import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.gson.Gson;

import java.util.*;
import java.io.*;
import java.sql.*;

@WebServlet("/validate")
public class ServerValidation {

    private static final long serialVersionUID = 1L;

                Gson gson = new Gson();

    Connection conn = null;
    Statement stmt;

    public void init(ServletConfig config) throws ServletException {
        // init method is run once at the start of the servlet loading
        // This will load the driver and establish a connection
        super.init(config);
        String user = "enter_your_mysql_username_here";
        String password = "enter_your_mysql_password_here";

        String url = "jdbc:mysql://mudfoot.doc.stu.mmu.ac.uk:6306/" + user;

        // Load the database driver
        try {
            Class.forName("com.mysql.jdbc.Driver");
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }

        // get a connection with the user/pass
        try {
            conn = DriverManager.getConnection(url, user, password);
            System.out.println("Sensor to DB  server is up and running\n");

            System.out.println("DEBUG: Connection to database successful.");
            stmt = conn.createStatement();
        } catch (SQLException se) {
            System.out.println(se);
        }
    }

    public void destroy() {
        try {
            conn.close();
        } catch (SQLException se) {
            System.out.println(se);
        }
    }

    public ServerValidation() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
                    response.setStatus(HttpServletResponse.SC_OK);

                    // Check to see whether the client is sending the tag id
                    String tagParam = request.getParameter("tag");

                    if (tagParam != null){

            Tag tag = gson.fromJson(tagParam, Tag.class);

            boolean valid = checktag(tag.getTagId());
            String str;

            if (valid == true)
                str = "true";
            else
                str = "false";

            Response serverResponse = new Response(str);

            String validJson = gson.toJson(serverResponse);

            PrintWriter writer = response.getWriter();
            writer.println(str);
            writer.close();

            updateLockHistory(tag, str);

                                }
    }

    public void updateLockHistory(Tag tag, String valid) {
        String sql = "insert into LockHistory (tagId, lockTime, tagIsValid) VALUES (\"" + tag.getTagId() + "\", now(), \"" + valid + "\");";
        try {
            stmt.executeUpdate(sql);
            System.out.println("History added to database");
        } catch (Exception e) {
            System.out.println(e.getMessage());
            System.out.println9("History not updated");
        }
    }

    public boolean checktag(String id) {
        ResultSet rs;
        String sql = "select * from ValidTags where tagId = " + id + ";";
        try {
            rs = stmt.executeQuery(sql);

            if (rs.next() == true)
                return true;
        } catch (SQLException se) {
            System.out.println(se);
            System.out.println("\nDEBUG: Update error - see error trace above for help. ");
            return false;
        }
        return false;
    }
}