<?php
/**
 * Notification Management Class
 * Handles creation, retrieval, and delivery of user notifications
 */

class VNotifications {
    private $db;
    private $logger;
    
    public function __construct() {
        global $class_database;
        $this->db = $class_database;
        $this->logger = new VLogger('notifications');
    }
    
    /**
     * Create a new notification
     * 
     * @param int $usr_id User receiving the notification
     * @param string $type Notification type (comment, like, subscribe, video_upload, mention, system)
     * @param string $title Notification title
     * @param string $message Optional detailed message
     * @param string $link Optional link URL
     * @param int $actor_id User who triggered the notification
     * @param int $related_video_id Related video ID
     * @param int $related_comment_id Related comment ID
     * @return int|false Notification ID or false on failure
     */
    public function create($usr_id, $type, $title, $message = '', $link = '', $actor_id = null, $related_video_id = null, $related_comment_id = null) {
        // Don't notify users about their own actions
        if ($actor_id && $usr_id == $actor_id) {
            return false;
        }
        
        // Insert notification
        $sql = "INSERT INTO db_notifications 
                (usr_id, type, title, message, link, actor_id, related_video_id, related_comment_id) 
                VALUES (?, ?, ?, ?, ?, ?, ?, ?)";
        
        $result = $this->db->execute($sql, [
            $usr_id,
            $type,
            $title,
            $message,
            $link,
            $actor_id,
            $related_video_id,
            $related_comment_id
        ]);
        
        if (!$result) {
            $this->logger->error("Failed to create notification for user $usr_id");
            return false;
        }
        
        $notification_id = $this->db->lastInsertId();
        
        // Queue email if user preferences allow
        $this->queueEmail($usr_id, $type, $title, $message, $link);
        
        $this->logger->info("Created notification $notification_id for user $usr_id (type: $type)");
        
        return $notification_id;
    }
    
    /**
     * Get unread notification count for a user
     */
    public function getUnreadCount($usr_id) {
        $sql = "SELECT COUNT(*) as count FROM db_notifications 
                WHERE usr_id = ? AND is_read = 0";
        
        $result = $this->db->execute($sql, [$usr_id]);
        
        if (!$result) {
            return 0;
        }
        
        $row = $this->db->fetch($result);
        return intval($row['count'] ?? 0);
    }
    
    /**
     * Get notifications for a user
     */
    public function getUserNotifications($usr_id, $limit = 20, $offset = 0, $unread_only = false) {
        $where = $unread_only ? "AND is_read = 0" : "";
        
        $sql = "SELECT n.*, u.usr_user as actor_username, u.usr_avatar as actor_avatar 
                FROM db_notifications n 
                LEFT JOIN db_accountuser u ON n.actor_id = u.usr_id 
                WHERE n.usr_id = ? $where 
                ORDER BY n.created_at DESC 
                LIMIT ? OFFSET ?";
        
        $result = $this->db->execute($sql, [$usr_id, $limit, $offset]);
        
        if (!$result) {
            return [];
        }
        
        return $this->db->resultsToArray($result);
    }
    
    /**
     * Mark notification(s) as read
     */
    public function markAsRead($notification_id, $usr_id = null) {
        if (is_array($notification_id)) {
            $ids = implode(',', array_map('intval', $notification_id));
            $sql = "UPDATE db_notifications 
                    SET is_read = 1, read_at = NOW() 
                    WHERE notification_id IN ($ids)";
            
            if ($usr_id) {
                $sql .= " AND usr_id = " . intval($usr_id);
            }
        } else {
            $sql = "UPDATE db_notifications 
                    SET is_read = 1, read_at = NOW() 
                    WHERE notification_id = " . intval($notification_id);
            
            if ($usr_id) {
                $sql .= " AND usr_id = " . intval($usr_id);
            }
        }
        
        return $this->db->execute($sql);
    }
    
    /**
     * Mark all notifications as read for a user
     */
    public function markAllAsRead($usr_id) {
        $sql = "UPDATE db_notifications 
                SET is_read = 1, read_at = NOW() 
                WHERE usr_id = ? AND is_read = 0";
        
        return $this->db->execute($sql, [$usr_id]);
    }
    
    /**
     * Mark notifications as seen (displayed to user, but not necessarily read)
     */
    public function markAsSeen($usr_id) {
        $sql = "UPDATE db_notifications 
                SET is_seen = 1 
                WHERE usr_id = ? AND is_seen = 0";
        
        return $this->db->execute($sql, [$usr_id]);
    }
    
    /**
     * Delete a notification
     */
    public function delete($notification_id, $usr_id) {
        $sql = "DELETE FROM db_notifications 
                WHERE notification_id = ? AND usr_id = ?";
        
        return $this->db->execute($sql, [$notification_id, $usr_id]);
    }
    
    /**
     * Get user notification preferences
     */
    public function getPreferences($usr_id) {
        $sql = "SELECT * FROM db_notification_preferences WHERE usr_id = ?";
        
        $result = $this->db->execute($sql, [$usr_id]);
        
        if (!$result || $this->db->rowCount($result) == 0) {
            // Create default preferences
            $this->createDefaultPreferences($usr_id);
            return $this->getPreferences($usr_id);
        }
        
        return $this->db->fetch($result);
    }
    
    /**
     * Update user notification preferences
     */
    public function updatePreferences($usr_id, $preferences) {
        $allowed_fields = [
            'email_comments', 'email_likes', 'email_subscribes', 'email_uploads', 'email_mentions',
            'email_digest', 'push_enabled', 'push_comments', 'push_likes', 'push_subscribes'
        ];
        
        $sets = [];
        $values = [];
        
        foreach ($preferences as $field => $value) {
            if (in_array($field, $allowed_fields)) {
                $sets[] = "$field = ?";
                $values[] = $value;
            }
        }
        
        if (empty($sets)) {
            return false;
        }
        
        $values[] = $usr_id;
        
        $sql = "UPDATE db_notification_preferences 
                SET " . implode(', ', $sets) . " 
                WHERE usr_id = ?";
        
        return $this->db->execute($sql, $values);
    }
    
    /**
     * Create default notification preferences for a user
     */
    private function createDefaultPreferences($usr_id) {
        $sql = "INSERT INTO db_notification_preferences (usr_id) VALUES (?)";
        return $this->db->execute($sql, [$usr_id]);
    }
    
    /**
     * Queue email notification
     */
    private function queueEmail($usr_id, $type, $title, $message, $link) {
        // Get user preferences
        $prefs = $this->getPreferences($usr_id);
        
        // Check if email is enabled for this type
        $email_field = "email_" . str_replace('_', 's', $type);
        if (isset($prefs[$email_field]) && !$prefs[$email_field]) {
            return false;
        }
        
        // Get user email
        $sql = "SELECT usr_email FROM db_accountuser WHERE usr_id = ?";
        $result = $this->db->execute($sql, [$usr_id]);
        
        if (!$result) {
            return false;
        }
        
        $user = $this->db->fetch($result);
        if (!$user || empty($user['usr_email'])) {
            return false;
        }
        
        // Determine send time based on digest preference
        $scheduled_for = 'NOW()';
        
        if ($prefs['email_digest'] === 'hourly') {
            $scheduled_for = "DATE_ADD(NOW(), INTERVAL 1 HOUR)";
        } elseif ($prefs['email_digest'] === 'daily') {
            $scheduled_for = "DATE_ADD(CURDATE(), INTERVAL 1 DAY)"; // Tomorrow at midnight
        } elseif ($prefs['email_digest'] === 'weekly') {
            $scheduled_for = "DATE_ADD(CURDATE(), INTERVAL (7 - WEEKDAY(CURDATE())) DAY)"; // Next Monday
        } elseif ($prefs['email_digest'] === 'never') {
            return false;
        }
        
        // Build email body
        $email_body = $this->buildEmailBody($title, $message, $link);
        
        // Queue email
        $sql = "INSERT INTO db_email_queue (usr_id, email, subject, body, scheduled_for) 
                VALUES (?, ?, ?, ?, $scheduled_for)";
        
        return $this->db->execute($sql, [
            $usr_id,
            $user['usr_email'],
            $title,
            $email_body
        ]);
    }
    
    /**
     * Build HTML email body
     */
    private function buildEmailBody($title, $message, $link) {
        $html = "<html><body style='font-family: Arial, sans-serif; line-height: 1.6;'>";
        $html .= "<h2 style='color: #007bff;'>$title</h2>";
        
        if ($message) {
            $html .= "<p>" . nl2br(htmlspecialchars($message)) . "</p>";
        }
        
        if ($link) {
            $base_url = $_SERVER['HTTP_HOST'] ?? 'localhost';
            $full_link = "http://$base_url$link";
            $html .= "<p><a href='$full_link' style='color: #007bff; text-decoration: none; font-weight: bold;'>View on EasyStream →</a></p>";
        }
        
        $html .= "<hr style='border: none; border-top: 1px solid #ddd; margin: 20px 0;'>";
        $html .= "<p style='font-size: 12px; color: #666;'>You received this email because you have notifications enabled on EasyStream. <a href='http://$base_url/settings#notifications'>Manage your notification preferences</a>.</p>";
        $html .= "</body></html>";
        
        return $html;
    }
    
    /**
     * Process email queue (called by cron)
     */
    public function processEmailQueue($limit = 50) {
        $sql = "SELECT * FROM db_email_queue 
                WHERE sent_at IS NULL 
                AND scheduled_for <= NOW() 
                AND attempts < 3 
                ORDER BY scheduled_for ASC 
                LIMIT $limit";
        
        $result = $this->db->execute($sql);
        
        if (!$result) {
            return 0;
        }
        
        $emails = $this->db->resultsToArray($result);
        $sent_count = 0;
        
        foreach ($emails as $email) {
            if ($this->sendEmail($email)) {
                $sent_count++;
                
                // Mark as sent
                $this->db->execute(
                    "UPDATE db_email_queue SET sent_at = NOW() WHERE queue_id = ?",
                    [$email['queue_id']]
                );
                
                // Mark notification as emailed
                $this->db->execute(
                    "UPDATE db_notifications SET email_sent = 1 WHERE usr_id = ? AND email_sent = 0 AND created_at >= ?",
                    [$email['usr_id'], $email['created_at']]
                );
            } else {
                // Increment attempts
                $this->db->execute(
                    "UPDATE db_email_queue SET attempts = attempts + 1, last_error = ? WHERE queue_id = ?",
                    ['Failed to send email', $email['queue_id']]
                );
            }
        }
        
        $this->logger->info("Processed email queue: $sent_count sent out of " . count($emails) . " pending");
        
        return $sent_count;
    }
    
    /**
     * Send an email
     */
    private function sendEmail($email) {
        // Use PHP mail() function
        // In production, integrate with SendGrid/Mailgun/etc.
        
        $headers = "From: EasyStream <noreply@easystream.com>\r\n";
        $headers .= "Reply-To: noreply@easystream.com\r\n";
        $headers .= "MIME-Version: 1.0\r\n";
        $headers .= "Content-Type: text/html; charset=UTF-8\r\n";
        
        return mail($email['email'], $email['subject'], $email['body'], $headers);
    }
    
    /**
     * Clean up old notifications (called by cron)
     */
    public function cleanup($days = 90) {
        $sql = "DELETE FROM db_notifications 
                WHERE created_at < DATE_SUB(NOW(), INTERVAL ? DAY) 
                AND is_read = 1";
        
        $result = $this->db->execute($sql, [$days]);
        
        $deleted = $this->db->affectedRows();
        $this->logger->info("Cleaned up $deleted old read notifications (older than $days days)");
        
        return $deleted;
    }
}