<?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
 * @since 1.35
 */

namespace Vector;

use Config;
use MediaWiki\User\UserOptionsLookup;
use User;
use WebRequest;

/**
 * Given initial dependencies, retrieve the current skin version. This class does no parsing, just
 * the lookup.
 *
 * Skin version is evaluated in the following order:
 *
 * - useskinversion URL query parameter override. See readme.
 *
 * - User preference. The User object for new accounts is updated (persisted as a user preference)
 *   by hook according to VectorDefaultSkinVersionForNewAccounts. See Hooks and skin.json. The user
 *   may then change the preference at will.
 *
 * - Site configuration default. The default is controlled by VectorDefaultSkinVersion and
 *   VectorDefaultSkinVersionForExistingAccounts based on login state. The former is used
 *   for anonymous users and as a fallback configuration, the latter is logged in users (existing
 *   accounts). See skin.json.
 *
 * @unstable
 *
 * @package Vector
 * @internal
 */
final class SkinVersionLookup {
	/**
	 * @var WebRequest
	 */
	private $request;
	/**
	 * @var User
	 */
	private $user;
	/**
	 * @var Config
	 */
	private $config;
	/**
	 * @var UserOptionsLookup
	 */
	private $userOptionsLookup;

	/**
	 * This constructor accepts all dependencies needed to obtain the skin version. The dependencies
	 * are lazily evaluated, not cached, meaning they always return the current results.
	 *
	 * @param WebRequest $request
	 * @param User $user
	 * @param Config $config
	 * @param UserOptionsLookup $userOptionsLookup
	 */
	public function __construct(
		WebRequest $request,
		User $user,
		Config $config,
		UserOptionsLookup $userOptionsLookup
	) {
		$this->request = $request;
		$this->user = $user;
		$this->config = $config;
		$this->userOptionsLookup = $userOptionsLookup;
	}

	/**
	 * Whether or not the legacy skin is being used.
	 *
	 * @return bool
	 * @throws \ConfigException
	 */
	public function isLegacy(): bool {
		return $this->getVersion() === Constants::SKIN_VERSION_LEGACY;
	}

	/**
	 * The skin version as a string. E.g., `Constants::SKIN_VERSION_LATEST`,
	 * `Constants::SKIN_VERSION_LATEST`, or maybe 'beta'. Note: it's likely someone will put arbitrary
	 * strings in the query parameter which means this function returns those strings as is.
	 *
	 * @return string
	 * @throws \ConfigException
	 */
	public function getVersion(): string {
		$migrationMode = $this->config->get( 'VectorSkinMigrationMode' );
		$useSkin = $this->request->getVal(
			Constants::QUERY_PARAM_SKIN
		);
		// In migration mode, the useskin parameter is the source of truth.
		if ( $migrationMode ) {
			if ( $useSkin ) {
				return $useSkin === Constants::SKIN_NAME_LEGACY ?
					Constants::SKIN_VERSION_LEGACY :
					Constants::SKIN_VERSION_LATEST;
			}
		}
		// [[phab:T299971]]
		if ( $useSkin === Constants::SKIN_NAME_MODERN ) {
			return Constants::SKIN_VERSION_LATEST;
		}

		// If skin key is not vector, then version should be considered legacy.

		// If skin is "Vector" invoke additional skin versioning detection.
		// Obtain the skin version from the 1) `useskinversion` URL query parameter override, 2) the
		// user preference, 3) the configured default for logged in users, 4) or the site default.
		//
		// The latter two configurations cannot be set by `Hooks::onUserGetDefaultOptions()` as user
		// sessions are unavailable at that time so it's not possible to determine whether the
		// preference is for a logged in user or an anonymous user. Since new users are known to have
		// had their user preferences initialized in `Hooks::onLocalUserCreated()`, that means all
		// subsequent requests to `User->getOption()` that do not have a preference set are either
		// existing accounts or anonymous users. Login state makes the distinction.
		$skin = $this->userOptionsLookup->getOption(
			$this->user,
			Constants::PREF_KEY_SKIN
		);

		if ( $skin === Constants::SKIN_NAME_MODERN ) {
			return Constants::SKIN_VERSION_LATEST;
		}

		$skinVersionPref = $this->userOptionsLookup->getOption(
			$this->user,
			Constants::PREF_KEY_SKIN_VERSION,
			$this->config->get(
				$this->user->isRegistered()
					? Constants::CONFIG_KEY_DEFAULT_SKIN_VERSION_FOR_EXISTING_ACCOUNTS
					: Constants::CONFIG_KEY_DEFAULT_SKIN_VERSION
			)
		);

		// If we are in migration mode...
		if ( $migrationMode ) {
			// ... we must check the skin version preference for logged in users.
			// No need to check for anons as wgDefaultSkin has already been consulted at this point.
			if (
				$this->user->isRegistered() &&
				$skin === Constants::SKIN_NAME_LEGACY &&
				$skinVersionPref === Constants::SKIN_VERSION_LATEST
			) {
				return Constants::SKIN_VERSION_LATEST;
			}
			return Constants::SKIN_VERSION_LEGACY;
		}
		return (string)$this->request->getVal(
			Constants::QUERY_PARAM_SKIN_VERSION,
			$skinVersionPref
		);
	}
}