import java.sql.*; // JDBC stuff.
import java.util.Properties;

public class PortalConnection {

    // For connecting to the portal database on your local machine
    static final String DATABASE = "jdbc:postgresql://localhost/portal";
    static final String USERNAME = "postgres";
    static final String PASSWORD = "postgres";

    // For connecting to the chalmers database server (from inside chalmers)
    // static final String DATABASE = "jdbc:postgresql://ate.ita.chalmers.se/";
    // static final String USERNAME = "tda357_nnn";
    // static final String PASSWORD = "yourPasswordGoesHere";


    // This is the JDBC connection object you will be using in your methods.
    private Connection conn;

    public PortalConnection() throws SQLException, ClassNotFoundException {
        this(DATABASE, USERNAME, PASSWORD);
    }

    // Initializes the connection, no need to change anything here
    public PortalConnection(String db, String user, String pwd) throws SQLException, ClassNotFoundException {
        Class.forName("org.postgresql.Driver");
        Properties props = new Properties();
        props.setProperty("user", user);
        props.setProperty("password", pwd);
        conn = DriverManager.getConnection(db, props);
    }


    // Register a student on a course, returns a tiny JSON document (as a String)
    public String register(String student, String courseCode){

    	try (PreparedStatement s = conn.prepareStatement(
    			"SELECT idnr,name FROM BasicInformation");){
    			ResultSet rs = s.executeQuery();

    			while(rs.next()){
    			String id = rs.getString(1);
    			String name = rs.getString(2);
    			System.out.println(id + " " + name);
    			}
    			return "{\"success\":true}";
    		}
    	catch (SQLException e) {
            return "{\"success\":false, \"error\":\""+getError(e)+"\"}";
        }

    }

    public String RegistrationCheck() {
    	try (PreparedStatement ps = conn.prepareStatement(
    			"SELECT * FROM Registered WHERE student=? AND course=?");){
    			ps.setString(1, "1111111111");
    			ps.setString(2, "CCC111");
    			ResultSet rs = ps.executeQuery();
    			if(rs.next()) {
    				System.out.println("Yes, you are registered :)");
    				return "{\"success\":true}";
    			}else {
    				System.out.println("No, you are not registered :(");
    				return "{\"success\":false}";
    			}
    	}
    	catch (SQLException e) {
            return "{\"success\":false, \"error\":\""+getError(e)+"\"}";
        }
    }

    // Unregister a student from a course, returns a tiny JSON document (as a String)
    public String unregister(String student, String courseCode){

    	try(PreparedStatement ps = conn.prepareStatement(
    			"DELETE FROM Registered WHERE student=? AND course=?");){
    			System.out.println(ps);

    			ps.setString(1,student);
    			ps.setString(2,courseCode); // Denna och den över kan ersättas med user input.

    			System.out.println("query is: " + ps);
    			int r = ps.executeUpdate();
    			}
    	catch (SQLException e) {
            return "{\"success\":false, \"error\":\""+getError(e)+"\"}";
        }
      return "{\"success\":false, \"error\":\"Unregistration is not implemented yet :(\"}";
    }

    // Return a JSON document containing lots of information about a student, it should validate against the schema found in information_schema.json
    public String getInfo(String student) throws SQLException{

        try(PreparedStatement st = conn.prepareStatement(
            // replace this with something more useful
            "SELECT jsonb_build_object('student',idnr,'name',name) AS jsondata FROM BasicInformation WHERE idnr=?"
            );){

            st.setString(1, student);

            ResultSet rs = st.executeQuery();

            if(rs.next())
              return rs.getString("jsondata");
            else
              return "{\"student\":\"does not exist :(\"}";

        }
    }

    // This is a hack to turn an SQLException into a JSON string error message. No need to change.
    public static String getError(SQLException e){
       String message = e.getMessage();
       int ix = message.indexOf('\n');
       if (ix > 0) message = message.substring(0, ix);
       message = message.replace("\"","\\\"");
       return message;
    }
}