NotesApp.java

import java.io.*;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.*;
import java.util.logging.*;


//  Simple text-based Notes app using FileWriter and BufferedReader/FileReader.

public class NotesApp {
    private static final String FILE_NAME = "notes.txt";
    private static final Logger LOGGER = Logger.getLogger(NotesApp.class.getName());
    private static final Scanner SC = new Scanner(System.in);
    private static final DateTimeFormatter TF = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");

    public static void main(String[] args) {
        setupLogger();
        System.out.println("=== Simple Notes App (file: " + FILE_NAME + ") ===");

        while (true) {
            printMenu();
            String choice = SC.nextLine().trim();
            switch (choice) {
                case "1": addNote(); break;
                case "2": listNotes(); break;
                case "3": searchNotes(); break;
                case "4": deleteNote(); break;
                case "5": clearNotes(); break;
                case "6": System.out.println("Goodbye!"); return;
                default: System.out.println("Invalid choice, try again.");
            }
        }
    }

    private static void setupLogger() {
        try {
            // write logs to errors.log (append)
            Handler fh = new FileHandler("errors.log", true);
            fh.setFormatter(new SimpleFormatter());
            LOGGER.addHandler(fh);
            LOGGER.setLevel(Level.ALL);
        } catch (IOException e) {
            System.err.println("Could not initialize file logger: " + e.getMessage());
        }
    }

    private static void printMenu() {
        System.out.println("\nMenu:");
        System.out.println("1. Add note");
        System.out.println("2. List notes");
        System.out.println("3. Search notes");
        System.out.println("4. Delete note");
        System.out.println("5. Clear all notes");
        System.out.println("6. Exit");
        System.out.print("Choose (1-6): ");
    }

    private static void addNote() {
        System.out.println("Enter your note (single line). Press Enter to save:");
        String text = SC.nextLine();
        String line = TF.format(LocalDateTime.now()) + " - " + text;
        // append mode -> second parameter true
        try (FileWriter fw = new FileWriter(FILE_NAME, true);
             BufferedWriter bw = new BufferedWriter(fw)) {
            bw.write(line);
            bw.newLine();
            System.out.println("Note saved.");
        } catch (IOException e) {
            LOGGER.log(Level.SEVERE, "Failed to write note", e);
            System.out.println("Error saving note: " + e.getMessage());
        }
    }

    private static void listNotes() {
        List<String> notes = readAllNotes();
        if (notes.isEmpty()) {
            System.out.println("(No notes found.)");
            return;
        }
        System.out.println("\n--- Notes ---");
        for (int i = 0; i < notes.size(); i++) {
            System.out.printf("%d. %s%n", i + 1, notes.get(i));
        }
    }

    private static void searchNotes() {
        List<String> notes = readAllNotes();
        if (notes.isEmpty()) {
            System.out.println("(No notes to search.)");
            return;
        }
        System.out.print("Enter search term: ");
        String q = SC.nextLine().toLowerCase();
        boolean found = false;
        for (int i = 0; i < notes.size(); i++) {
            if (notes.get(i).toLowerCase().contains(q)) {
                if (!found) System.out.println("\nMatches:");
                System.out.printf("%d. %s%n", i + 1, notes.get(i));
                found = true;
            }
        }
        if (!found) System.out.println("No matches found.");
    }

    private static void deleteNote() {
        List<String> notes = readAllNotes();
        if (notes.isEmpty()) {
            System.out.println("(No notes to delete.)");
            return;
        }
        listNotes();
        System.out.print("Enter number to delete (0 to cancel): ");
        String in = SC.nextLine();
        int num;
        try {
            num = Integer.parseInt(in);
        } catch (NumberFormatException e) {
            System.out.println("Invalid number.");
            return;
        }
        if (num == 0) {
            System.out.println("Cancelled.");
            return;
        }
        if (num < 1 || num > notes.size()) {
            System.out.println("Number out of range.");
            return;
        }
        notes.remove(num - 1);
        // overwrite file (append=false)
        try (FileWriter fw = new FileWriter(FILE_NAME, false);
             BufferedWriter bw = new BufferedWriter(fw)) {
            for (String n : notes) {
                bw.write(n);
                bw.newLine();
            }
            System.out.println("Deleted.");
        } catch (IOException e) {
            LOGGER.log(Level.SEVERE, "Failed to delete note", e);
            System.out.println("Error deleting note: " + e.getMessage());
        }
    }

    private static void clearNotes() {
        System.out.print("Are you sure? This will delete all notes. (y/N): ");
        String ans = SC.nextLine().trim();
        if (!ans.equalsIgnoreCase("y")) {
            System.out.println("Cancelled.");
            return;
        }
        try (FileWriter fw = new FileWriter(FILE_NAME, false)) {
            // opening with append=false truncates file
            System.out.println("All notes cleared.");
        } catch (IOException e) {
            LOGGER.log(Level.SEVERE, "Failed to clear notes", e);
            System.out.println("Error clearing notes: " + e.getMessage());
        }
    }

    private static List<String> readAllNotes() {
        File f = new File(FILE_NAME);
        List<String> lines = new ArrayList<>();
        if (!f.exists()) return lines;
        try (BufferedReader br = new BufferedReader(new FileReader(f))) {
            String line;
            while ((line = br.readLine()) != null) {
                lines.add(line);
            }
        } catch (IOException e) {
            LOGGER.log(Level.SEVERE, "Failed to read notes", e);
            System.out.println("Error reading notes: " + e.getMessage());
        }
        return lines;
    }
}