<?php

/*
 +-----------------------------------------------------------------------+
 | This file is part of the Roundcube Webmail client                     |
 |                                                                       |
 | Copyright (C) The Roundcube Dev Team                                  |
 | Copyright (C) Kolab Systems AG                                        |
 |                                                                       |
 | Licensed under the GNU General Public License version 3 or            |
 | any later version with exceptions for skins & plugins.                |
 | See the README file for a full license statement.                     |
 |                                                                       |
 | PURPOSE:                                                              |
 |   THREAD response handler                                             |
 +-----------------------------------------------------------------------+
 | Author: Thomas Bruederli <roundcube@gmail.com>                        |
 | Author: Aleksander Machniak <alec@alec.pl>                            |
 +-----------------------------------------------------------------------+
*/

/**
 * Class for accessing IMAP's THREAD result
 */
class rcube_result_thread
{
    public $incomplete = false;

    protected $raw_data;
    protected $mailbox;
    protected $meta = [];
    protected $order = 'ASC';

    public const SEPARATOR_ELEMENT = ' ';
    public const SEPARATOR_ITEM = '~';
    public const SEPARATOR_LEVEL = ':';

    /**
     * Object constructor.
     */
    public function __construct($mailbox = null, $data = null)
    {
        $this->mailbox = $mailbox;
        $this->init($data);
    }

    /**
     * Initializes object with IMAP command response
     *
     * @param string $data IMAP response string
     */
    public function init($data = null)
    {
        $this->meta = [];

        $data = explode('*', (string) $data);

        // ...skip unilateral untagged server responses
        for ($i = 0, $len = count($data); $i < $len; $i++) {
            if (preg_match('/^ THREAD/i', $data[$i])) {
                // valid response, initialize raw_data for is_error()
                $this->raw_data = '';
                $data[$i] = substr($data[$i], 7);
                break;
            }

            unset($data[$i]);
        }

        if (empty($data)) {
            return;
        }

        $data = array_first($data);
        $data = trim($data);
        $data = preg_replace('/[\r\n]/', '', $data);
        $data = preg_replace('/\s+/', ' ', $data);

        $this->raw_data = empty($data) ? '' : $this->parse_thread($data);
    }

    /**
     * Checks the result from IMAP command
     *
     * @return bool True if the result is an error, False otherwise
     */
    public function is_error()
    {
        return $this->raw_data === null;
    }

    /**
     * Checks if the result is empty
     *
     * @return bool True if the result is empty, False otherwise
     */
    public function is_empty()
    {
        return empty($this->raw_data);
    }

    /**
     * Returns number of elements (threads) in the result
     *
     * @return int Number of elements
     */
    public function count()
    {
        if (isset($this->meta['count'])) {
            return $this->meta['count'];
        }

        if (empty($this->raw_data)) {
            $this->meta['count'] = 0;
        } else {
            $this->meta['count'] = 1 + substr_count($this->raw_data, self::SEPARATOR_ELEMENT);
        }

        if (!$this->meta['count']) {
            $this->meta['messages'] = 0;
        }

        return $this->meta['count'];
    }

    /**
     * Returns number of all messages in the result
     *
     * @return int Number of elements
     */
    public function count_messages()
    {
        if (isset($this->meta['messages'])) {
            return $this->meta['messages'];
        }

        if (empty($this->raw_data)) {
            $this->meta['messages'] = 0;
        } else {
            $this->meta['messages'] = 1
                + substr_count($this->raw_data, self::SEPARATOR_ELEMENT)
                + substr_count($this->raw_data, self::SEPARATOR_ITEM);
        }

        if ($this->meta['messages'] == 0 || $this->meta['messages'] == 1) {
            $this->meta['count'] = $this->meta['messages'];
        }

        return $this->meta['messages'];
    }

    /**
     * Returns maximum message identifier in the result
     *
     * @return int|null Maximum message identifier
     */
    public function max()
    {
        if ($this->is_empty()) {
            return null;
        }

        if (!isset($this->meta['max'])) {
            $this->meta['max'] = (int) @max($this->get());
        }

        return $this->meta['max'];
    }

    /**
     * Returns minimum message identifier in the result
     *
     * @return int|null Minimum message identifier
     */
    public function min()
    {
        if ($this->is_empty()) {
            return null;
        }

        if (!isset($this->meta['min'])) {
            $this->meta['min'] = (int) @min($this->get());
        }

        return $this->meta['min'];
    }

    /**
     * Slices data set.
     *
     * @param int $offset Offset (as for PHP's array_slice())
     * @param int $length Number of elements (as for PHP's array_slice())
     */
    public function slice($offset, $length)
    {
        $data = explode(self::SEPARATOR_ELEMENT, $this->raw_data);
        $data = array_slice($data, $offset, $length);

        $this->meta = [];
        $this->meta['count'] = count($data);
        $this->raw_data = implode(self::SEPARATOR_ELEMENT, $data);
    }

    /**
     * Filters data set. Removes threads not listed in $roots list.
     *
     * @param array $roots list of IDs of thread roots
     */
    public function filter($roots)
    {
        $datalen = strlen($this->raw_data);
        $roots = array_flip($roots);
        $result = '';
        $start = 0;

        $this->meta = ['count' => 0];

        while ($start < $datalen
            // @phpstan-ignore-next-line
            && (($pos = strpos($this->raw_data, self::SEPARATOR_ELEMENT, $start)) !== false || ($pos = $datalen))
        ) {
            $len = $pos - $start;
            $elem = substr($this->raw_data, $start, $len);
            $start = $pos + 1;

            // extract root message ID
            if ($npos = strpos($elem, self::SEPARATOR_ITEM)) {
                $root = (int) substr($elem, 0, $npos);
            } else {
                $root = $elem;
            }

            if (isset($roots[$root])) {
                $this->meta['count']++;
                $result .= self::SEPARATOR_ELEMENT . $elem;
            }
        }

        $this->raw_data = ltrim($result, self::SEPARATOR_ELEMENT);
    }

    /**
     * Reverts order of elements in the result
     */
    public function revert()
    {
        $this->order = $this->order == 'ASC' ? 'DESC' : 'ASC';

        if (empty($this->raw_data)) {
            return;
        }

        $data = explode(self::SEPARATOR_ELEMENT, $this->raw_data);
        $data = array_reverse($data);
        $this->raw_data = implode(self::SEPARATOR_ELEMENT, $data);

        $this->meta['pos'] = [];
    }

    /**
     * Check if the given message ID exists in the object
     *
     * @param int  $msgid     Message ID
     * @param bool $get_index When enabled element's index will be returned.
     *                        Elements are indexed starting with 0
     *
     * @return int|bool False if message ID doesn't exist, True if exists or
     *                  index of the element if $get_index=true
     */
    public function exists($msgid, $get_index = false)
    {
        $msgid = (int) $msgid;
        $begin = implode('|', [
            '^',
            preg_quote(self::SEPARATOR_ELEMENT, '/'),
            preg_quote(self::SEPARATOR_LEVEL, '/'),
        ]);
        $end = implode('|', [
            '$',
            preg_quote(self::SEPARATOR_ELEMENT, '/'),
            preg_quote(self::SEPARATOR_ITEM, '/'),
        ]);

        if (preg_match("/({$begin}){$msgid}({$end})/", $this->raw_data, $m,
            $get_index ? \PREG_OFFSET_CAPTURE : 0)
        ) {
            if ($get_index) {
                $idx = 0;
                if ($m[0][1]) {
                    $idx = substr_count($this->raw_data, self::SEPARATOR_ELEMENT, 0, $m[0][1] + 1)
                        + substr_count($this->raw_data, self::SEPARATOR_ITEM, 0, $m[0][1] + 1);
                }
                // cache position of this element, so we can use it in get_element()
                $this->meta['pos'][$idx] = (int) $m[0][1];

                return $idx;
            }

            return true;
        }

        return false;
    }

    /**
     * Return IDs of all messages in the result. Threaded data will be flattened.
     *
     * @return array List of message identifiers
     */
    public function get()
    {
        if (empty($this->raw_data)) {
            return [];
        }

        $regexp = '/(' . preg_quote(self::SEPARATOR_ELEMENT, '/')
            . '|' . preg_quote(self::SEPARATOR_ITEM, '/') . '[0-9]+' . preg_quote(self::SEPARATOR_LEVEL, '/')
            . ')/';

        return preg_split($regexp, $this->raw_data);
    }

    /**
     * Return all messages in the result.
     *
     * @return string List of message identifiers
     */
    public function get_compressed()
    {
        if (empty($this->raw_data)) {
            return '';
        }

        return rcube_imap_generic::compressMessageSet($this->get());
    }

    /**
     * Return result element at specified index (all messages, not roots)
     *
     * @param int|string $index Element's index or "FIRST" or "LAST"
     *
     * @return ?int Element value
     */
    public function get_element($index)
    {
        $count = $this->count();

        if (!$count) {
            return null;
        }

        // first element
        if ($index === 0 || $index === '0' || $index === 'FIRST') {
            preg_match('/^([0-9]+)/', $this->raw_data, $m);
            return (int) $m[1];
        }

        // last element
        if ($index === 'LAST' || $index == $count - 1) {
            preg_match('/([0-9]+)$/', $this->raw_data, $m);
            return (int) $m[1];
        }

        // do we know the position of the element or the neighbour of it?
        if (!empty($this->meta['pos'])) {
            $element = preg_quote(self::SEPARATOR_ELEMENT, '/');
            $item = preg_quote(self::SEPARATOR_ITEM, '/') . '[0-9]+' . preg_quote(self::SEPARATOR_LEVEL, '/') . '?';
            $regexp = '(' . $element . '|' . $item . ')';

            if (isset($this->meta['pos'][$index])) {
                if (preg_match('/([0-9]+)/', $this->raw_data, $m, 0, $this->meta['pos'][$index])) {
                    $result = $m[1];
                }
            } elseif (isset($this->meta['pos'][$index - 1])) {
                // get chunk of data after previous element
                $data = substr($this->raw_data, $this->meta['pos'][$index - 1] + 1, 50);
                $data = preg_replace('/^[0-9]+/', '', $data); // remove UID at $index position
                $data = preg_replace("/^{$regexp}/", '', $data); // remove separator
                if (preg_match('/^([0-9]+)/', $data, $m)) {
                    $result = $m[1];
                }
            } elseif (isset($this->meta['pos'][$index + 1])) {
                // get chunk of data before next element
                $pos = max(0, $this->meta['pos'][$index + 1] - 50);
                $len = min(50, $this->meta['pos'][$index + 1]);
                $data = substr($this->raw_data, $pos, $len);
                $data = preg_replace("/{$regexp}\$/", '', $data); // remove separator

                if (preg_match('/([0-9]+)$/', $data, $m)) {
                    $result = $m[1];
                }
            }

            if (isset($result)) {
                return (int) $result;
            }
        }

        // Finally use less effective method
        $data = $this->get();

        return !empty($data[$index]) ? intval($data[$index]) : null;
    }

    /**
     * Returns response parameters e.g. MAILBOX, ORDER
     *
     * @param string $param Parameter name
     *
     * @return array|string Response parameters or parameter value
     */
    public function get_parameters($param = null)
    {
        $params = [
            'MAILBOX' => $this->mailbox,
            'ORDER' => $this->order,
        ];

        if ($param !== null) {
            return $params[$param];
        }

        return $params;
    }

    /**
     * THREAD=REFS sorting implementation (based on provided index)
     *
     * @param rcube_result_index $index Sorted message identifiers
     */
    public function sort($index)
    {
        $this->order = $index->get_parameters('ORDER');

        if (empty($this->raw_data)) {
            return;
        }

        // when sorting search result it's good to make the index smaller
        if ($index->count() != $this->count_messages()) {
            $index->filter($this->get());
        }

        $result = array_fill_keys($index->get(), null);
        $datalen = strlen($this->raw_data);
        $start = 0;

        // Here we're parsing raw_data twice, we want only one big array
        // in memory at a time

        // Assign roots
        while (
            ($start < $datalen && ($pos = strpos($this->raw_data, self::SEPARATOR_ELEMENT, $start)))
            || ($start < $datalen && ($pos = $datalen)) // @phpstan-ignore-line
        ) {
            $len = $pos - $start;
            $elem = substr($this->raw_data, $start, $len);
            $start = $pos + 1;

            $items = explode(self::SEPARATOR_ITEM, $elem);
            $root = (int) array_shift($items);

            if ($root) {
                $result[$root] = $root;
                foreach ($items as $item) {
                    [$lv, $id] = explode(self::SEPARATOR_LEVEL, $item);
                    $result[$id] = $root;
                }
            }
        }

        // get only unique roots
        $result = array_filter($result); // make sure there are no nulls
        $result = array_unique($result);

        // Re-sort raw data
        $result = array_fill_keys($result, null);
        $start = 0;

        while (
            ($start < $datalen && ($pos = strpos($this->raw_data, self::SEPARATOR_ELEMENT, $start)))
            || ($start < $datalen && ($pos = $datalen)) // @phpstan-ignore-line
        ) {
            $len = $pos - $start;
            $elem = substr($this->raw_data, $start, $len);
            $start = $pos + 1;

            $npos = strpos($elem, self::SEPARATOR_ITEM);
            $root = (int) ($npos ? substr($elem, 0, $npos) : $elem);

            $result[$root] = $elem;
        }

        $this->raw_data = implode(self::SEPARATOR_ELEMENT, $result);
    }

    /**
     * Returns data as tree
     *
     * @return array Data tree
     */
    public function get_tree()
    {
        $datalen = strlen($this->raw_data);
        $result = [];
        $start = 0;

        while ($start < $datalen
            // @phpstan-ignore-next-line
            && (($pos = strpos($this->raw_data, self::SEPARATOR_ELEMENT, $start)) !== false || ($pos = $datalen))
        ) {
            $len = $pos - $start;
            $elem = substr($this->raw_data, $start, $len);
            $items = explode(self::SEPARATOR_ITEM, $elem);
            $result[array_shift($items)] = $this->build_thread($items);
            $start = $pos + 1;
        }

        return $result;
    }

    /**
     * Returns thread depth and children data
     *
     * @return array Thread data
     */
    public function get_thread_data()
    {
        $data = $this->get_tree();
        $depth = [];
        $children = [];

        $this->build_thread_data($data, $depth, $children);

        return [$depth, $children];
    }

    /**
     * Creates 'depth' and 'children' arrays from stored thread 'tree' data.
     */
    protected function build_thread_data($data, &$depth, &$children, $level = 0)
    {
        foreach ((array) $data as $key => $val) {
            $empty = empty($val) || !is_array($val);
            $children[$key] = !$empty;
            $depth[$key] = $level;
            if (!$empty) {
                $this->build_thread_data($val, $depth, $children, $level + 1);
            }
        }
    }

    /**
     * Converts part of the raw thread into an array
     */
    protected function build_thread($items, $level = 1, &$pos = 0)
    {
        $result = [];

        for ($len = count($items); $pos < $len; $pos++) {
            [$lv, $id] = explode(self::SEPARATOR_LEVEL, $items[$pos]);
            if ($level == $lv) {
                $pos++;
                $result[$id] = $this->build_thread($items, $level + 1, $pos);
            } else {
                $pos--;
                break;
            }
        }

        return $result;
    }

    /**
     * IMAP THREAD response parser
     */
    protected function parse_thread($str, $begin = 0, $end = 0, $depth = 0)
    {
        // Don't be tempted to change $str to pass by reference to speed this up - it will slow it down by about
        // 7 times instead :-) See comments on https://www.php.net/references and this article:
        // https://derickrethans.nl/files/phparch-php-variables-article.pdf
        $node = '';
        if (!$end) {
            $end = strlen($str);
        }

        // Let's try to store data in max. compacted structure as a string,
        // arrays handling is much more expensive
        // For the following structure: THREAD (2)(3 6 (4 23)(44 7 96))((11)(12))
        // -- 2
        // -- 3
        //     \-- 6
        //         |-- 4
        //         |    \-- 23
        //         |
        //         \-- 44
        //               \-- 7
        //                    \-- 96
        // -- 11
        //      \-- 12
        //
        // The output will be: 2 3~1:6~2:4~3:23~2:44~3:7~4:96 11~1:12
        // Note: The "11" thread has no root, we use the first message as root

        if ($str[$begin] != '(') {
            // find next bracket
            $stop = $begin + strcspn($str, '()', $begin, $end - $begin);
            $messages = explode(' ', trim(substr($str, $begin, $stop - $begin)));

            if (empty($messages[0])) {
                return $node;
            }

            foreach ($messages as $msg) {
                if ($msg) {
                    $node .= ($depth ? self::SEPARATOR_ITEM . $depth . self::SEPARATOR_LEVEL : '') . $msg;
                    if (isset($this->meta['messages'])) {
                        $this->meta['messages']++;
                    } else {
                        $this->meta['messages'] = 1;
                    }
                    $depth++;
                }
            }

            if ($stop < $end) {
                $node .= $this->parse_thread($str, $stop, $end, $depth);
            }
        } else {
            $off = $begin;
            while ($off < $end) {
                $start = $off;
                $off++;
                $n = 1;
                while ($n > 0) {
                    $p = strpos($str, ')', $off);
                    if ($p === false) {
                        // error, wrong structure, mismatched brackets in IMAP THREAD response
                        // @TODO: write error to the log or maybe set $this->raw_data = null;
                        return $node;
                    }

                    $p1 = strpos($str, '(', $off);
                    if ($p1 !== false && $p1 < $p) {
                        $off = $p1 + 1;
                        $n++;
                    } else {
                        $off = $p + 1;
                        $n--;
                    }
                }

                // Handle threads with missing parent by using first message as root
                if (substr_compare($str, '((', $start, 2) === 0) {
                    // Extract the current thread, e.g. "((1)(2))"
                    $thread = substr($str, $start, $off - $start);
                    // Length of the first token, e.g. "(1)"
                    $len = strspn($thread, '(0123456789', 1) + 1;
                    // Extract the token and modify it to look like a thread root
                    $token = substr($thread, 1, $len);
                    // Warning: The order is important
                    $token = str_replace('(', '', $token);
                    $token = str_replace(' ', ' (', $token);
                    $token = str_replace(')', ' ', $token);
                    $thread = substr_replace($thread, $token, 1, $len);
                    // Parse the thread
                    $thread = $this->parse_thread($thread, 0, 0, $depth);
                } else {
                    $thread = $this->parse_thread($str, $start + 1, $off - 1, $depth);
                }

                if ($thread) {
                    if (!$depth) {
                        if ($node) {
                            $node .= self::SEPARATOR_ELEMENT;
                        }
                    }
                    $node .= $thread;
                }
            }
        }

        return $node;
    }
}
