import java.sql.*;

public class Pakollinen2 {
   private static final String DRIVER = "org.postgresql.Driver";
   private static final String PROTOCOL = "jdbc:postgresql:";
   private static final String SERVER = "localhost";
   private static final int PORT = 5432;
   private static final String DATABASE = "teht2";
   private static final String USER = "postgres";
   private static final String PASSWORD = "kiiwisato";


   public static void main(String args[]) throws SQLException {
      try {
         Class.forName(DRIVER);
      }
      catch (ClassNotFoundException exception) {
         System.out.println("Problem loading the driver, exiting.");
         return;
      }
      // Getting inputs using In-class from Laki1, Laki2 and Oope by Jorma Laurikkala
      System.out.println("Please enter the account from which the transaction will be funded:");
      int account = In.readInt();
      System.out.println("Please enter the account which you want to transact the money to:");
      int account2 = In.readInt();
      System.out.println("Please enter the amount:");
      double amount = In.readDouble();
      double account1balance = 0;
      double account2balance = 0;
      boolean foundAccount1 = false;
      boolean foundAccount2 = false;
      PreparedStatement test = null;
      PreparedStatement stmt = null;
      PreparedStatement subtract = null;
      PreparedStatement stmt2 = null;
      PreparedStatement add = null;
      Connection con = null;
      try {
         con = DriverManager.getConnection(PROTOCOL + "//" + SERVER + ":" + PORT +
         "/" + DATABASE, USER, PASSWORD);
         con.setAutoCommit(false);
         // Testing that account exists in database.
         test = con.prepareStatement("SELECT tilinumero FROM tilit WHERE tilinumero = ?");
         test.clearParameters();
         test.setInt(1, account);
         ResultSet ts = test.executeQuery();
         if(ts.next())
         {
            foundAccount1 = true;
         }
         // Getting accounts balance.
         stmt = con.prepareStatement("SELECT saldo FROM TILIT WHERE tilinumero = ?");
         stmt.clearParameters();
         stmt.setInt(1, account);
         ResultSet rs = stmt.executeQuery();
         while(rs.next())
         {
            account1balance = rs.getDouble(1);
         }
         // Updating accounts balance.
         account1balance = (account1balance - amount);
         subtract = con.prepareStatement("UPDATE tilit SET saldo = ? WHERE tilinumero = ?");
         subtract.clearParameters();
         subtract.setInt(2, account);
         subtract.setDouble(1, account1balance);
         subtract.executeUpdate();
         // Testing that account exists in database.
         test.clearParameters();
         test.setInt(1, account2);
         ts = test.executeQuery();
         if(ts.next())
         {
            foundAccount2 = true;
         }
         // Getting accounts balance.
         stmt2 = con.prepareStatement("SELECT saldo FROM TILIT WHERE tilinumero = ?");
         stmt2.clearParameters();
         stmt2.setInt(1, account2);
         ResultSet rs2 = stmt2.executeQuery();
         while(rs2.next())
         {
            account2balance = rs2.getDouble(1);
         }
         // Updating accounts balance.
         account2balance = (account2balance + amount);
         add = con.prepareStatement("UPDATE tilit SET saldo = ? WHERE tilinumero = ?");
         add.clearParameters();
         add.setInt(2, account2);
         add.setDouble(1, account2balance);
         add.executeUpdate();
         // If both accounts existed, commiting.
         if(foundAccount1 && foundAccount2)
         {
            con.commit();
            System.out.println("Transaction complete!");
         }
         // Else errormsg and rollback.
         else if (!foundAccount1 && !foundAccount2)
         {
            con.rollback();
            System.out.println("Accounts " + account + " and " + account2 + " do not exist!");
         }
         else if (!foundAccount1)
         {
            con.rollback();
            System.out.println("Account " + account + " does not exist!");
         }
         else if (!foundAccount2)
         {
            con.rollback();
            System.out.println("Account " + account2 + " does not exist!");
         }
         test.close();
         stmt.close();
         stmt2.close();
         subtract.close();
         add.close();
         con.setAutoCommit(true);
      }
      catch (SQLException exception) {
         System.out.println("Error1: " + exception.getMessage());
         con.rollback();
      }



      if(con != null)
      {
         try {
            con.close();
         }
         catch (SQLException exception) {
            System.out.println("Error closing connection to database. Exiting");
            return;
         }
      }
   }
}