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package graphql.kickstart.servlet.core.internal;

import java.util.List;
import java.util.Map;
import java.util.regex.Pattern;
import jakarta.servlet.http.Part;

public class VariableMapper {

  private static final Pattern PERIOD = Pattern.compile("\\.");

  private static final Mapper> MAP_MAPPER =
      new Mapper>() {
        @Override
        public Object set(Map location, String target, Part value) {
          return location.put(target, value);
        }

        @Override
        public Object recurse(Map location, String target) {
          return location.get(target);
        }
      };
  private static final Mapper> LIST_MAPPER =
      new Mapper>() {
        @Override
        public Object set(List location, String target, Part value) {
          return location.set(Integer.parseInt(target), value);
        }

        @Override
        public Object recurse(List location, String target) {
          return location.get(Integer.parseInt(target));
        }
      };

  @SuppressWarnings({"unchecked", "rawtypes"})
  public static void mapVariable(String objectPath, Map variables, Part part) {
    String[] segments = PERIOD.split(objectPath);

    if (segments.length < 2) {
      throw new VariableMapException("object-path in map must have at least two segments");
    } else if (!"variables".equals(segments[0])) {
      throw new VariableMapException("can only map into variables");
    }

    Object currentLocation = variables;
    for (int i = 1; i < segments.length; i++) {
      String segmentName = segments[i];
      Mapper mapper = determineMapper(currentLocation, objectPath, segmentName);

      if (i == segments.length - 1) {
        if (null != mapper.set(currentLocation, segmentName, part)) {
          throw new VariableMapException("expected null value when mapping " + objectPath);
        }
      } else {
        currentLocation = mapper.recurse(currentLocation, segmentName);
        if (null == currentLocation) {
          throw new VariableMapException(
              "found null intermediate value when trying to map " + objectPath);
        }
      }
    }
  }

  private static Mapper determineMapper(
      Object currentLocation, String objectPath, String segmentName) {
    if (currentLocation instanceof Map) {
      return MAP_MAPPER;
    } else if (currentLocation instanceof List) {
      return LIST_MAPPER;
    }

    throw new VariableMapException(
        "expected a map or list at " + segmentName + " when trying to map " + objectPath);
  }

  interface Mapper {

    Object set(T location, String target, Part value);

    Object recurse(T location, String target);
  }
}
    

    

    

            

    

            



    
    






    
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