<?php
/**
 * Base classes for actions done on pages.
 *
 * 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
 *
 * @file
 */

/**
 * @defgroup Actions Action done on pages
 */

/**
 * Actions are things which can be done to pages (edit, delete, rollback, etc).  They
 * are distinct from Special Pages because an action must apply to exactly one page.
 *
 * To add an action in an extension, create a subclass of Action, and add the key to
 * $wgActions.  There is also the deprecated UnknownAction hook
 *
 * Actions generally fall into two groups: the show-a-form-then-do-something-with-the-input
 * format (protect, delete, move, etc), and the just-do-something format (watch, rollback,
 * patrol, etc). The FormAction and FormlessAction classes represent these two groups.
 */
abstract class Action {

	/**
	 * Page on which we're performing the action
	 * @since 1.17
	 * @var WikiPage|Article|ImagePage|CategoryPage|Page $page
	 */
	protected $page;

	/**
	 * IContextSource if specified; otherwise we'll use the Context from the Page
	 * @since 1.17
	 * @var IContextSource $context
	 */
	protected $context;

	/**
	 * The fields used to create the HTMLForm
	 * @since 1.17
	 * @var array $fields
	 */
	protected $fields;

	/**
	 * Get the Action subclass which should be used to handle this action, false if
	 * the action is disabled, or null if it's not recognised
	 * @param string $action
	 * @param array $overrides
	 * @return bool|null|string|callable|Action
	 */
	final private static function getClass( $action, array $overrides ) {
		global $wgActions;
		$action = strtolower( $action );

		if ( !isset( $wgActions[$action] ) ) {
			return null;
		}

		if ( $wgActions[$action] === false ) {
			return false;
		} elseif ( $wgActions[$action] === true && isset( $overrides[$action] ) ) {
			return $overrides[$action];
		} elseif ( $wgActions[$action] === true ) {
			return ucfirst( $action ) . 'Action';
		} else {
			return $wgActions[$action];
		}
	}

	/**
	 * Get an appropriate Action subclass for the given action
	 * @since 1.17
	 * @param string $action
	 * @param Page $page
	 * @param IContextSource|null $context
	 * @return Action|bool|null False if the action is disabled, null
	 *     if it is not recognised
	 */
	final public static function factory( $action, Page $page, IContextSource $context = null ) {
		$classOrCallable = self::getClass( $action, $page->getActionOverrides() );

		if ( is_string( $classOrCallable ) ) {
			if ( !class_exists( $classOrCallable ) ) {
				return false;
			}
			$obj = new $classOrCallable( $page, $context );
			return $obj;
		}

		if ( is_callable( $classOrCallable ) ) {
			return call_user_func_array( $classOrCallable, [ $page, $context ] );
		}

		return $classOrCallable;
	}

	/**
	 * Get the action that will be executed, not necessarily the one passed
	 * passed through the "action" request parameter. Actions disabled in
	 * $wgActions will be replaced by "nosuchaction".
	 *
	 * @since 1.19
	 * @param IContextSource $context
	 * @return string Action name
	 */
	final public static function getActionName( IContextSource $context ) {
		global $wgActions;

		$request = $context->getRequest();
		$actionName = $request->getVal( 'action', 'view' );

		// Check for disabled actions
		if ( isset( $wgActions[$actionName] ) && $wgActions[$actionName] === false ) {
			$actionName = 'nosuchaction';
		}

		// Workaround for bug #20966: inability of IE to provide an action dependent
		// on which submit button is clicked.
		if ( $actionName === 'historysubmit' ) {
			if ( $request->getBool( 'revisiondelete' ) ) {
				$actionName = 'revisiondelete';
			} elseif ( $request->getBool( 'editchangetags' ) ) {
				$actionName = 'editchangetags';
			} else {
				$actionName = 'view';
			}
		} elseif ( $actionName == 'editredlink' ) {
			$actionName = 'edit';
		}

		// Trying to get a WikiPage for NS_SPECIAL etc. will result
		// in WikiPage::factory throwing "Invalid or virtual namespace -1 given."
		// For SpecialPages et al, default to action=view.
		if ( !$context->canUseWikiPage() ) {
			return 'view';
		}

		$action = Action::factory( $actionName, $context->getWikiPage(), $context );
		if ( $action instanceof Action ) {
			return $action->getName();
		}

		return 'nosuchaction';
	}

	/**
	 * Check if a given action is recognised, even if it's disabled
	 * @since 1.17
	 *
	 * @param string $name Name of an action
	 * @return bool
	 */
	final public static function exists( $name ) {
		return self::getClass( $name, [] ) !== null;
	}

	/**
	 * Get the IContextSource in use here
	 * @since 1.17
	 * @return IContextSource
	 */
	final public function getContext() {
		if ( $this->context instanceof IContextSource ) {
			return $this->context;
		} elseif ( $this->page instanceof Article ) {
			// NOTE: $this->page can be a WikiPage, which does not have a context.
			wfDebug( __METHOD__ . ": no context known, falling back to Article's context.\n" );
			return $this->page->getContext();
		}

		wfWarn( __METHOD__ . ': no context known, falling back to RequestContext::getMain().' );
		return RequestContext::getMain();
	}

	/**
	 * Get the WebRequest being used for this instance
	 * @since 1.17
	 *
	 * @return WebRequest
	 */
	final public function getRequest() {
		return $this->getContext()->getRequest();
	}

	/**
	 * Get the OutputPage being used for this instance
	 * @since 1.17
	 *
	 * @return OutputPage
	 */
	final public function getOutput() {
		return $this->getContext()->getOutput();
	}

	/**
	 * Shortcut to get the User being used for this instance
	 * @since 1.17
	 *
	 * @return User
	 */
	final public function getUser() {
		return $this->getContext()->getUser();
	}

	/**
	 * Shortcut to get the Skin being used for this instance
	 * @since 1.17
	 *
	 * @return Skin
	 */
	final public function getSkin() {
		return $this->getContext()->getSkin();
	}

	/**
	 * Shortcut to get the user Language being used for this instance
	 *
	 * @return Language
	 */
	final public function getLanguage() {
		return $this->getContext()->getLanguage();
	}

	/**
	 * Shortcut to get the Title object from the page
	 * @since 1.17
	 *
	 * @return Title
	 */
	final public function getTitle() {
		return $this->page->getTitle();
	}

	/**
	 * Get a Message object with context set
	 * Parameters are the same as wfMessage()
	 *
	 * @return Message
	 */
	final public function msg() {
		$params = func_get_args();
		return call_user_func_array( [ $this->getContext(), 'msg' ], $params );
	}

	/**
	 * Constructor.
	 *
	 * Only public since 1.21
	 *
	 * @param Page $page
	 * @param IContextSource|null $context
	 */
	public function __construct( Page $page, IContextSource $context = null ) {
		if ( $context === null ) {
			wfWarn( __METHOD__ . ' called without providing a Context object.' );
			// NOTE: We could try to initialize $context using $page->getContext(),
			//      if $page is an Article. That however seems to not work seamlessly.
		}

		$this->page = $page;
		$this->context = $context;
	}

	/**
	 * Return the name of the action this object responds to
	 * @since 1.17
	 *
	 * @return string Lowercase name
	 */
	abstract public function getName();

	/**
	 * Get the permission required to perform this action.  Often, but not always,
	 * the same as the action name
	 * @since 1.17
	 *
	 * @return string|null
	 */
	public function getRestriction() {
		return null;
	}

	/**
	 * Checks if the given user (identified by an object) can perform this action.  Can be
	 * overridden by sub-classes with more complicated permissions schemes.  Failures here
	 * must throw subclasses of ErrorPageError
	 * @since 1.17
	 *
	 * @param User $user The user to check, or null to use the context user
	 * @throws UserBlockedError|ReadOnlyError|PermissionsError
	 */
	protected function checkCanExecute( User $user ) {
		$right = $this->getRestriction();
		if ( $right !== null ) {
			$errors = $this->getTitle()->getUserPermissionsErrors( $right, $user );
			if ( count( $errors ) ) {
				throw new PermissionsError( $right, $errors );
			}
		}

		if ( $this->requiresUnblock() && $user->isBlocked() ) {
			$block = $user->getBlock();
			throw new UserBlockedError( $block );
		}

		// This should be checked at the end so that the user won't think the
		// error is only temporary when he also don't have the rights to execute
		// this action
		if ( $this->requiresWrite() && wfReadOnly() ) {
			throw new ReadOnlyError();
		}
	}

	/**
	 * Whether this action requires the wiki not to be locked
	 * @since 1.17
	 *
	 * @return bool
	 */
	public function requiresWrite() {
		return true;
	}

	/**
	 * Whether this action can still be executed by a blocked user
	 * @since 1.17
	 *
	 * @return bool
	 */
	public function requiresUnblock() {
		return true;
	}

	/**
	 * Set output headers for noindexing etc.  This function will not be called through
	 * the execute() entry point, so only put UI-related stuff in here.
	 * @since 1.17
	 */
	protected function setHeaders() {
		$out = $this->getOutput();
		$out->setRobotPolicy( "noindex,nofollow" );
		$out->setPageTitle( $this->getPageTitle() );
		$out->setSubtitle( $this->getDescription() );
		$out->setArticleRelated( true );
	}

	/**
	 * Returns the name that goes in the \<h1\> page title
	 *
	 * @return string
	 */
	protected function getPageTitle() {
		return $this->getTitle()->getPrefixedText();
	}

	/**
	 * Returns the description that goes below the \<h1\> tag
	 * @since 1.17
	 *
	 * @return string HTML
	 */
	protected function getDescription() {
		return $this->msg( strtolower( $this->getName() ) )->escaped();
	}

	/**
	 * Adds help link with an icon via page indicators.
	 * Link target can be overridden by a local message containing a wikilink:
	 * the message key is: lowercase action name + '-helppage'.
	 * @param string $to Target MediaWiki.org page title or encoded URL.
	 * @param bool $overrideBaseUrl Whether $url is a full URL, to avoid MW.o.
	 * @since 1.25
	 */
	public function addHelpLink( $to, $overrideBaseUrl = false ) {
		global $wgContLang;
		$msg = wfMessage( $wgContLang->lc(
			Action::getActionName( $this->getContext() )
			) . '-helppage' );

		if ( !$msg->isDisabled() ) {
			$helpUrl = Skin::makeUrl( $msg->plain() );
			$this->getOutput()->addHelpLink( $helpUrl, true );
		} else {
			$this->getOutput()->addHelpLink( $to, $overrideBaseUrl );
		}
	}

	/**
	 * The main action entry point.  Do all output for display and send it to the context
	 * output.  Do not use globals $wgOut, $wgRequest, etc, in implementations; use
	 * $this->getOutput(), etc.
	 * @since 1.17
	 *
	 * @throws ErrorPageError
	 */
	abstract public function show();

	/**
	 * Call wfTransactionalTimeLimit() if this request was POSTed
	 * @since 1.26
	 */
	protected function useTransactionalTimeLimit() {
		if ( $this->getRequest()->wasPosted() ) {
			wfTransactionalTimeLimit();
		}
	}

	/**
	 * Indicates whether this action may perform database writes
	 * @return bool
	 * @since 1.27
	 */
	public function doesWrites() {
		return false;
	}
}
