/**
 * 课程管理实现类
 * 提供课程管理接口的具体实现
 * 遵循单一职责原则，专注于课程的CRUD操作
 */
package com.employeetraining.course;

import java.util.*;
import java.util.concurrent.ConcurrentHashMap;

public class CourseManagerImpl implements CourseManager {
    // 使用线程安全的集合存储课程
    private final Map<String, Course> courseMap = new ConcurrentHashMap<>();
    
    @Override
    public void addCourse(Course course) {
        if (course == null) {
            throw new IllegalArgumentException("Course cannot be null");
        }
        if (course.getCourseId() == null || course.getCourseId().trim().isEmpty()) {
            throw new IllegalArgumentException("Course ID cannot be empty");
        }
        courseMap.put(course.getCourseId(), course);
    }
    
    @Override
    public boolean updateCourse(Course course) {
        if (course == null || course.getCourseId() == null) {
            return false;
        }
        if (courseMap.containsKey(course.getCourseId())) {
            courseMap.put(course.getCourseId(), course);
            return true;
        }
        return false;
    }
    
    @Override
    public boolean deleteCourse(String courseId) {
        if (courseId == null) {
            return false;
        }
        return courseMap.remove(courseId) != null;
    }
    
    @Override
    public Optional<Course> findCourseById(String courseId) {
        if (courseId == null) {
            return Optional.empty();
        }
        return Optional.ofNullable(courseMap.get(courseId));
    }
    
    @Override
    public List<Course> findCoursesByCategory(String category) {
        if (category == null) {
            return Collections.emptyList();
        }
        return courseMap.values().stream()
                .filter(course -> category.equalsIgnoreCase(course.getCategory()))
                .toList();
    }
    
    @Override
    public List<Course> findRequiredCourses() {
        return courseMap.values().stream()
                .filter(Course::isRequired)
                .toList();
    }
    
    @Override
    public List<Course> getAllCourses() {
        return new ArrayList<>(courseMap.values());
    }
}