Backend/src/main/java/cc/fascinated/common/IPUtils.java

package cc.fascinated.common;

import jakarta.servlet.http.HttpServletRequest;
import lombok.experimental.UtilityClass;

@UtilityClass
public class IPUtils {
    /**
     * The headers that contain the IP.
     */
    private static final String[] IP_HEADERS = new String[] {
            "CF-Connecting-IP",
            "X-Forwarded-For"
    };

    /**
     * Get the real IP from the given request.
     *
     * @param request the request
     * @return the real IP
     */
    public static String getRealIp(HttpServletRequest request) {
        String ip = request.getRemoteAddr();
        for (String headerName : IP_HEADERS) {
            String header = request.getHeader(headerName);
            if (header == null) {
                continue;
            }
            if (!header.contains(",")) { // Handle single IP
                ip = header;
                break;
            }
            // Handle multiple IPs
            String[] ips = header.split(",");
            for (String ipHeader : ips) {
                ip = ipHeader;
                break;
            }
        }
        return ip;
    }
}