tinker_tickets/models/TicketModel.php

<?php

class TicketModel
{
    private mysqli $conn;

    public function __construct(mysqli $conn)
    {
        $this->conn = $conn;
    }

    public function getTicketById(int $id): ?array
    {
        $sql = "SELECT t.*,
                u_created.username as creator_username,
                u_created.display_name as creator_display_name,
                u_updated.username as updater_username,
                u_updated.display_name as updater_display_name,
                u_assigned.username as assigned_username,
                u_assigned.display_name as assigned_display_name
                FROM tickets t
                LEFT JOIN users u_created ON t.created_by = u_created.user_id
                LEFT JOIN users u_updated ON t.updated_by = u_updated.user_id
                LEFT JOIN users u_assigned ON t.assigned_to = u_assigned.user_id
                WHERE t.ticket_id = ?";
        $stmt = $this->conn->prepare($sql);
        $stmt->bind_param("i", $id);
        $stmt->execute();
        $result = $stmt->get_result();

        if ($result->num_rows === 0) {
            return null;
        }

        return $result->fetch_assoc();
    }

    public function getAllTickets(int $page = 1, int $limit = 15, ?string $status = 'Open', string $sortColumn = 'ticket_id', string $sortDirection = 'desc', ?string $category = null, ?string $type = null, ?string $search = null, array $filters = [], ?array $user = null): array
    {
        // Calculate offset
        $offset = ($page - 1) * $limit;

        // Build WHERE clause
        $whereConditions = [];
        $params = [];
        $paramTypes = '';

        // Visibility filtering
        if ($user !== null) {
            $visFilter = $this->getVisibilityFilter($user);
            if ($visFilter['sql'] !== '1=1') {
                $whereConditions[] = $visFilter['sql'];
                $params = array_merge($params, $visFilter['params']);
                $paramTypes .= $visFilter['types'];
            }
        }

        // Status filtering
        if ($status) {
            $statuses = explode(',', $status);
            $placeholders = str_repeat('?,', count($statuses) - 1) . '?';
            $whereConditions[] = "status IN ($placeholders)";
            $params = array_merge($params, $statuses);
            $paramTypes .= str_repeat('s', count($statuses));
        }

        // Category filtering
        if ($category) {
            $categories = explode(',', $category);
            $placeholders = str_repeat('?,', count($categories) - 1) . '?';
            $whereConditions[] = "category IN ($placeholders)";
            $params = array_merge($params, $categories);
            $paramTypes .= str_repeat('s', count($categories));
        }

        // Type filtering
        if ($type) {
            $types = explode(',', $type);
            $placeholders = str_repeat('?,', count($types) - 1) . '?';
            $whereConditions[] = "type IN ($placeholders)";
            $params = array_merge($params, $types);
            $paramTypes .= str_repeat('s', count($types));
        }

        // Search Functionality — use FULLTEXT when available, fall back to LIKE
        if ($search && !empty($search)) {
            if ($this->hasFulltextIndex()) {
                // MATCH...AGAINST for indexed full-text search (much faster at scale)
                // Strip MySQL boolean mode special chars to prevent parse errors on user input
                $ftSearch = preg_replace('/[+\-><()\~*"@]+/', ' ', $search);
                $ftSearch = trim(preg_replace('/\s+/', ' ', $ftSearch)) . '*';
                $whereConditions[] = "(MATCH(t.title, t.description) AGAINST (? IN BOOLEAN MODE) OR t.ticket_id LIKE ? OR t.category LIKE ? OR t.type LIKE ?)";
                $searchTerm = "%$search%";
                $params = array_merge($params, [$ftSearch, $searchTerm, $searchTerm, $searchTerm]);
                $paramTypes .= 'ssss';
            } else {
                $whereConditions[] = "(t.title LIKE ? OR t.description LIKE ? OR t.ticket_id LIKE ? OR t.category LIKE ? OR t.type LIKE ?)";
                $searchTerm = "%$search%";
                $params = array_merge($params, [$searchTerm, $searchTerm, $searchTerm, $searchTerm, $searchTerm]);
                $paramTypes .= 'sssss';
            }
        }

        // Advanced search filters
        // Date range - created_at
        if (!empty($filters['created_from'])) {
            $whereConditions[] = "DATE(t.created_at) >= ?";
            $params[] = $filters['created_from'];
            $paramTypes .= 's';
        }
        if (!empty($filters['created_to'])) {
            $whereConditions[] = "DATE(t.created_at) <= ?";
            $params[] = $filters['created_to'];
            $paramTypes .= 's';
        }

        // Date range - updated_at
        if (!empty($filters['updated_from'])) {
            $whereConditions[] = "DATE(t.updated_at) >= ?";
            $params[] = $filters['updated_from'];
            $paramTypes .= 's';
        }
        if (!empty($filters['updated_to'])) {
            $whereConditions[] = "DATE(t.updated_at) <= ?";
            $params[] = $filters['updated_to'];
            $paramTypes .= 's';
        }

        // Date range - closed_at
        if (!empty($filters['closed_from'])) {
            $whereConditions[] = "DATE(t.closed_at) >= ?";
            $params[] = $filters['closed_from'];
            $paramTypes .= 's';
        }
        if (!empty($filters['closed_to'])) {
            $whereConditions[] = "DATE(t.closed_at) <= ?";
            $params[] = $filters['closed_to'];
            $paramTypes .= 's';
        }

        // Priority range
        if (!empty($filters['priority_min'])) {
            $whereConditions[] = "t.priority >= ?";
            $params[] = (int)$filters['priority_min'];
            $paramTypes .= 'i';
        }
        if (!empty($filters['priority_max'])) {
            $whereConditions[] = "t.priority <= ?";
            $params[] = (int)$filters['priority_max'];
            $paramTypes .= 'i';
        }

        // Created by user
        if (!empty($filters['created_by'])) {
            $whereConditions[] = "t.created_by = ?";
            $params[] = (int)$filters['created_by'];
            $paramTypes .= 'i';
        }

        // Assigned to user (including unassigned option)
        if (!empty($filters['assigned_to'])) {
            if ($filters['assigned_to'] === 'unassigned') {
                $whereConditions[] = "t.assigned_to IS NULL";
            } else {
                $whereConditions[] = "t.assigned_to = ?";
                $params[] = (int)$filters['assigned_to'];
                $paramTypes .= 'i';
            }
        }

        $whereClause = '';
        if (!empty($whereConditions)) {
            $whereClause = 'WHERE ' . implode(' AND ', $whereConditions);
        }

        // Validate sort column to prevent SQL injection
        $allowedColumns = ['ticket_id', 'title', 'status', 'priority', 'category', 'type', 'created_at', 'updated_at', 'created_by', 'assigned_to'];
        if (!in_array($sortColumn, $allowedColumns)) {
            $sortColumn = 'ticket_id';
        }

        // Map column names to actual sort expressions
        // For user columns, sort by display name with NULL handling for unassigned
        $sortExpression = $sortColumn;
        if ($sortColumn === 'created_by') {
            $sortExpression = "COALESCE(u_created.display_name, u_created.username, 'System')";
        } elseif ($sortColumn === 'assigned_to') {
            // Put unassigned (NULL) at the end regardless of sort direction
            $sortExpression = "CASE WHEN t.assigned_to IS NULL THEN 1 ELSE 0 END, COALESCE(u_assigned.display_name, u_assigned.username)";
        } else {
            $sortExpression = "t.$sortColumn";
        }

        // Validate sort direction
        $sortDirection = strtolower($sortDirection) === 'asc' ? 'ASC' : 'DESC';

        // Single query: use COUNT(*) OVER() window function to get total + page in one pass
        $sql = "SELECT t.*,
                u_created.username as creator_username,
                u_created.display_name as creator_display_name,
                u_assigned.username as assigned_username,
                u_assigned.display_name as assigned_display_name,
                COUNT(*) OVER() as _total_count
                FROM tickets t
                LEFT JOIN users u_created ON t.created_by = u_created.user_id
                LEFT JOIN users u_assigned ON t.assigned_to = u_assigned.user_id
                $whereClause
                ORDER BY $sortExpression $sortDirection
                LIMIT ? OFFSET ?";

        $params[] = $limit;
        $params[] = $offset;
        $paramTypes .= 'ii';

        $stmt = $this->conn->prepare($sql);
        if (!empty($params)) {
            $stmt->bind_param($paramTypes, ...$params);
        }
        $stmt->execute();
        $result = $stmt->get_result();

        $tickets     = [];
        $totalTickets = 0;
        while ($row = $result->fetch_assoc()) {
            $totalTickets = (int)$row['_total_count'];
            unset($row['_total_count']);
            $tickets[] = $row;
        }
        $stmt->close();

        return [
            'tickets' => $tickets,
            'total' => $totalTickets,
            'pages' => $totalTickets > 0 ? ceil($totalTickets / $limit) : 0,
            'current_page' => $page
        ];
    }

    /**
     * Update a ticket with optional optimistic locking
     *
     * @param array $ticketData Ticket data including ticket_id
     * @param int|null $updatedBy User ID performing the update
     * @param string|null $expectedUpdatedAt If provided, update will fail if ticket was modified since this timestamp
     * @return array ['success' => bool, 'error' => string|null, 'conflict' => bool]
     */
    public function updateTicket(array $ticketData, ?int $updatedBy = null, ?string $expectedUpdatedAt = null): array
    {
        // closed_at: set on close (preserve if already set), clear on reopen
        $closedAtClause = "closed_at = CASE WHEN ? = 'Closed' THEN COALESCE(closed_at, NOW()) ELSE NULL END";

        // Build query with optional optimistic locking
        if ($expectedUpdatedAt !== null) {
            // Optimistic locking enabled - check that updated_at hasn't changed
            $sql = "UPDATE tickets SET
                    title = ?,
                    priority = ?,
                    status = ?,
                    description = ?,
                    category = ?,
                    type = ?,
                    updated_by = ?,
                    updated_at = NOW(),
                    $closedAtClause
                    WHERE ticket_id = ? AND updated_at = ?";
        } else {
            // No optimistic locking
            $sql = "UPDATE tickets SET
                    title = ?,
                    priority = ?,
                    status = ?,
                    description = ?,
                    category = ?,
                    type = ?,
                    updated_by = ?,
                    updated_at = NOW(),
                    $closedAtClause
                    WHERE ticket_id = ?";
        }

        $stmt = $this->conn->prepare($sql);
        if (!$stmt) {
            return ['success' => false, 'error' => 'Failed to prepare statement', 'conflict' => false];
        }

        if ($expectedUpdatedAt !== null) {
            $stmt->bind_param(
                "sissssisis",
                $ticketData['title'],
                $ticketData['priority'],
                $ticketData['status'],
                $ticketData['description'],
                $ticketData['category'],
                $ticketData['type'],
                $updatedBy,
                $ticketData['status'],
                $ticketData['ticket_id'],
                $expectedUpdatedAt
            );
        } else {
            $stmt->bind_param(
                "sissssisi",
                $ticketData['title'],
                $ticketData['priority'],
                $ticketData['status'],
                $ticketData['description'],
                $ticketData['category'],
                $ticketData['type'],
                $updatedBy,
                $ticketData['status'],
                $ticketData['ticket_id']
            );
        }

        $result = $stmt->execute();
        $affectedRows = $stmt->affected_rows;
        $stmt->close();

        if (!$result) {
            return ['success' => false, 'error' => 'Database error: ' . $this->conn->error, 'conflict' => false];
        }

        // Check for optimistic locking conflict
        if ($expectedUpdatedAt !== null && $affectedRows === 0) {
            // Either ticket doesn't exist or was modified by someone else
            $ticket = $this->getTicketById($ticketData['ticket_id']);
            if ($ticket) {
                return [
                    'success' => false,
                    'error' => 'This ticket was modified by another user. Please refresh and try again.',
                    'conflict' => true,
                    'current_updated_at' => $ticket['updated_at']
                ];
            } else {
                return ['success' => false, 'error' => 'Ticket not found', 'conflict' => false];
            }
        }

        return ['success' => true, 'error' => null, 'conflict' => false];
    }

    public function createTicket(array $ticketData, ?int $createdBy = null): array
    {
        // Generate unique ticket ID (9-digit format with leading zeros)
        // Uses cryptographically secure random numbers for better distribution
        // Includes exponential backoff and fallback for reliability under high load
        $maxAttempts = 50;
        $attempts = 0;
        $ticket_id = null;

        do {
            // Use random_int for cryptographically secure random number
            try {
                $candidate_id = sprintf('%09d', random_int(100000000, 999999999));
            } catch (Exception $e) {
                // Fallback to mt_rand if random_int fails (shouldn't happen)
                $candidate_id = sprintf('%09d', mt_rand(100000000, 999999999));
            }

            // Check if this ID already exists
            $checkSql = "SELECT ticket_id FROM tickets WHERE ticket_id = ? LIMIT 1";
            $checkStmt = $this->conn->prepare($checkSql);
            $checkStmt->bind_param("s", $candidate_id);
            $checkStmt->execute();
            $checkResult = $checkStmt->get_result();

            if ($checkResult->num_rows === 0) {
                $ticket_id = $candidate_id;
            }
            $checkStmt->close();
            $attempts++;

            // Exponential backoff: sleep longer as attempts increase
            // This helps reduce contention under high load
            if ($ticket_id === null && $attempts < $maxAttempts) {
                usleep(min($attempts * 1000, 10000)); // Max 10ms delay
            }
        } while ($ticket_id === null && $attempts < $maxAttempts);

        // Fallback: use timestamp-based ID if random generation fails
        if ($ticket_id === null) {
            // Generate ID from timestamp + random suffix for uniqueness
            $timestamp = (int)(microtime(true) * 1000) % 1000000000;
            $ticket_id = sprintf('%09d', $timestamp);

            // Verify this fallback ID is unique
            $checkStmt = $this->conn->prepare("SELECT ticket_id FROM tickets WHERE ticket_id = ? LIMIT 1");
            $checkStmt->bind_param("s", $ticket_id);
            $checkStmt->execute();
            if ($checkStmt->get_result()->num_rows > 0) {
                $checkStmt->close();
                error_log("Ticket ID generation failed after {$maxAttempts} attempts + fallback");
                return [
                    'success' => false,
                    'error' => 'Failed to generate unique ticket ID. Please try again.'
                ];
            }
            $checkStmt->close();
            error_log("Ticket ID generation used fallback after {$maxAttempts} random attempts");
        }

        $sql = "INSERT INTO tickets (ticket_id, title, description, status, priority, category, type, created_by, assigned_to, visibility, visibility_groups)
                VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)";

        $stmt = $this->conn->prepare($sql);

        // Set default values if not provided
        $status = $ticketData['status'] ?? 'Open';
        $priority = $ticketData['priority'] ?? '4';
        $category = $ticketData['category'] ?? 'General';
        $type = $ticketData['type'] ?? 'Issue';
        $visibility = $ticketData['visibility'] ?? 'public';
        $visibilityGroups = $ticketData['visibility_groups'] ?? null;
        $assignedTo = !empty($ticketData['assigned_to']) ? (int)$ticketData['assigned_to'] : null;

        // Validate visibility
        $allowedVisibilities = ['public', 'internal', 'confidential'];
        if (!in_array($visibility, $allowedVisibilities)) {
            $visibility = 'public';
        }

        // Validate internal visibility requires groups
        if ($visibility === 'internal') {
            if (empty($visibilityGroups) || trim($visibilityGroups) === '') {
                return [
                    'success' => false,
                    'error' => 'Internal visibility requires at least one group to be specified'
                ];
            }
        } else {
            // Clear visibility_groups if not internal
            $visibilityGroups = null;
        }

        $stmt->bind_param(
            "sssssssiiss",
            $ticket_id,
            $ticketData['title'],
            $ticketData['description'],
            $status,
            $priority,
            $category,
            $type,
            $createdBy,
            $assignedTo,
            $visibility,
            $visibilityGroups
        );

        try {
            if ($stmt->execute()) {
                return [
                    'success' => true,
                    'ticket_id' => $ticket_id
                ];
            }
            return ['success' => false, 'error' => $this->conn->error];
        } catch (mysqli_sql_exception $e) {
            // Handle duplicate key (errno 1062) caused by race condition between
            // the uniqueness SELECT above and this INSERT — regenerate and retry once
            if ($e->getCode() !== 1062) {
                throw $e;
            }
            $stmt->close();
            try {
                $ticket_id = (string)random_int(100000000, 999999999);
            } catch (Exception $ex) {
                $ticket_id = (string)mt_rand(100000000, 999999999);
            }
            $stmt = $this->conn->prepare($sql);
            $stmt->bind_param(
                "sssssssiiss",
                $ticket_id,
                $ticketData['title'],
                $ticketData['description'],
                $status,
                $priority,
                $category,
                $type,
                $createdBy,
                $assignedTo,
                $visibility,
                $visibilityGroups
            );
            try {
                if ($stmt->execute()) {
                    return ['success' => true, 'ticket_id' => $ticket_id];
                }
            } catch (mysqli_sql_exception $e2) {
                // Second attempt also hit duplicate — extremely rare
            }
            return ['success' => false, 'error' => 'Failed to create ticket due to ID collision'];
        }
    }

    public function addComment(int $ticketId, array $commentData): array
    {
        $sql = "INSERT INTO ticket_comments (ticket_id, user_name, comment_text, markdown_enabled) 
                VALUES (?, ?, ?, ?)";

        $stmt = $this->conn->prepare($sql);

        // Set default username
        $username = $commentData['user_name'] ?? 'User';
        $markdownEnabled = $commentData['markdown_enabled'] ? 1 : 0;

        $stmt->bind_param(
            "issi",
            $ticketId,
            $username,
            $commentData['comment_text'],
            $markdownEnabled
        );

        if ($stmt->execute()) {
            return [
                'success' => true,
                'user_name' => $username,
                'created_at' => date('M d, Y H:i')
            ];
        } else {
            return [
                'success' => false,
                'error' => $this->conn->error
            ];
        }
    }

    /**
     * Assign ticket to a user
     *
     * @param int $ticketId Ticket ID
     * @param int $userId User ID to assign to
     * @param int $assignedBy User ID performing the assignment
     * @return bool Success status
     */
    public function assignTicket(int $ticketId, int $userId, int $assignedBy): bool
    {
        $sql = "UPDATE tickets SET assigned_to = ?, updated_by = ?, updated_at = NOW() WHERE ticket_id = ?";
        $stmt = $this->conn->prepare($sql);
        $stmt->bind_param("iii", $userId, $assignedBy, $ticketId);
        $result = $stmt->execute();
        $stmt->close();
        return $result;
    }

    /**
     * Unassign ticket (set assigned_to to NULL)
     *
     * @param int $ticketId Ticket ID
     * @param int $updatedBy User ID performing the unassignment
     * @return bool Success status
     */
    public function unassignTicket(int $ticketId, int $updatedBy): bool
    {
        $sql = "UPDATE tickets SET assigned_to = NULL, updated_by = ?, updated_at = NOW() WHERE ticket_id = ?";
        $stmt = $this->conn->prepare($sql);
        $stmt->bind_param("ii", $updatedBy, $ticketId);
        $result = $stmt->execute();
        $stmt->close();
        return $result;
    }

    /**
     * Get multiple tickets by IDs in a single query (batch loading)
     * Eliminates N+1 query problem in bulk operations
     *
     * @param array $ticketIds Array of ticket IDs
     * @return array Associative array keyed by ticket_id
     */
    public function getTicketsByIds(array $ticketIds): array
    {
        if (empty($ticketIds)) {
            return [];
        }

        // Sanitize ticket IDs: cast to string to preserve leading zeros
        $ticketIds = array_map('strval', $ticketIds);

        // Create placeholders for IN clause
        $placeholders = str_repeat('?,', count($ticketIds) - 1) . '?';

        $sql = "SELECT t.*,
                u_created.username as creator_username,
                u_created.display_name as creator_display_name,
                u_updated.username as updater_username,
                u_updated.display_name as updater_display_name,
                u_assigned.username as assigned_username,
                u_assigned.display_name as assigned_display_name
                FROM tickets t
                LEFT JOIN users u_created ON t.created_by = u_created.user_id
                LEFT JOIN users u_updated ON t.updated_by = u_updated.user_id
                LEFT JOIN users u_assigned ON t.assigned_to = u_assigned.user_id
                WHERE t.ticket_id IN ($placeholders)";

        $stmt = $this->conn->prepare($sql);
        $types = str_repeat('s', count($ticketIds));
        $stmt->bind_param($types, ...$ticketIds);
        $stmt->execute();
        $result = $stmt->get_result();

        $tickets = [];
        while ($row = $result->fetch_assoc()) {
            $tickets[$row['ticket_id']] = $row;
        }

        $stmt->close();
        return $tickets;
    }

    /**
     * Check if a user can access a ticket based on visibility settings
     *
     * @param array $ticket The ticket data
     * @param array $user The user data (must include user_id, is_admin, groups)
     * @return bool True if user can access the ticket
     */
    public function canUserAccessTicket(array $ticket, array $user): bool
    {
        // Admins can access all tickets
        if (!empty($user['is_admin'])) {
            return true;
        }

        $visibility = $ticket['visibility'] ?? 'public';

        // Public tickets are accessible to all authenticated users
        if ($visibility === 'public') {
            return true;
        }

        // Confidential tickets: only creator, assignee, and admins
        if ($visibility === 'confidential') {
            $userId = $user['user_id'] ?? null;
            return ((int)$ticket['created_by'] === (int)$userId || (int)$ticket['assigned_to'] === (int)$userId);
        }

        // Internal tickets: check if user is in any of the allowed groups
        if ($visibility === 'internal') {
            $allowedGroups = array_filter(array_map('trim', explode(',', $ticket['visibility_groups'] ?? '')));
            if (empty($allowedGroups)) {
                return false; // No groups specified means no access
            }

            $userGroups = array_filter(array_map('trim', explode(',', $user['groups'] ?? '')));
            // Check if any user group matches any allowed group
            return !empty(array_intersect($userGroups, $allowedGroups));
        }

        return false;
    }

    /**
     * Build visibility filter SQL for queries
     *
     * @param array $user The current user
     * @return array ['sql' => string, 'params' => array, 'types' => string]
     */
    public function getVisibilityFilter(array $user): array
    {
        // Admins see all tickets
        if (!empty($user['is_admin'])) {
            return ['sql' => '1=1', 'params' => [], 'types' => ''];
        }

        $userId = $user['user_id'] ?? 0;
        $userGroups = array_filter(array_map('trim', explode(',', $user['groups'] ?? '')));

        // Build the visibility filter
        // 1. Public tickets
        // 2. Confidential tickets where user is creator or assignee
        // 3. Internal tickets where user's groups overlap with visibility_groups
        $conditions = [];
        $params = [];
        $types = '';

        // Public visibility
        $conditions[] = "(t.visibility = 'public' OR t.visibility IS NULL)";

        // Confidential - user is creator or assignee
        $conditions[] = "(t.visibility = 'confidential' AND (t.created_by = ? OR t.assigned_to = ?))";
        $params[] = $userId;
        $params[] = $userId;
        $types .= 'ii';

        // Internal - check group membership
        if (!empty($userGroups)) {
            $groupConditions = [];
            foreach ($userGroups as $group) {
                $groupConditions[] = "FIND_IN_SET(?, REPLACE(t.visibility_groups, ' ', ''))";
                $params[] = $group;
                $types .= 's';
            }
            $conditions[] = "(t.visibility = 'internal' AND (" . implode(' OR ', $groupConditions) . "))";
        }

        return [
            'sql' => '(' . implode(' OR ', $conditions) . ')',
            'params' => $params,
            'types' => $types
        ];
    }

    /**
     * Update ticket visibility settings
     *
     * @param int $ticketId
     * @param string $visibility ('public', 'internal', 'confidential')
     * @param string|null $visibilityGroups Comma-separated group names for 'internal' visibility
     * @param int $updatedBy User ID
     * @return bool
     */
    public function updateVisibility(int $ticketId, string $visibility, ?string $visibilityGroups, int $updatedBy): bool
    {
        $allowedVisibilities = ['public', 'internal', 'confidential'];
        if (!in_array($visibility, $allowedVisibilities)) {
            $visibility = 'public';
        }

        // Validate internal visibility requires groups
        if ($visibility === 'internal') {
            if (empty($visibilityGroups) || trim($visibilityGroups) === '') {
                return false; // Internal visibility requires groups
            }
        } else {
            // Clear visibility_groups if not internal
            $visibilityGroups = null;
        }

        $sql = "UPDATE tickets SET visibility = ?, visibility_groups = ?, updated_by = ?, updated_at = NOW() WHERE ticket_id = ?";
        $stmt = $this->conn->prepare($sql);
        $stmt->bind_param("ssii", $visibility, $visibilityGroups, $updatedBy, $ticketId);
        $result = $stmt->execute();
        $stmt->close();
        return $result;
    }

    /**
     * Delete a ticket and all its associated records.
     * Admin-only operation. Removes comments, attachments, watchers, dependencies.
     *
     * @param string $ticketId Ticket ID
     * @return bool Success status
     */
    public function deleteTicket(string $ticketId): bool
    {
        // Collect attachment filenames before deleting DB rows
        $attachmentFiles = [];
        $attStmt = $this->conn->prepare("SELECT filename FROM ticket_attachments WHERE ticket_id = ?");
        if ($attStmt) {
            $attStmt->bind_param('s', $ticketId);
            $attStmt->execute();
            $attResult = $attStmt->get_result();
            while ($row = $attResult->fetch_assoc()) {
                $attachmentFiles[] = $row['filename'];
            }
            $attStmt->close();
        }

        // Delete child records first to avoid FK constraint failures
        $children = [
            "DELETE FROM ticket_comments WHERE ticket_id = ?",
            "DELETE FROM ticket_watchers WHERE ticket_id = ?",
            "DELETE FROM ticket_dependencies WHERE ticket_id = ? OR depends_on_id = ?",
            "DELETE FROM ticket_attachments WHERE ticket_id = ?",
            "DELETE FROM ticket_custom_fields WHERE ticket_id = ?",
        ];

        foreach ($children as $sql) {
            try {
                $stmt = $this->conn->prepare($sql);
                if (!$stmt) {
                    continue;
                }
                // ticket_dependencies uses two placeholders
                if (strpos($sql, 'depends_on_id') !== false) {
                    $stmt->bind_param('ss', $ticketId, $ticketId);
                } else {
                    $stmt->bind_param('s', $ticketId);
                }
                $stmt->execute();
                $stmt->close();
            } catch (mysqli_sql_exception $e) {
                // Skip optional tables that may not exist in all deployments
                if (strpos($e->getMessage(), "doesn't exist") === false) {
                    throw $e;
                }
            }
        }

        $stmt = $this->conn->prepare("DELETE FROM tickets WHERE ticket_id = ?");
        if (!$stmt) {
            return false;
        }
        $stmt->bind_param('s', $ticketId);
        $result = $stmt->execute();
        $affected = $stmt->affected_rows;
        $stmt->close();

        if ($result && $affected > 0) {
            // Clean up physical attachment files
            $uploadDir = defined('UPLOAD_DIR')
                ? UPLOAD_DIR
                : (isset($GLOBALS['config']['UPLOAD_DIR']) ? $GLOBALS['config']['UPLOAD_DIR'] : dirname(__DIR__) . '/uploads');
            $ticketDir = rtrim($uploadDir, '/') . '/' . $ticketId;
            if (is_dir($ticketDir)) {
                foreach ($attachmentFiles as $filename) {
                    $file = $ticketDir . '/' . basename($filename);
                    if (file_exists($file)) {
                        @unlink($file);
                    }
                }
                @rmdir($ticketDir); // Remove dir only if empty
            }
            return true;
        }
        return false;
    }

    /**
     * Check whether the FULLTEXT index on tickets(title, description) exists.
     * Result is cached for the process lifetime (static).
     */
    private function hasFulltextIndex(): bool
    {
        static $result = null;
        if ($result !== null) {
            return $result;
        }
        $r = $this->conn->query(
            "SELECT COUNT(*) as cnt FROM information_schema.STATISTICS
             WHERE table_schema = DATABASE()
               AND table_name = 'tickets'
               AND index_type = 'FULLTEXT'
               AND index_name = 'ft_title_description'"
        );
        $result = $r && (int)$r->fetch_assoc()['cnt'] > 0;
        return $result;
    }
}