<?php
/**
 * A collection of static methods to play with strings.
 */
class StringUtils {
    /**
     * Perform an operation equivalent to
     *
     *     preg_replace( "!$startDelim(.*?)$endDelim!", $replace, $subject );
     *
     * except that it's worst-case O(N) instead of O(N^2)
     *
     * Compared to delimiterReplace(), this implementation is fast but memory-
     * hungry and inflexible. The memory requirements are such that I don't
     * recommend using it on anything but guaranteed small chunks of text.
     */
    static function hungryDelimiterReplace( $startDelim, $endDelim, $replace, $subject ) {
        $segments = explode( $startDelim, $subject );
        $output = array_shift( $segments );
        foreach ( $segments as $s ) {
            $endDelimPos = strpos( $s, $endDelim );
            if ( $endDelimPos === false ) {
                $output .= $startDelim . $s;
            } else {
                $output .= $replace . substr( $s, $endDelimPos + strlen( $endDelim ) );
            }
        }
        return $output;
    }

    /**
     * Perform an operation equivalent to
     *
     *   preg_replace_callback( "!$startDelim(.*)$endDelim!s$flags", $callback, $subject )
     *
     * This implementation is slower than hungryDelimiterReplace but uses far less
     * memory. The delimiters are literal strings, not regular expressions.
     *
     * @param string $flags Regular expression flags
     */
    # If the start delimiter ends with an initial substring of the end delimiter,
    # e.g. in the case of C-style comments, the behaviour differs from the model
    # regex. In this implementation, the end must share no characters with the
    # start, so e.g. /*/ is not considered to be both the start and end of a
    # comment. /*/xy/*/ is considered to be a single comment with contents /xy/.
    static function delimiterReplaceCallback( $startDelim, $endDelim, $callback, $subject, $flags = '' ) {
        $inputPos = 0;
        $outputPos = 0;
        $output = '';
        $foundStart = false;
        $encStart = preg_quote( $startDelim, '!' );
        $encEnd = preg_quote( $endDelim, '!' );
        $strcmp = strpos( $flags, 'i' ) === false ? 'strcmp' : 'strcasecmp';
        $endLength = strlen( $endDelim );
        $m = array();

        while ( $inputPos < strlen( $subject ) &&
          preg_match( "!($encStart)|($encEnd)!S$flags", $subject, $m, PREG_OFFSET_CAPTURE, $inputPos ) )
        {
            $tokenOffset = $m[0][1];
            if ( $m[1][0] != '' ) {
                if ( $foundStart &&
                  $strcmp( $endDelim, substr( $subject, $tokenOffset, $endLength ) ) == 0 )
                {
                    # An end match is present at the same location
                    $tokenType = 'end';
                    $tokenLength = $endLength;
                } else {
                    $tokenType = 'start';
                    $tokenLength = strlen( $m[0][0] );
                }
            } elseif ( $m[2][0] != '' ) {
                $tokenType = 'end';
                $tokenLength = strlen( $m[0][0] );
            } else {
                throw new MWException( 'Invalid delimiter given to ' . __METHOD__ );
            }

            if ( $tokenType == 'start' ) {
                $inputPos = $tokenOffset + $tokenLength;
                # Only move the start position if we haven't already found a start
                # This means that START START END matches outer pair
                if ( !$foundStart ) {
                    # Found start
                    # Write out the non-matching section
                    $output .= substr( $subject, $outputPos, $tokenOffset - $outputPos );
                    $outputPos = $tokenOffset;
                    $contentPos = $inputPos;
                    $foundStart = true;
                }
            } elseif ( $tokenType == 'end' ) {
                if ( $foundStart ) {
                    # Found match
                    $output .= call_user_func( $callback, array(
                        substr( $subject, $outputPos, $tokenOffset + $tokenLength - $outputPos ),
                        substr( $subject, $contentPos, $tokenOffset - $contentPos )
                    ));
                    $foundStart = false;
                } else {
                    # Non-matching end, write it out
                    $output .= substr( $subject, $inputPos, $tokenOffset + $tokenLength - $outputPos );
                }
                $inputPos = $outputPos = $tokenOffset + $tokenLength;
            } else {
                throw new MWException( 'Invalid delimiter given to ' . __METHOD__ );
            }
        }
        if ( $outputPos < strlen( $subject ) ) {
            $output .= substr( $subject, $outputPos );
        }
        return $output;
    }

    /*
     * Perform an operation equivalent to
     *
     *   preg_replace( "!$startDelim(.*)$endDelim!$flags", $replace, $subject )
     *
     * @param string $startDelim Start delimiter regular expression
     * @param string $endDelim End delimiter regular expression
     * @param string $replace Replacement string. May contain $1, which will be
     *               replaced by the text between the delimiters
     * @param string $subject String to search
     * @return string The string with the matches replaced
     */
    static function delimiterReplace( $startDelim, $endDelim, $replace, $subject, $flags = '' ) {
        $replacer = new RegexlikeReplacer( $replace );
        return self::delimiterReplaceCallback( $startDelim, $endDelim,
            $replacer->cb(), $subject, $flags );
    }

    /**
     * More or less "markup-safe" explode()
     * Ignores any instances of the separator inside <...>
     * @param string $separator
     * @param string $text
     * @return array
     */
    static function explodeMarkup( $separator, $text ) {
        $placeholder = "\x00";

        // Remove placeholder instances
        $text = str_replace( $placeholder, '', $text );

        // Replace instances of the separator inside HTML-like tags with the placeholder
        $replacer = new DoubleReplacer( $separator, $placeholder );
        $cleaned = StringUtils::delimiterReplaceCallback( '<', '>', $replacer->cb(), $text );

        // Explode, then put the replaced separators back in
        $items = explode( $separator, $cleaned );
        foreach( $items as $i => $str ) {
            $items[$i] = str_replace( $placeholder, $separator, $str );
        }

        return $items;
    }

    /**
     * Escape a string to make it suitable for inclusion in a preg_replace()
     * replacement parameter.
     *
     * @param string $string
     * @return string
     */
    static function escapeRegexReplacement( $string ) {
        $string = str_replace( '\\', '\\\\', $string );
        $string = str_replace( '$', '\\$', $string );
        return $string;
    }

    /**
     * Workalike for explode() with limited memory usage.
     * Returns an Iterator
     */
    static function explode( $separator, $subject ) {
        if ( substr_count( $subject, $separator ) > 1000 ) {
            return new ExplodeIterator( $separator, $subject );
        } else {
            return new ArrayIterator( explode( $separator, $subject ) );
        }
    }
}

/**
 * Base class for "replacers", objects used in preg_replace_callback() and
 * StringUtils::delimiterReplaceCallback()
 */
class Replacer {
    function cb() {
        return array( &$this, 'replace' );
    }
}

/**
 * Class to replace regex matches with a string similar to that used in preg_replace()
 */
class RegexlikeReplacer extends Replacer {
    var $r;
    function __construct( $r ) {
        $this->r = $r;
    }

    function replace( $matches ) {
        $pairs = array();
        foreach ( $matches as $i => $match ) {
            $pairs["\$$i"] = $match;
        }
        return strtr( $this->r, $pairs );
    }

}

/**
 * Class to perform secondary replacement within each replacement string
 */
class DoubleReplacer extends Replacer {
    function __construct( $from, $to, $index = 0 ) {
        $this->from = $from;
        $this->to = $to;
        $this->index = $index;
    }

    function replace( $matches ) {
        return str_replace( $this->from, $this->to, $matches[$this->index] );
    }
}

/**
 * Class to perform replacement based on a simple hashtable lookup
 */
class HashtableReplacer extends Replacer {
    var $table, $index;

    function __construct( $table, $index = 0 ) {
        $this->table = $table;
        $this->index = $index;
    }

    function replace( $matches ) {
        return $this->table[$matches[$this->index]];
    }
}

/**
 * Replacement array for FSS with fallback to strtr()
 * Supports lazy initialisation of FSS resource
 */
class ReplacementArray {
    /*mostly private*/ var $data = false;
    /*mostly private*/ var $fss = false;

    /**
     * Create an object with the specified replacement array
     * The array should have the same form as the replacement array for strtr()
     */
    function __construct( $data = array() ) {
        $this->data = $data;
    }

    function __sleep() {
        return array( 'data' );
    }

    function __wakeup() {
        $this->fss = false;
    }

    /**
     * Set the whole replacement array at once
     */
    function setArray( $data ) {
        $this->data = $data;
        $this->fss = false;
    }

    function getArray() {
        return $this->data;
    }

    /**
     * Set an element of the replacement array
     */
    function setPair( $from, $to ) {
        $this->data[$from] = $to;
        $this->fss = false;
    }

    function mergeArray( $data ) {
        $this->data = array_merge( $this->data, $data );
        $this->fss = false;
    }

    function merge( $other ) {
        $this->data = array_merge( $this->data, $other->data );
        $this->fss = false;
    }

    function removePair( $from ) {
        unset($this->data[$from]);
        $this->fss = false;
    }

    function removeArray( $data ) {
        foreach( $data as $from => $to )
            $this->removePair( $from );
        $this->fss = false;
    }

    function replace( $subject ) {
        if ( function_exists( 'fss_prep_replace' ) ) {
            if ( $this->fss === false ) {
                $this->fss = fss_prep_replace( $this->data );
            }
            $result = fss_exec_replace( $this->fss, $subject );
        } else {
            $result = strtr( $subject, $this->data );
        }
        return $result;
    }
}

/**
 * An iterator which works exactly like:
 * 
 * foreach ( explode( $delim, $s ) as $element ) {
 *    ...
 * }
 *
 * Except it doesn't use 193 byte per element
 */
class ExplodeIterator implements Iterator {
    // The subject string
    var $subject, $subjectLength;

    // The delimiter
    var $delim, $delimLength;

    // The position of the start of the line
    var $curPos;

    // The position after the end of the next delimiter
    var $endPos;

    // The current token
    var $current;

    /** 
     * Construct a DelimIterator
     */
    function __construct( $delim, $s ) {
        $this->subject = $s;
        $this->delim = $delim;

        // Micro-optimisation (theoretical)
        $this->subjectLength = strlen( $s );
        $this->delimLength = strlen( $delim );

        $this->rewind();
    }

    function rewind() {
        $this->curPos = 0;
        $this->endPos = strpos( $this->subject, $this->delim );
        $this->refreshCurrent();
    }


    function refreshCurrent() {
        if ( $this->curPos === false ) {
            $this->current = false;
        } elseif ( $this->curPos >= $this->subjectLength ) {
            $this->current = '';
        } elseif ( $this->endPos === false ) {
            $this->current = substr( $this->subject, $this->curPos );
        } else {
            $this->current = substr( $this->subject, $this->curPos, $this->endPos - $this->curPos );
        }
    }

    function current() {
        return $this->current;
    }

    function key() {
        return $this->curPos;
    }

    function next() {
        if ( $this->endPos === false ) {
            $this->curPos = false;
        } else {
            $this->curPos = $this->endPos + $this->delimLength;
            if ( $this->curPos >= $this->subjectLength ) {
                $this->endPos = false;
            } else {
                $this->endPos = strpos( $this->subject, $this->delim, $this->curPos );
            }
        }
        $this->refreshCurrent();
        return $this->current;
    }

    function valid() {
        return $this->curPos !== false;
    }
}