import java.util.HashMap;
import java.util.Map;
import java.util.stream.Stream;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.core.ParameterizedTypeReference;
import org.springframework.hateoas.PagedResources;
import org.springframework.hateoas.Resource;
import org.springframework.hateoas.Resources;
import org.springframework.hateoas.mvc.TypeReferences;
import org.springframework.http.HttpMethod;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Component;
import org.springframework.web.client.RestTemplate;

@Component
public class StudentsClient {

    private static final String URL = "http://students-service/students?page={page}&size={size}";

    @Autowired
    RestTemplate template;

    public Stream<Student> getStudents(int offset, int limit) {
        Map<String, Integer> params = new HashMap<>();
        params.put("page", offset / limit);
        params.put("size", limit);

        // Using external class
        final ResponseEntity<StudentResources> studentResponse = template
                .getForEntity(URL, StudentResources.class, params);

        // Using instantiated ParametrizedTypeReference Resources 
        final ResponseEntity<Resources<Student>> studentResponse = template
                .exchange(URL, HttpMethod.GET, null,
                        new ParameterizedTypeReference<Resources<Student>>() {
                        }, params);

        // Using instantiated ParametrizedTypeReference Resources
        final ResponseEntity<PagedResources<Student>> studentResponse = template
                .exchange(URL, HttpMethod.GET, null,
                        new ParameterizedTypeReference<PagedResources<Student>>() {
                        }, params);

        // Does not work for some reason, ends up with empty Resources inside Resources
        // final ResponseEntity<Resources<Resource<Student>>> studentResponse = template
        //         .exchange(URL, HttpMethod.GET, null,
        //                 new TypeReferences.ResourcesType<Resource<Student>>() {
        //                 }, params);

        // Using provided PagedResources type class, note the required {}
        // This is used for return
        final ResponseEntity<PagedResources<Resource<Student>>> studentResponse =
                template
                .exchange(URL, HttpMethod.GET, null,
                        new TypeReferences.PagedResourcesType<Resource<Student>>(){},
                        params);

        return studentResponse.getBody().getContent().stream()
                .map(Resource::getContent);
    }
}