TugasP15

/**
 * Tugas P15.
 * NPM 202043500047
 * Kelas S3A
 * By Ahmad Al Desrahim (original author)
 *
 * @author Ahmad Al Desrahim
 * @version 1.0.0
 */
import java.sql.*;
import java.util.Scanner;

public class Barang {
    Scanner scanner = new Scanner(System.in);
    Connection connection = null;
    PreparedStatement preparedStatement = null;
    ResultSet rs = null;
    String dotDB = "D:/Private/Kuliah/Pemgoraman Sqlite/db_barang.db";
    String leftAlignFormat = "| %-6s | %-13s | %-4s | %-11s |%n";

    public static void main(String[] args) {
        Barang v = new Barang();
        v.displayMenu();
    }

    public Connection getConnection() throws SQLException {
        // mencegah terjadinya LOCK TABLES SQLITE
        return this.connection != null ? this.connection :DriverManager.getConnection("jdbc:sqlite:" + this.dotDB);
    }

    public Statement getStatement() throws SQLException {
        Statement statement;

        this.connection = getConnection();
        statement = this.connection.createStatement();
        statement.setQueryTimeout(30);

        return statement;
    }

    /**
     * Menu utama
     */
    public void displayMenu() {
        this.breakLines(50);
        System.out.println("[1] Lihat data barang");
        System.out.println("[2] Tambah data barang");
        System.out.println("[3] Ubah data barang");
        System.out.println("[4] Hapus data barang");
        System.out.println("[5] Keluar");
        System.out.print(">> ");

        showForm(scanner.nextLine());
    }

    /**
     * Menu selection
     * @param menu
     */
    public void showForm(String menu) {
        this.breakLines(50);

        switch (menu) {
            case "1":
                this.formShow();
                break;
            case "2":
                this.formAdd();
                break;
            case "3":
                this.formUpdate();
                break;
            case "4":
                this.formDelete();
                break;
            case "5":
                return;
            default:
                this.displayMenu();
                return;
        }

        this.goToMenu();
    }

    /**
     * Fungsi untuk mengambil data barang dari DB
     * @param code kode barang yang ingin dicari, biarkan kosong jika ingin mengambil semua data
     * @return boolean
     * @throws SQLException
     */
    public boolean findBarang(String code) throws SQLException {
        String sql = "SELECT * FROM barang";

        if (code != "") {
            sql += " WHERE kode_barang = '"+ code +"'";
        }

        this.rs = this.getStatement().executeQuery(sql);
        return !this.isRSEmpty();
    }

    /**
     * Form Menampilkan barang
     */
    public void formShow() {
        try {
            System.out.println("+--------+---------------+------+-------------+");
            System.out.println("| kode   | nama          | stok | harga       |");
            System.out.println("+--------+---------------+------+-------------+");

            if (this.findBarang("")) while(this.rs.next()) {
                System.out.format(
                        this.leftAlignFormat,
                        this.rs.getString("kode_barang"),
                        this.rs.getString("nama_barang"),
                        this.rs.getString("stok"),
                        this.rs.getString("harga"));
            } else System.out.format("| %-43s |%n", "Data barang kosong");

            System.out.println("+--------+---------------+------+-------------+");
        } catch (Exception e) {
            this.exceptionToMenu(e);
        } finally {
            this.rs = null;
        }
    }

    /**
     * Form Tambah barang
     */
    public void formAdd() {
        String code = "", name = "", stock = "", price ="";
        boolean codeExists = true,
                isInputEmpty = true;

        try {
            this.connection = this.getConnection();
            this.preparedStatement = this.connection.prepareStatement("INSERT INTO barang(kode_barang,nama_barang,stok,harga) VALUES (?,?,?,?)");

            this.formShow();
            System.out.println("\nTambah data baru: ");

            while (isInputEmpty) {
                System.out.print("Kode: ");
                code = scanner.nextLine();

                isInputEmpty = code.isEmpty();
                codeExists = this.findBarang(code);

                if (isInputEmpty || codeExists) {
                    System.out.println(isInputEmpty ? "Kode tidak boleh kosong." : codeExists ? "Kode barang sudah ada." : "");
                    isInputEmpty = true;
                }
            }
            this.preparedStatement.setString(1, code);

            isInputEmpty = true;
            while (isInputEmpty) {
                System.out.print("Nama: "); name = scanner.nextLine();
                isInputEmpty = name.isEmpty();
                if (isInputEmpty) System.out.println("Nama tidak boleh kosong.");
            }
            this.preparedStatement.setString(2, name);

            isInputEmpty = true;
            while (isInputEmpty) {
                System.out.print("Stok: ");
                stock = scanner.nextLine();
                isInputEmpty = stock.isEmpty();
                if (isInputEmpty) System.out.println("Stok tidak boleh kosong.");
            }
            this.preparedStatement.setInt(3, Integer.parseInt(stock));

            isInputEmpty = true;
            while (isInputEmpty) {
                System.out.print("Harga: ");
                price = scanner.nextLine();
                isInputEmpty = price.isEmpty();
                if (isInputEmpty) System.out.println("Harga tidak boleh kosong.");
            }
            this.preparedStatement.setDouble(4, Double.parseDouble(price));

            this.preparedStatement.executeUpdate();
            this.preparedStatement.close();

            System.out.println("Barang " + name + " berhasil ditambah.");
        } catch (Exception e) {
            this.exceptionToMenu(e);
        } finally {
            this.preparedStatement = null;
            this.rs = null;
        }
    }

    /**
     * Form Update barang
     */
    public void formUpdate() {
        String code = "", name = "", stock = "", price ="", nameInput = "", stockInput = "", priceInput ="";
        boolean notFound = true;

        try {
            this.connection = this.getConnection();
            this.preparedStatement = this.connection.prepareStatement("UPDATE barang SET nama_barang = ?,stok = ?,harga = ? WHERE kode_barang = ?");

            this.formShow();

            while (notFound) {
                System.out.print("\nUbah data [masukkan kode barang] >> ");
                code = scanner.nextLine();
                notFound = !this.findBarang(code);

                if (!notFound && this.rs.next()) {
                    System.out.println("Anda akan mengubah data berikut ini: ");

                    code = this.rs.getString("kode_barang");
                    System.out.println("Kode: " + code);

                    name = this.rs.getString("nama_barang");
                    System.out.println("Nama: " + name);

                    stock = this.rs.getString("stok");
                    System.out.println("Stok: " + stock);

                    price = this.rs.getString("harga");
                    System.out.println("Harga: " + price);

                    System.out.print("Apakah anda yakin ? [Y/n] ");
                    notFound = scanner.nextLine().trim().equalsIgnoreCase("n");
                } else {
                    System.out.println("Barang dengan kode " + code + " tidak dapat ditemukan.");
                }
            }

            System.out.println("\nLangsung enter jika tidak ingin mengubah data.");
            System.out.println("Ketik - jika ingin mengosongkan data.");
            System.out.println("Kode barang tidak bisa diubah.\n");

            System.out.print("Nama ["+ name +"]: "); nameInput = scanner.nextLine();
            this.preparedStatement.setString(1, nameInput.isEmpty() ? name : nameInput);

            System.out.print("Stok ["+ stock +"]: "); stockInput = scanner.nextLine();
            this.preparedStatement.setInt(2, Integer.parseInt(stockInput.isEmpty() ? stock : stockInput));

            System.out.print("Harga ["+ price +"]: "); priceInput = scanner.nextLine();
            this.preparedStatement.setDouble(3, Double.parseDouble(priceInput.isEmpty() ? price : priceInput));

            this.preparedStatement.setString(4, code);

            this.preparedStatement.executeUpdate();
            this.preparedStatement.close();

            System.out.println("Barang dengan kode " + code + " berhasil diubah.");
        } catch (Exception e) {
            this.exceptionToMenu(e);
        } finally {
            this.preparedStatement = null;
            this.rs = null;
        }
    }

    /**
     * Form Hapus barang
     */
    public void formDelete() {
        String code = "", name = "", stock = "", price ="";
        boolean notFound = true;

        try {
            this.connection = this.getConnection();
            this.preparedStatement = this.connection.prepareStatement("DELETE FROM barang WHERE kode_barang = ?");

            this.formShow();

            while (notFound) {
                System.out.print("\nHapus data [masukkan kode barang] >> ");
                code = scanner.nextLine();
                notFound = !this.findBarang(code);

                if (!notFound && this.rs.next()) {
                    System.out.println("Anda akan menghapus data berikut ini: ");

                    code = this.rs.getString("kode_barang");
                    System.out.println("Kode: " + code);

                    name = this.rs.getString("nama_barang");
                    System.out.println("Nama: " + name);

                    stock = this.rs.getString("stok");
                    System.out.println("Stok: " + stock);

                    price = this.rs.getString("harga");
                    System.out.println("Harga: " + price);

                    System.out.print("Apakah anda yakin ? [Y/n] ");
                    notFound = scanner.nextLine().trim().equalsIgnoreCase("n");
                } else {
                    System.out.println("Barang dengan kode " + code + " tidak dapat ditemukan.");
                }
            }

            this.preparedStatement.setString(1, code);

            this.preparedStatement.executeUpdate();
            this.preparedStatement.close();

            System.out.println("Barang dengan kode " + code + " berhasil dihapus.");
        } catch (Exception e) {
            this.exceptionToMenu(e);
        } finally {
            this.preparedStatement = null;
            this.rs = null;
        }
    }

    /**
     * Prompt untuk kembali ke menu utama, agar user tidak langsung di arahkan ke menu utama
     */
    public void goToMenu() {
        System.out.print("Tekan enter untuk kembali ke menu...\n");
        scanner.nextLine();
        showForm("0");
    }

    /**
     * Untuk handle exception agar aplikasi tidak force close
     * @param e
     */
    public void exceptionToMenu(Exception e) {
        System.err.println("Terjadi kesalahan. error: " + e.getMessage());
        this.goToMenu();
    }

    /**
     * Cek apakah ResultSet kosong
     * @return boolean
     * @throws SQLException
     */
    public boolean isRSEmpty() throws SQLException {
        return (!this.rs.isBeforeFirst() && this.rs.getRow() == 0) || this.rs == null;
    }

    /**
     * Java console ribet buat bikin fungsi clear screen, jadi ini alternatif nya
     * @param howMuch berapa banyak baris yang ingin disisipkan
     */
    public void breakLines(int howMuch) {
        if (howMuch < 1) return;
        for (int i = 0; i < howMuch; i++) System.out.println("\n");
    }
}