UstringLibrary.php

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<?php
 
use UtfNormal\Validator;
 
class Scribunto_LuaUstringLibrary extends Scribunto_LuaLibraryBase {
    private $patternLengthLimit = 10000;
 
    private $stringLengthLimit = null;
 
    private $phpBug53823 = false;
 
    private $patternRegexCache = null;
 
    public function __construct( $engine ) {
        if ( $this->stringLengthLimit === null ) {
            global $wgMaxArticleSize;
            $this->stringLengthLimit = $wgMaxArticleSize * 1024;
        }
 
        $this->phpBug53823 = preg_replace( '//us', 'x', "\xc3\xa1" ) === "x\xc3x\xa1x";
        $this->patternRegexCache = new MapCacheLRU( 100 );
 
        parent::__construct( $engine );
    }
 
    public function register() {
        $perf = $this->getEngine()->getPerformanceCharacteristics();
 
        if ( $perf['phpCallsRequireSerialization'] ) {
            $lib = [
                // Pattern matching is still much faster in PHP, even with the
                // overhead of serialization
                'find' => [ $this, 'ustringFind' ],
                'match' => [ $this, 'ustringMatch' ],
                'gmatch_init' => [ $this, 'ustringGmatchInit' ],
                'gmatch_callback' => [ $this, 'ustringGmatchCallback' ],
                'gsub' => [ $this, 'ustringGsub' ],
            ];
        } else {
            $lib = [
                'isutf8' => [ $this, 'ustringIsUtf8' ],
                'byteoffset' => [ $this, 'ustringByteoffset' ],
                'codepoint' => [ $this, 'ustringCodepoint' ],
                'gcodepoint_init' => [ $this, 'ustringGcodepointInit' ],
                'toNFC' => [ $this, 'ustringToNFC' ],
                'toNFD' => [ $this, 'ustringToNFD' ],
                'toNFKC' => [ $this, 'ustringToNFKC' ],
                'toNFKD' => [ $this, 'ustringToNFKD' ],
                'char' => [ $this, 'ustringChar' ],
                'len' => [ $this, 'ustringLen' ],
                'sub' => [ $this, 'ustringSub' ],
                'upper' => [ $this, 'ustringUpper' ],
                'lower' => [ $this, 'ustringLower' ],
                'find' => [ $this, 'ustringFind' ],
                'match' => [ $this, 'ustringMatch' ],
                'gmatch_init' => [ $this, 'ustringGmatchInit' ],
                'gmatch_callback' => [ $this, 'ustringGmatchCallback' ],
                'gsub' => [ $this, 'ustringGsub' ],
            ];
        }
        return $this->getEngine()->registerInterface( 'mw.ustring.lua', $lib, [
            'stringLengthLimit' => $this->stringLengthLimit,
            'patternLengthLimit' => $this->patternLengthLimit,
        ] );
    }
 
    private function checkString( $name, $s, $checkEncoding = true ) {
        if ( $this->getLuaType( $s ) == 'number' ) {
            $s = (string)$s;
        } else {
            $this->checkType( $name, 1, $s, 'string' );
            if ( $checkEncoding && !mb_check_encoding( $s, 'UTF-8' ) ) {
                throw new Scribunto_LuaError( "bad argument #1 to '$name' (string is not UTF-8)" );
            }
            if ( strlen( $s ) > $this->stringLengthLimit ) {
                throw new Scribunto_LuaError(
                    "bad argument #1 to '$name' (string is longer than $this->stringLengthLimit bytes)"
                );
            }
        }
    }
 
    public function ustringIsUtf8( $s ) {
        $this->checkString( 'isutf8', $s, false );
        return [ mb_check_encoding( $s, 'UTF-8' ) ];
    }
 
    public function ustringByteoffset( $s, $l = 1, $i = 1 ) {
        $this->checkString( 'byteoffset', $s );
        $this->checkTypeOptional( 'byteoffset', 2, $l, 'number', 1 );
        $this->checkTypeOptional( 'byteoffset', 3, $i, 'number', 1 );
 
        $bytelen = strlen( $s );
        if ( $i < 0 ) {
            $i = $bytelen + $i + 1;
        }
        if ( $i < 1 || $i > $bytelen ) {
            return [ null ];
        }
        $i--;
        $j = $i;
        while ( ( ord( $s[$i] ) & 0xc0 ) === 0x80 ) {
            $i--;
        }
        if ( $l > 0 && $j === $i ) {
            $l--;
        }
        $char = mb_strlen( substr( $s, 0, $i ), 'UTF-8' ) + $l;
        if ( $char < 0 || $char >= mb_strlen( $s, 'UTF-8' ) ) {
            return [ null ];
        } else {
            return [ strlen( mb_substr( $s, 0, $char, 'UTF-8' ) ) + 1 ];
        }
    }
 
    public function ustringCodepoint( $s, $i = 1, $j = null ) {
        $this->checkString( 'codepoint', $s );
        $this->checkTypeOptional( 'codepoint', 2, $i, 'number', 1 );
        $this->checkTypeOptional( 'codepoint', 3, $j, 'number', $i );
 
        $l = mb_strlen( $s, 'UTF-8' );
        if ( $i < 0 ) {
            $i = $l + $i + 1;
        }
        if ( $j < 0 ) {
            $j = $l + $j + 1;
        }
        if ( $j < $i ) {
            return [];
        }
        $i = max( 1, min( $i, $l + 1 ) );
        $j = max( 1, min( $j, $l + 1 ) );
        $s = mb_substr( $s, $i - 1, $j - $i + 1, 'UTF-8' );
        return unpack( 'N*', mb_convert_encoding( $s, 'UTF-32BE', 'UTF-8' ) );
    }
 
    public function ustringGcodepointInit( $s, $i = 1, $j = null ) {
        return [ $this->ustringCodepoint( $s, $i, $j ) ];
    }
 
    public function ustringToNFC( $s ) {
        $this->checkString( 'toNFC', $s, false );
        if ( !mb_check_encoding( $s, 'UTF-8' ) ) {
            return [ null ];
        }
        return [ Validator::toNFC( $s ) ];
    }
 
    public function ustringToNFD( $s ) {
        $this->checkString( 'toNFD', $s, false );
        if ( !mb_check_encoding( $s, 'UTF-8' ) ) {
            return [ null ];
        }
        return [ Validator::toNFD( $s ) ];
    }
 
    public function ustringToNFKC( $s ) {
        $this->checkString( 'toNFKC', $s, false );
        if ( !mb_check_encoding( $s, 'UTF-8' ) ) {
            return [ null ];
        }
        return [ Validator::toNFKC( $s ) ];
    }
 
    public function ustringToNFKD( $s ) {
        $this->checkString( 'toNFKD', $s, false );
        if ( !mb_check_encoding( $s, 'UTF-8' ) ) {
            return [ null ];
        }
        return [ Validator::toNFKD( $s ) ];
    }
 
    public function ustringChar() {
        $args = func_get_args();
        if ( count( $args ) > $this->stringLengthLimit ) {
            throw new Scribunto_LuaError( "too many arguments to 'char'" );
        }
        foreach ( $args as $k => &$v ) {
            if ( !is_numeric( $v ) ) {
                $this->checkType( 'char', $k + 1, $v, 'number' );
            }
            $v = (int)floor( $v );
            if ( $v < 0 || $v > 0x10ffff ) {
                $k++;
                throw new Scribunto_LuaError( "bad argument #$k to 'char' (value out of range)" );
            }
        }
        $s = pack( 'N*', ...$args );
        $s = mb_convert_encoding( $s, 'UTF-8', 'UTF-32BE' );
        if ( strlen( $s ) > $this->stringLengthLimit ) {
            throw new Scribunto_LuaError( "result to long for 'char'" );
        }
        return [ $s ];
    }
 
    public function ustringLen( $s ) {
        $this->checkString( 'len', $s, false );
        if ( !mb_check_encoding( $s, 'UTF-8' ) ) {
            return [ null ];
        }
        return [ mb_strlen( $s, 'UTF-8' ) ];
    }
 
    public function ustringSub( $s, $i = 1, $j = -1 ) {
        $this->checkString( 'sub', $s );
        $this->checkTypeOptional( 'sub', 2, $i, 'number', 1 );
        $this->checkTypeOptional( 'sub', 3, $j, 'number', -1 );
 
        $len = mb_strlen( $s, 'UTF-8' );
        if ( $i < 0 ) {
            $i = $len + $i + 1;
        }
        if ( $j < 0 ) {
            $j = $len + $j + 1;
        }
        if ( $j < $i ) {
            return [ '' ];
        }
        $i = max( 1, min( $i, $len + 1 ) );
        $j = max( 1, min( $j, $len + 1 ) );
        $s = mb_substr( $s, $i - 1, $j - $i + 1, 'UTF-8' );
        return [ $s ];
    }
 
    public function ustringUpper( $s ) {
        $this->checkString( 'upper', $s );
        return [ mb_strtoupper( $s, 'UTF-8' ) ];
    }
 
    public function ustringLower( $s ) {
        $this->checkString( 'lower', $s );
        return [ mb_strtolower( $s, 'UTF-8' ) ];
    }
 
    private function checkPattern( $name, $pattern ) {
        if ( $this->getLuaType( $pattern ) == 'number' ) {
            $pattern = (string)$pattern;
        }
        $this->checkType( $name, 2, $pattern, 'string' );
        if ( !mb_check_encoding( $pattern, 'UTF-8' ) ) {
            throw new Scribunto_LuaError( "bad argument #2 to '$name' (string is not UTF-8)" );
        }
        if ( strlen( $pattern ) > $this->patternLengthLimit ) {
            throw new Scribunto_LuaError(
                "bad argument #2 to '$name' (pattern is longer than $this->patternLengthLimit bytes)"
            );
        }
    }
 
    /* Convert a Lua pattern into a PCRE regex */
    private function patternToRegex( $pattern, $anchor, $name ) {
        $cacheKey = serialize( [ $pattern, $anchor ] );
        if ( !$this->patternRegexCache->has( $cacheKey ) ) {
            $this->checkPattern( $name, $pattern );
            $pat = preg_split( '//us', $pattern, null, PREG_SPLIT_NO_EMPTY );
 
            static $charsets = null, $brcharsets = null;
            if ( $charsets === null ) {
                $charsets = [
                    // If you change these, also change lualib/ustring/make-tables.php
                    // (and run it to regenerate charsets.lua)
                    'a' => '\p{L}',
                    'c' => '\p{Cc}',
                    'd' => '\p{Nd}',
                    'l' => '\p{Ll}',
                    'p' => '\p{P}',
                    's' => '\p{Xps}',
                    'u' => '\p{Lu}',
                    'w' => '[\p{L}\p{Nd}]',
                    'x' => '[0-9A-Fa-f０-９Ａ-Ｆａ-ｆ]',
                    'z' => '\0',
 
                    // These *must* be the inverse of the above
                    'A' => '\P{L}',
                    'C' => '\P{Cc}',
                    'D' => '\P{Nd}',
                    'L' => '\P{Ll}',
                    'P' => '\P{P}',
                    'S' => '\P{Xps}',
                    'U' => '\P{Lu}',
                    'W' => '[^\p{L}\p{Nd}]',
                    'X' => '[^0-9A-Fa-f０-９Ａ-Ｆａ-ｆ]',
                    'Z' => '[^\0]',
                ];
                $brcharsets = [
                    'w' => '\p{L}\p{Nd}',
                    'x' => '0-9A-Fa-f０-９Ａ-Ｆａ-ｆ',
 
                    // Negated sets that are not expressable as a simple \P{} are
                    // unfortunately complicated.
 
                    // Xan is L plus N, so ^Xan plus Nl plus No is anything that's not L or Nd
                    'W' => '\P{Xan}\p{Nl}\p{No}',
 
                    // Manually constructed. Fun.
                    'X' => '\x00-\x2f\x3a-\x40\x47-\x60\x67-\x{ff0f}'
                        . '\x{ff1a}-\x{ff20}\x{ff27}-\x{ff40}\x{ff47}-\x{10ffff}',
 
                    // Ha!
                    'Z' => '\x01-\x{10ffff}',
                ] + $charsets;
            }
 
            $re = '/';
            $len = count( $pat );
            $capt = [];
            $anypos = false;
            $captparen = [];
            $opencapt = [];
            $bct = 0;
 
            for ( $i = 0; $i < $len; $i++ ) {
                $ii = $i + 1;
                $q = false;
                switch ( $pat[$i] ) {
                case '^':
                    $q = $i;
                    $re .= ( $anchor === false || $q ) ? '\\^' : $anchor;
                    break;
 
                case '$':
                    $q = ( $i < $len - 1 );
                    $re .= $q ? '\\$' : '$';
                    break;
 
                case '(':
                    if ( $i + 1 >= $len ) {
                        throw new Scribunto_LuaError( "Unmatched open-paren at pattern character $ii" );
                    }
                    $n = count( $capt ) + 1;
                    $capt[$n] = ( $pat[$i + 1] === ')' );
                    if ( $capt[$n] ) {
                        $anypos = true;
                    }
                    $re .= "(?<m$n>";
                    $opencapt[] = $n;
                    $captparen[$n] = $ii;
                    break;
 
                case ')':
                    if ( count( $opencapt ) <= 0 ) {
                        throw new Scribunto_LuaError( "Unmatched close-paren at pattern character $ii" );
                    }
                    array_pop( $opencapt );
                    $re .= $pat[$i];
                    break;
 
                case '%':
                    $i++;
                    if ( $i >= $len ) {
                        throw new Scribunto_LuaError( "malformed pattern (ends with '%')" );
                    }
                    if ( isset( $charsets[$pat[$i]] ) ) {
                        $re .= $charsets[$pat[$i]];
                        $q = true;
                    } elseif ( $pat[$i] === 'b' ) {
                        if ( $i + 2 >= $len ) {
                            throw new Scribunto_LuaError( "malformed pattern (missing arguments to \'%b\')" );
                        }
                        $d1 = preg_quote( $pat[++$i], '/' );
                        $d2 = preg_quote( $pat[++$i], '/' );
                        if ( $d1 === $d2 ) {
                            $re .= "{$d1}[^$d1]*$d1";
                        } else {
                            $bct++;
                            $re .= "(?<b$bct>$d1(?:(?>[^$d1$d2]+)|(?P>b$bct))*$d2)";
                        }
                    } elseif ( $pat[$i] === 'f' ) {
                        if ( $i + 1 >= $len || $pat[++$i] !== '[' ) {
                            throw new Scribunto_LuaError( "missing '[' after %f in pattern at pattern character $ii" );
                        }
                        list( $i, $re2 ) = $this->bracketedCharSetToRegex( $pat, $i, $len, $brcharsets );
                        // Because %f considers the beginning and end of the string
                        // to be \0, determine if $re2 matches that and take it
                        // into account with "^" and "$".
                        // @phan-suppress-next-line PhanParamSuspiciousOrder
                        if ( preg_match( "/$re2/us", "\0" ) ) {
                            $re .= "(?<!^)(?<!$re2)(?=$re2|$)";
                        } else {
                            $re .= "(?<!$re2)(?=$re2)";
                        }
                    } elseif ( $pat[$i] >= '0' && $pat[$i] <= '9' ) {
                        $n = ord( $pat[$i] ) - 0x30;
                        if ( $n === 0 || $n > count( $capt ) || in_array( $n, $opencapt ) ) {
                            throw new Scribunto_LuaError( "invalid capture index %$n at pattern character $ii" );
                        }
                        $re .= "\\g{m$n}";
                    } else {
                        $re .= preg_quote( $pat[$i], '/' );
                        $q = true;
                    }
                    break;
 
                case '[':
                    list( $i, $re2 ) = $this->bracketedCharSetToRegex( $pat, $i, $len, $brcharsets );
                    $re .= $re2;
                    $q = true;
                    break;
 
                case ']':
                    throw new Scribunto_LuaError( "Unmatched close-bracket at pattern character $ii" );
 
                case '.':
                    $re .= $pat[$i];
                    $q = true;
                    break;
 
                default:
                    $re .= preg_quote( $pat[$i], '/' );
                    $q = true;
                    break;
                }
                if ( $q && $i + 1 < $len ) {
                    switch ( $pat[$i + 1] ) {
                    case '*':
                    case '+':
                    case '?':
                        $re .= $pat[++$i];
                        break;
                    case '-':
                        $re .= '*?';
                        $i++;
                        break;
                    }
                }
            }
            if ( count( $opencapt ) ) {
                $ii = $captparen[$opencapt[0]];
                throw new Scribunto_LuaError( "Unclosed capture beginning at pattern character $ii" );
            }
            $re .= '/us';
 
            $this->patternRegexCache->set( $cacheKey, [ $re, $capt, $anypos ] );
        }
        return $this->patternRegexCache->get( $cacheKey );
    }
 
    private function bracketedCharSetToRegex( $pat, $i, $len, $brcharsets ) {
        $ii = $i + 1;
        $re = '[';
        $i++;
        if ( $i < $len && $pat[$i] === '^' ) {
            $re .= '^';
            $i++;
        }
        for ( $j = $i; $i < $len && ( $j == $i || $pat[$i] !== ']' ); $i++ ) {
            if ( $pat[$i] === '%' ) {
                $i++;
                if ( $i >= $len ) {
                    break;
                }
                if ( isset( $brcharsets[$pat[$i]] ) ) {
                    $re .= $brcharsets[$pat[$i]];
                } else {
                    $re .= preg_quote( $pat[$i], '/' );
                }
            } elseif ( $i + 2 < $len &&
                $pat[$i + 1] === '-' && $pat[$i + 2] !== ']' && $pat[$i + 2] !== '%'
            ) {
                if ( $pat[$i] <= $pat[$i + 2] ) {
                    $re .= preg_quote( $pat[$i], '/' ) . '-' . preg_quote( $pat[$i + 2], '/' );
                }
                $i += 2;
            } else {
                $re .= preg_quote( $pat[$i], '/' );
            }
        }
        if ( $i >= $len ) {
            throw new Scribunto_LuaError(
                "Missing close-bracket for character set beginning at pattern character $ii"
            );
        }
        $re .= ']';
 
        // Lua just ignores invalid ranges, while pcre throws an error.
        // We filter them out above, but then we need to special-case empty sets
        if ( $re === '[]' ) {
            // Can't directly quantify (*FAIL), so wrap it.
            // "(?!)" would be simpler and could be quantified if not for a bug in PCRE 8.13 to 8.33
            $re = '(?:(*FAIL))';
        } elseif ( $re === '[^]' ) {
            $re = '.'; // 's' modifier is always used, so this works
        }
 
        return [ $i, $re ];
    }
 
    private function addCapturesFromMatch( $arr, $s, $m, $capt, $m0_if_no_captures ) {
        if ( count( $capt ) ) {
            foreach ( $capt as $n => $pos ) {
                if ( $pos ) {
                    $o = mb_strlen( substr( $s, 0, $m["m$n"][1] ), 'UTF-8' ) + 1;
                    $arr[] = $o;
                } else {
                    $arr[] = $m["m$n"][0];
                }
            }
        } elseif ( $m0_if_no_captures ) {
            $arr[] = $m[0][0];
        }
        return $arr;
    }
 
    public function ustringFind( $s, $pattern, $init = 1, $plain = false ) {
        $this->checkString( 'find', $s );
        $this->checkTypeOptional( 'find', 3, $init, 'number', 1 );
        $this->checkTypeOptional( 'find', 4, $plain, 'boolean', false );
 
        $len = mb_strlen( $s, 'UTF-8' );
        if ( $init < 0 ) {
            $init = $len + $init + 1;
        } elseif ( $init > $len + 1 ) {
            $init = $len + 1;
        }
 
        if ( $init > 1 ) {
            $offset = strlen( mb_substr( $s, 0, $init - 1, 'UTF-8' ) );
        } else {
            $init = 1;
            $offset = 0;
        }
 
        if ( $plain ) {
            $this->checkPattern( 'find', $pattern );
            if ( $pattern !== '' ) {
                $ret = mb_strpos( $s, $pattern, $init - 1, 'UTF-8' );
            } else {
                $ret = $init - 1;
            }
            if ( $ret === false ) {
                return [ null ];
            } else {
                return [ $ret + 1, $ret + mb_strlen( $pattern ) ];
            }
        } else {
            list( $re, $capt ) = $this->patternToRegex( $pattern, '\G', 'find' );
            if ( !preg_match( $re, $s, $m, PREG_OFFSET_CAPTURE, $offset ) ) {
                return [ null ];
            }
            $o = mb_strlen( substr( $s, 0, $m[0][1] ), 'UTF-8' );
            $ret = [ $o + 1, $o + mb_strlen( $m[0][0], 'UTF-8' ) ];
            return $this->addCapturesFromMatch( $ret, $s, $m, $capt, false );
        }
    }
 
    public function ustringMatch( $s, $pattern, $init = 1 ) {
        $this->checkString( 'match', $s );
        $this->checkTypeOptional( 'match', 3, $init, 'number', 1 );
 
        $len = mb_strlen( $s, 'UTF-8' );
        if ( $init < 0 ) {
            $init = $len + $init + 1;
        } elseif ( $init > $len + 1 ) {
            $init = $len + 1;
        }
        if ( $init > 1 ) {
            $offset = strlen( mb_substr( $s, 0, $init - 1, 'UTF-8' ) );
        } else {
            $offset = 0;
        }
 
        list( $re, $capt ) = $this->patternToRegex( $pattern, '\G', 'match' );
        if ( !preg_match( $re, $s, $m, PREG_OFFSET_CAPTURE, $offset ) ) {
            return [ null ];
        }
        return $this->addCapturesFromMatch( [], $s, $m, $capt, true );
    }
 
    public function ustringGmatchInit( $s, $pattern ) {
        $this->checkString( 'gmatch', $s );
 
        list( $re, $capt ) = $this->patternToRegex( $pattern, false, 'gmatch' );
        return [ $re, $capt ];
    }
 
    public function ustringGmatchCallback( $s, $re, $capt, $pos ) {
        if ( !preg_match( $re, $s, $m, PREG_OFFSET_CAPTURE, $pos ) ) {
            return [ $pos, [] ];
        }
        $pos = $m[0][1] + strlen( $m[0][0] );
        return [ $pos, $this->addCapturesFromMatch( [ null ], $s, $m, $capt, true ) ];
    }
 
    public function ustringGsub( $s, $pattern, $repl, $n = null ) {
        $this->checkString( 'gsub', $s );
        $this->checkTypeOptional( 'gsub', 4, $n, 'number', null );
 
        if ( $n === null ) {
            $n = -1;
        } elseif ( $n < 1 ) {
            return [ $s, 0 ];
        }
 
        list( $re, $capt, $anypos ) = $this->patternToRegex( $pattern, '^', 'gsub' );
        $captures = [];
 
        if ( $this->phpBug53823 ) {
            // PHP bug 53823 means that a zero-length match before a UTF-8
            // character will match again before every byte of that character.
            // The workaround is to capture the first "character" of/after the
            // match and verify that its first byte is legal to start a UTF-8
            // character.
            $re = '/(?=(?<phpBug53823>.|$))' . substr( $re, 1 );
        }
 
        if ( $anypos ) {
            // preg_replace_callback doesn't take a "flags" argument, so we
            // can't pass PREG_OFFSET_CAPTURE to it, which is needed to handle
            // position captures. So instead we have to do a preg_match_all and
            // handle the captures ourself.
            $ct = preg_match_all( $re, $s, $mm, PREG_OFFSET_CAPTURE | PREG_SET_ORDER );
            for ( $i = 0; $i < $ct; $i++ ) {
                $m = $mm[$i];
                if ( $this->phpBug53823 ) {
                    $c = ord( $m['phpBug53823'][0] );
                    if ( $c >= 0x80 && $c <= 0xbf ) {
                        continue;
                    }
                }
                $c = [ $m[0][0] ];
                foreach ( $this->addCapturesFromMatch( [], $s, $m, $capt, false ) as $k => $v ) {
                    $k++;
                    $c["m$k"] = $v;
                }
                $captures[] = $c;
                if ( $n >= 0 && count( $captures ) >= $n ) {
                    break;
                }
            }
        }
 
        switch ( $this->getLuaType( $repl ) ) {
        case 'string':
        case 'number':
            $cb = function ( $m ) use ( $repl, $anypos, &$captures ) {
                if ( $anypos ) {
                    $m = array_shift( $captures );
                }
                return preg_replace_callback( '/%([%0-9])/', function ( $m2 ) use ( $m ) {
                    $x = $m2[1];
                    if ( $x === '%' ) {
                        return '%';
                    } elseif ( $x === '0' ) {
                        return $m[0];
                    } elseif ( isset( $m["m$x"] ) ) {
                        return $m["m$x"];
                    } elseif ( $x === '1' ) {
                        // Match undocumented Lua string.gsub behavior
                        return $m[0];
                    } else {
                        throw new Scribunto_LuaError( "invalid capture index %$x in replacement string" );
                    }
                }, $repl );
            };
            break;
 
        case 'table':
            $cb = function ( $m ) use ( $repl, $anypos, &$captures ) {
                if ( $anypos ) {
                    $m = array_shift( $captures );
                }
                $x = $m['m1'] ?? $m[0];
                if ( !isset( $repl[$x] ) || $repl[$x] === null ) {
                    return $m[0];
                }
                $type = $this->getLuaType( $repl[$x] );
                if ( $type !== 'string' && $type !== 'number' ) {
                    throw new Scribunto_LuaError( "invalid replacement value (a $type)" );
                }
                return $repl[$x];
            };
            break;
 
        case 'function':
            $interpreter = $this->getInterpreter();
            $cb = function ( $m ) use ( $interpreter, $capt, $repl, $anypos, &$captures ) {
                if ( $anypos ) {
                    $m = array_shift( $captures );
                }
                $args = [];
                if ( count( $capt ) ) {
                    foreach ( $capt as $i => $pos ) {
                        $args[] = $m["m$i"];
                    }
                } else {
                    $args[] = $m[0];
                }
                $ret = $interpreter->callFunction( $repl, ...$args );
                if ( count( $ret ) === 0 || $ret[0] === null ) {
                    return $m[0];
                }
                $type = $this->getLuaType( $ret[0] );
                if ( $type !== 'string' && $type !== 'number' ) {
                    throw new Scribunto_LuaError( "invalid replacement value (a $type)" );
                }
                return $ret[0];
            };
            break;
 
        default:
            $this->checkType( 'gsub', 3, $repl, 'function or table or string' );
        }
 
        $skippedMatches = 0;
        if ( $this->phpBug53823 ) {
            // Since we're having bogus matches, we need to keep track of the
            // necessary adjustment and stop manually once we hit the limit.
            $maxMatches = $n < 0 ? INF : $n;
            $n = -1;
            $realCallback = $cb;
            $cb = function ( $m ) use ( $realCallback, &$skippedMatches, &$maxMatches ) {
                $c = ord( $m['phpBug53823'] );
                if ( $c >= 0x80 && $c <= 0xbf || $maxMatches <= 0 ) {
                    $skippedMatches++;
                    return $m[0];
                } else {
                    $maxMatches--;
                    return $realCallback( $m );
                }
            };
        }
 
        $count = 0;
        $s2 = preg_replace_callback( $re, $cb, $s, $n, $count );
        if ( $s2 === null ) {
            self::handlePCREError( preg_last_error(), $pattern );
        }
        return [ $s2, $count - $skippedMatches ];
    }
 
    private function handlePCREError( $error, $pattern ) {
        $PREG_JIT_STACKLIMIT_ERROR = defined( 'PREG_JIT_STACKLIMIT_ERROR' )
            ? PREG_JIT_STACKLIMIT_ERROR
            : 'PREG_JIT_STACKLIMIT_ERROR';
 
        $error = preg_last_error();
        switch ( $error ) {
            case PREG_NO_ERROR:
                // Huh?
                break;
            case PREG_INTERNAL_ERROR:
                throw new Scribunto_LuaError( "PCRE internal error" );
            case PREG_BACKTRACK_LIMIT_ERROR:
                throw new Scribunto_LuaError(
                    "PCRE backtrack limit reached while matching pattern '$pattern'"
                );
            case PREG_RECURSION_LIMIT_ERROR:
                throw new Scribunto_LuaError(
                    "PCRE recursion limit reached while matching pattern '$pattern'"
                );
            case PREG_BAD_UTF8_ERROR:
                // Should have alreay been caught, but just in case
                throw new Scribunto_LuaError( "PCRE bad UTF-8 error" );
            case PREG_BAD_UTF8_OFFSET_ERROR:
                // Shouldn't happen, but just in case
                throw new Scribunto_LuaError( "PCRE bad UTF-8 offset error" );
            case $PREG_JIT_STACKLIMIT_ERROR:
                throw new Scribunto_LuaError(
                    "PCRE JIT stack limit reached while matching pattern '$pattern'"
                );
            default:
                throw new Scribunto_LuaError(
                    "PCRE error code $error while matching pattern '$pattern'"
                );
        }
    }
}