<?php

namespace Mediawiki\Api;

use DOMDocument;
use DOMXPath;
use GuzzleHttp\Client;
use GuzzleHttp\ClientInterface;
use GuzzleHttp\Exception\RequestException;
use GuzzleHttp\Promise\PromiseInterface;
use InvalidArgumentException;
use Mediawiki\Api\Guzzle\ClientFactory;
use Psr\Http\Message\ResponseInterface;
use Psr\Log\LoggerAwareInterface;
use Psr\Log\LoggerInterface;
use Psr\Log\LogLevel;
use Psr\Log\NullLogger;
use SimpleXMLElement;

/**
 * Main class for this library
 *
 * @since 0.1
 *
 * @author Addshore
 */
class MediawikiApi implements MediawikiApiInterface, LoggerAwareInterface {

	/**
	 * @var ClientInterface|null Should be accessed through getClient
	 */
	private $client = null;

	/**
	 * @var bool|string
	 */
	private $isLoggedIn;

	/**
	 * @var MediawikiSession
	 */
	private $session;

	/**
	 * @var string
	 */
	private $version;

	/**
	 * @var LoggerInterface
	 */
	private $logger;

	/**
	 * @var string
	 */
	private $apiUrl;

	/**
	 * @since 2.0
	 *
	 * @param string $apiEndpoint e.g. https://en.wikipedia.org/w/api.php
	 *
	 * @return self returns a MediawikiApi instance using $apiEndpoint
	 */
	public static function newFromApiEndpoint( $apiEndpoint ) {
		return new self( $apiEndpoint );
	}

	/**
	 * Create a new MediawikiApi object from a URL to any page in a MediaWiki website.
	 *
	 * @since 2.0
	 * @see https://en.wikipedia.org/wiki/Really_Simple_Discovery
	 *
	 * @param string $url e.g. https://en.wikipedia.org OR https://de.wikipedia.org/wiki/Berlin
	 * @return self returns a MediawikiApi instance using the apiEndpoint provided by the RSD
	 *              file accessible on all Mediawiki pages
	 * @throws RsdException If the RSD URL could not be found in the page's HTML.
	 */
	public static function newFromPage( $url ) {
		// Set up HTTP client and HTML document.
		$tempClient = new Client( [ 'headers' => [ 'User-Agent' => 'addwiki-mediawiki-client' ] ] );
		$pageHtml = $tempClient->get( $url )->getBody();
		$pageDoc = new DOMDocument();

		// Try to load the HTML (turn off errors temporarily; most don't matter, and if they do get
		// in the way of finding the API URL, will be reported in the RsdException below).
		$internalErrors = libxml_use_internal_errors( true );
		$pageDoc->loadHTML( $pageHtml );
		$libXmlErrors = libxml_get_errors();
		libxml_use_internal_errors( $internalErrors );

		// Extract the RSD link.
		$xpath = 'head/link[@type="application/rsd+xml"][@href]';
		$link = ( new DOMXpath( $pageDoc ) )->query( $xpath );
		if ( $link->length === 0 ) {
			// Format libxml errors for display.
			$libXmlErrorStr = array_reduce( $libXmlErrors, function ( $prevErr, $err ) {
				return $prevErr . ', ' . $err->message . ' (line '.$err->line . ')';
			} );
			if ( $libXmlErrorStr ) {
				$libXmlErrorStr = "In addition, libxml had the following errors: $libXmlErrorStr";
			}
			throw new RsdException( "Unable to find RSD URL in page: $url $libXmlErrorStr" );
		}
		$rsdUrl = $link->item( 0 )->attributes->getnamedItem( 'href' )->nodeValue;

		// Then get the RSD XML, and return the API link.
		$rsdXml = new SimpleXMLElement( $tempClient->get( $rsdUrl )->getBody() );
		return self::newFromApiEndpoint( (string)$rsdXml->service->apis->api->attributes()->apiLink );
	}

	/**
	 * @param string $apiUrl The API Url
	 * @param ClientInterface|null $client Guzzle Client
	 * @param MediawikiSession|null $session Inject a custom session here
	 */
	public function __construct( $apiUrl, ClientInterface $client = null,
								 MediawikiSession $session = null ) {
		if ( !is_string( $apiUrl ) ) {
			throw new InvalidArgumentException( '$apiUrl must be a string' );
		}
		if ( $session === null ) {
			$session = new MediawikiSession( $this );
		}

		$this->apiUrl = $apiUrl;
		$this->client = $client;
		$this->session = $session;

		$this->logger = new NullLogger();
	}

	/**
	 * Get the API URL (the URL to which API requests are sent, usually ending in api.php).
	 * This is useful if you've created this object via MediawikiApi::newFromPage().
	 *
	 * @since 2.3
	 *
	 * @return string The API URL.
	 */
	public function getApiUrl() {
		return $this->apiUrl;
	}

	/**
	 * @return ClientInterface
	 */
	private function getClient() {
		if ( $this->client === null ) {
			$clientFactory = new ClientFactory();
			$clientFactory->setLogger( $this->logger );
			$this->client = $clientFactory->getClient();
		}
		return $this->client;
	}

	/**
	 * Sets a logger instance on the object
	 *
	 * @since 1.1
	 *
	 * @param LoggerInterface $logger The new Logger object.
	 *
	 * @return null
	 */
	public function setLogger( LoggerInterface $logger ) {
		$this->logger = $logger;
		$this->session->setLogger( $logger );
	}

	/**
	 * @since 2.0
	 *
	 * @param Request $request The GET request to send.
	 *
	 * @return PromiseInterface
	 *         Normally promising an array, though can be mixed (json_decode result)
	 *         Can throw UsageExceptions or RejectionExceptions
	 */
	public function getRequestAsync( Request $request ) {
		$promise = $this->getClient()->requestAsync(
			'GET',
			$this->apiUrl,
			$this->getClientRequestOptions( $request, 'query' )
		);

		return $promise->then( function ( ResponseInterface $response ) {
			return call_user_func( [ $this, 'decodeResponse' ], $response );
		} );
	}

	/**
	 * @since 2.0
	 *
	 * @param Request $request The POST request to send.
	 *
	 * @return PromiseInterface
	 *         Normally promising an array, though can be mixed (json_decode result)
	 *         Can throw UsageExceptions or RejectionExceptions
	 */
	public function postRequestAsync( Request $request ) {
		$promise = $this->getClient()->requestAsync(
			'POST',
			$this->apiUrl,
			$this->getClientRequestOptions( $request, $this->getPostRequestEncoding( $request ) )
		);

		return $promise->then( function ( ResponseInterface $response ) {
			return call_user_func( [ $this, 'decodeResponse' ], $response );
		} );
	}

	/**
	 * @since 0.2
	 *
	 * @param Request $request The GET request to send.
	 *
	 * @return mixed Normally an array
	 */
	public function getRequest( Request $request ) {
		$response = $this->getClient()->request(
			'GET',
			$this->apiUrl,
			$this->getClientRequestOptions( $request, 'query' )
		);

		return $this->decodeResponse( $response );
	}

	/**
	 * @since 0.2
	 *
	 * @param Request $request The POST request to send.
	 *
	 * @return mixed Normally an array
	 */
	public function postRequest( Request $request ) {
		$response = $this->getClient()->request(
			'POST',
			$this->apiUrl,
			$this->getClientRequestOptions( $request, $this->getPostRequestEncoding( $request ) )
		);

		return $this->decodeResponse( $response );
	}

	/**
	 * @param ResponseInterface $response
	 *
	 * @return mixed
	 * @throws UsageException
	 */
	private function decodeResponse( ResponseInterface $response ) {
		$resultArray = json_decode( $response->getBody(), true );

		$this->logWarnings( $resultArray );
		$this->throwUsageExceptions( $resultArray );

		return $resultArray;
	}

	/**
	 * @param Request $request
	 *
	 * @return string
	 */
	private function getPostRequestEncoding( Request $request ) {
		if ( $request instanceof MultipartRequest ) {
			return 'multipart';
		}
		foreach ( $request->getParams() as $value ) {
			if ( is_resource( $value ) ) {
				return 'multipart';
			}
		}
		return 'form_params';
	}

	/**
	 * @param Request $request
	 * @param string $paramsKey either 'query' or 'multipart'
	 *
	 * @throws RequestException
	 *
	 * @return array as needed by ClientInterface::get and ClientInterface::post
	 */
	private function getClientRequestOptions( Request $request, $paramsKey ) {
		$params = array_merge( $request->getParams(), [ 'format' => 'json' ] );
		if ( $paramsKey === 'multipart' ) {
			$params = $this->encodeMultipartParams( $request, $params );
		}

		return [
			$paramsKey => $params,
			'headers' => array_merge( $this->getDefaultHeaders(), $request->getHeaders() ),
		];
	}

	/**
	 * Turn the normal key-value array of request parameters into a multipart array where each
	 * parameter is a new array with a 'name' and 'contents' elements (and optionally more, if the
	 * request is a MultipartRequest).
	 *
	 * @param Request $request The request to which the parameters belong.
	 * @param string[] $params The existing parameters. Not the same as $request->getParams().
	 *
	 * @return array
	 */
	private function encodeMultipartParams( Request $request, $params ) {
		// See if there are any multipart parameters in this request.
		$multipartParams = ( $request instanceof MultipartRequest )
			? $request->getMultipartParams()
			: [];
		return array_map(
			function ( $name, $value ) use ( $multipartParams ) {
				$partParams = [
					'name' => $name,
					'contents' => $value,
				];
				if ( isset( $multipartParams[ $name ] ) ) {
					// If extra parameters have been set for this part, use them.
					$partParams = array_merge( $multipartParams[ $name ], $partParams );
				}
				return $partParams;
			},
			array_keys( $params ),
			$params
		);
	}

	/**
	 * @return array
	 */
	private function getDefaultHeaders() {
		return [
			'User-Agent' => $this->getUserAgent(),
		];
	}

	private function getUserAgent() {
		$loggedIn = $this->isLoggedin();
		if ( $loggedIn ) {
			return 'addwiki-mediawiki-client/' . $loggedIn;
		}
		return 'addwiki-mediawiki-client';
	}

	/**
	 * @param $result
	 */
	private function logWarnings( $result ) {
		if ( is_array( $result ) && array_key_exists( 'warnings', $result ) ) {
			foreach ( $result['warnings'] as $module => $warningData ) {
				// Accomodate both formatversion=2 and old-style API results
				$logPrefix = $module . ': ';
				if ( isset( $warningData['*'] ) ) {
					$this->logger->warning( $logPrefix . $warningData['*'], [ 'data' => $warningData ] );
				} else {
					$this->logger->warning( $logPrefix . $warningData['warnings'], [ 'data' => $warningData ] );
				}
			}
		}
	}

	/**
	 * @param array $result
	 *
	 * @throws UsageException
	 */
	private function throwUsageExceptions( $result ) {
		if ( is_array( $result ) && array_key_exists( 'error', $result ) ) {
			throw new UsageException(
				$result['error']['code'],
				$result['error']['info'],
				$result
			);
		}
	}

	/**
	 * @since 0.1
	 *
	 * @return bool|string false or the name of the current user
	 */
	public function isLoggedin() {
		return $this->isLoggedIn;
	}

	/**
	 * @since 0.1
	 *
	 * @param ApiUser $apiUser The ApiUser to log in as.
	 *
	 * @throws UsageException
	 * @return bool success
	 */
	public function login( ApiUser $apiUser ) {
		$this->logger->log( LogLevel::DEBUG, 'Logging in' );
		$credentials = $this->getLoginParams( $apiUser );
		$result = $this->postRequest( new SimpleRequest( 'login', $credentials ) );
		if ( $result['login']['result'] == "NeedToken" ) {
			$params = array_merge( [ 'lgtoken' => $result['login']['token'] ], $credentials );
			$result = $this->postRequest( new SimpleRequest( 'login', $params ) );
		}
		if ( $result['login']['result'] == "Success" ) {
			$this->isLoggedIn = $apiUser->getUsername();
			return true;
		}

		$this->isLoggedIn = false;
		$this->logger->log( LogLevel::DEBUG, 'Login failed.', $result );
		$this->throwLoginUsageException( $result );
		return false;
	}

	/**
	 * @param ApiUser $apiUser
	 *
	 * @return string[]
	 */
	private function getLoginParams( ApiUser $apiUser ) {
		$params = [
			'lgname' => $apiUser->getUsername(),
			'lgpassword' => $apiUser->getPassword(),
		];

		if ( !is_null( $apiUser->getDomain() ) ) {
			$params['lgdomain'] = $apiUser->getDomain();
		}
		return $params;
	}

	/**
	 * @param array $result
	 *
	 * @throws UsageException
	 */
	private function throwLoginUsageException( $result ) {
		$loginResult = $result['login']['result'];

		throw new UsageException(
			'login-' . $loginResult,
			array_key_exists( 'reason', $result['login'] )
				? $result['login']['reason']
				: 'No Reason given',
			$result
		);
	}

	/**
	 * @since 0.1
	 *
	 * @return bool success
	 */
	public function logout() {
		$this->logger->log( LogLevel::DEBUG, 'Logging out' );
		$result = $this->postRequest( new SimpleRequest( 'logout' ) );
		if ( $result === [] ) {
			$this->isLoggedIn = false;
			$this->clearTokens();
			return true;
		}
		return false;
	}

	/**
	 * @since 0.1
	 *
	 * @param string $type The token type to get.
	 *
	 * @return string
	 */
	public function getToken( $type = 'csrf' ) {
		return $this->session->getToken( $type );
	}

	/**
	 * Clear all tokens stored by the API.
	 *
	 * @since 0.1
	 */
	public function clearTokens() {
		$this->session->clearTokens();
	}

	/**
	 * @return string
	 */
	public function getVersion() {
		if ( !isset( $this->version ) ) {
			$result = $this->getRequest( new SimpleRequest( 'query', [
				'meta' => 'siteinfo',
				'continue' => '',
			] ) );
			preg_match(
				'/\d+(?:\.\d+)+/',
				$result['query']['general']['generator'],
				$versionParts
			);
			$this->version = $versionParts[0];
		}
		return $this->version;
	}

}