<?php

/**
 * Finding open tickets whose titles look like a given title (LIKE + SOUNDEX +
 * word overlap), limited to tickets the user can see, best match first.
 *
 * Shared by the web UI (api/check_duplicates.php, the ticket page's
 * "possible duplicates" list) and the MCP find_similar_tickets tool.
 * Extracted from check_duplicates.php.
 */

require_once dirname(__DIR__) . '/models/TicketModel.php';

class SimilarTicketService
{
    /**
     * @param array $currentUser Authenticated user row (for visibility)
     * @return array Matches: ticket_id, title, status, priority, created_at, similarity (0-100)
     */
    public static function find(mysqli $conn, array $currentUser, string $title, int $limit = 5): array
    {
        $title = trim($title);

        if (strlen($title) < 5) {
            return [];
        }

        // Search for similar titles
        // Use both LIKE for substring matching and SOUNDEX for phonetic matching
        $duplicates = [];

        // Prepare search term for LIKE
        $searchTerm = '%' . $title . '%';
        $titleWords = self::words($title);

        // Build visibility filter so users only see titles they have access to
        $ticketModel = new TicketModel($conn);
        $visFilter = $ticketModel->getVisibilityFilter($currentUser);

        // Candidates: the whole title as a substring, a SOUNDEX match, or any
        // significant word (4+ letters) in common. The scoring below decides
        // what counts as similar; without the word candidates its
        // word-overlap branch could never match anything, so e.g. "Printer
        // jammed again" never surfaced "Printer is jammed".
        $words = array_slice(array_values(array_filter($titleWords, fn($w) => mb_strlen($w) >= 4)), 0, 8);
        $wordSql = str_repeat(' OR t.title LIKE ?', count($words));
        $wordParams = array_map(fn($w) => '%' . addcslashes($w, '%_\\') . '%', $words);

        // Aliased as `t`: the visibility filter's SQL refers to t.* columns.
        // Without the alias the query failed for every non-admin and the
        // error was swallowed below, so they never saw any matches.
        // SOUNDEX is compared in SQL on both sides: PHP's soundex() keeps only
        // 4 characters (effectively the first word), which never equalled
        // MariaDB's full-length code in the WHERE and, in the scoring, made any
        // two titles sharing a first word score as "sounds alike".
        $sql = "SELECT t.ticket_id, t.title, t.status, t.priority, t.created_at,
                       SOUNDEX(t.title) = SOUNDEX(?) AS sounds_alike
                FROM tickets t
                WHERE (
                    t.title LIKE ?
                    OR SOUNDEX(t.title) = SOUNDEX(?){$wordSql}
                )
                AND t.status != 'Closed'
                AND ({$visFilter['sql']})
                ORDER BY t.created_at DESC
                LIMIT 50";

        $types = "sss" . str_repeat('s', count($words)) . $visFilter['types'];
        $params = array_merge([$title, $searchTerm, $title], $wordParams, $visFilter['params']);

        // Duplicate detection is advisory (it must not block ticket creation), so on any
        // DB error degrade gracefully to "no duplicates" rather than fataling the request.
        // mysqli may throw (default exception mode) or return false depending on config.
        try {
            $stmt = $conn->prepare($sql);
            if (!$stmt) {
                throw new RuntimeException('prepare failed: ' . $conn->error);
            }
            if (!empty($params)) {
                $stmt->bind_param($types, ...$params);
            }
            $stmt->execute();
            $result = $stmt->get_result();
            if ($result === false) {
                // Non-exception mysqli mode: execute/get_result return false instead of
                // throwing. Treat as a query failure so we don't fatal on $result below.
                throw new RuntimeException('query failed: ' . $conn->error);
            }
        } catch (Throwable $e) {
            error_log('check_duplicates: ' . $e->getMessage());
            return [];
        }

        while ($row = $result->fetch_assoc()) {
            // Calculate similarity score
            $similarity = 0;

            // Check for exact substring match
            if (stripos($row['title'], $title) !== false) {
                $similarity = 90;
            // Check SOUNDEX match
            } elseif (!empty($row['sounds_alike'])) {
                $similarity = 70;
            // Check word overlap
            } else {
                // At least two shared words: one common word (e.g. the
                // "[problem]" tag every automated ticket carries) is not
                // similarity, however short the searched title is.
                $matchingWords = array_intersect($titleWords, self::words($row['title']));
                if (count($matchingWords) >= 2) {
                    $similarity = (count($matchingWords) / max(count($titleWords), 1)) * 60;
                }
            }

            if ($similarity >= 30) {
                $duplicates[] = [
                    'ticket_id' => $row['ticket_id'],
                    'title' => $row['title'],
                    'status' => $row['status'],
                    'priority' => $row['priority'],
                    'created_at' => $row['created_at'],
                    'similarity' => round($similarity)
                ];
            }
        }

        $stmt->close();

        // Sort by similarity descending
        usort($duplicates, function ($a, $b) {
            return $b['similarity'] - $a['similarity'];
        });

        // Keep the best matches
        return array_slice($duplicates, 0, $limit);
    }

    /**
     * Distinct lowercase words of a title, split on anything that isn't a
     * letter or digit (so "[ceph]" and "ceph" are the same word).
     *
     * @return list<string>
     */
    private static function words(string $title): array
    {
        return array_values(array_unique(array_filter(
            preg_split('/[^\p{L}\p{N}]+/u', mb_strtolower($title)),
            fn($w) => $w !== ''
        )));
    }
}