content: /*
   * Copyright The OpenTelemetry Authors
   * SPDX-License-Identifier: Apache-2.0
   */
  
  package io.opentelemetry.javaagent.instrumentation.servlet;
  
  import static java.util.Collections.emptyList;
  
  import io.opentelemetry.api.common.AttributeKey;
  import io.opentelemetry.api.common.AttributesBuilder;
  import io.opentelemetry.context.Context;
  import io.opentelemetry.instrumentation.api.instrumenter.AttributesExtractor;
  import io.opentelemetry.javaagent.bootstrap.internal.AgentInstrumentationConfig;
  import java.util.List;
  import java.util.Locale;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.function.BiConsumer;
  import javax.annotation.Nullable;
  
  public class ServletRequestParametersExtractor<REQUEST, RESPONSE>
      implements AttributesExtractor<
          ServletRequestContext<REQUEST>, ServletResponseContext<RESPONSE>> {
    private static final List<String> CAPTURE_REQUEST_PARAMETERS =
        AgentInstrumentationConfig.get()
            .getList(
                "otel.instrumentation.servlet.experimental.capture-request-parameters", emptyList());
  
    private static final ConcurrentMap<String, AttributeKey<List<String>>> parameterKeysCache =
        new ConcurrentHashMap<>();
  
    private final ServletAccessor<REQUEST, RESPONSE> accessor;
  
    public ServletRequestParametersExtractor(ServletAccessor<REQUEST, RESPONSE> accessor) {
      this.accessor = accessor;
    }
  
    public static boolean enabled() {
      return !CAPTURE_REQUEST_PARAMETERS.isEmpty();
    }
  
    public void setAttributes(
        REQUEST request, BiConsumer<AttributeKey<List<String>>, List<String>> consumer) {
      for (String name : CAPTURE_REQUEST_PARAMETERS) {
        List<String> values = accessor.getRequestParameterValues(request, name);
        if (!values.isEmpty()) {
          consumer.accept(parameterAttributeKey(name), values);
        }
      }
    }
  
    @Override
    public void onStart(
        AttributesBuilder attributes,
        Context parentContext,
        ServletRequestContext<REQUEST> requestContext) {}
  
    @Override
    public void onEnd(
        AttributesBuilder attributes,
        Context context,
        ServletRequestContext<REQUEST> requestContext,
        @Nullable ServletResponseContext<RESPONSE> responseContext,
        @Nullable Throwable error) {
      // request parameters are extracted at the end of the request to make sure that we don't access
      // them before request encoding has been set
      REQUEST request = requestContext.request();
      setAttributes(request, attributes::put);
    }
  
    private static AttributeKey<List<String>> parameterAttributeKey(String headerName) {
      return parameterKeysCache.computeIfAbsent(
          headerName, ServletRequestParametersExtractor::createKey);
    }
  
    private static AttributeKey<List<String>> createKey(String parameterName) {
      // normalize parameter name similarly as is done with header names when header values are
      // captured as span attributes
      parameterName = parameterName.toLowerCase(Locale.ROOT);
      String key = "servlet.request.parameter." + parameterName;
      return AttributeKey.stringArrayKey(key);
    }
  }
  