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factoryfx dependency injection framework
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package io.github.factoryfx.jetty;

import java.io.IOException;
import java.util.Collection;
import java.util.List;
import java.util.Optional;
import java.util.Set;
import java.util.stream.Collectors;

import org.eclipse.jetty.http.pathmap.ServletPathSpec;
import org.eclipse.jetty.server.Request;
import org.eclipse.jetty.server.ServletPathMapping;

import jakarta.servlet.Servlet;
import jakarta.servlet.ServletConfig;
import jakarta.servlet.ServletException;
import jakarta.servlet.ServletRequest;
import jakarta.servlet.ServletResponse;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletRequestWrapper;
import jakarta.servlet.http.HttpServletResponse;

/**
 * workaround for servlet limitation, you can't dynamically add/remove servlet if the context is started.
 */
public class UpdateableServlet implements Servlet {

    private volatile Collection servlets;
    private ServletConfig servletConfig = null;

    public UpdateableServlet(Collection newServlets) {
        this.servlets = newServlets;
    }

    public void update(Collection newServlets){
        update(this.servlets,newServlets);
        this.servlets = newServlets;
    }

    private void update(Collection previousServlets, Collection newServlets){
        Set previousServletsMapped = previousServlets.stream().map((s)->s.servlet).collect(Collectors.toSet());

        newServlets.forEach(servletAndPath -> {
            try {
                if (!previousServletsMapped.contains(servletAndPath.servlet)){
                    servletAndPath.servlet.init(servletConfig);
                }
            } catch (ServletException e) {
                throw new RuntimeException(e);
            }
        });
    }


    @Override
    public void init(ServletConfig config) {
        this.servletConfig = config;
        update(List.of(),this.servlets);
    }

    @Override
    public ServletConfig getServletConfig() {
        return servletConfig;
    }

    @Override
    public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
        HttpServletRequest httpReq = (HttpServletRequest)req;
        String pathMatch = null;
        String pathInfo = null;
        Servlet bestMatch = null;
        String servletPath = httpReq.getRequestURI().substring(httpReq.getServletPath().length());
        for (ServletAndPath servletAndPath : servlets) {
            Servlet servlet = servletAndPath.servlet;
            String thisPathMatch = servletAndPath.getPathMatch(servletPath);
            if (thisPathMatch != null) {
                if (pathMatch == null || thisPathMatch.length() > pathMatch.length()) {
                    pathMatch = thisPathMatch;
                    pathInfo = servletAndPath.getPathInfo(servletPath);
                    bestMatch = servlet;
                }
            }
        }
        if (bestMatch != null) {
            Request baseRequest = null;
            if (httpReq instanceof Request) {
                baseRequest = (Request)httpReq;
            }
            dispatch(bestMatch,pathMatch,pathInfo,baseRequest,httpReq, (HttpServletResponse) res);
        } else {
            HttpServletResponse response =(HttpServletResponse) res;
            response.sendError(HttpServletResponse.SC_NOT_FOUND);
        }
    }

    @Override
    public String getServletInfo() {
        return "factoryfx updateable servlets";
    }

    @Override
    public void destroy() {
    }


    public void dispatch(Servlet servlet, String servletPath, String pathInfo, Request baseRequest, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException
    {
        final String oldPath = request.getServletPath();
        final String oldInfo = request.getPathInfo();

        try
        {
            //We will presumably always run under a jetty environment, yet we support other environments as well
            if (baseRequest != null) {
                baseRequest.setServletPathMapping(new ServletPathMapping(new ServletPathSpec(servletPath),
                                                                         null,
                                                                         Optional.ofNullable(pathInfo).orElse("")));
                //baseRequest.setServletPath(servletPath);
                //baseRequest.setPathInfo(pathInfo);
            } else {
                request = new HttpServletRequestWrapper(request) {
                    @Override
                    public String getPathInfo() {
                        return pathInfo;
                    }

                    @Override
                    public String getServletPath() {
                        return servletPath;
                    }
                };
            }
            servlet.service(request,response);
        }
        finally
        {
            if (baseRequest != null) {
                baseRequest.setServletPathMapping(new ServletPathMapping(new ServletPathSpec(oldPath), null, oldInfo));
                //baseRequest.setServletPath(oldPath);
                //baseRequest.setPathInfo(oldInfo);
            }
        }
    }

}