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| 1 | <?php |
| 2 | /** |
| 3 | * @license GPL-2.0-or-later |
| 4 | * @file |
| 5 | */ |
| 6 | |
| 7 | namespace MediaWiki\Specials; |
| 8 | |
| 9 | use BadMethodCallException; |
| 10 | use MediaWiki\Deferred\LinksUpdate\CategoryLinksTable; |
| 11 | use MediaWiki\HTMLForm\HTMLForm; |
| 12 | use MediaWiki\SpecialPage\FormSpecialPage; |
| 13 | use MediaWiki\Status\Status; |
| 14 | use MediaWiki\Title\Title; |
| 15 | use stdClass; |
| 16 | use Wikimedia\Rdbms\IConnectionProvider; |
| 17 | use Wikimedia\Rdbms\SelectQueryBuilder; |
| 18 | use Wikimedia\Timestamp\TimestampFormat as TS; |
| 19 | |
| 20 | /** |
| 21 | * Redirect to a random page in a category |
| 22 | * |
| 23 | * @note The method used here is rather biased. It is assumed that |
| 24 | * the use of this page will be people wanting to get a random page |
| 25 | * out of a maintenance category, to fix it up. The method used by |
| 26 | * this page should return different pages in an unpredictable fashion |
| 27 | * which is hoped to be sufficient, even if some pages are selected |
| 28 | * more often than others. |
| 29 | * |
| 30 | * A more unbiased method could be achieved by adding a cl_random field |
| 31 | * to the categorylinks table. |
| 32 | * |
| 33 | * The method used here is as follows: |
| 34 | * * Find the smallest and largest timestamp in the category |
| 35 | * * Pick a random timestamp in between |
| 36 | * * Pick an offset between 0 and 30 |
| 37 | * * Get the offset'ed page that is newer than the timestamp selected |
| 38 | * The offset is meant to counter the fact the timestamps aren't usually |
| 39 | * uniformly distributed, so if things are very non-uniform at least we |
| 40 | * won't have the same page selected 99% of the time. |
| 41 | * |
| 42 | * @ingroup SpecialPage |
| 43 | * @author Brian Wolff |
| 44 | */ |
| 45 | class SpecialRandomInCategory extends FormSpecialPage { |
| 46 | /** @var string[] Extra SQL statements */ |
| 47 | protected $extra = []; |
| 48 | /** @var Title|false Title object of category */ |
| 49 | protected $category = false; |
| 50 | /** @var int Max amount to fudge randomness by */ |
| 51 | protected $maxOffset = 30; |
| 52 | /** @var int|null */ |
| 53 | private $maxTimestamp = null; |
| 54 | /** @var int|null */ |
| 55 | private $minTimestamp = null; |
| 56 | |
| 57 | public function __construct( |
| 58 | private readonly IConnectionProvider $dbProvider, |
| 59 | ) { |
| 60 | parent::__construct( 'RandomInCategory' ); |
| 61 | } |
| 62 | |
| 63 | /** |
| 64 | * Set which category to use. |
| 65 | */ |
| 66 | public function setCategory( Title $cat ) { |
| 67 | $this->category = $cat; |
| 68 | $this->maxTimestamp = null; |
| 69 | $this->minTimestamp = null; |
| 70 | } |
| 71 | |
| 72 | /** @inheritDoc */ |
| 73 | protected function getFormFields() { |
| 74 | $this->addHelpLink( 'Help:RandomInCategory' ); |
| 75 | |
| 76 | return [ |
| 77 | 'category' => [ |
| 78 | 'type' => 'title', |
| 79 | 'namespace' => NS_CATEGORY, |
| 80 | 'relative' => true, |
| 81 | 'label-message' => 'randomincategory-category', |
| 82 | 'required' => true, |
| 83 | ] |
| 84 | ]; |
| 85 | } |
| 86 | |
| 87 | /** @inheritDoc */ |
| 88 | public function requiresPost() { |
| 89 | return false; |
| 90 | } |
| 91 | |
| 92 | /** @inheritDoc */ |
| 93 | protected function getDisplayFormat() { |
| 94 | return 'ooui'; |
| 95 | } |
| 96 | |
| 97 | protected function alterForm( HTMLForm $form ) { |
| 98 | $form->setSubmitTextMsg( 'randomincategory-submit' ); |
| 99 | } |
| 100 | |
| 101 | /** @inheritDoc */ |
| 102 | protected function getSubpageField() { |
| 103 | return 'category'; |
| 104 | } |
| 105 | |
| 106 | /** @inheritDoc */ |
| 107 | public function onSubmit( array $data ) { |
| 108 | $cat = false; |
| 109 | |
| 110 | $categoryStr = $data['category']; |
| 111 | |
| 112 | if ( $categoryStr ) { |
| 113 | $cat = Title::newFromText( $categoryStr, NS_CATEGORY ); |
| 114 | } |
| 115 | |
| 116 | if ( $cat && $cat->getNamespace() !== NS_CATEGORY ) { |
| 117 | // Someone searching for something like "Wikipedia:Foo" |
| 118 | $cat = Title::makeTitleSafe( NS_CATEGORY, $categoryStr ); |
| 119 | } |
| 120 | |
| 121 | if ( $cat ) { |
| 122 | $this->setCategory( $cat ); |
| 123 | } |
| 124 | |
| 125 | if ( !$this->category && $categoryStr ) { |
| 126 | $msg = $this->msg( 'randomincategory-invalidcategory', |
| 127 | wfEscapeWikiText( $categoryStr ) ); |
| 128 | |
| 129 | return Status::newFatal( $msg ); |
| 130 | |
| 131 | } elseif ( !$this->category ) { |
| 132 | return false; // no data sent |
| 133 | } |
| 134 | |
| 135 | $title = $this->getRandomTitle(); |
| 136 | |
| 137 | if ( $title === null ) { |
| 138 | $msg = $this->msg( 'randomincategory-nopages', |
| 139 | $this->category->getText() ); |
| 140 | |
| 141 | return Status::newFatal( $msg ); |
| 142 | } |
| 143 | |
| 144 | $query = $this->getRequest()->getQueryValues(); |
| 145 | unset( $query['title'] ); |
| 146 | $this->getOutput()->redirect( $title->getFullURL( $query ) ); |
| 147 | } |
| 148 | |
| 149 | /** |
| 150 | * Choose a random title. |
| 151 | * @return Title|null Title object or null if nothing to choose from |
| 152 | */ |
| 153 | public function getRandomTitle() { |
| 154 | // Convert to float, since we do math with the random number. |
| 155 | $rand = (float)wfRandom(); |
| 156 | |
| 157 | // Given that timestamps are rather unevenly distributed, we also |
| 158 | // use an offset between 0 and 30 to make any biases less noticeable. |
| 159 | $offset = mt_rand( 0, $this->maxOffset ); |
| 160 | |
| 161 | if ( mt_rand( 0, 1 ) ) { |
| 162 | $up = true; |
| 163 | } else { |
| 164 | $up = false; |
| 165 | } |
| 166 | |
| 167 | $row = $this->selectRandomPageFromDB( $rand, $offset, $up, __METHOD__ ); |
| 168 | |
| 169 | // Try again without the timestamp offset (wrap around the end) |
| 170 | if ( !$row ) { |
| 171 | $row = $this->selectRandomPageFromDB( false, $offset, $up, __METHOD__ ); |
| 172 | } |
| 173 | |
| 174 | // Maybe the category is really small and offset too high |
| 175 | if ( !$row ) { |
| 176 | $row = $this->selectRandomPageFromDB( $rand, 0, $up, __METHOD__ ); |
| 177 | } |
| 178 | |
| 179 | // Just get the first entry. |
| 180 | if ( !$row ) { |
| 181 | $row = $this->selectRandomPageFromDB( false, 0, true, __METHOD__ ); |
| 182 | } |
| 183 | |
| 184 | if ( $row ) { |
| 185 | return Title::makeTitle( $row->page_namespace, $row->page_title ); |
| 186 | } |
| 187 | |
| 188 | return null; |
| 189 | } |
| 190 | |
| 191 | /** |
| 192 | * @note The $up parameter is supposed to counteract what would happen if there |
| 193 | * was a large gap in the distribution of cl_timestamp values. This way instead |
| 194 | * of things to the right of the gap being favoured, both sides of the gap |
| 195 | * are favoured. |
| 196 | * |
| 197 | * @param float|false $rand Random number between 0 and 1 |
| 198 | * @param int $offset Extra offset to fudge randomness |
| 199 | * @param bool $up True to get the result above the random number, false for below |
| 200 | * @return SelectQueryBuilder |
| 201 | */ |
| 202 | protected function getQueryBuilder( $rand, $offset, $up ) { |
| 203 | if ( !$this->category instanceof Title ) { |
| 204 | throw new BadMethodCallException( 'No category set' ); |
| 205 | } |
| 206 | $dbr = $this->dbProvider->getReplicaDatabase( CategoryLinksTable::VIRTUAL_DOMAIN ); |
| 207 | $queryBuilder = $dbr->newSelectQueryBuilder() |
| 208 | ->select( [ 'page_title', 'page_namespace' ] ) |
| 209 | ->from( 'categorylinks' ) |
| 210 | ->join( 'linktarget', null, 'cl_target_id = lt_id' ) |
| 211 | ->join( 'page', null, 'cl_from = page_id' ) |
| 212 | ->where( [ 'lt_title' => $this->category->getDBkey(), 'lt_namespace' => NS_CATEGORY ] ) |
| 213 | ->andWhere( $this->extra ) |
| 214 | ->orderBy( 'cl_timestamp', $up ? SelectQueryBuilder::SORT_ASC : SelectQueryBuilder::SORT_DESC ) |
| 215 | ->limit( 1 ) |
| 216 | ->offset( $offset ); |
| 217 | |
| 218 | $minClTime = $this->getTimestampOffset( $rand ); |
| 219 | if ( $minClTime ) { |
| 220 | $op = $up ? '>=' : '<='; |
| 221 | $queryBuilder->andWhere( |
| 222 | $dbr->expr( 'cl_timestamp', $op, $dbr->timestamp( $minClTime ) ) |
| 223 | ); |
| 224 | } |
| 225 | |
| 226 | return $queryBuilder; |
| 227 | } |
| 228 | |
| 229 | /** |
| 230 | * @param float|false $rand Random number between 0 and 1 |
| 231 | * @return int|false A random (unix) timestamp from the range of the category or false on failure |
| 232 | */ |
| 233 | protected function getTimestampOffset( $rand ) { |
| 234 | if ( $rand === false ) { |
| 235 | return false; |
| 236 | } |
| 237 | if ( !$this->minTimestamp || !$this->maxTimestamp ) { |
| 238 | $minAndMax = $this->getMinAndMaxForCat(); |
| 239 | if ( $minAndMax === null ) { |
| 240 | // No entries in this category. |
| 241 | return false; |
| 242 | } |
| 243 | [ $this->minTimestamp, $this->maxTimestamp ] = $minAndMax; |
| 244 | } |
| 245 | |
| 246 | $ts = ( $this->maxTimestamp - $this->minTimestamp ) * $rand + $this->minTimestamp; |
| 247 | |
| 248 | return intval( $ts ); |
| 249 | } |
| 250 | |
| 251 | /** |
| 252 | * Get the lowest and highest timestamp for a category. |
| 253 | * |
| 254 | * @return array|null The lowest and highest timestamp, or null if the category has no entries. |
| 255 | */ |
| 256 | protected function getMinAndMaxForCat() { |
| 257 | $dbr = $this->dbProvider->getReplicaDatabase( CategoryLinksTable::VIRTUAL_DOMAIN ); |
| 258 | $res = $dbr->newSelectQueryBuilder() |
| 259 | ->select( [ 'low' => 'MIN( cl_timestamp )', 'high' => 'MAX( cl_timestamp )' ] ) |
| 260 | ->from( 'categorylinks' ) |
| 261 | ->join( 'linktarget', null, 'cl_target_id = lt_id' ) |
| 262 | ->where( [ 'lt_title' => $this->category->getDBkey(), 'lt_namespace' => NS_CATEGORY ] ) |
| 263 | ->caller( __METHOD__ ) |
| 264 | ->fetchRow(); |
| 265 | |
| 266 | if ( !$res ) { |
| 267 | return null; |
| 268 | } |
| 269 | |
| 270 | return [ (int)wfTimestamp( TS::UNIX, $res->low ), (int)wfTimestamp( TS::UNIX, $res->high ) ]; |
| 271 | } |
| 272 | |
| 273 | /** |
| 274 | * @param float|false $rand A random number that is converted to a random timestamp |
| 275 | * @param int $offset A small offset to make the result seem more "random" |
| 276 | * @param bool $up Get the result above the random value |
| 277 | * @param string $fname The name of the calling method |
| 278 | * @return stdClass|false Info for the title selected. |
| 279 | */ |
| 280 | private function selectRandomPageFromDB( $rand, $offset, $up, $fname ) { |
| 281 | return $this->getQueryBuilder( $rand, $offset, $up )->caller( $fname )->fetchRow(); |
| 282 | } |
| 283 | |
| 284 | /** @inheritDoc */ |
| 285 | protected function getGroupName() { |
| 286 | return 'redirects'; |
| 287 | } |
| 288 | } |
| 289 | |
| 290 | // @codeCoverageIgnoreStart |
| 291 | /** |
| 292 | * Retain the old class name for backwards compatibility. |
| 293 | * @deprecated since 1.41 |
| 294 | */ |
| 295 | class_alias( SpecialRandomInCategory::class, 'SpecialRandomInCategory' ); |
| 296 | // @codeCoverageIgnoreEnd |