package example;

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

/*
 * This example application demonstrates some of the drivers other features
 * by implementing a simple psql replacement in Java.
 *
 */

public class psql
{
    Connection db;  // The connection to the database
    Statement st;  // Our statement to run queries with
    DatabaseMetaData dbmd; // This defines the structure of the database
    boolean done = false;    // Added by CWJ to permit \q command

    public psql(String args[]) throws ClassNotFoundException, FileNotFoundException, IOException, SQLException
    {
        String url = args[0];
        String usr = args[1];
        String pwd = args[2];

        // Load the driver
        Class.forName("org.postgresql.Driver");

        // Connect to database
        System.out.println("Connecting to Database URL = " + url);
        db = DriverManager.getConnection(url, usr, pwd);

        dbmd = db.getMetaData();
        st = db.createStatement();

        // This prints the backend's version
        System.out.println("Connected to " + dbmd.getDatabaseProductName() + " " + dbmd.getDatabaseProductVersion());

        System.out.println();

        // This provides us the means of reading from stdin
        StreamTokenizer input = new StreamTokenizer(new InputStreamReader(System.in));
        input.resetSyntax();
        input.slashSlashComments(true); // allow // as a comment delimiter
        input.eolIsSignificant(false); // treat eol's as spaces
        input.wordChars(32, 126);
        input.whitespaceChars(59, 59);
        // input.quoteChar(39); *** CWJ: messes up literals in query string ***

        // Now the main loop.
        int tt = 0, lineno = 1;
        while (tt != StreamTokenizer.TT_EOF && ! done)
        {
            System.out.print("[" + lineno + "] ");
            System.out.flush();

            // Here, we trap SQLException so they don't terminate the application
            try
            {
                if ((tt = input.nextToken()) == StreamTokenizer.TT_WORD)
                {
                    processLine(input.sval);
                    lineno++;
                }
            }
            catch (SQLException ex)
            {
                System.out.println(ex.getMessage());
            }
        }

        System.out.println("Now closing the connection");
        st.close();
        db.close();
    }

    /*
     * This processes a statement
     */
    public void processLine(String line) throws SQLException
    {
        if (line.startsWith("\\"))
        {
            processSlashCommand(line);
            return ;
        }

        boolean type = st.execute(line);
        boolean loop = true;
        while (loop)
        {
            if (type)
            {
                // A ResultSet was returned
                ResultSet rs = st.getResultSet();
                displayResult(rs);
            }
            else
            {
                int count = st.getUpdateCount();

                if (count == -1)
                {
                    // This indicates nothing left
                    loop = false;
                }
                else
                {
                    // An update count was returned
                    System.out.println("Updated " + st.getUpdateCount() + " rows");
                }
            }

            if (loop)
                type = st.getMoreResults();
        }
    }

    /*
     * This displays a result set.
     * Note: it closes the result once complete.
     */
    public void displayResult(ResultSet rs) throws SQLException
    {
        ResultSetMetaData rsmd = rs.getMetaData();

        // Print the result column names
        int cols = rsmd.getColumnCount();
        for (int i = 1;i <= cols;i++)
            System.out.print(rsmd.getColumnLabel(i) + (i < cols ? "\t" : "\n"));

        // now the results
        while (rs.next())
        {
            for (int i = 1;i <= cols;i++)
            {
                Object o = rs.getObject(i);
                if (rs.wasNull())
                    System.out.print("{null}" + (i < cols ? "\t" : "\n"));
                else
                    System.out.print(o.toString() + (i < cols ? "\t" : "\n"));
            }
        }

        // finally close the result set
        rs.close();
    }

    /*
     * This process / commands (for now just /d)
     */
    public void processSlashCommand(String line) throws SQLException
    {
        if (line.startsWith("\\d"))
        {

            if (line.startsWith("\\d "))
            {
                // Display details about a table
                String table = line.substring(3);
                displayResult(dbmd.getColumns(null, null, table, "%"));
            }
            else
            {
                String types[] = null;
                if (line.equals("\\d"))
                    types = allUserTables;
                else if (line.equals("\\di"))
                    types = usrIndices;
                else if (line.equals("\\dt"))
                    types = usrTables;
                else if (line.equals("\\ds"))
                    types = usrSequences;
                else if (line.equals("\\dS"))
                    types = sysTables;
                else
                    throw new SQLException("Unsupported \\d command: " + line);

                // Display details about all system tables
                //
                // Note: the first two arguments are ignored. To keep to the spec,
                //   you must put null here
                //
                displayResult(dbmd.getTables(null, null, "%", types));
            }
        }
        else if (line.equals("\\q")) // Added by CWJ to permit \q command
            done = true;
        else
            throw new SQLException("Unsupported \\ command: " + line);
    }

    private static final String allUserTables[] = {"TABLE", "INDEX", "SEQUENCE"};
    private static final String usrIndices[] = {"INDEX"};
    private static final String usrTables[] = {"TABLE"};
    private static final String usrSequences[] = {"SEQUENCE"};
    private static final String sysTables[] = {"SYSTEM TABLE", "SYSTEM INDEX"};

    /*
     * Display some instructions on how to run the example
     */
    public static void instructions()
    {
        System.out.println("\nThis example shows how some of the other JDBC features work within the\ndriver. It does this by implementing a very simple psql equivalent in java.\nNot everything that psql does is implemented.\n");
        System.out.println("Useage:\n java example.psql jdbc:postgresql:database user password [debug]\n\nThe debug field can be anything. It's presence will enable DriverManager's\ndebug trace. Unless you want to see screens of items, don't put anything in\nhere.");
        System.exit(1);
    }

    /*
     * This little lot starts the test
     */
    public static void main(String args[])
    {
        System.out.println("PostgreSQL psql example v6.3 rev 1\n");

        if (args.length < 3)
            instructions();

        // This line outputs debug information to stderr. To enable this, simply
        // add an extra parameter to the command line
        if (args.length > 3)
            DriverManager.setLogStream(System.err);

        // Now run the tests
        try
        {
            psql test = new psql(args);
        }
        catch (Exception ex)
        {
            System.err.println("Exception caught.\n" + ex);
            ex.printStackTrace();
        }
    }
}