/**** DatabaseManager.java ****/

package database;

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

public class DatabaseManager implements Serializable {

  private String driver;
  private String url;
  private String sql;
  private String user = "";
  private String password = "";
  private String result = "";
  private String message = "";
  private Connection con = null;
  private Statement stmt = null;
  private boolean debug = false;

  public DatabaseManager(String driver, String subprotocol,
      String subprotocolData, String sql) {
    //
    // your constructors will differ ...
    //
  }

  public DatabaseManager() {
    //
    // your constructors will differ ...
    //
  }

  public static void main(String[] args) {
    if (usageOnly(args))
      return;
    DatabaseManager dm;
    if (args.length == 4) {
      dm = new DatabaseManager(args[0], args[1], args[2], args[3]);
      dm.connectToDB();
      dm.executeSql();
      System.out.println(dm.getResult());
      dm.closeDB();
    }
  }

  private static boolean usageOnly(String[] args) {
    if (args.length != 4 || (args.length > 0 &&
          (args[0].equalsIgnoreCase("-help") ||
          args[0].equalsIgnoreCase("-h") ||
          args[0].equalsIgnoreCase("-usage")))) {
      System.out.println("Usage: java DatabaseManager" +
        " [<driver> <subprotocol> <subprotocolData> <sql>]");
      return true;
    }
    else
      return false;
  }

  private void handleMessage(String msg) {
    if (debug)
      System.out.println(msg);
    message = msg;
  }

  synchronized public void connectToDB() {
    closeDB();
    try {
      //
      // ...
      //
    }
    catch (Exception e) {
      result = "";
      handleMessage("Error connecting to database: " + url);
    }
  }

  synchronized public void closeDB() {
    try {
      closeStatement();
      if (con != null) {
        connected = false;
        stmt = null;
        con.close();
        con = null;
      }
    }
    catch (Exception e) {
      con = null;
      handleMessage(
        "Error closing the database connection: " + url);
    }
  }

  private void closeStatement() {
    try {
      if (stmt != null)
        stmt.close();
    }
    catch (Exception e) {
      handleMessage("Error closing the current statement.");
    }
  }

  synchronized public void executeSql() {
    if (con == null || stmt == null) {
      handleMessage("Please connect to a database.");
      return;
    }
    int len = sql.length();
    if (len == 0) {
      handleMessage("SQL statement is empty.");
      return;
    }
    if (len < 6) {
      handleMessage("SQL statement is invalid.");
      return;
    }
    try {
      String keyword = sql.substring(0, 6);
      if (keyword.equalsIgnoreCase("select")) {
        // handle query ...
      }
      else if (keyword.equalsIgnoreCase("update") ||
          keyword.equalsIgnoreCase("insert") ||
          keyword.equalsIgnoreCase("delete")) {
        // handle update ...
      }
      else {
        // handle general SQL ...
      }
      // notify targets, if any ...
    }
    catch (Exception e) {
      handleMessage("Error executing the current statement.");
    }
  }

  public String executeSqlGetResult() {
    executeSql();
    return result;
  }

  public void printResult() {
    System.out.println(result);
  }

  synchronized public String getResultAsHtmlParagraph() {
    if (result.indexOf("<p>") != -1 ||
        result.indexOf("<br>") != -1 ||
        result.indexOf("<table>") != -1)
      return result;
    String html = "<p>";
    StringTokenizer st = new StringTokenizer(result, "\n");
    while (st.hasMoreTokens())
      html += st.nextToken() + "<br>";
    html += "</p>";
    return html;
  }

  synchronized public String getResultAsHtmlTextArea() {
    String html = "<textarea name=result rows=4 cols=60>";
    html += result;
    html += "</textarea>";
    return html;
  }

  //
  // properties:
  //

  public String getMessage() {
    return message;
  }

  public void setMessage(String message) {
    // do nothing -- read-only property
  }

  public String getResult() {
    return result;
  }

  public void setResult(String result) {
    // do nothing -- read-only property
  }

  public String getDriver() {
    return driver;
  }

  synchronized public void setDriver(String str) {
    driver = str;
  }

  public String getUrl() {
    return url;
  }

  synchronized public void setUrl(String str) {
    url = str;
  }

  public String getUser() {
    return user;
  }

  synchronized public void setUser(String str) {
    user = str;
  }

  public String getPassword() {
    return password;
  }

  synchronized public void setPassword(String str) {
    password = str;
  }

  public String getSql() {
    return sql;
  }

  synchronized public void setSql(String str) {
    sql = str;
  }

  public boolean getDebug() {
    return debug;
  }

  synchronized public void setDebug(boolean state) {
    debug = state;
  }
}