Abstract getUsers method and adhere to data flow in RTS

src/main/java/nl/tudelft/ewi/queue/model/Course.java

@@ -22,9 +22,8 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Optional;
 import java.util.OptionalDouble;
-import java.util.function.Function;
+import java.util.function.Predicate;
 import java.util.stream.Collectors;
-import java.util.stream.Stream;
 
 import javax.persistence.*;
 import javax.validation.constraints.NotNull;
@@ -184,43 +183,27 @@ public class Course implements Serializable {
 				.collect(Collectors.toList());
 	}
 
-	public List<User> getRequestHandlers() {
+	private List<User> getUsers(Predicate<Role> f) {
 		return roles.stream()
-				.filter(r -> r instanceof Assistant || r instanceof Manager || r instanceof Teacher)
+				.filter(f)
 				.map(Role::getUser)
 				.collect(Collectors.toList());
 	}
 
 	public List<User> getAssistants() {
-		return roles.stream()
-				.filter(r -> r instanceof Assistant)
-				.map(Role::getUser)
-				.collect(Collectors.toList());
+		return getUsers(r -> r instanceof Assistant);
 	}
 
 	public List<User> getManagers() {
-		return roles.stream()
-				.filter(r -> r instanceof Manager)
-				.map(Role::getUser)
-				.collect(Collectors.toList());
+		return getUsers(r -> r instanceof Manager);
 	}
 
 	public List<User> getTeachers() {
-		return roles.stream()
-				.filter(r -> r instanceof Teacher)
-				.map(Role::getUser)
-				.collect(Collectors.toList());
+		return getUsers(r -> r instanceof Teacher);
 	}
 
 	public List<User> getPrivileged() {
-		Stream<User> teaches = getTeachers().stream();
-		Stream<User> manages = getManagers().stream();
-		Stream<User> assists = getAssistants().stream();
-
-		return Stream
-				.of(teaches, manages, assists)
-				.flatMap(Function.identity())
-				.collect(Collectors.toList());
+		return getUsers(r -> r instanceof Assistant || r instanceof Manager || r instanceof Teacher);
 	}
 
 	public List<Role> getRoles(Class<Role> role) {

src/main/java/nl/tudelft/ewi/queue/service/RequestTableService.java

@@ -172,7 +172,7 @@ public class RequestTableService {
 						}));
 
 		// Add the created model attributes
-		addToModel(model, activeLabs, filteredRequests, filters);
+		addToModel(model, courses, activeLabs, filteredRequests, filters);
 		model.addAttribute("queued", queueCount);
 	}
 
@@ -218,47 +218,32 @@ public class RequestTableService {
 				(currentGroup.or(currentUser)).and(predicate), pageable);
 
 		// Add the created model attributes
-		addToModel(model, labs, filteredRequests, filters);
+		addToModel(model, courses, labs, filteredRequests, filters);
 	}
 
 	/**
 	 * Adds the given information to the model using the variable names used in the "request/list.html" page.
 	 *
 	 * @param model    The model to The model to add attributes to.
+	 * @param courses  The courses that should be displayed in filters.
 	 * @param labs     The labs that should be displayed in filters.
 	 * @param requests The requests that should be displayed on the page.
 	 * @param filters  The state of the filters.
 	 */
 	private void addToModel(Model model,
+							List<Course> courses,
 							List<Lab> labs,
 							Page<Request> requests,
 							Object filters) {
-		List<Room> rooms = labs.stream()
-				.flatMap(lab -> lab.getRooms().stream())
-				.distinct()
-				.collect(Collectors.toList());
-
-		// Fetch the courses from the given list of labs to make sure only currently active
-		// or relevant courses are shown.
-		List<Course> courses = labs.stream()
-				.map(Lab::getCourse)
-				.distinct()
-				.collect(Collectors.toList());
-
-		List<User> assistants = courses.stream()
-				.flatMap(course -> course.getRequestHandlers().stream())
-				.distinct()
-				.collect(Collectors.toList());
-
 		model
-				.addAttribute("rooms", rooms)
+				.addAttribute("rooms", rooms(labs))
 				.addAttribute("requestTypes", requestTypeRepository.findAll())
 				.addAttribute("courses", courses)
 				.addAttribute("activeLabs", labs)
 				.addAttribute("requests", requests)
 				.addAttribute("state", filters)
 				.addAttribute("assignments", assignments(labs))
-				.addAttribute("assistants", assistants);
+				.addAttribute("assistants", assistants(courses));
 	}
 
 	/**
@@ -320,6 +305,32 @@ public class RequestTableService {
 				.collect(Collectors.toList());
 	}
 
+	/**
+	 * Flatmaps the given labs to a list of distinct rooms.
+	 *
+	 * @param  labs The labs in which to find rooms.
+	 * @return      The list of unique rooms available to the given labs.
+	 */
+	private List<Room> rooms(List<Lab> labs) {
+		return labs.stream()
+				.flatMap(lab -> lab.getRooms().stream())
+				.distinct()
+				.collect(Collectors.toList());
+	}
+
+	/**
+	 * Flatmaps the given courses to a list of distinct request-assignable users.
+	 *
+	 * @param  courses The courses to find assistants in.
+	 * @return         The list of unique assistants in the given set of courses.
+	 */
+	private List<User> assistants(List<Course> courses) {
+		return courses.stream()
+				.flatMap(course -> course.getPrivileged().stream())
+				.distinct()
+				.collect(Collectors.toList());
+	}
+
 	/**
 	 * Uses the given HttpServletRequest to extract the path of the current endpoint. This can in turn be used
 	 * as the key to store filters on.