgMWOauthDisabledApiModules as $badModule ) {
			if ( $module instanceof $badModule ) {
				$message = ApiMessage::create(
					[ 'mwoauth-api-module-disabled', $module->getModuleName() ],
					'mwoauth-api-module-disabled'
				);
				return false;
			}
		}

		return true;
	}

	/**
	 * Record the fact that OAuth was used for anything added to RecentChanges.
	 *
	 * @param RecentChange $rc
	 * @return bool true
	 */
	public function onRecentChange_save( $rc ) {
		$consumerId = $this->getPublicConsumerId( $rc->getPerformerIdentity() );
		if ( $consumerId !== null ) {
			$rc->addTags( Utils::getTagName( $consumerId ) );
		}
		return true;
	}

	/**
	 * Get the consumer ID of the non-owner-only OAuth consumer associated with this user, or null.
	 * @param UserIdentity|null $userIdentity
	 * @return int|null
	 */
	protected function getPublicConsumerId( ?UserIdentity $userIdentity = null ) {
		$data = $this->getSessionData( $userIdentity );
		if ( $data && isset( $data['consumerId'] ) ) {
			return $data['consumerId'];
		}
		return null;
	}

	/**
	 * Record the fact that OAuth was used for marking an existing RecentChange as patrolled.
	 * (RecentChange::doMarkPatrolled() does not use RecentChange::save()
	 * and therefore bypasses the above hook handler.)
	 *
	 * @param int $rcid
	 * @param User $user
	 * @param bool $wcOnlySysopsCanPatrol
	 * @param bool $auto
	 * @param string[] &$tags
	 *
	 * @return bool true
	 */
	public function onMarkPatrolled(
		$rcid,
		$user,
		$wcOnlySysopsCanPatrol,
		$auto,
		&$tags
	) {
		$consumerId = $this->getPublicConsumerId( $user );
		if ( $consumerId !== null ) {
			$tags[] = Utils::getTagName( $consumerId );
		}
		return true;
	}

	/**
	 * OAuth tokens already protect against CSRF. CSRF tokens are not required.
	 *
	 * @return bool true
	 */
	public function safeAgainstCsrf() {
		return true;
	}
}