StudentStore.java

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.*;
import java.util.ArrayList;
import java.util.List;

public class StudentStore {
    private final Path csvPath;

    public StudentStore(String path) {
        this.csvPath = Paths.get(path);
        ensureFileExists();
    }

    private void ensureFileExists() {
        try {
            Path parent = csvPath.getParent();
            if (parent != null && !Files.exists(parent)) {
                Files.createDirectories(parent);
            }

            if (!Files.exists(csvPath)) {
                try (BufferedWriter bw = Files.newBufferedWriter(csvPath, StandardCharsets.UTF_8,
                        StandardOpenOption.CREATE, StandardOpenOption.WRITE)) {
                    bw.write("id,name,age,email,program,gpa");
                    bw.newLine();
                }
            }
        } catch (IOException e) {
            throw new RuntimeException("Failed to initialize storage file: " + e.getMessage());
        }
    }

    public List<Student> loadAll() {
        List<Student> students = new ArrayList<Student>();
        try (BufferedReader br = Files.newBufferedReader(csvPath, StandardCharsets.UTF_8)) {
            String line;
            boolean first = true;
            while ((line = br.readLine()) != null) {
                if (first) { first = false; continue; } // header
                if (line.trim().isEmpty()) continue;
                students.add(Student.fromCsvRow(line));
            }
        } catch (IOException e) {
            throw new RuntimeException("Failed to read CSV: " + e.getMessage());
        }
        return students;
    }

    public void saveAll(List<Student> students) {
        try (BufferedWriter bw = Files.newBufferedWriter(csvPath, StandardCharsets.UTF_8,
                StandardOpenOption.CREATE, StandardOpenOption.TRUNCATE_EXISTING)) {
            bw.write("id,name,age,email,program,gpa");
            bw.newLine();
            for (Student s : students) {
                bw.write(s.toCsvRow());
                bw.newLine();
            }
        } catch (IOException e) {
            throw new RuntimeException("Failed to write CSV: " + e.getMessage());
        }
    }

    public int nextId(List<Student> students) {
        int max = 0;
        for (Student s : students) {
            if (s.getId() > max) max = s.getId();
        }
        return max + 1;
    }

    public int findIndexById(List<Student> students, int id) {
        for (int i = 0; i < students.size(); i++) {
            if (students.get(i).getId() == id) return i;
        }
        return -1;
    }
}