<?php
namespace dokuwiki\Search;

use dokuwiki\Extension\Event;
use dokuwiki\Search\Indexer;
use dokuwiki\Utf8;

/**
 * Class DokuWiki Fulltext Search
 *
 * @license    GPL 2 (http://www.gnu.org/licenses/gpl.html)
 * @author     Andreas Gohr <andi@splitbrain.org>
 */
class FulltextSearch
{
    /**
     *  Fulltext Search constructor. prevent direct object creation
     */
    protected function __construct() {}

    /**
     * The fulltext search
     *
     * Returns a list of matching documents for the given query
     *
     * refactored into ft_pageSearch(), _ft_pageSearch() and trigger_event()
     *
     * @param string     $query
     * @param array      $highlight
     * @param string     $sort
     * @param int|string $after  only show results with mtime after this date,
     *                           accepts timestap or strtotime arguments
     * @param int|string $before only show results with mtime before this date,
     *                           accepts timestap or strtotime arguments
     *
     * @return array
     */
    public static function pageSearch($query, &$highlight, $sort = null, $after = null, $before = null)
    {
        if ($sort === null) {
            $sort = 'hits';
        }
        $data = [
            'query' => $query,
            'sort' => $sort,
            'after' => $after,
            'before' => $before
        ];
        $data['highlight'] =& $highlight;
        $action = static::class.'::callback_pageSearch';
        return Event::createAndTrigger('SEARCH_QUERY_FULLPAGE', $data, $action);
    }

    /**
     * Returns a list of matching documents for the given query
     *
     * @author Andreas Gohr <andi@splitbrain.org>
     * @author Kazutaka Miyasaka <kazmiya@gmail.com>
     *
     * @param array $data event data
     * @return array matching documents
     */
    public static function callback_pageSearch(&$data)
    {
        $Indexer = Indexer::getInstance();

        // parse the given query
        $q = static::queryParser($Indexer, $data['query']);
        $data['highlight'] = $q['highlight'];

        if (empty($q['parsed_ary'])) return array();

        // lookup all words found in the query
        $lookup = $Indexer->lookup($q['words']);

        // get all pages in this dokuwiki site (!: includes nonexistent pages)
        $pages_all = array();
        foreach ($Indexer->getPages() as $id) {
            $pages_all[$id] = 0; // base: 0 hit
        }

        // process the query
        $stack = array();
        foreach ($q['parsed_ary'] as $token) {
            switch (substr($token, 0, 3)) {
                case 'W+:':
                case 'W-:':
                case 'W_:': // word
                    $word    = substr($token, 3);
                    $stack[] = (array) $lookup[$word];
                    break;
                case 'P+:':
                case 'P-:': // phrase
                    $phrase = substr($token, 3);
                    // since phrases are always parsed as ((W1)(W2)...(P)),
                    // the end($stack) always points the pages that contain
                    // all words in this phrase
                    $pages  = end($stack);
                    $pages_matched = array();
                    foreach (array_keys($pages) as $id) {
                        $evdata = array(
                            'id' => $id,
                            'phrase' => $phrase,
                            'text' => rawWiki($id)
                        );
                        $evt = new Event('FULLTEXT_PHRASE_MATCH', $evdata);
                        if ($evt->advise_before() && $evt->result !== true) {
                            $text = Utf8\PhpString::strtolower($evdata['text']);
                            if (strpos($text, $phrase) !== false) {
                                $evt->result = true;
                            }
                        }
                        $evt->advise_after();
                        if ($evt->result === true) {
                            $pages_matched[$id] = 0; // phrase: always 0 hit
                        }
                    }
                    $stack[] = $pages_matched;
                    break;
                case 'N+:':
                case 'N-:': // namespace
                    $ns = cleanID(substr($token, 3)) . ':';
                    $pages_matched = array();
                    foreach (array_keys($pages_all) as $id) {
                        if (strpos($id, $ns) === 0) {
                            $pages_matched[$id] = 0; // namespace: always 0 hit
                        }
                    }
                    $stack[] = $pages_matched;
                    break;
                case 'AND': // and operation
                    list($pages1, $pages2) = array_splice($stack, -2);
                    $stack[] = static::resultCombine(array($pages1, $pages2));
                    break;
                case 'OR':  // or operation
                    list($pages1, $pages2) = array_splice($stack, -2);
                    $stack[] = static::resultUnite(array($pages1, $pages2));
                    break;
                case 'NOT': // not operation (unary)
                    $pages   = array_pop($stack);
                    $stack[] = static::resultComplement(array($pages_all, $pages));
                    break;
            }
        }
        $docs = array_pop($stack);

        if (empty($docs)) return array();

        // check: settings, acls, existence
        foreach (array_keys($docs) as $id) {
            if (isHiddenPage($id)
                || auth_quickaclcheck($id) < AUTH_READ
                || !page_exists($id, '', false)
            ) {
                unset($docs[$id]);
            }
        }

        $docs = static::filterResultsByTime($docs, $data['after'], $data['before']);

        if ($data['sort'] === 'mtime') {
            uksort($docs, static::class.'::pagemtimesorter');
        } else {
            // sort docs by count
            arsort($docs);
        }

        return $docs;
    }

    /**
     * Quicksearch for pagenames
     *
     * By default it only matches the pagename and ignores the
     * namespace. This can be changed with the second parameter.
     * The third parameter allows to search in titles as well.
     *
     * The function always returns titles as well
     *
     * @triggers SEARCH_QUERY_PAGELOOKUP
     * @author   Andreas Gohr <andi@splitbrain.org>
     * @author   Adrian Lang <lang@cosmocode.de>
     *
     * @param string     $id       page id
     * @param bool       $in_ns    match against namespace as well?
     * @param bool       $in_title search in title?
     * @param int|string $after    only show results with mtime after this date,
     *                             accepts timestap or strtotime arguments
     * @param int|string $before   only show results with mtime before this date,
     *                             accepts timestap or strtotime arguments
     *
     * @return string[]
     */
    public static function pageLookup($id, $in_ns=false, $in_title=false, $after = null, $before = null)
    {
        $data = [
            'id' => $id,
            'in_ns' => $in_ns,
            'in_title' => $in_title,
            'after' => $after,
            'before' => $before
        ];
        $data['has_titles'] = true; // for plugin backward compatibility check
        $action = static::class.'::callback_pageLookup';
        return Event::createAndTrigger('SEARCH_QUERY_PAGELOOKUP', $data, $action);
    }

    /**
     * Returns list of pages as array(pageid => First Heading)
     *
     * @param array &$data event data
     * @return string[]
     */
    public static function callback_pageLookup(&$data)
    {
        $Indexer = Indexer::getInstance();

        // split out original parameters
        $id = $data['id'];
        $parsedQuery = static::queryParser($Indexer, $id);
        if (count($parsedQuery['ns']) > 0) {
            $ns = cleanID($parsedQuery['ns'][0]) . ':';
            $id = implode(' ', $parsedQuery['highlight']);
        }

        $in_ns    = $data['in_ns'];
        $in_title = $data['in_title'];
        $cleaned = cleanID($id);

        $pages = array();
        if ($id !== '' && $cleaned !== '') {
            $page_idx = $Indexer->getPages();
            foreach ($page_idx as $p_id) {
                if ((strpos($in_ns ? $p_id : noNSorNS($p_id), $cleaned) !== false)) {
                    if (!isset($pages[$p_id])) {
                        $pages[$p_id] = p_get_first_heading($p_id, METADATA_DONT_RENDER);
                    }
                }
            }
            if ($in_title) {
                $func = static::class.'::pageLookupTitleCompare';
                foreach ($Indexer->lookupKey('title', $id, $func) as $p_id) {
                    if (!isset($pages[$p_id])) {
                        $pages[$p_id] = p_get_first_heading($p_id, METADATA_DONT_RENDER);
                    }
                }
            }
        }

        if (isset($ns)) {
            foreach (array_keys($pages) as $p_id) {
                if (strpos($p_id, $ns) !== 0) {
                    unset($pages[$p_id]);
                }
            }
        }

        // discard hidden pages
        // discard nonexistent pages
        // check ACL permissions
        foreach (array_keys($pages) as $idx) {
            if (!isVisiblePage($idx) || !page_exists($idx) || auth_quickaclcheck($idx) < AUTH_READ) {
                unset($pages[$idx]);
            }
        }

        $pages = static::filterResultsByTime($pages, $data['after'], $data['before']);

        uksort($pages, static::class.'::pagesorter');
        return $pages;
    }

    /**
     * @param array      $results search results in the form pageid => value
     * @param int|string $after   only returns results with mtime after this date,
     *                            accepts timestap or strtotime arguments
     * @param int|string $before  only returns results with mtime after this date,
     *                            accepts timestap or strtotime arguments
     *
     * @return array
     */
    protected static function filterResultsByTime(array $results, $after, $before)
    {
        if ($after || $before) {
            $after = is_int($after) ? $after : strtotime($after);
            $before = is_int($before) ? $before : strtotime($before);

            foreach ($results as $id => $value) {
                $mTime = filemtime(wikiFN($id));
                if ($after && $after > $mTime) {
                    unset($results[$id]);
                    continue;
                }
                if ($before && $before < $mTime) {
                    unset($results[$id]);
                }
            }
        }

        return $results;
    }

    /**
     * Tiny helper function for comparing the searched title with the title
     * from the search index. This function is a wrapper around stripos with
     * adapted argument order and return value.
     *
     * @param string $search searched title
     * @param string $title  title from index
     * @return bool
     */
    protected static function pageLookupTitleCompare($search, $title)
    {
        return stripos($title, $search) !== false;
    }

    /**
     * Sort pages based on their namespace level first, then on their string
     * values. This makes higher hierarchy pages rank higher than lower hierarchy
     * pages.
     *
     * @param string $a
     * @param string $b
     * @return int Returns < 0 if $a is less than $b; > 0 if $a is greater than $b,
     *             and 0 if they are equal.
     */
    protected static function pagesorter($a, $b)
    {
        $ac = count(explode(':',$a));
        $bc = count(explode(':',$b));
        if ($ac < $bc) {
            return -1;
        } elseif ($ac > $bc) {
            return 1;
        }
        return strcmp ($a,$b);
    }

    /**
     * Sort pages by their mtime, from newest to oldest
     *
     * @param string $a
     * @param string $b
     *
     * @return int Returns < 0 if $a is newer than $b, > 0 if $b is newer than $a
     *             and 0 if they are of the same age
     */
    protected static function pagemtimesorter($a, $b)
    {
        $mtimeA = filemtime(wikiFN($a));
        $mtimeB = filemtime(wikiFN($b));
        return $mtimeB - $mtimeA;
    }

    /**
     * Creates a snippet extract
     *
     * @author Andreas Gohr <andi@splitbrain.org>
     * @triggers FULLTEXT_SNIPPET_CREATE
     *
     * @param string $id page id
     * @param array $highlight
     * @return mixed
     */
    public static function snippet($id, $highlight)
    {
        $text = rawWiki($id);
        $text = str_replace("\xC2\xAD",'',$text); // remove soft-hyphens
        $evdata = array(
            'id'        => $id,
            'text'      => &$text,
            'highlight' => &$highlight,
            'snippet'   => '',
        );

        $evt = new Event('FULLTEXT_SNIPPET_CREATE', $evdata);
        if ($evt->advise_before()) {
            $match = array();
            $snippets = array();
            $utf8_offset = $offset = $end = 0;
            $len = Utf8\PhpString::strlen($text);

            // build a regexp from the phrases to highlight
            $re1 = '(' .
                join(
                    '|',
                    array_map(
                        static::class.'::snippet_re_preprocess',
                        array_map(
                            'preg_quote_cb',
                            array_filter((array) $highlight)
                        )
                    )
                ) .
                ')';
            $re2 = "$re1.{0,75}(?!\\1)$re1";
            $re3 = "$re1.{0,45}(?!\\1)$re1.{0,45}(?!\\1)(?!\\2)$re1";

            for ($cnt=4; $cnt--;) {
                if (0) {
                } elseif (preg_match('/'.$re3.'/iu', $text, $match, PREG_OFFSET_CAPTURE, $offset)) {
                } elseif (preg_match('/'.$re2.'/iu', $text, $match, PREG_OFFSET_CAPTURE, $offset)) {
                } elseif (preg_match('/'.$re1.'/iu', $text, $match, PREG_OFFSET_CAPTURE, $offset)) {
                } else {
                    break;
                }

                list($str, $idx) = $match[0];

                // convert $idx (a byte offset) into a utf8 character offset
                $utf8_idx = Utf8\PhpString::strlen(substr($text, 0, $idx));
                $utf8_len = Utf8\PhpString::strlen($str);

                // establish context, 100 bytes surrounding the match string
                // first look to see if we can go 100 either side,
                // then drop to 50 adding any excess if the other side can't go to 50,
                $pre = min($utf8_idx - $utf8_offset, 100);
                $post = min($len - $utf8_idx - $utf8_len, 100);

                if ($pre > 50 && $post > 50) {
                    $pre = $post = 50;
                } elseif ($pre > 50) {
                    $pre = min($pre, 100 - $post);
                } elseif ($post > 50) {
                    $post = min($post, 100 - $pre);
                } elseif ($offset == 0) {
                    // both are less than 50, means the context is the whole string
                    // make it so and break out of this loop - there is no need for the
                    // complex snippet calculations
                    $snippets = array($text);
                    break;
                }

                // establish context start and end points, try to append to previous
                // context if possible
                $start = $utf8_idx - $pre;
                $append = ($start < $end) ? $end : false;  // still the end of the previous context snippet
                $end = $utf8_idx + $utf8_len + $post;      // now set it to the end of this context

                if ($append) {
                    $snippets[count($snippets)-1] .= Utf8\PhpString::substr($text, $append, $end-$append);
                } else {
                    $snippets[] = Utf8\PhpString::substr($text, $start, $end-$start);
                }

                // set $offset for next match attempt
                // continue matching after the current match
                // if the current match is not the longest possible match starting at the current offset
                // this prevents further matching of this snippet but for possible matches of length
                // smaller than match length + context (at least 50 characters) this match is part of the context
                $utf8_offset = $utf8_idx + $utf8_len;
                $offset = $idx + strlen(Utf8\PhpString::substr($text, $utf8_idx, $utf8_len));
                $offset = Utf8\Clean::correctIdx($text, $offset);
            }

            $m = "\1";
            $snippets = preg_replace('/'.$re1.'/iu', $m.'$1'.$m, $snippets);
            $snippet = preg_replace(
                '/' . $m . '([^' . $m . ']*?)' . $m . '/iu',
                '<strong class="search_hit">$1</strong>',
                hsc(join('... ', $snippets))
            );

            $evdata['snippet'] = $snippet;
        }
        $evt->advise_after();
        unset($evt);

        return $evdata['snippet'];
    }

    /**
     * Wraps a search term in regex boundary checks.
     *
     * @param string $term
     * @return string
     */
    public static function snippet_re_preprocess($term)
    {
        // do not process asian terms where word boundaries are not explicit
        if (Utf8\Asian::isAsianWords($term)) return $term;

        if (UTF8_PROPERTYSUPPORT) {
            // unicode word boundaries
            // see http://stackoverflow.com/a/2449017/172068
            $BL = '(?<!\pL)';
            $BR = '(?!\pL)';
        } else {
            // not as correct as above, but at least won't break
            $BL = '\b';
            $BR = '\b';
        }

        if (substr($term, 0, 2) == '\\*') {
            $term = substr($term, 2);
        } else {
            $term = $BL.$term;
        }

        if (substr($term, -2, 2) == '\\*') {
            $term = substr($term, 0, -2);
        } else {
            $term = $term.$BR;
        }

        if ($term == $BL || $term == $BR || $term == $BL.$BR) {
            $term = '';
        }
        return $term;
    }

    /**
     * Combine found documents and sum up their scores
     *
     * This function is used to combine searched words with a logical
     * AND. Only documents available in all arrays are returned.
     *
     * based upon PEAR's PHP_Compat function for array_intersect_key()
     *
     * @param array $args An array of page arrays
     * @return array
     */
    protected static function resultCombine($args)
    {
        $array_count = count($args);
        if ($array_count == 1) {
            return $args[0];
        }

        $result = array();
        if ($array_count > 1) {
            foreach ($args[0] as $key => $value) {
                $result[$key] = $value;
                for ($i = 1; $i !== $array_count; $i++) {
                    if (!isset($args[$i][$key])) {
                        unset($result[$key]);
                        break;
                    }
                    $result[$key] += $args[$i][$key];
                }
            }
        }
        return $result;
    }

    /**
     * Unites found documents and sum up their scores
     * based upon resultCombine() method
     *
     * @param array $args An array of page arrays
     * @return array
     *
     * @author Kazutaka Miyasaka <kazmiya@gmail.com>
     */
    protected static function resultUnite($args)
    {
        $array_count = count($args);
        if ($array_count === 1) {
            return $args[0];
        }

        $result = $args[0];
        for ($i = 1; $i !== $array_count; $i++) {
            foreach (array_keys($args[$i]) as $id) {
                $result[$id] += $args[$i][$id];
            }
        }
        return $result;
    }

    /**
     * Computes the difference of documents using page id for comparison
     * nearly identical to PHP5's array_diff_key()
     *
     * @param array $args An array of page arrays
     * @return array
     *
     * @author Kazutaka Miyasaka <kazmiya@gmail.com>
     */
    protected static function resultComplement($args)
    {
        $array_count = count($args);
        if ($array_count === 1) {
            return $args[0];
        }

        $result = $args[0];
        foreach (array_keys($result) as $id) {
            for ($i = 1; $i !== $array_count; $i++) {
                if (isset($args[$i][$id])) unset($result[$id]);
            }
        }
        return $result;
    }

    /**
     * Parses a search query and builds an array of search formulas
     *
     * @author Andreas Gohr <andi@splitbrain.org>
     * @author Kazutaka Miyasaka <kazmiya@gmail.com>
     *
     * @param Indexer $Indexer
     * @param string $query search query
     * @return array of search formulas
     */
    public static function queryParser($Indexer, $query)
    {
        /**
         * parse a search query and transform it into intermediate representation
         *
         * in a search query, you can use the following expressions:
         *
         *   words:
         *     include
         *     -exclude
         *   phrases:
         *     "phrase to be included"
         *     -"phrase you want to exclude"
         *   namespaces:
         *     @include:namespace (or ns:include:namespace)
         *     ^exclude:namespace (or -ns:exclude:namespace)
         *   groups:
         *     ()
         *     -()
         *   operators:
         *     and ('and' is the default operator: you can always omit this)
         *     or  (or pipe symbol '|', lower precedence than 'and')
         *
         * e.g. a query [ aa "bb cc" @dd:ee ] means "search pages which contain
         *      a word 'aa', a phrase 'bb cc' and are within a namespace 'dd:ee'".
         *      this query is equivalent to [ -(-aa or -"bb cc" or -ns:dd:ee) ]
         *      as long as you don't mind hit counts.
         *
         * intermediate representation consists of the following parts:
         *
         *   ( )           - group
         *   AND           - logical and
         *   OR            - logical or
         *   NOT           - logical not
         *   W+:, W-:, W_: - word      (underscore: no need to highlight)
         *   P+:, P-:      - phrase    (minus sign: logically in NOT group)
         *   N+:, N-:      - namespace
         */
        $parsed_query = '';
        $parens_level = 0;
        $terms = preg_split('/(-?".*?")/u', Utf8\PhpString::strtolower($query),
                    -1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY
        );

        foreach ($terms as $term) {
            $parsed = '';
            if (preg_match('/^(-?)"(.+)"$/u', $term, $matches)) {
                // phrase-include and phrase-exclude
                $not = $matches[1] ? 'NOT' : '';
                $parsed = $not . static::termParser($Indexer, $matches[2], false, true);
            } else {
                // fix incomplete phrase
                $term = str_replace('"', ' ', $term);

                // fix parentheses
                $term = str_replace(')'  , ' ) ', $term);
                $term = str_replace('('  , ' ( ', $term);
                $term = str_replace('- (', ' -(', $term);

                // treat pipe symbols as 'OR' operators
                $term = str_replace('|', ' or ', $term);

                // treat ideographic spaces (U+3000) as search term separators
                // FIXME: some more separators?
                $term = preg_replace('/[ \x{3000}]+/u', ' ',  $term);
                $term = trim($term);
                if ($term === '') continue;

                $tokens = explode(' ', $term);
                foreach ($tokens as $token) {
                    if ($token === '(') {
                        // parenthesis-include-open
                        $parsed .= '(';
                        ++$parens_level;
                    } elseif ($token === '-(') {
                        // parenthesis-exclude-open
                        $parsed .= 'NOT(';
                        ++$parens_level;
                    } elseif ($token === ')') {
                        // parenthesis-any-close
                        if ($parens_level === 0) continue;
                        $parsed .= ')';
                        $parens_level--;
                    } elseif ($token === 'and') {
                        // logical-and (do nothing)
                    } elseif ($token === 'or') {
                        // logical-or
                        $parsed .= 'OR';
                    } elseif (preg_match('/^(?:\^|-ns:)(.+)$/u', $token, $matches)) {
                        // namespace-exclude
                        $parsed .= 'NOT(N+:'.$matches[1].')';
                    } elseif (preg_match('/^(?:@|ns:)(.+)$/u', $token, $matches)) {
                        // namespace-include
                        $parsed .= '(N+:'.$matches[1].')';
                    } elseif (preg_match('/^-(.+)$/', $token, $matches)) {
                        // word-exclude
                        $parsed .= 'NOT('.static::termParser($Indexer, $matches[1]).')';
                    } else {
                        // word-include
                        $parsed .= static::termParser($Indexer, $token);
                    }
                }
            }
            $parsed_query .= $parsed;
        }

        // cleanup (very sensitive)
        $parsed_query .= str_repeat(')', $parens_level);
        do {
            $parsed_query_old = $parsed_query;
            $parsed_query = preg_replace('/(NOT)?\(\)/u', '', $parsed_query);
        } while ($parsed_query !== $parsed_query_old);
        $parsed_query = preg_replace('/(NOT|OR)+\)/u', ')'      , $parsed_query);
        $parsed_query = preg_replace('/(OR)+/u'      , 'OR'     , $parsed_query);
        $parsed_query = preg_replace('/\(OR/u'       , '('      , $parsed_query);
        $parsed_query = preg_replace('/^OR|OR$/u'    , ''       , $parsed_query);
        $parsed_query = preg_replace('/\)(NOT)?\(/u' , ')AND$1(', $parsed_query);

        // adjustment: make highlightings right
        $parens_level     = 0;
        $notgrp_levels    = array();
        $parsed_query_new = '';
        $tokens = preg_split('/(NOT\(|[()])/u', $parsed_query,
                    -1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY
        );
        foreach ($tokens as $token) {
            if ($token === 'NOT(') {
                $notgrp_levels[] = ++$parens_level;
            } elseif ($token === '(') {
                ++$parens_level;
            } elseif ($token === ')') {
                if ($parens_level-- === end($notgrp_levels)) array_pop($notgrp_levels);
            } elseif (count($notgrp_levels) % 2 === 1) {
                // turn highlight-flag off if terms are logically in "NOT" group
                $token = preg_replace('/([WPN])\+\:/u', '$1-:', $token);
            }
            $parsed_query_new .= $token;
        }
        $parsed_query = $parsed_query_new;

        /**
         * convert infix notation string into postfix (Reverse Polish notation) array
         * by Shunting-yard algorithm
         *
         * see: http://en.wikipedia.org/wiki/Reverse_Polish_notation
         * see: http://en.wikipedia.org/wiki/Shunting-yard_algorithm
         */
        $parsed_ary     = array();
        $ope_stack      = array();
        $ope_precedence = array(')' => 1, 'OR' => 2, 'AND' => 3, 'NOT' => 4, '(' => 5);
        $ope_regex      = '/([()]|OR|AND|NOT)/u';

        $tokens = preg_split($ope_regex, $parsed_query,
                    -1, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY
        );
        foreach ($tokens as $token) {
            if (preg_match($ope_regex, $token)) {
                // operator
                $last_ope = end($ope_stack);
                while ($last_ope !== false
                    && $ope_precedence[$token] <= $ope_precedence[$last_ope]
                    && $last_ope != '('
                ) {
                    $parsed_ary[] = array_pop($ope_stack);
                    $last_ope = end($ope_stack);
                }
                if ($token == ')') {
                    array_pop($ope_stack); // this array_pop always deletes '('
                } else {
                    $ope_stack[] = $token;
                }
            } else {
                // operand
                $token_decoded = str_replace(['OP','CP'], ['(',')'], $token);
                $parsed_ary[] = $token_decoded;
            }
        }
        $parsed_ary = array_values(array_merge($parsed_ary, array_reverse($ope_stack)));

        // cleanup: each double "NOT" in RPN array actually does nothing
        $parsed_ary_count = count($parsed_ary);
        for ($i = 1; $i < $parsed_ary_count; ++$i) {
            if ($parsed_ary[$i] === 'NOT' && $parsed_ary[$i - 1] === 'NOT') {
                unset($parsed_ary[$i], $parsed_ary[$i - 1]);
            }
        }
        $parsed_ary = array_values($parsed_ary);

        // build return value
        $q = array();
        $q['query']      = $query;
        $q['parsed_str'] = $parsed_query;
        $q['parsed_ary'] = $parsed_ary;

        foreach ($q['parsed_ary'] as $token) {
            if ($token[2] !== ':') continue;
            $body = substr($token, 3);

            switch (substr($token, 0, 3)) {
                case 'N+:':
                     $q['ns'][]        = $body; // for backward compatibility
                     break;
                case 'N-:':
                     $q['notns'][]     = $body; // for backward compatibility
                     break;
                case 'W_:':
                     $q['words'][]     = $body;
                     break;
                case 'W-:':
                     $q['words'][]     = $body;
                     $q['not'][]       = $body; // for backward compatibility
                     break;
                case 'W+:':
                     $q['words'][]     = $body;
                     $q['highlight'][] = $body;
                     $q['and'][]       = $body; // for backward compatibility
                     break;
                case 'P-:':
                     $q['phrases'][]   = $body;
                     break;
                case 'P+:':
                     $q['phrases'][]   = $body;
                     $q['highlight'][] = $body;
                     break;
            }
        }
        foreach (['words', 'phrases', 'highlight', 'ns', 'notns', 'and', 'not'] as $key) {
            $q[$key] = empty($q[$key]) ? array() : array_values(array_unique($q[$key]));
        }

        return $q;
    }

    /**
     * Transforms given search term into intermediate representation
     *
     * This function is used in ft_queryParser() and not for general purpose use.
     *
     * @author Kazutaka Miyasaka <kazmiya@gmail.com>
     *
     * @param Indexer      $Indexer
     * @param string       $term
     * @param bool         $consider_asian
     * @param bool         $phrase_mode
     * @return string
     */
    protected static function termParser($Indexer, $term, $consider_asian = true, $phrase_mode = false)
    {
        $parsed = '';
        if ($consider_asian) {
            // successive asian characters need to be searched as a phrase
            $words = Utf8\Asian::splitAsianWords($term);
            foreach ($words as $word) {
                $phrase_mode = $phrase_mode ? true : Utf8\Asian::isAsianWords($word);
                $parsed .= static::termParser($Indexer, $word, false, $phrase_mode);
            }
        } else {
            $term_noparen = str_replace(['(',')'], ' ', $term);
            $words = $Indexer->tokenizer($term_noparen, true);

            // W_: no need to highlight
            if (empty($words)) {
                $parsed = '()'; // important: do not remove
            } elseif ($words[0] === $term) {
                $parsed = '(W+:'.$words[0].')';
            } elseif ($phrase_mode) {
                $term_encoded = str_replace(['(',')'], ['OP','CP'], $term);
                $parsed = '((W_:'.implode(')(W_:', $words).')(P+:'.$term_encoded.'))';
            } else {
                $parsed = '((W+:'.implode(')(W+:', $words).'))';
            }
        }
        return $parsed;
    }

    /**
     * Recreate a search query string based on parsed parts,
     * doesn't support negated phrases and `OR` searches
     *
     * @param array $and
     * @param array $not
     * @param array $phrases
     * @param array $ns
     * @param array $notns
     *
     * @return string
     */
    public static function queryUnparser_simple(
                        array $and, array $not, array $phrases, array $ns, array $notns
    ) {
        $query = implode(' ', $and);

        if (!empty($not)) {
            $query .= ' -' . implode(' -', $not);
        }
        if (!empty($phrases)) {
            $query .= ' "' . implode('" "', $phrases) . '"';
        }
        if (!empty($ns)) {
            $query .= ' @' . implode(' @', $ns);
        }
        if (!empty($notns)) {
            $query .= ' ^' . implode(' ^', $notns);
        }
        return $query;
    }
}