content: /*
   * Copyright The OpenTelemetry Authors
   * SPDX-License-Identifier: Apache-2.0
   */
  
  package io.opentelemetry.instrumentation.spring.webmvc.v5_3;
  
  import static java.util.Objects.requireNonNull;
  import static org.springframework.web.util.ServletRequestPathUtils.PATH_ATTRIBUTE;
  
  import io.opentelemetry.context.Context;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.concurrent.atomic.AtomicBoolean;
  import javax.annotation.Nullable;
  import javax.servlet.FilterConfig;
  import javax.servlet.http.HttpServletRequest;
  import org.springframework.context.ApplicationListener;
  import org.springframework.context.event.ContextRefreshedEvent;
  import org.springframework.web.context.ConfigurableWebApplicationContext;
  import org.springframework.web.context.WebApplicationContext;
  import org.springframework.web.context.support.WebApplicationContextUtils;
  import org.springframework.web.servlet.DispatcherServlet;
  import org.springframework.web.servlet.HandlerExecutionChain;
  import org.springframework.web.servlet.HandlerMapping;
  import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;
  import org.springframework.web.util.ServletRequestPathUtils;
  
  final class HttpRouteSupport {
  
    private final AtomicBoolean contextRefreshTriggered = new AtomicBoolean();
    @Nullable private volatile DispatcherServlet dispatcherServlet;
    @Nullable private volatile List<HandlerMapping> handlerMappings;
    private volatile boolean parseRequestPath;
  
    void onFilterInit(FilterConfig filterConfig) {
      WebApplicationContext context =
          WebApplicationContextUtils.getWebApplicationContext(filterConfig.getServletContext());
      if (!(context instanceof ConfigurableWebApplicationContext)) {
        return;
      }
  
      DispatcherServlet servlet = context.getBeanProvider(DispatcherServlet.class).getIfAvailable();
      if (servlet != null) {
        dispatcherServlet = servlet;
  
        ((ConfigurableWebApplicationContext) context)
            .addApplicationListener(new WebContextRefreshListener());
      }
    }
  
    // we can't retrieve the handler mappings from the DispatcherServlet in the onRefresh listener,
    // because it loads them just after the application context refreshed event is processed
    // to work around this, we're setting a boolean flag that'll cause this filter to load the
    // mappings the next time it attempts to set the http.route
    final class WebContextRefreshListener implements ApplicationListener<ContextRefreshedEvent> {
  
      @Override
      public void onApplicationEvent(ContextRefreshedEvent event) {
        contextRefreshTriggered.set(true);
      }
    }
  
    boolean hasMappings() {
      if (contextRefreshTriggered.compareAndSet(true, false)) {
        // reload the handler mappings only if the web app context was recently refreshed
        DispatcherServlet dispatcherServlet = this.dispatcherServlet;
        if (dispatcherServlet != null) {
          List<HandlerMapping> mappings = dispatcherServlet.getHandlerMappings();
          if (mappings != null) {
            setHandlerMappings(mappings);
          }
        }
      }
      return handlerMappings != null;
    }
  
    private void setHandlerMappings(List<HandlerMapping> mappings) {
      List<HandlerMapping> handlerMappings = new ArrayList<>();
      for (HandlerMapping mapping : mappings) {
        // Originally we ran findMapping at the very beginning of the request. This turned out to have
        // application-crashing side-effects with grails. That is why we don't add all HandlerMapping
        // classes here. Although now that we run findMapping after the request, and only when server
        // span name has not been updated by a controller, the probability of bad side-effects is much
        // reduced even if we did add all HandlerMapping classes here.
        if (mapping instanceof RequestMappingHandlerMapping) {
          handlerMappings.add(mapping);
          if (mapping.usesPathPatterns()) {
            this.parseRequestPath = true;
          }
        }
      }
      if (!handlerMappings.isEmpty()) {
        this.handlerMappings = handlerMappings;
      }
    }
  
    @Nullable
    String getHttpRoute(Context context, HttpServletRequest request) {
      boolean parsePath = this.parseRequestPath;
      Object previousValue = null;
      if (parsePath) {
        previousValue = request.getAttribute(PATH_ATTRIBUTE);
        // sets new value for PATH_ATTRIBUTE of request
        ServletRequestPathUtils.parseAndCache(request);
      }
      try {
        if (findMapping(request)) {
          // Name the parent span based on the matching pattern
          // Let the parent span resource name be set with the attribute set in findMapping.
          Object bestMatchingPattern =
              request.getAttribute(HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE);
          if (bestMatchingPattern != null) {
            return prependContextPath(request, bestMatchingPattern.toString());
          }
        }
      } finally {
        // mimic spring DispatcherServlet and restore the previous value of PATH_ATTRIBUTE
        if (parsePath) {
          if (previousValue == null) {
            request.removeAttribute(PATH_ATTRIBUTE);
          } else {
            request.setAttribute(PATH_ATTRIBUTE, previousValue);
          }
        }
      }
      return null;
    }
  
    /**
     * When a HandlerMapping matches a request, it sets HandlerMapping.BEST_MATCHING_PATTERN_ATTRIBUTE
     * as an attribute on the request. This attribute set as the HTTP route.
     */
    private boolean findMapping(HttpServletRequest request) {
      try {
        // handlerMapping already null-checked above
        for (HandlerMapping mapping : requireNonNull(handlerMappings)) {
          HandlerExecutionChain handler = mapping.getHandler(request);
          if (handler != null) {
            return true;
          }
        }
      } catch (Exception ignored) {
        // mapping.getHandler() threw exception. Ignore
      }
      return false;
    }
  
    private static String prependContextPath(HttpServletRequest request, String route) {
      String contextPath = request.getContextPath();
      if (contextPath == null) {
        return route;
      }
      return contextPath + (route.startsWith("/") ? route : ("/" + route));
    }
  }
  