Apparently we can commit code that doesn't compile but I am not allowed to have commi...

[mediawiki.git] / includes / Collation.php

<?php

abstract class Collation {
        static $instance;

        /**
         * @return Collation
         */
        static function singleton() {
                if ( !self::$instance ) {
                        global $wgCategoryCollation;
                        self::$instance = self::factory( $wgCategoryCollation );
                }
                return self::$instance;
        }

        /**
         * @throws MWException
         * @param $collationName string
         * @return Collation
         */
        static function factory( $collationName ) {
                switch( $collationName ) {
                        case 'uppercase':
                                return new UppercaseCollation;
                        case 'identity':
                                return new IdentityCollation;
                        case 'uca-default':
                                return new IcuCollation( 'root' );
                        default:
                                # Provide a mechanism for extensions to hook in.

                                $collationObject = null;
                                wfRunHooks( 'Collation::factory', array( $collationName, &$collationObject ) );

                                if ( $collationObject instanceof Collation ) {
                                        return $collationObject;
                                }

                                // If all else fails...
                                throw new MWException( __METHOD__.": unknown collation type \"$collationName\"" );
                }
        }

        /**
         * Given a string, convert it to a (hopefully short) key that can be used
         * for efficient sorting.  A binary sort according to the sortkeys
         * corresponds to a logical sort of the corresponding strings.  Current
         * code expects that a line feed character should sort before all others, but
         * has no other particular expectations (and that one can be changed if
         * necessary).
         *
         * @param string $string UTF-8 string
         * @return string Binary sortkey
         */
        abstract function getSortKey( $string );

        /**
         * Given a string, return the logical "first letter" to be used for
         * grouping on category pages and so on.  This has to be coordinated
         * carefully with convertToSortkey(), or else the sorted list might jump
         * back and forth between the same "initial letters" or other pathological
         * behavior.  For instance, if you just return the first character, but "a"
         * sorts the same as "A" based on getSortKey(), then you might get a
         * list like
         *
         * == A ==
         * * [[Aardvark]]
         *
         * == a ==
         * * [[antelope]]
         *
         * == A ==
         * * [[Ape]]
         *
         * etc., assuming for the sake of argument that $wgCapitalLinks is false.
         *
         * @param string $string UTF-8 string
         * @return string UTF-8 string corresponding to the first letter of input
         */
        abstract function getFirstLetter( $string );
}

class UppercaseCollation extends Collation {
        var $lang;
        function __construct() {
                // Get a language object so that we can use the generic UTF-8 uppercase
                // function there
                $this->lang = Language::factory( 'en' );
        }

        function getSortKey( $string ) {
                return $this->lang->uc( $string );
        }

        function getFirstLetter( $string ) {
                if ( $string[0] == "\0" ) {
                        $string = substr( $string, 1 );
                }
                return $this->lang->ucfirst( $this->lang->firstChar( $string ) );
        }
}

/**
 * Collation class that's essentially a no-op.
 *
 * Does sorting based on binary value of the string.
 * Like how things were pre 1.17.
 */
class IdentityCollation extends Collation {

        function getSortKey( $string ) {
                return $string;
        }

        function getFirstLetter( $string ) {
                global $wgContLang;
                // Copied from UppercaseCollation.
                // I'm kind of unclear on when this could happen...
                if ( $string[0] == "\0" ) {
                        $string = substr( $string, 1 );
                }
                return $wgContLang->firstChar( $string );
        }
}


class IcuCollation extends Collation {
        var $primaryCollator, $mainCollator, $locale;
        var $firstLetterData;

        /**
         * Unified CJK blocks.
         *
         * The same definition of a CJK block must be used for both Collation and 
         * generateCollationData.php. These blocks are omitted from the first 
         * letter data, as an optimisation measure and because the default UCA table 
         * is pretty useless for sorting Chinese text anyway. Japanese and Korean 
         * blocks are not included here, because they are smaller and more useful.
         */
        static $cjkBlocks = array(
                array( 0x2E80, 0x2EFF ), // CJK Radicals Supplement
                array( 0x2F00, 0x2FDF ), // Kangxi Radicals
                array( 0x2FF0, 0x2FFF ), // Ideographic Description Characters
                array( 0x3000, 0x303F ), // CJK Symbols and Punctuation
                array( 0x31C0, 0x31EF ), // CJK Strokes
                array( 0x3200, 0x32FF ), // Enclosed CJK Letters and Months
                array( 0x3300, 0x33FF ), // CJK Compatibility
                array( 0x3400, 0x4DBF ), // CJK Unified Ideographs Extension A
                array( 0x4E00, 0x9FFF ), // CJK Unified Ideographs
                array( 0xF900, 0xFAFF ), // CJK Compatibility Ideographs
                array( 0xFE30, 0xFE4F ), // CJK Compatibility Forms
                array( 0x20000, 0x2A6DF ), // CJK Unified Ideographs Extension B
                array( 0x2A700, 0x2B73F ), // CJK Unified Ideographs Extension C
                array( 0x2B740, 0x2B81F ), // CJK Unified Ideographs Extension D
                array( 0x2F800, 0x2FA1F ), // CJK Compatibility Ideographs Supplement
        );

        const RECORD_LENGTH = 14;

        function __construct( $locale ) {
                if ( !extension_loaded( 'intl' ) ) {
                        throw new MWException( 'An ICU collation was requested, ' . 
                                'but the intl extension is not available.' );
                }
                $this->locale = $locale;
                $this->mainCollator = Collator::create( $locale );
                if ( !$this->mainCollator ) {
                        throw new MWException( "Invalid ICU locale specified for collation: $locale" );
                }

                $this->primaryCollator = Collator::create( $locale );
                $this->primaryCollator->setStrength( Collator::PRIMARY );
        }

        function getSortKey( $string ) {
                // intl extension produces non null-terminated
                // strings. Appending '' fixes it so that it doesn't generate
                // a warning on each access in debug php.
                wfSuppressWarnings();
                $key = $this->mainCollator->getSortKey( $string ) . '';
                wfRestoreWarnings();
                return $key;
        }

        function getPrimarySortKey( $string ) {
                wfSuppressWarnings();
                $key = $this->primaryCollator->getSortKey( $string ) . '';
                wfRestoreWarnings();
                return $key;
        }

        function getFirstLetter( $string ) {
                $string = strval( $string );
                if ( $string === '' ) {
                        return '';
                }

                // Check for CJK
                $firstChar = mb_substr( $string, 0, 1, 'UTF-8' );
                if ( ord( $firstChar ) > 0x7f 
                        && self::isCjk( utf8ToCodepoint( $firstChar ) ) ) 
                {
                        return $firstChar;
                }

                $sortKey = $this->getPrimarySortKey( $string );

                // Do a binary search to find the correct letter to sort under
                $min = $this->findLowerBound(
                        array( $this, 'getSortKeyByLetterIndex' ),
                        $this->getFirstLetterCount(),
                        'strcmp',
                        $sortKey );

                if ( $min === false ) {
                        // Before the first letter
                        return '';
                }
                return $this->getLetterByIndex( $min );
        }

        function getFirstLetterData() {
                if ( $this->firstLetterData !== null ) {
                        return $this->firstLetterData;
                }

                $cache = wfGetCache( CACHE_ANYTHING );
                $cacheKey = wfMemcKey( 'first-letters', $this->locale );
                $cacheEntry = $cache->get( $cacheKey );

                if ( $cacheEntry ) {
                        $this->firstLetterData = $cacheEntry;
                        return $this->firstLetterData;
                }

                // Generate data from serialized data file

                $letters = wfGetPrecompiledData( "first-letters-{$this->locale}.ser" );
                if ( $letters === false ) {
                        throw new MWException( "MediaWiki does not support ICU locale " .
                                "\"{$this->locale}\"" );
                }

                // Sort the letters.
                //
                // It's impossible to have the precompiled data file properly sorted,
                // because the sort order changes depending on ICU version. If the 
                // array is not properly sorted, the binary search will return random 
                // results. 
                //
                // We also take this opportunity to remove primary collisions.
                $letterMap = array();
                foreach ( $letters as $letter ) {
                        $key = $this->getPrimarySortKey( $letter );
                        if ( isset( $letterMap[$key] ) ) {
                                // Primary collision
                                // Keep whichever one sorts first in the main collator
                                if ( $this->mainCollator->compare( $letter, $letterMap[$key] ) < 0 ) {
                                        $letterMap[$key] = $letter;
                                }
                        } else {
                                $letterMap[$key] = $letter;
                        }
                }
                ksort( $letterMap, SORT_STRING );
                $data = array(
                        'chars' => array_values( $letterMap ),
                        'keys' => array_keys( $letterMap )
                );

                // Reduce memory usage before caching
                unset( $letterMap );

                // Save to cache
                $this->firstLetterData = $data;
                $cache->set( $cacheKey, $data, 86400 * 7 /* 1 week */ );
                return $data;
        }

        function getLetterByIndex( $index ) {
                if ( $this->firstLetterData === null ) {
                        $this->getFirstLetterData();
                }
                return $this->firstLetterData['chars'][$index];
        }

        function getSortKeyByLetterIndex( $index ) {
                if ( $this->firstLetterData === null ) {
                        $this->getFirstLetterData();
                }
                return $this->firstLetterData['keys'][$index];
        }

        function getFirstLetterCount() {
                if ( $this->firstLetterData === null ) {
                        $this->getFirstLetterData();
                }
                return count( $this->firstLetterData['chars'] );
        }

        /**
         * Do a binary search, and return the index of the largest item that sorts 
         * less than or equal to the target value.
         *
         * @param $valueCallback array A function to call to get the value with
         *     a given array index.
         * @param $valueCount int The number of items accessible via $valueCallback,
         *     indexed from 0 to $valueCount - 1
         * @param $comparisonCallback array A callback to compare two values, returning
         *     -1, 0 or 1 in the style of strcmp().
         * @param $target string The target value to find.
         *
         * @return The item index of the lower bound, or false if the target value
         *     sorts before all items.
         */
        function findLowerBound( $valueCallback, $valueCount, $comparisonCallback, $target ) {
                $min = 0;
                $max = $valueCount - 1;
                do {
                        $mid = $min + ( ( $max - $min ) >> 1 );
                        $item = call_user_func( $valueCallback, $mid );
                        $comparison = call_user_func( $comparisonCallback, $target, $item );
                        if ( $comparison > 0 ) {
                                $min = $mid;
                        } elseif ( $comparison == 0 ) {
                                $min = $mid;
                                break;
                        } else {
                                $max = $mid;
                        }
                } while ( $min < $max - 1 );

                if ( $min == 0 && $max == 0 && $comparison > 0 ) {
                        // Before the first item
                        return false;
                } else {
                        return $min;
                }
        }

        static function isCjk( $codepoint ) {
                foreach ( self::$cjkBlocks as $block ) {
                        if ( $codepoint >= $block[0] && $codepoint <= $block[1] ) {
                                return true;
                        }
                }
                return false;
        }
}