DataManager.java

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Scanner;

public class DataManager{

private static String ensureCSV(String fileName){
    if(!fileName.endsWith(".csv")){
	fileName += ".csv";
	}
	return "data/" + fileName; 
}
	
	// going to save each students information to .csv file
public static void saveStudentsToFile(HashMap<String,Student> students, String fileName){
	fileName = DataManager.ensureCSV(fileName);
	try(PrintWriter fileS=new PrintWriter(fileName)){
		fileS.println("name,id,tuition");
		for(Student s: students.values()){
			fileS.printf("%s,%s,%.2f\n",s.getName(),s.getID(),s.getTuition());
		}
	}
		catch(FileNotFoundException e){
			System.out.println("Error: "+ e.getMessage());
		}
}


public static void saveProfessorsToFile(HashMap<String,Professor> professors, String fileName){
	fileName = DataManager.ensureCSV(fileName);
	try(PrintWriter fileS=new PrintWriter(fileName)){
		fileS.println("name,id");
		for(Professor p: professors.values()){
    		fileS.printf("%s,%s\n", p.getName(), p.getID());
}
		}catch(FileNotFoundException e){
			System.out.println("There was an error:" + e.getMessage());
		}
}

public static void saveCoursesToFile(HashMap<String, Course> courses,String fileName){
	fileName = DataManager.ensureCSV(fileName);
	try(PrintWriter fileS = new PrintWriter(fileName)){
		fileS.println("title,credits");
		for(Course p: courses.values()){
			fileS.printf("%s,%d\n",p.getCourseTitle(), p.getCourseCredits());
		}
	}catch(FileNotFoundException e){
		System.out.println("There was an error: " + e.getMessage());
	}
}



	public static ArrayList<Student> loadStudentsFromFile(String filename) {
	    ArrayList<Student> students = new ArrayList<>();
	    File file = new File(DataManager.ensureCSV(filename));

	    try (Scanner sc = new Scanner(file)) {
	        while (sc.hasNextLine()) {
	            String line = sc.nextLine().trim();
	            if (line.isEmpty() || line.startsWith("<<<<<<<") || line.startsWith("=======") || line.startsWith(">>>>>>>")) continue;
	            if (line.equalsIgnoreCase("name,id,tuition")) continue;

	            String[] parts = line.split(",");
	            if (parts.length != 3) continue;

	            String name = parts[0].trim();
	            String id = parts[1].trim();
	            String tuitionText = parts[2].trim();
	            if (name.equalsIgnoreCase("name") && id.equalsIgnoreCase("id") && tuitionText.equalsIgnoreCase("tuition")) continue;
	            double tuition;
	            try {
	            	tuition = Double.parseDouble(tuitionText);
	            } catch (NumberFormatException e) {
	            	continue;
	            }

	            students.add(new Student(name, id, tuition));
	        }
	    } catch (Exception e) {
	        System.out.println("Error loading file: " + e.getMessage());
    }

    return students;
}

public static ArrayList<Professor> loadProfessorFromFile(String fileName){
	ArrayList<Professor> professors = new ArrayList<>();
	File file = new File(DataManager.ensureCSV(fileName));

	try(Scanner sc = new Scanner(file)){
			while(sc.hasNextLine()){
				String line = sc.nextLine().trim();
				if(line.isEmpty() || line.startsWith("<<<<<<<") || line.startsWith("=======") || line.startsWith(">>>>>>>")) continue;
				if(line.equalsIgnoreCase("name,id")) continue;
				
				String[] parts = line.split(",");
				if(parts.length!=2) continue;
				
				String name = parts[0].trim();
				String id = parts[1].trim();
				if(name.equalsIgnoreCase("name") && id.equalsIgnoreCase("id")) continue;
				
				professors.add(new Professor(name, id));
			}
	}catch (FileNotFoundException e){
		System.out.println("Error loading file: " + fileName);
	}
	return professors;
}

public static ArrayList<Course> loadCourseFromFile(String fileName){
	ArrayList<Course> loadedCourses = new ArrayList<>();
	File file = new File(DataManager.ensureCSV(fileName));
	
		try(Scanner sc = new Scanner(file)){
			while(sc.hasNextLine()){
				String line = sc.nextLine().trim();
				if(line.isEmpty() || line.equalsIgnoreCase("title,credits")) continue;
				
				String[] parts = line.split(",");
				if(parts.length != 2) continue;
				
				String name = parts[0].trim();
				int credits=Integer.parseInt(parts[1].trim());

			loadedCourses.add(new Course(name, credits));
		}
	}catch(Exception e){
		System.out.println("Error loading file: " + fileName);
	}
	return loadedCourses;
}

}