Support offsets in prefix searching

[mediawiki.git] / includes / Collation.php

<?php
/**
 * Database row sorting.
 *
 * 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
 */

abstract class Collation {
        private static $instance;

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

        /**
         * @throws MWException
         * @param string $collationName
         * @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' );
                        case 'xx-uca-ckb':
                                return new CollationCkb;
                        case 'xx-uca-et':
                                return new CollationEt;
                        default:
                                $match = array();
                                if ( preg_match( '/^uca-([a-z@=-]+)$/', $collationName, $match ) ) {
                                        return new IcuCollation( $match[1] );
                                }

                                # 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 {
        private $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 {
        const FIRST_LETTER_VERSION = 2;

        /** @var Collator */
        private $primaryCollator;

        /** @var Collator */
        private $mainCollator;

        /** @var string */
        private $locale;

        /** @var Language */
        protected $digitTransformLanguage;

        /** @var array */
        private $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.
         */
        private 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
        );

        /**
         * Additional characters (or character groups) to be considered separate
         * letters for given languages, or to be removed from the list of such
         * letters (denoted by keys starting with '-').
         *
         * These are additions to (or subtractions from) the data stored in the
         * first-letters-root.ser file (which among others includes full basic latin,
         * cyrillic and greek alphabets).
         *
         * "Separate letter" is a letter that would have a separate heading/section
         * for it in a dictionary or a phone book in this language. This data isn't
         * used for sorting (the ICU library handles that), only for deciding which
         * characters (or character groups) to use as headings.
         *
         * Initially generated based on the primary level of Unicode collation
         * tailorings available at http://developer.mimer.com/charts/tailorings.htm ,
         * later modified.
         *
         * Empty arrays are intended; this signifies that the data for the language is
         * available and that there are, in fact, no additional letters to consider.
         */
        private static $tailoringFirstLetters = array(
                // Verified by native speakers
                'be' => array( "Ё" ),
                'be-tarask' => array( "Ё" ),
                'cy' => array( "Ch", "Dd", "Ff", "Ng", "Ll", "Ph", "Rh", "Th" ),
                'en' => array(),
                'fa' => array( "آ", "ء", "ه" ),
                'fi' => array( "Å", "Ä", "Ö" ),
                'fr' => array(),
                'hu' => array( "Cs", "Dz", "Dzs", "Gy", "Ly", "Ny", "Ö", "Sz", "Ty", "Ü", "Zs" ),
                'is' => array( "Á", "Ð", "É", "Í", "Ó", "Ú", "Ý", "Þ", "Æ", "Ö", "Å" ),
                'it' => array(),
                'lv' => array( "Č", "Ģ", "Ķ", "Ļ", "Ņ", "Š", "Ž" ),
                'pl' => array( "Ą", "Ć", "Ę", "Ł", "Ń", "Ó", "Ś", "Ź", "Ż" ),
                'pt' => array(),
                'ru' => array(),
                'sv' => array( "Å", "Ä", "Ö" ),
                'sv@collation=standard' => array( "Å", "Ä", "Ö" ),
                'uk' => array( "Ґ", "Ь" ),
                'vi' => array( "Ă", "Â", "Đ", "Ê", "Ô", "Ơ", "Ư" ),
                // Not verified, but likely correct
                'af' => array(),
                'ast' => array( "Ch", "Ll", "Ñ" ),
                'az' => array( "Ç", "Ə", "Ğ", "İ", "Ö", "Ş", "Ü" ),
                'bg' => array(),
                'br' => array( "Ch", "C'h" ),
                'bs' => array( "Č", "Ć", "Dž", "Đ", "Lj", "Nj", "Š", "Ž" ),
                'ca' => array(),
                'co' => array(),
                'cs' => array( "Č", "Ch", "Ř", "Š", "Ž" ),
                'da' => array( "Æ", "Ø", "Å" ),
                'de' => array(),
                'dsb' => array( "Č", "Ć", "Dź", "Ě", "Ch", "Ł", "Ń", "Ŕ", "Š", "Ś", "Ž", "Ź" ),
                'el' => array(),
                'eo' => array( "Ĉ", "Ĝ", "Ĥ", "Ĵ", "Ŝ", "Ŭ" ),
                'es' => array( "Ñ" ),
                'et' => array( "Š", "Ž", "Õ", "Ä", "Ö", "Ü", "W" ), // added W for CollationEt (xx-uca-et)
                'eu' => array( "Ñ" ),
                'fo' => array( "Á", "Ð", "Í", "Ó", "Ú", "Ý", "Æ", "Ø", "Å" ),
                'fur' => array( "À", "Á", "Â", "È", "Ì", "Ò", "Ù" ),
                'fy' => array(),
                'ga' => array(),
                'gd' => array(),
                'gl' => array( "Ch", "Ll", "Ñ" ),
                'hr' => array( "Č", "Ć", "Dž", "Đ", "Lj", "Nj", "Š", "Ž" ),
                'hsb' => array( "Č", "Dź", "Ě", "Ch", "Ł", "Ń", "Ř", "Š", "Ć", "Ž" ),
                'kk' => array( "Ү", "І" ),
                'kl' => array( "Æ", "Ø", "Å" ),
                'ku' => array( "Ç", "Ê", "Î", "Ş", "Û" ),
                'ky' => array( "Ё" ),
                'la' => array(),
                'lb' => array(),
                'lt' => array( "Č", "Š", "Ž" ),
                'mk' => array(),
                'mo' => array( "Ă", "Â", "Î", "Ş", "Ţ" ),
                'mt' => array( "Ċ", "Ġ", "Għ", "Ħ", "Ż" ),
                'nl' => array(),
                'no' => array( "Æ", "Ø", "Å" ),
                'oc' => array(),
                'rm' => array(),
                'ro' => array( "Ă", "Â", "Î", "Ş", "Ţ" ),
                'rup' => array( "Ă", "Â", "Î", "Ľ", "Ń", "Ş", "Ţ" ),
                'sco' => array(),
                'sk' => array( "Ä", "Č", "Ch", "Ô", "Š", "Ž" ),
                'sl' => array( "Č", "Š", "Ž" ),
                'smn' => array( "Á", "Č", "Đ", "Ŋ", "Š", "Ŧ", "Ž", "Æ", "Ø", "Å", "Ä", "Ö" ),
                'sq' => array( "Ç", "Dh", "Ë", "Gj", "Ll", "Nj", "Rr", "Sh", "Th", "Xh", "Zh" ),
                'sr' => array(),
                'tk' => array( "Ç", "Ä", "Ž", "Ň", "Ö", "Ş", "Ü", "Ý" ),
                'tl' => array( "Ñ", "Ng" ),
                'tr' => array( "Ç", "Ğ", "İ", "Ö", "Ş", "Ü" ),
                'tt' => array( "Ә", "Ө", "Ү", "Җ", "Ң", "Һ" ),
                'uz' => array( "Ch", "G'", "Ng", "O'", "Sh" ),
        );

        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;
                // Drop everything after the '@' in locale's name
                $localeParts = explode( '@', $locale );
                $this->digitTransformLanguage = Language::factory( $locale === 'root' ? 'en' : $localeParts[0] );

                $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 = ArrayUtils::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,
                        $this->digitTransformLanguage->getCode(),
                        self::getICUVersion()
                );
                $cacheEntry = $cache->get( $cacheKey );

                if ( $cacheEntry && isset( $cacheEntry['version'] )
                        && $cacheEntry['version'] == self::FIRST_LETTER_VERSION
                ) {
                        $this->firstLetterData = $cacheEntry;
                        return $this->firstLetterData;
                }

                // Generate data from serialized data file

                if ( isset( self::$tailoringFirstLetters[$this->locale] ) ) {
                        $letters = wfGetPrecompiledData( "first-letters-root.ser" );
                        // Append additional characters
                        $letters = array_merge( $letters, self::$tailoringFirstLetters[$this->locale] );
                        // Remove unnecessary ones, if any
                        if ( isset( self::$tailoringFirstLetters['-' . $this->locale] ) ) {
                                $letters = array_diff( $letters, self::$tailoringFirstLetters['-' . $this->locale] );
                        }
                        // Apply digit transforms
                        $digits = array( '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' );
                        $letters = array_diff( $letters, $digits );
                        foreach ( $digits as $digit ) {
                                $letters[] = $this->digitTransformLanguage->formatNum( $digit, true );
                        }
                } else {
                        $letters = wfGetPrecompiledData( "first-letters-{$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 );
                // Remove duplicate prefixes. Basically if something has a sortkey
                // which is a prefix of some other sortkey, then it is an
                // expansion and probably should not be considered a section
                // header.
                //
                // For example 'þ' is sometimes sorted as if it is the letters
                // 'th'. Other times it is its own primary element. Another
                // example is '₨'. Sometimes its a currency symbol. Sometimes it
                // is an 'R' followed by an 's'.
                //
                // Additionally an expanded element should always sort directly
                // after its first element due to they way sortkeys work.
                //
                // UCA sortkey elements are of variable length but no collation
                // element should be a prefix of some other element, so I think
                // this is safe. See:
                // * https://ssl.icu-project.org/repos/icu/icuhtml/trunk/design/collation/ICU_collation_design.htm
                // * http://site.icu-project.org/design/collation/uca-weight-allocation
                //
                // Additionally, there is something called primary compression to
                // worry about. Basically, if you have two primary elements that
                // are more than one byte and both start with the same byte then
                // the first byte is dropped on the second primary. Additionally
                // either \x03 or \xFF may be added to mean that the next primary
                // does not start with the first byte of the first primary.
                //
                // This shouldn't matter much, as the first primary is not
                // changed, and that is what we are comparing against.
                //
                // tl;dr: This makes some assumptions about how icu implements
                // collations. It seems incredibly unlikely these assumptions
                // will change, but nonetheless they are assumptions.

                $prev = false;
                $duplicatePrefixes = array();
                foreach ( $letterMap as $key => $value ) {
                        // Remove terminator byte. Otherwise the prefix
                        // comparison will get hung up on that.
                        $trimmedKey = rtrim( $key, "\0" );
                        if ( $prev === false || $prev === '' ) {
                                $prev = $trimmedKey;
                                // We don't yet have a collation element
                                // to compare against, so continue.
                                continue;
                        }

                        // Due to the fact the array is sorted, we only have
                        // to compare with the element directly previous
                        // to the current element (skipping expansions).
                        // An element "X" will always sort directly
                        // before "XZ" (Unless we have "XY", but we
                        // do not update $prev in that case).
                        if ( substr( $trimmedKey, 0, strlen( $prev ) ) === $prev ) {
                                $duplicatePrefixes[] = $key;
                                // If this is an expansion, we don't want to
                                // compare the next element to this element,
                                // but to what is currently $prev
                                continue;
                        }
                        $prev = $trimmedKey;
                }
                foreach ( $duplicatePrefixes as $badKey ) {
                        wfDebug( "Removing '{$letterMap[$badKey]}' from first letters.\n" );
                        unset( $letterMap[$badKey] );
                        // This code assumes that unsetting does not change sort order.
                }
                $data = array(
                        'chars' => array_values( $letterMap ),
                        'keys' => array_keys( $letterMap ),
                        'version' => self::FIRST_LETTER_VERSION,
                );

                // 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'] );
        }

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

        /**
         * Return the version of ICU library used by PHP's intl extension,
         * or false when the extension is not installed of the version
         * can't be determined.
         *
         * The constant INTL_ICU_VERSION this function refers to isn't really
         * documented. It is available since PHP 5.3.7 (see PHP bug 54561).
         * This function will return false on older PHPs.
         *
         * @since 1.21
         * @return string|bool
         */
        static function getICUVersion() {
                return defined( 'INTL_ICU_VERSION' ) ? INTL_ICU_VERSION : false;
        }

        /**
         * Return the version of Unicode appropriate for the version of ICU library
         * currently in use, or false when it can't be determined.
         *
         * @since 1.21
         * @return string|bool
         */
        static function getUnicodeVersionForICU() {
                $icuVersion = IcuCollation::getICUVersion();
                if ( !$icuVersion ) {
                        return false;
                }

                $versionPrefix = substr( $icuVersion, 0, 3 );
                // Source: http://site.icu-project.org/download
                $map = array(
                        '50.' => '6.2',
                        '49.' => '6.1',
                        '4.8' => '6.0',
                        '4.6' => '6.0',
                        '4.4' => '5.2',
                        '4.2' => '5.1',
                        '4.0' => '5.1',
                        '3.8' => '5.0',
                        '3.6' => '5.0',
                        '3.4' => '4.1',
                );

                if ( isset( $map[$versionPrefix] ) ) {
                        return $map[$versionPrefix];
                } else {
                        return false;
                }
        }
}

/**
 * Workaround for the lack of support of Sorani Kurdish / Central Kurdish language ('ckb') in ICU.
 *
 * Uses the same collation rules as Persian / Farsi ('fa'), but different characters for digits.
 */
class CollationCkb extends IcuCollation {
        function __construct() {
                // This will set $locale and collators, which affect the actual sorting order
                parent::__construct( 'fa' );
                // Override the 'fa' language set by parent constructor, which affects #getFirstLetterData()
                $this->digitTransformLanguage = Language::factory( 'ckb' );
        }
}

/**
 * Workaround for incorrect collation of Estonian language ('et') in ICU (bug 54168).
 *
 * 'W' and 'V' should not be considered the same letter for the purposes of collation in modern
 * Estonian. We work around this by replacing 'W' and 'w' with 'ᴡ' U+1D21 'LATIN LETTER SMALL
 * CAPITAL W' for sortkey generation, which is collated like 'W' and is not tailored to have the
 * same primary weight as 'V' in Estonian.
 */
class CollationEt extends IcuCollation {
        function __construct() {
                parent::__construct( 'et' );
        }

        private static function mangle( $string ) {
                return str_replace(
                        array( 'w', 'W' ),
                        'ᴡ', // U+1D21 'LATIN LETTER SMALL CAPITAL W'
                        $string
                );
        }

        private static function unmangle( $string ) {
                // Casing data is lost…
                return str_replace(
                        'ᴡ', // U+1D21 'LATIN LETTER SMALL CAPITAL W'
                        'W',
                        $string
                );
        }

        function getSortKey( $string ) {
                return parent::getSortKey( self::mangle( $string ) );
        }

        function getFirstLetter( $string ) {
                return self::unmangle( parent::getFirstLetter( self::mangle( $string ) ) );
        }
}