includes/Pager.php

   1 <?php
   2 /**
   3  * Efficient paging for SQL queries.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Pager
  22  */
  23
  24 /**
  25  * @defgroup Pager Pager
  26  */
  27
  28 /**
  29  * Basic pager interface.
  30  * @ingroup Pager
  31  */
  32 interface Pager {
  33         function getNavigationBar();
  34         function getBody();
  35 }
  36
  37 /**
  38  * IndexPager is an efficient pager which uses a (roughly unique) index in the
  39  * data set to implement paging, rather than a "LIMIT offset,limit" clause.
  40  * In MySQL, such a limit/offset clause requires counting through the
  41  * specified number of offset rows to find the desired data, which can be
  42  * expensive for large offsets.
  43  *
  44  * ReverseChronologicalPager is a child class of the abstract IndexPager, and
  45  * contains  some formatting and display code which is specific to the use of
  46  * timestamps as  indexes. Here is a synopsis of its operation:
  47  *
  48  *    * The query is specified by the offset, limit and direction (dir)
  49  *      parameters, in addition to any subclass-specific parameters.
  50  *    * The offset is the non-inclusive start of the DB query. A row with an
  51  *      index value equal to the offset will never be shown.
  52  *    * The query may either be done backwards, where the rows are returned by
  53  *      the database in the opposite order to which they are displayed to the
  54  *      user, or forwards. This is specified by the "dir" parameter, dir=prev
  55  *      means backwards, anything else means forwards. The offset value
  56  *      specifies the start of the database result set, which may be either
  57  *      the start or end of the displayed data set. This allows "previous"
  58  *      links to be implemented without knowledge of the index value at the
  59  *      start of the previous page.
  60  *    * An additional row beyond the user-specified limit is always requested.
  61  *      This allows us to tell whether we should display a "next" link in the
  62  *      case of forwards mode, or a "previous" link in the case of backwards
  63  *      mode. Determining whether to display the other link (the one for the
  64  *      page before the start of the database result set) can be done
  65  *      heuristically by examining the offset.
  66  *
  67  *    * An empty offset indicates that the offset condition should be omitted
  68  *      from the query. This naturally produces either the first page or the
  69  *      last page depending on the dir parameter.
  70  *
  71  *  Subclassing the pager to implement concrete functionality should be fairly
  72  *  simple, please see the examples in HistoryPage.php and
  73  *  SpecialBlockList.php. You just need to override formatRow(),
  74  *  getQueryInfo() and getIndexField(). Don't forget to call the parent
  75  *  constructor if you override it.
  76  *
  77  * @ingroup Pager
  78  */
  79 abstract class IndexPager extends ContextSource implements Pager {
  80         public $mRequest;
  81         public $mLimitsShown = array( 20, 50, 100, 250, 500 );
  82         public $mDefaultLimit = 50;
  83         public $mOffset, $mLimit;
  84         public $mQueryDone = false;
  85         public $mDb;
  86         public $mPastTheEndRow;
  87
  88         /**
  89          * The index to actually be used for ordering. This is a single column,
  90          * for one ordering, even if multiple orderings are supported.
  91          */
  92         protected $mIndexField;
  93         /**
  94          * An array of secondary columns to order by. These fields are not part of the offset.
  95          * This is a column list for one ordering, even if multiple orderings are supported.
  96          */
  97         protected $mExtraSortFields;
  98         /** For pages that support multiple types of ordering, which one to use.
  99          */
 100         protected $mOrderType;
 101         /**
 102          * $mDefaultDirection gives the direction to use when sorting results:
 103          * false for ascending, true for descending.  If $mIsBackwards is set, we
 104          * start from the opposite end, but we still sort the page itself according
 105          * to $mDefaultDirection.  E.g., if $mDefaultDirection is false but we're
 106          * going backwards, we'll display the last page of results, but the last
 107          * result will be at the bottom, not the top.
 108          *
 109          * Like $mIndexField, $mDefaultDirection will be a single value even if the
 110          * class supports multiple default directions for different order types.
 111          */
 112         public $mDefaultDirection;
 113         public $mIsBackwards;
 114
 115         /** True if the current result set is the first one */
 116         public $mIsFirst;
 117         public $mIsLast;
 118
 119         protected $mLastShown, $mFirstShown, $mPastTheEndIndex, $mDefaultQuery, $mNavigationBar;
 120
 121         /**
 122          * Whether to include the offset in the query
 123          */
 124         protected $mIncludeOffset = false;
 125
 126         /**
 127          * Result object for the query. Warning: seek before use.
 128          *
 129          * @var ResultWrapper
 130          */
 131         public $mResult;
 132
 133         public function __construct( IContextSource $context = null ) {
 134                 if ( $context ) {
 135                         $this->setContext( $context );
 136                 }
 137
 138                 $this->mRequest = $this->getRequest();
 139
 140                 # NB: the offset is quoted, not validated. It is treated as an
 141                 # arbitrary string to support the widest variety of index types. Be
 142                 # careful outputting it into HTML!
 143                 $this->mOffset = $this->mRequest->getText( 'offset' );
 144
 145                 # Use consistent behavior for the limit options
 146                 $this->mDefaultLimit = intval( $this->getUser()->getOption( 'rclimit' ) );
 147                 list( $this->mLimit, /* $offset */ ) = $this->mRequest->getLimitOffset();
 148
 149                 $this->mIsBackwards = ( $this->mRequest->getVal( 'dir' ) == 'prev' );
 150                 $this->mDb = wfGetDB( DB_SLAVE );
 151
 152                 $index = $this->getIndexField(); // column to sort on
 153                 $extraSort = $this->getExtraSortFields(); // extra columns to sort on for query planning
 154                 $order = $this->mRequest->getVal( 'order' );
 155                 if( is_array( $index ) && isset( $index[$order] ) ) {
 156                         $this->mOrderType = $order;
 157                         $this->mIndexField = $index[$order];
 158                         $this->mExtraSortFields = isset( $extraSort[$order] )
 159                                 ? (array)$extraSort[$order]
 160                                 : array();
 161                 } elseif( is_array( $index ) ) {
 162                         # First element is the default
 163                         reset( $index );
 164                         list( $this->mOrderType, $this->mIndexField ) = each( $index );
 165                         $this->mExtraSortFields = isset( $extraSort[$this->mOrderType] )
 166                                 ? (array)$extraSort[$this->mOrderType]
 167                                 : array();
 168                 } else {
 169                         # $index is not an array
 170                         $this->mOrderType = null;
 171                         $this->mIndexField = $index;
 172                         $this->mExtraSortFields = (array)$extraSort;
 173                 }
 174
 175                 if( !isset( $this->mDefaultDirection ) ) {
 176                         $dir = $this->getDefaultDirections();
 177                         $this->mDefaultDirection = is_array( $dir )
 178                                 ? $dir[$this->mOrderType]
 179                                 : $dir;
 180                 }
 181         }
 182
 183         /**
 184          * Get the Database object in use
 185          *
 186          * @return DatabaseBase
 187          */
 188         public function getDatabase() {
 189                 return $this->mDb;
 190         }
 191
 192         /**
 193          * Do the query, using information from the object context. This function
 194          * has been kept minimal to make it overridable if necessary, to allow for
 195          * result sets formed from multiple DB queries.
 196          */
 197         public function doQuery() {
 198                 # Use the child class name for profiling
 199                 $fname = __METHOD__ . ' (' . get_class( $this ) . ')';
 200                 wfProfileIn( $fname );
 201
 202                 $descending = ( $this->mIsBackwards == $this->mDefaultDirection );
 203                 # Plus an extra row so that we can tell the "next" link should be shown
 204                 $queryLimit = $this->mLimit + 1;
 205
 206                 $this->mResult = $this->reallyDoQuery(
 207                         $this->mOffset,
 208                         $queryLimit,
 209                         $descending
 210                 );
 211
 212                 $this->extractResultInfo( $this->mOffset, $queryLimit, $this->mResult );
 213                 $this->mQueryDone = true;
 214
 215                 $this->preprocessResults( $this->mResult );
 216                 $this->mResult->rewind(); // Paranoia
 217
 218                 wfProfileOut( $fname );
 219         }
 220
 221         /**
 222          * @return ResultWrapper The result wrapper.
 223          */
 224         function getResult() {
 225                 return $this->mResult;
 226         }
 227
 228         /**
 229          * Set the offset from an other source than the request
 230          *
 231          * @param $offset Int|String
 232          */
 233         function setOffset( $offset ) {
 234                 $this->mOffset = $offset;
 235         }
 236         /**
 237          * Set the limit from an other source than the request
 238          *
 239          * @param $limit Int|String
 240          */
 241         function setLimit( $limit ) {
 242                 $this->mLimit = $limit;
 243         }
 244
 245         /**
 246          * Set whether a row matching exactly the offset should be also included
 247          * in the result or not. By default this is not the case, but when the
 248          * offset is user-supplied this might be wanted.
 249          *
 250          * @param $include bool
 251          */
 252         public function setIncludeOffset( $include ) {
 253                 $this->mIncludeOffset = $include;
 254         }
 255
 256         /**
 257          * Extract some useful data from the result object for use by
 258          * the navigation bar, put it into $this
 259          *
 260          * @param $offset String: index offset, inclusive
 261          * @param $limit Integer: exact query limit
 262          * @param $res ResultWrapper
 263          */
 264         function extractResultInfo( $offset, $limit, ResultWrapper $res ) {
 265                 $numRows = $res->numRows();
 266                 if ( $numRows ) {
 267                         # Remove any table prefix from index field
 268                         $parts = explode( '.', $this->mIndexField );
 269                         $indexColumn = end( $parts );
 270
 271                         $row = $res->fetchRow();
 272                         $firstIndex = $row[$indexColumn];
 273
 274                         # Discard the extra result row if there is one
 275                         if ( $numRows > $this->mLimit && $numRows > 1 ) {
 276                                 $res->seek( $numRows - 1 );
 277                                 $this->mPastTheEndRow = $res->fetchObject();
 278                                 $indexField = $this->mIndexField;
 279                                 $this->mPastTheEndIndex = $this->mPastTheEndRow->$indexField;
 280                                 $res->seek( $numRows - 2 );
 281                                 $row = $res->fetchRow();
 282                                 $lastIndex = $row[$indexColumn];
 283                         } else {
 284                                 $this->mPastTheEndRow = null;
 285                                 # Setting indexes to an empty string means that they will be
 286                                 # omitted if they would otherwise appear in URLs. It just so
 287                                 # happens that this  is the right thing to do in the standard
 288                                 # UI, in all the relevant cases.
 289                                 $this->mPastTheEndIndex = '';
 290                                 $res->seek( $numRows - 1 );
 291                                 $row = $res->fetchRow();
 292                                 $lastIndex = $row[$indexColumn];
 293                         }
 294                 } else {
 295                         $firstIndex = '';
 296                         $lastIndex = '';
 297                         $this->mPastTheEndRow = null;
 298                         $this->mPastTheEndIndex = '';
 299                 }
 300
 301                 if ( $this->mIsBackwards ) {
 302                         $this->mIsFirst = ( $numRows < $limit );
 303                         $this->mIsLast = ( $offset == '' );
 304                         $this->mLastShown = $firstIndex;
 305                         $this->mFirstShown = $lastIndex;
 306                 } else {
 307                         $this->mIsFirst = ( $offset == '' );
 308                         $this->mIsLast = ( $numRows < $limit );
 309                         $this->mLastShown = $lastIndex;
 310                         $this->mFirstShown = $firstIndex;
 311                 }
 312         }
 313
 314         /**
 315          * Get some text to go in brackets in the "function name" part of the SQL comment
 316          *
 317          * @return String
 318          */
 319         function getSqlComment() {
 320                 return get_class( $this );
 321         }
 322
 323         /**
 324          * Do a query with specified parameters, rather than using the object
 325          * context
 326          *
 327          * @param $offset String: index offset, inclusive
 328          * @param $limit Integer: exact query limit
 329          * @param $descending Boolean: query direction, false for ascending, true for descending
 330          * @return ResultWrapper
 331          */
 332         public function reallyDoQuery( $offset, $limit, $descending ) {
 333                 list( $tables, $fields, $conds, $fname, $options, $join_conds ) = $this->buildQueryInfo( $offset, $limit, $descending );
 334                 return $this->mDb->select( $tables, $fields, $conds, $fname, $options, $join_conds );
 335         }
 336
 337         /**
 338          * Build variables to use by the database wrapper.
 339          *
 340          * @param $offset String: index offset, inclusive
 341          * @param $limit Integer: exact query limit
 342          * @param $descending Boolean: query direction, false for ascending, true for descending
 343          * @return array
 344          */
 345         protected function buildQueryInfo( $offset, $limit, $descending ) {
 346                 $fname = __METHOD__ . ' (' . $this->getSqlComment() . ')';
 347                 $info = $this->getQueryInfo();
 348                 $tables = $info['tables'];
 349                 $fields = $info['fields'];
 350                 $conds = isset( $info['conds'] ) ? $info['conds'] : array();
 351                 $options = isset( $info['options'] ) ? $info['options'] : array();
 352                 $join_conds = isset( $info['join_conds'] ) ? $info['join_conds'] : array();
 353                 $sortColumns = array_merge( array( $this->mIndexField ), $this->mExtraSortFields );
 354                 if ( $descending ) {
 355                         $options['ORDER BY'] = $sortColumns;
 356                         $operator = $this->mIncludeOffset ? '>=' : '>';
 357                 } else {
 358                         $orderBy = array();
 359                         foreach ( $sortColumns as $col ) {
 360                                 $orderBy[] = $col . ' DESC';
 361                         }
 362                         $options['ORDER BY'] = $orderBy;
 363                         $operator = $this->mIncludeOffset ? '<=' : '<';
 364                 }
 365                 if ( $offset != '' ) {
 366                         $conds[] = $this->mIndexField . $operator . $this->mDb->addQuotes( $offset );
 367                 }
 368                 $options['LIMIT'] = intval( $limit );
 369                 return array( $tables, $fields, $conds, $fname, $options, $join_conds );
 370         }
 371
 372         /**
 373          * Pre-process results; useful for performing batch existence checks, etc.
 374          *
 375          * @param $result ResultWrapper
 376          */
 377         protected function preprocessResults( $result ) {}
 378
 379         /**
 380          * Get the formatted result list. Calls getStartBody(), formatRow() and
 381          * getEndBody(), concatenates the results and returns them.
 382          *
 383          * @return String
 384          */
 385         public function getBody() {
 386                 if ( !$this->mQueryDone ) {
 387                         $this->doQuery();
 388                 }
 389
 390                 if ( $this->mResult->numRows() ) {
 391                         # Do any special query batches before display
 392                         $this->doBatchLookups();
 393                 }
 394
 395                 # Don't use any extra rows returned by the query
 396                 $numRows = min( $this->mResult->numRows(), $this->mLimit );
 397
 398                 $s = $this->getStartBody();
 399                 if ( $numRows ) {
 400                         if ( $this->mIsBackwards ) {
 401                                 for ( $i = $numRows - 1; $i >= 0; $i-- ) {
 402                                         $this->mResult->seek( $i );
 403                                         $row = $this->mResult->fetchObject();
 404                                         $s .= $this->formatRow( $row );
 405                                 }
 406                         } else {
 407                                 $this->mResult->seek( 0 );
 408                                 for ( $i = 0; $i < $numRows; $i++ ) {
 409                                         $row = $this->mResult->fetchObject();
 410                                         $s .= $this->formatRow( $row );
 411                                 }
 412                         }
 413                 } else {
 414                         $s .= $this->getEmptyBody();
 415                 }
 416                 $s .= $this->getEndBody();
 417                 return $s;
 418         }
 419
 420         /**
 421          * Make a self-link
 422          *
 423          * @param $text String: text displayed on the link
 424          * @param $query Array: associative array of paramter to be in the query string
 425          * @param $type String: value of the "rel" attribute
 426          *
 427          * @return String: HTML fragment
 428          */
 429         function makeLink( $text, array $query = null, $type = null ) {
 430                 if ( $query === null ) {
 431                         return $text;
 432                 }
 433
 434                 $attrs = array();
 435                 if( in_array( $type, array( 'first', 'prev', 'next', 'last' ) ) ) {
 436                         # HTML5 rel attributes
 437                         $attrs['rel'] = $type;
 438                 }
 439
 440                 if( $type ) {
 441                         $attrs['class'] = "mw-{$type}link";
 442                 }
 443
 444                 return Linker::linkKnown(
 445                         $this->getTitle(),
 446                         $text,
 447                         $attrs,
 448                         $query + $this->getDefaultQuery()
 449                 );
 450         }
 451
 452         /**
 453          * Called from getBody(), before getStartBody() is called and
 454          * after doQuery() was called. This will be called only if there
 455          * are rows in the result set.
 456          *
 457          * @return void
 458          */
 459         protected function doBatchLookups() {}
 460
 461         /**
 462          * Hook into getBody(), allows text to be inserted at the start. This
 463          * will be called even if there are no rows in the result set.
 464          *
 465          * @return String
 466          */
 467         protected function getStartBody() {
 468                 return '';
 469         }
 470
 471         /**
 472          * Hook into getBody() for the end of the list
 473          *
 474          * @return String
 475          */
 476         protected function getEndBody() {
 477                 return '';
 478         }
 479
 480         /**
 481          * Hook into getBody(), for the bit between the start and the
 482          * end when there are no rows
 483          *
 484          * @return String
 485          */
 486         protected function getEmptyBody() {
 487                 return '';
 488         }
 489
 490         /**
 491          * Get an array of query parameters that should be put into self-links.
 492          * By default, all parameters passed in the URL are used, except for a
 493          * short blacklist.
 494          *
 495          * @return array Associative array
 496          */
 497         function getDefaultQuery() {
 498                 if ( !isset( $this->mDefaultQuery ) ) {
 499                         $this->mDefaultQuery = $this->getRequest()->getQueryValues();
 500                         unset( $this->mDefaultQuery['title'] );
 501                         unset( $this->mDefaultQuery['dir'] );
 502                         unset( $this->mDefaultQuery['offset'] );
 503                         unset( $this->mDefaultQuery['limit'] );
 504                         unset( $this->mDefaultQuery['order'] );
 505                         unset( $this->mDefaultQuery['month'] );
 506                         unset( $this->mDefaultQuery['year'] );
 507                 }
 508                 return $this->mDefaultQuery;
 509         }
 510
 511         /**
 512          * Get the number of rows in the result set
 513          *
 514          * @return Integer
 515          */
 516         function getNumRows() {
 517                 if ( !$this->mQueryDone ) {
 518                         $this->doQuery();
 519                 }
 520                 return $this->mResult->numRows();
 521         }
 522
 523         /**
 524          * Get a URL query array for the prev, next, first and last links.
 525          *
 526          * @return Array
 527          */
 528         function getPagingQueries() {
 529                 if ( !$this->mQueryDone ) {
 530                         $this->doQuery();
 531                 }
 532
 533                 # Don't announce the limit everywhere if it's the default
 534                 $urlLimit = $this->mLimit == $this->mDefaultLimit ? null : $this->mLimit;
 535
 536                 if ( $this->mIsFirst ) {
 537                         $prev = false;
 538                         $first = false;
 539                 } else {
 540                         $prev = array(
 541                                 'dir' => 'prev',
 542                                 'offset' => $this->mFirstShown,
 543                                 'limit' => $urlLimit
 544                         );
 545                         $first = array( 'limit' => $urlLimit );
 546                 }
 547                 if ( $this->mIsLast ) {
 548                         $next = false;
 549                         $last = false;
 550                 } else {
 551                         $next = array( 'offset' => $this->mLastShown, 'limit' => $urlLimit );
 552                         $last = array( 'dir' => 'prev', 'limit' => $urlLimit );
 553                 }
 554                 return array(
 555                         'prev' => $prev,
 556                         'next' => $next,
 557                         'first' => $first,
 558                         'last' => $last
 559                 );
 560         }
 561
 562         /**
 563          * Returns whether to show the "navigation bar"
 564          *
 565          * @return Boolean
 566          */
 567         function isNavigationBarShown() {
 568                 if ( !$this->mQueryDone ) {
 569                         $this->doQuery();
 570                 }
 571                 // Hide navigation by default if there is nothing to page
 572                 return !($this->mIsFirst && $this->mIsLast);
 573         }
 574
 575         /**
 576          * Get paging links. If a link is disabled, the item from $disabledTexts
 577          * will be used. If there is no such item, the unlinked text from
 578          * $linkTexts will be used. Both $linkTexts and $disabledTexts are arrays
 579          * of HTML.
 580          *
 581          * @param $linkTexts Array
 582          * @param $disabledTexts Array
 583          * @return Array
 584          */
 585         function getPagingLinks( $linkTexts, $disabledTexts = array() ) {
 586                 $queries = $this->getPagingQueries();
 587                 $links = array();
 588
 589                 foreach ( $queries as $type => $query ) {
 590                         if ( $query !== false ) {
 591                                 $links[$type] = $this->makeLink(
 592                                         $linkTexts[$type],
 593                                         $queries[$type],
 594                                         $type
 595                                 );
 596                         } elseif ( isset( $disabledTexts[$type] ) ) {
 597                                 $links[$type] = $disabledTexts[$type];
 598                         } else {
 599                                 $links[$type] = $linkTexts[$type];
 600                         }
 601                 }
 602
 603                 return $links;
 604         }
 605
 606         function getLimitLinks() {
 607                 $links = array();
 608                 if ( $this->mIsBackwards ) {
 609                         $offset = $this->mPastTheEndIndex;
 610                 } else {
 611                         $offset = $this->mOffset;
 612                 }
 613                 foreach ( $this->mLimitsShown as $limit ) {
 614                         $links[] = $this->makeLink(
 615                                 $this->getLanguage()->formatNum( $limit ),
 616                                 array( 'offset' => $offset, 'limit' => $limit ),
 617                                 'num'
 618                         );
 619                 }
 620                 return $links;
 621         }
 622
 623         /**
 624          * Abstract formatting function. This should return an HTML string
 625          * representing the result row $row. Rows will be concatenated and
 626          * returned by getBody()
 627          *
 628          * @param $row Object: database row
 629          * @return String
 630          */
 631         abstract function formatRow( $row );
 632
 633         /**
 634          * This function should be overridden to provide all parameters
 635          * needed for the main paged query. It returns an associative
 636          * array with the following elements:
 637          *    tables => Table(s) for passing to Database::select()
 638          *    fields => Field(s) for passing to Database::select(), may be *
 639          *    conds => WHERE conditions
 640          *    options => option array
 641          *    join_conds => JOIN conditions
 642          *
 643          * @return Array
 644          */
 645         abstract function getQueryInfo();
 646
 647         /**
 648          * This function should be overridden to return the name of the index fi-
 649          * eld.  If the pager supports multiple orders, it may return an array of
 650          * 'querykey' => 'indexfield' pairs, so that a request with &count=querykey
 651          * will use indexfield to sort.  In this case, the first returned key is
 652          * the default.
 653          *
 654          * Needless to say, it's really not a good idea to use a non-unique index
 655          * for this!  That won't page right.
 656          *
 657          * @return string|Array
 658          */
 659         abstract function getIndexField();
 660
 661         /**
 662          * This function should be overridden to return the names of secondary columns
 663          * to order by in addition to the column in getIndexField(). These fields will
 664          * not be used in the pager offset or in any links for users.
 665          *
 666          * If getIndexField() returns an array of 'querykey' => 'indexfield' pairs then
 667          * this must return a corresponding array of 'querykey' => array( fields...) pairs
 668          * in order for a request with &count=querykey to use array( fields...) to sort.
 669          *
 670          * This is useful for pagers that GROUP BY a unique column (say page_id)
 671          * and ORDER BY another (say page_len). Using GROUP BY and ORDER BY both on
 672          * page_len,page_id avoids temp tables (given a page_len index). This would
 673          * also work if page_id was non-unique but we had a page_len,page_id index.
 674          *
 675          * @return Array
 676          */
 677         protected function getExtraSortFields() { return array(); }
 678
 679         /**
 680          * Return the default sorting direction: false for ascending, true for de-
 681          * scending.  You can also have an associative array of ordertype => dir,
 682          * if multiple order types are supported.  In this case getIndexField()
 683          * must return an array, and the keys of that must exactly match the keys
 684          * of this.
 685          *
 686          * For backward compatibility, this method's return value will be ignored
 687          * if $this->mDefaultDirection is already set when the constructor is
 688          * called, for instance if it's statically initialized.  In that case the
 689          * value of that variable (which must be a boolean) will be used.
 690          *
 691          * Note that despite its name, this does not return the value of the
 692          * $this->mDefaultDirection member variable.  That's the default for this
 693          * particular instantiation, which is a single value.  This is the set of
 694          * all defaults for the class.
 695          *
 696          * @return Boolean
 697          */
 698         protected function getDefaultDirections() { return false; }
 699 }
 700
 701
 702 /**
 703  * IndexPager with an alphabetic list and a formatted navigation bar
 704  * @ingroup Pager
 705  */
 706 abstract class AlphabeticPager extends IndexPager {
 707
 708         /**
 709          * Shamelessly stolen bits from ReverseChronologicalPager,
 710          * didn't want to do class magic as may be still revamped
 711          *
 712          * @return String HTML
 713          */
 714         function getNavigationBar() {
 715                 if ( !$this->isNavigationBarShown() ) {
 716                         return '';
 717                 }
 718
 719                 if( isset( $this->mNavigationBar ) ) {
 720                         return $this->mNavigationBar;
 721                 }
 722
 723                 $linkTexts = array(
 724                         'prev' => $this->msg( 'prevn' )->numParams( $this->mLimit )->escaped(),
 725                         'next' => $this->msg( 'nextn' )->numParams( $this->mLimit )->escaped(),
 726                         'first' => $this->msg( 'page_first' )->escaped(),
 727                         'last' => $this->msg( 'page_last' )->escaped()
 728                 );
 729
 730                 $lang = $this->getLanguage();
 731
 732                 $pagingLinks = $this->getPagingLinks( $linkTexts );
 733                 $limitLinks = $this->getLimitLinks();
 734                 $limits = $lang->pipeList( $limitLinks );
 735
 736                 $this->mNavigationBar = $this->msg( 'parentheses' )->rawParams(
 737                         $lang->pipeList( array( $pagingLinks['first'],
 738                         $pagingLinks['last'] ) ) )->escaped() . " " .
 739                         $this->msg( 'viewprevnext' )->rawParams( $pagingLinks['prev'],
 740                                 $pagingLinks['next'], $limits )->escaped();
 741
 742                 if( !is_array( $this->getIndexField() ) ) {
 743                         # Early return to avoid undue nesting
 744                         return $this->mNavigationBar;
 745                 }
 746
 747                 $extra = '';
 748                 $first = true;
 749                 $msgs = $this->getOrderTypeMessages();
 750                 foreach( array_keys( $msgs ) as $order ) {
 751                         if( $first ) {
 752                                 $first = false;
 753                         } else {
 754                                 $extra .= $this->msg( 'pipe-separator' )->escaped();
 755                         }
 756
 757                         if( $order == $this->mOrderType ) {
 758                                 $extra .= $this->msg( $msgs[$order] )->escaped();
 759                         } else {
 760                                 $extra .= $this->makeLink(
 761                                         $this->msg( $msgs[$order] )->escaped(),
 762                                         array( 'order' => $order )
 763                                 );
 764                         }
 765                 }
 766
 767                 if( $extra !== '' ) {
 768                         $extra = ' ' . $this->msg( 'parentheses' )->rawParams( $extra )->escaped();
 769                         $this->mNavigationBar .= $extra;
 770                 }
 771
 772                 return $this->mNavigationBar;
 773         }
 774
 775         /**
 776          * If this supports multiple order type messages, give the message key for
 777          * enabling each one in getNavigationBar.  The return type is an associa-
 778          * tive array whose keys must exactly match the keys of the array returned
 779          * by getIndexField(), and whose values are message keys.
 780          *
 781          * @return Array
 782          */
 783         protected function getOrderTypeMessages() {
 784                 return null;
 785         }
 786 }
 787
 788 /**
 789  * IndexPager with a formatted navigation bar
 790  * @ingroup Pager
 791  */
 792 abstract class ReverseChronologicalPager extends IndexPager {
 793         public $mDefaultDirection = true;
 794         public $mYear;
 795         public $mMonth;
 796
 797         function getNavigationBar() {
 798                 if ( !$this->isNavigationBarShown() ) {
 799                         return '';
 800                 }
 801
 802                 if ( isset( $this->mNavigationBar ) ) {
 803                         return $this->mNavigationBar;
 804                 }
 805
 806                 $linkTexts = array(
 807                         'prev' => $this->msg( 'pager-newer-n' )->numParams( $this->mLimit )->escaped(),
 808                         'next' => $this->msg( 'pager-older-n' )->numParams( $this->mLimit )->escaped(),
 809                         'first' => $this->msg( 'histlast' )->escaped(),
 810                         'last' => $this->msg( 'histfirst' )->escaped()
 811                 );
 812
 813                 $pagingLinks = $this->getPagingLinks( $linkTexts );
 814                 $limitLinks = $this->getLimitLinks();
 815                 $limits = $this->getLanguage()->pipeList( $limitLinks );
 816                 $firstLastLinks = $this->msg( 'parentheses' )->rawParams( "{$pagingLinks['first']}" .
 817                         $this->msg( 'pipe-separator' )->escaped() .
 818                         "{$pagingLinks['last']}" )->escaped();
 819
 820                 $this->mNavigationBar = $firstLastLinks . ' ' .
 821                         $this->msg( 'viewprevnext' )->rawParams(
 822                                 $pagingLinks['prev'], $pagingLinks['next'], $limits )->escaped();
 823
 824                 return $this->mNavigationBar;
 825         }
 826
 827         function getDateCond( $year, $month ) {
 828                 $year = intval( $year );
 829                 $month = intval( $month );
 830
 831                 // Basic validity checks
 832                 $this->mYear = $year > 0 ? $year : false;
 833                 $this->mMonth = ( $month > 0 && $month < 13 ) ? $month : false;
 834
 835                 // Given an optional year and month, we need to generate a timestamp
 836                 // to use as "WHERE rev_timestamp <= result"
 837                 // Examples: year = 2006 equals < 20070101 (+000000)
 838                 // year=2005, month=1    equals < 20050201
 839                 // year=2005, month=12   equals < 20060101
 840                 if ( !$this->mYear && !$this->mMonth ) {
 841                         return;
 842                 }
 843
 844                 if ( $this->mYear ) {
 845                         $year = $this->mYear;
 846                 } else {
 847                         // If no year given, assume the current one
 848                         $year = gmdate( 'Y' );
 849                         // If this month hasn't happened yet this year, go back to last year's month
 850                         if( $this->mMonth > gmdate( 'n' ) ) {
 851                                 $year--;
 852                         }
 853                 }
 854
 855                 if ( $this->mMonth ) {
 856                         $month = $this->mMonth + 1;
 857                         // For December, we want January 1 of the next year
 858                         if ($month > 12) {
 859                                 $month = 1;
 860                                 $year++;
 861                         }
 862                 } else {
 863                         // No month implies we want up to the end of the year in question
 864                         $month = 1;
 865                         $year++;
 866                 }
 867
 868                 // Y2K38 bug
 869                 if ( $year > 2032 ) {
 870                         $year = 2032;
 871                 }
 872
 873                 $ymd = (int)sprintf( "%04d%02d01", $year, $month );
 874
 875                 if ( $ymd > 20320101 ) {
 876                         $ymd = 20320101;
 877                 }
 878
 879                 $this->mOffset = $this->mDb->timestamp( "${ymd}000000" );
 880         }
 881 }
 882
 883 /**
 884  * Table-based display with a user-selectable sort order
 885  * @ingroup Pager
 886  */
 887 abstract class TablePager extends IndexPager {
 888         var $mSort;
 889         var $mCurrentRow;
 890
 891         public function __construct( IContextSource $context = null ) {
 892                 if ( $context ) {
 893                         $this->setContext( $context );
 894                 }
 895
 896                 $this->mSort = $this->getRequest()->getText( 'sort' );
 897                 if ( !array_key_exists( $this->mSort, $this->getFieldNames() ) ) {
 898                         $this->mSort = $this->getDefaultSort();
 899                 }
 900                 if ( $this->getRequest()->getBool( 'asc' ) ) {
 901                         $this->mDefaultDirection = false;
 902                 } elseif ( $this->getRequest()->getBool( 'desc' ) ) {
 903                         $this->mDefaultDirection = true;
 904                 } /* Else leave it at whatever the class default is */
 905
 906                 parent::__construct();
 907         }
 908
 909         /**
 910          * @protected
 911          * @return string
 912          */
 913         function getStartBody() {
 914                 global $wgStylePath;
 915                 $tableClass = htmlspecialchars( $this->getTableClass() );
 916                 $sortClass = htmlspecialchars( $this->getSortHeaderClass() );
 917
 918                 $s = "<table style='border:1;' class=\"mw-datatable $tableClass\"><thead><tr>\n";
 919                 $fields = $this->getFieldNames();
 920
 921                 # Make table header
 922                 foreach ( $fields as $field => $name ) {
 923                         if ( strval( $name ) == '' ) {
 924                                 $s .= "<th>&#160;</th>\n";
 925                         } elseif ( $this->isFieldSortable( $field ) ) {
 926                                 $query = array( 'sort' => $field, 'limit' => $this->mLimit );
 927                                 if ( $field == $this->mSort ) {
 928                                         # This is the sorted column
 929                                         # Prepare a link that goes in the other sort order
 930                                         if ( $this->mDefaultDirection ) {
 931                                                 # Descending
 932                                                 $image = 'Arr_d.png';
 933                                                 $query['asc'] = '1';
 934                                                 $query['desc'] = '';
 935                                                 $alt = $this->msg( 'descending_abbrev' )->escaped();
 936                                         } else {
 937                                                 # Ascending
 938                                                 $image = 'Arr_u.png';
 939                                                 $query['asc'] = '';
 940                                                 $query['desc'] = '1';
 941                                                 $alt = $this->msg( 'ascending_abbrev' )->escaped();
 942                                         }
 943                                         $image = htmlspecialchars( "$wgStylePath/common/images/$image" );
 944                                         $link = $this->makeLink(
 945                                                 "<img width=\"12\" height=\"12\" alt=\"$alt\" src=\"$image\" />" .
 946                                                         htmlspecialchars( $name ), $query );
 947                                         $s .= "<th class=\"$sortClass\">$link</th>\n";
 948                                 } else {
 949                                         $s .= '<th>' . $this->makeLink( htmlspecialchars( $name ), $query ) . "</th>\n";
 950                                 }
 951                         } else {
 952                                 $s .= '<th>' . htmlspecialchars( $name ) . "</th>\n";
 953                         }
 954                 }
 955                 $s .= "</tr></thead><tbody>\n";
 956                 return $s;
 957         }
 958
 959         /**
 960          * @protected
 961          * @return string
 962          */
 963         function getEndBody() {
 964                 return "</tbody></table>\n";
 965         }
 966
 967         /**
 968          * @protected
 969          * @return string
 970          */
 971         function getEmptyBody() {
 972                 $colspan = count( $this->getFieldNames() );
 973                 $msgEmpty = $this->msg( 'table_pager_empty' )->escaped();
 974                 return "<tr><td colspan=\"$colspan\">$msgEmpty</td></tr>\n";
 975         }
 976
 977         /**
 978          * @protected
 979          * @param stdClass $row
 980          * @return String HTML
 981          */
 982         function formatRow( $row ) {
 983                 $this->mCurrentRow = $row; // In case formatValue etc need to know
 984                 $s = Xml::openElement( 'tr', $this->getRowAttrs( $row ) );
 985                 $fieldNames = $this->getFieldNames();
 986
 987                 foreach ( $fieldNames as $field => $name ) {
 988                         $value = isset( $row->$field ) ? $row->$field : null;
 989                         $formatted = strval( $this->formatValue( $field, $value ) );
 990
 991                         if ( $formatted == '' ) {
 992                                 $formatted = '&#160;';
 993                         }
 994
 995                         $s .= Xml::tags( 'td', $this->getCellAttrs( $field, $value ), $formatted );
 996                 }
 997
 998                 $s .= "</tr>\n";
 999
1000                 return $s;
1001         }
1002
1003         /**
1004          * Get a class name to be applied to the given row.
1005          *
1006          * @protected
1007          *
1008          * @param $row Object: the database result row
1009          * @return String
1010          */
1011         function getRowClass( $row ) {
1012                 return '';
1013         }
1014
1015         /**
1016          * Get attributes to be applied to the given row.
1017          *
1018          * @protected
1019          *
1020          * @param $row Object: the database result row
1021          * @return Array of attribute => value
1022          */
1023         function getRowAttrs( $row ) {
1024                 $class = $this->getRowClass( $row );
1025                 if ( $class === '' ) {
1026                         // Return an empty array to avoid clutter in HTML like class=""
1027                         return array();
1028                 } else {
1029                         return array( 'class' => $this->getRowClass( $row ) );
1030                 }
1031         }
1032
1033         /**
1034          * Get any extra attributes to be applied to the given cell. Don't
1035          * take this as an excuse to hardcode styles; use classes and
1036          * CSS instead.  Row context is available in $this->mCurrentRow
1037          *
1038          * @protected
1039          *
1040          * @param $field String The column
1041          * @param $value String The cell contents
1042          * @return Array of attr => value
1043          */
1044         function getCellAttrs( $field, $value ) {
1045                 return array( 'class' => 'TablePager_col_' . $field );
1046         }
1047
1048         /**
1049          * @protected
1050          * @return string
1051          */
1052         function getIndexField() {
1053                 return $this->mSort;
1054         }
1055
1056         /**
1057          * @protected
1058          * @return string
1059          */
1060         function getTableClass() {
1061                 return 'TablePager';
1062         }
1063
1064         /**
1065          * @protected
1066          * @return string
1067          */
1068         function getNavClass() {
1069                 return 'TablePager_nav';
1070         }
1071
1072         /**
1073          * @protected
1074          * @return string
1075          */
1076         function getSortHeaderClass() {
1077                 return 'TablePager_sort';
1078         }
1079
1080         /**
1081          * A navigation bar with images
1082          * @return String HTML
1083          */
1084         public function getNavigationBar() {
1085                 global $wgStylePath;
1086
1087                 if ( !$this->isNavigationBarShown() ) {
1088                         return '';
1089                 }
1090
1091                 $path = "$wgStylePath/common/images";
1092                 $labels = array(
1093                         'first' => 'table_pager_first',
1094                         'prev' => 'table_pager_prev',
1095                         'next' => 'table_pager_next',
1096                         'last' => 'table_pager_last',
1097                 );
1098                 $images = array(
1099                         'first' => 'arrow_first_25.png',
1100                         'prev' => 'arrow_left_25.png',
1101                         'next' => 'arrow_right_25.png',
1102                         'last' => 'arrow_last_25.png',
1103                 );
1104                 $disabledImages = array(
1105                         'first' => 'arrow_disabled_first_25.png',
1106                         'prev' => 'arrow_disabled_left_25.png',
1107                         'next' => 'arrow_disabled_right_25.png',
1108                         'last' => 'arrow_disabled_last_25.png',
1109                 );
1110                 if( $this->getLanguage()->isRTL() ) {
1111                         $keys = array_keys( $labels );
1112                         $images = array_combine( $keys, array_reverse( $images ) );
1113                         $disabledImages = array_combine( $keys, array_reverse( $disabledImages ) );
1114                 }
1115
1116                 $linkTexts = array();
1117                 $disabledTexts = array();
1118                 foreach ( $labels as $type => $label ) {
1119                         $msgLabel = $this->msg( $label )->escaped();
1120                         $linkTexts[$type] = "<img src=\"$path/{$images[$type]}\" alt=\"$msgLabel\"/><br />$msgLabel";
1121                         $disabledTexts[$type] = "<img src=\"$path/{$disabledImages[$type]}\" alt=\"$msgLabel\"/><br />$msgLabel";
1122                 }
1123                 $links = $this->getPagingLinks( $linkTexts, $disabledTexts );
1124
1125                 $navClass = htmlspecialchars( $this->getNavClass() );
1126                 $s = "<table class=\"$navClass\"><tr>\n";
1127                 $width = 100 / count( $links ) . '%';
1128                 foreach ( $labels as $type => $label ) {
1129                         $s .= "<td style='width:$width;'>{$links[$type]}</td>\n";
1130                 }
1131                 $s .= "</tr></table>\n";
1132                 return $s;
1133         }
1134
1135         /**
1136          * Get a "<select>" element which has options for each of the allowed limits
1137          *
1138          * @return String: HTML fragment
1139          */
1140         public function getLimitSelect() {
1141                 # Add the current limit from the query string
1142                 # to avoid that the limit is lost after clicking Go next time
1143                 if ( !in_array( $this->mLimit, $this->mLimitsShown ) ) {
1144                         $this->mLimitsShown[] = $this->mLimit;
1145                         sort( $this->mLimitsShown );
1146                 }
1147                 $s = Html::openElement( 'select', array( 'name' => 'limit' ) ) . "\n";
1148                 foreach ( $this->mLimitsShown as $key => $value ) {
1149                         # The pair is either $index => $limit, in which case the $value
1150                         # will be numeric, or $limit => $text, in which case the $value
1151                         # will be a string.
1152                         if( is_int( $value ) ){
1153                                 $limit = $value;
1154                                 $text = $this->getLanguage()->formatNum( $limit );
1155                         } else {
1156                                 $limit = $key;
1157                                 $text = $value;
1158                         }
1159                         $s .= Xml::option( $text, $limit, $limit == $this->mLimit ) . "\n";
1160                 }
1161                 $s .= Html::closeElement( 'select' );
1162                 return $s;
1163         }
1164
1165         /**
1166          * Get \<input type="hidden"\> elements for use in a method="get" form.
1167          * Resubmits all defined elements of the query string, except for a
1168          * blacklist, passed in the $blacklist parameter.
1169          *
1170          * @param $blacklist Array parameters from the request query which should not be resubmitted
1171          * @return String: HTML fragment
1172          */
1173         function getHiddenFields( $blacklist = array() ) {
1174                 $blacklist = (array)$blacklist;
1175                 $query = $this->getRequest()->getQueryValues();
1176                 foreach ( $blacklist as $name ) {
1177                         unset( $query[$name] );
1178                 }
1179                 $s = '';
1180                 foreach ( $query as $name => $value ) {
1181                         $encName = htmlspecialchars( $name );
1182                         $encValue = htmlspecialchars( $value );
1183                         $s .= "<input type=\"hidden\" name=\"$encName\" value=\"$encValue\"/>\n";
1184                 }
1185                 return $s;
1186         }
1187
1188         /**
1189          * Get a form containing a limit selection dropdown
1190          *
1191          * @return String: HTML fragment
1192          */
1193         function getLimitForm() {
1194                 global $wgScript;
1195
1196                 return Xml::openElement(
1197                         'form',
1198                         array(
1199                                 'method' => 'get',
1200                                 'action' => $wgScript
1201                         ) ) . "\n" . $this->getLimitDropdown() . "</form>\n";
1202         }
1203
1204         /**
1205          * Gets a limit selection dropdown
1206          *
1207          * @return string
1208          */
1209         function getLimitDropdown() {
1210                 # Make the select with some explanatory text
1211                 $msgSubmit = $this->msg( 'table_pager_limit_submit' )->escaped();
1212
1213                 return $this->msg( 'table_pager_limit' )
1214                         ->rawParams( $this->getLimitSelect() )->escaped() .
1215                         "\n<input type=\"submit\" value=\"$msgSubmit\"/>\n" .
1216                         $this->getHiddenFields( array( 'limit' ) );
1217         }
1218
1219         /**
1220          * Return true if the named field should be sortable by the UI, false
1221          * otherwise
1222          *
1223          * @param $field String
1224          */
1225         abstract function isFieldSortable( $field );
1226
1227         /**
1228          * Format a table cell. The return value should be HTML, but use an empty
1229          * string not &#160; for empty cells. Do not include the <td> and </td>.
1230          *
1231          * The current result row is available as $this->mCurrentRow, in case you
1232          * need more context.
1233          *
1234          * @protected
1235          *
1236          * @param $name String: the database field name
1237          * @param $value String: the value retrieved from the database
1238          */
1239         abstract function formatValue( $name, $value );
1240
1241         /**
1242          * The database field name used as a default sort order.
1243          *
1244          * @protected
1245          *
1246          * @return string
1247          */
1248         abstract function getDefaultSort();
1249
1250         /**
1251          * An array mapping database field names to a textual description of the
1252          * field name, for use in the table header. The description should be plain
1253          * text, it will be HTML-escaped later.
1254          *
1255          * @return Array
1256          */
1257         abstract function getFieldNames();
1258 }