Implement two endpoints for employee information

pom.xml

@@ -49,6 +49,18 @@
 			<artifactId>spring-boot-starter-test</artifactId>
 			<scope>test</scope>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-test</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>junit</groupId>
+			<artifactId>junit</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.mockito</groupId>
+			<artifactId>mockito-core</artifactId>
+		</dependency>
 	</dependencies>
 
 	<build>
@@ -57,6 +69,14 @@
 				<groupId>org.springframework.boot</groupId>
 				<artifactId>spring-boot-maven-plugin</artifactId>
 			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-compiler-plugin</artifactId>
+				<configuration>
+					<source>9</source>
+					<target>9</target>
+				</configuration>
+			</plugin>
 		</plugins>
 	</build>
 

src/main/java/com/zoomcare/candidatechallenge/controllers/EmployeeController.java

@@ -0,0 +1,54 @@
+package com.zoomcare.candidatechallenge.controllers;
+
+import com.zoomcare.candidatechallenge.models.Employee;
+import com.zoomcare.candidatechallenge.services.EmployeeService;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.List;
+
+/**
+ * Endpoints for obtaining information about an employee or collections of employees.
+ */
+@RestController
+@RequestMapping("/employees")
+public class EmployeeController {
+
+    private final EmployeeService employeeService;
+
+    public EmployeeController(EmployeeService employeeService) {
+        this.employeeService = employeeService;
+    }
+
+    /**
+     * Retrieves the employee with the given ID.
+     *
+     * @param id the ID of the employee to retrieve
+     * @return a {@code ResponseEntity} representing the requested employee. The entity will contain the
+     *         employee data, or a {@code NOT_FOUND} status if an employee with the given ID could not be found.
+     */
+    @GetMapping("/{id}")
+    public ResponseEntity<Employee> getEmployeeById(@PathVariable long id) {
+        Employee employee = employeeService.getEmployeeById(id);
+        if (employee == null) {
+            return new ResponseEntity<>(HttpStatus.NOT_FOUND);
+        }
+        return new ResponseEntity<>(employee, HttpStatus.OK);
+    }
+
+    /**
+     * Retrieves all top-level employees (employees with no managers).
+     *
+     * @return a {@code ResponseEntity} representing the collection of top-level employees. The entity will contain
+     *         the employee data.
+     */
+    @GetMapping("/top-level-employees")
+    public ResponseEntity<List<Employee>> getAllTopLevelEmployees() {
+        List<Employee> topLevelEmployees = employeeService.getAllTopLevelEmployees();
+        return new ResponseEntity<>(topLevelEmployees, HttpStatus.OK);
+    }
+}

src/main/java/com/zoomcare/candidatechallenge/models/Employee.java

@@ -0,0 +1,61 @@
+package com.zoomcare.candidatechallenge.models;
+
+import org.springframework.data.annotation.Transient;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Domain representation of an employee as it is stored in the database.
+ */
+public class Employee {
+    private Long id;
+    private Long supervisorId;
+    @Transient private List<Property> properties;
+    @Transient private List<Employee> directReports;
+
+    public Employee(Long id, Long supervisorId) {
+        this.id = id;
+        this.supervisorId = supervisorId;
+    }
+
+    public Employee() {
+        this.properties = new ArrayList<>();
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public Long getSupervisorId() {
+        return supervisorId;
+    }
+
+    public void setSupervisorId(Long supervisorId) {
+        this.supervisorId = supervisorId;
+    }
+
+    public List<Property> getProperties() {
+        return properties;
+    }
+
+    public void setProperties(List<Property> properties) {
+        this.properties = properties;
+    }
+
+    public void addEmployeeProperty(Property property) {
+        this.properties.add(property);
+    }
+
+    public List<Employee> getDirectReports() {
+        return directReports;
+    }
+
+    public void setDirectReports(List<Employee> directReports) {
+        this.directReports = directReports;
+    }
+}

src/main/java/com/zoomcare/candidatechallenge/models/Property.java

@@ -0,0 +1,42 @@
+package com.zoomcare.candidatechallenge.models;
+
+/**
+ * Domain representation of a property of an employee as it is stored in the database.
+ */
+public class Property {
+    private Long employeeId;
+    private String key;
+    private String value;
+
+    public Property(Long employeeId, String key, String value) {
+        this.employeeId = employeeId;
+        this.key = key;
+        this.value = value;
+    }
+
+    public Property() {}
+
+    public Long getEmployeeId() {
+        return employeeId;
+    }
+
+    public void setEmployeeId(Long employeeId) {
+        this.employeeId = employeeId;
+    }
+
+    public String getKey() {
+        return key;
+    }
+
+    public void setKey(String key) {
+        this.key = key;
+    }
+
+    public String getValue() {
+        return value;
+    }
+
+    public void setValue(String value) {
+        this.value = value;
+    }
+}

src/main/java/com/zoomcare/candidatechallenge/repositories/EmployeeRepository.java

@@ -0,0 +1,24 @@
+package com.zoomcare.candidatechallenge.repositories;
+
+import com.zoomcare.candidatechallenge.models.Employee;
+import org.springframework.data.jdbc.repository.query.Query;
+import org.springframework.data.repository.CrudRepository;
+import org.springframework.stereotype.Repository;
+
+import java.util.List;
+import java.util.Optional;
+
+/**
+ * Access layer for the employee table.
+ */
+@Repository
+public interface EmployeeRepository extends CrudRepository<Employee, Long> {
+    @Query("SELECT * FROM Employee WHERE id = :id")
+    Optional<Employee> findById(Long id);
+
+    @Query("SELECT * FROM Employee WHERE supervisor_id = :supervisorId")
+    Optional<List<Employee>> findDirectReports(Long supervisorId);
+
+    @Query("SELECT * FROM Employee WHERE supervisor_id IS NULL")
+    Optional<List<Employee>> findBySupervisorIdIsNull();
+}

src/main/java/com/zoomcare/candidatechallenge/repositories/PropertyRepository.java

@@ -0,0 +1,16 @@
+package com.zoomcare.candidatechallenge.repositories;
+
+import com.zoomcare.candidatechallenge.models.Property;
+import org.springframework.data.jdbc.repository.query.Query;
+import org.springframework.data.repository.CrudRepository;
+
+import java.util.List;
+import java.util.Optional;
+
+/**
+ * Access layer for the property table.
+ */
+public interface PropertyRepository extends CrudRepository<Property, Long> {
+    @Query("SELECT * FROM Property WHERE employee_id = :employeeId")
+    Optional<List<Property>> findByEmployeeId(Long employeeId);
+}

src/main/java/com/zoomcare/candidatechallenge/services/EmployeeService.java

@@ -0,0 +1,62 @@
+package com.zoomcare.candidatechallenge.services;
+
+import com.zoomcare.candidatechallenge.models.Employee;
+import com.zoomcare.candidatechallenge.models.Property;
+import com.zoomcare.candidatechallenge.repositories.EmployeeRepository;
+import com.zoomcare.candidatechallenge.repositories.PropertyRepository;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+
+/**
+ * Handles employee information requests.
+ */
+@Service
+public class EmployeeService {
+
+    private final EmployeeRepository employeeRepository;
+    private final PropertyRepository propertyRepository;
+
+    @Autowired
+    public EmployeeService(EmployeeRepository employeeRepository, PropertyRepository propertyRepository) {
+        this.employeeRepository = employeeRepository;
+        this.propertyRepository = propertyRepository;
+    }
+
+    public Employee getEmployeeById(Long id) {
+        Employee employee = employeeRepository.findById(id).orElse(null);
+        if (employee == null) {
+            return null;
+        }
+
+        List<Property> properties = propertyRepository.findByEmployeeId(id).orElse(Collections.emptyList());
+        employee.setProperties(properties);
+
+        List<Employee> directReports = employeeRepository.findDirectReports(id).orElse(Collections.emptyList());
+        employee.setDirectReports(directReports);
+
+        List<Employee> employees = new ArrayList<>(directReports);
+        while (!employees.isEmpty()) {
+            Employee currentEmployee = employees.remove(0);
+            List<Property> currentProperties = propertyRepository.findByEmployeeId(currentEmployee.getId()).orElse(Collections.emptyList());
+            currentEmployee.setProperties(currentProperties);
+            directReports = employeeRepository.findDirectReports(currentEmployee.getId()).orElse(Collections.emptyList());
+            currentEmployee.setDirectReports(directReports);
+            employees.addAll(directReports);
+        }
+
+        return employee;
+    }
+
+    public List<Employee> getAllTopLevelEmployees() {
+        List<Employee> topLevelEmployees = employeeRepository.findBySupervisorIdIsNull().orElse(Collections.emptyList());
+        return topLevelEmployees.stream()
+                .map(employee -> getEmployeeById(employee.getId()))
+                .collect(Collectors.toList());
+    }
+}