Main.java

import java.time.LocalDate;
import java.util.*;

public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        List<StudySession> sessions = FileManager.loadSessions();

        int nextId = sessions.size() + 1;

        Thread autoSaveThread = new Thread(() -> {
            while (true) {
                try {
                    Thread.sleep(10000);
                    FileManager.saveSessions(sessions);
                } catch (InterruptedException e) {
                    break;
                }
            }
        });

        autoSaveThread.setDaemon(true);
        autoSaveThread.start();

        while (true) {
            System.out.println("\n--- Study Tracker ---");
            System.out.println("1. Add Session");
            System.out.println("2. View Sessions");
            System.out.println("3. Search by Subject");
            System.out.println("4. Delete Session");
            System.out.println("5. Show Stats");
            System.out.println("6. Start Live Session");
            System.out.println("7. Save & Exit");

            System.out.print("Enter choice: ");
            int choice = sc.nextInt();

            switch (choice) {

                case 1:
                    sc.nextLine();

                    System.out.println("Choose subject:");
                    System.out.println("1. Math");
                    System.out.println("2. Physics");
                    System.out.println("3. Coding");

                    int subChoice = sc.nextInt();
                    sc.nextLine();

                    String subject = switch (subChoice) {
                        case 1 -> "Math";
                        case 2 -> "Physics";
                        case 3 -> "Coding";
                        default -> "Other";
                    };

                    System.out.print("Enter hours: ");
                    int h = sc.nextInt();

                    System.out.print("Enter minutes: ");
                    int m = sc.nextInt();

                    int totalSeconds = h * 3600 + m * 60; // no seconds input

                    sessions.add(new StudySession(
                            nextId++,
                            subject,
                            totalSeconds,
                            LocalDate.now()
                    ));

                    System.out.println("Session added!");
                    break;

                case 2:
                    if (sessions.isEmpty()) {
                        System.out.println("No sessions found.");
                    } else {
                        sessions.forEach(System.out::println);
                    }
                    break;

                case 3:
                    sc.nextLine();

                    System.out.print("Enter subject to search: ");
                    String search = sc.nextLine();

                    boolean found = false;

                    for (StudySession s1 : sessions) {
                        if (s1.getSubject().equalsIgnoreCase(search)) {
                            System.out.println(s1);
                            found = true;
                        }
                    }

                    if (!found) {
                        System.out.println("No sessions found.");
                    }
                    break;

                case 4:
                    System.out.print("Enter ID to delete: ");
                    int id = sc.nextInt();

                    boolean removed = sessions.removeIf(s1 -> s1.getId() == id);

                    System.out.println(removed ? "Deleted." : "ID not found.");
                    break;

                case 5:
                    if (sessions.isEmpty()) {
                        System.out.println("No data available.");
                        break;
                    }

                    Map<String, Integer> stats = new HashMap<>();

                    for (StudySession s1 : sessions) {
                        stats.put(
                                s1.getSubject(),
                                stats.getOrDefault(s1.getSubject(), 0) + s1.getDurationSeconds()
                        );
                    }

                    System.out.println("\n--- Study Stats ---");

                    String topSubject = "";
                    int maxTime = 0;

                    for (String key : stats.keySet()) {
                        int sec = stats.get(key);

                        int hr = sec / 3600;
                        int min = (sec % 3600) / 60;
                        int secRem = sec % 60;

                        System.out.println(key + ": " + hr + "h " + min + "m " + secRem + "s");

                        if (sec > maxTime) {
                            maxTime = sec;
                            topSubject = key;
                        }
                    }

                    System.out.println("Most Studied Subject: " + topSubject);
                    break;

                case 6:
                    sc.nextLine();

                    System.out.println("Choose subject:");
                    System.out.println("1. Math");
                    System.out.println("2. Physics");
                    System.out.println("3. Coding");

                    int subChoiceLive = sc.nextInt();
                    sc.nextLine();

                    String subjectLive = switch (subChoiceLive) {
                        case 1 -> "Math";
                        case 2 -> "Physics";
                        case 3 -> "Coding";
                        default -> "Other";
                    };

                    System.out.println("Session started... Press ENTER to stop");

                    long startTime = System.currentTimeMillis();

                    sc.nextLine();

                    long endTime = System.currentTimeMillis();

                    int seconds = (int)((endTime - startTime) / 1000);

                    sessions.add(new StudySession(
                            nextId++,
                            subjectLive,
                            seconds,
                            LocalDate.now()
                    ));

                    int hr = seconds / 3600;
                    int min = (seconds % 3600) / 60;
                    int secRem = seconds % 60;

                    System.out.println("Session recorded: " + hr + "h " + min + "m " + secRem + "s");
                    break;

                case 7:
                    FileManager.saveSessions(sessions);
                    System.out.println("Saved. Goodbye!");
                    return;

                default:
                    System.out.println("Invalid choice.");
            }
        }
    }
}