/* Database : Manipulate a simple key:value "database" as a map.
 *
 * Parke Godfrey, 2009-2-18
 *
*/
import java.io.*;
import java.util.*;

public class Database
{
    @SuppressWarnings("unchecked")
    public static void main(String[] args)
    {
        final String DB = "db.ser";  // File to store the map.

        Scanner input = new Scanner(System.in);
        PrintStream output = System.out;

        Map<String, String> db;
        // Try restoring DB fom previous run.
        // First, open the file.
        try
        {
            FileInputStream fis = new FileInputStream(DB);

            // Second, open an ObjectInputStream on the FileInputStream.
            try
            {
                ObjectInputStream inStr = new ObjectInputStream(fis);
                Object obj = inStr.readObject();
                inStr.close();

                if (obj instanceof HashMap)
                {
                    db = (HashMap<String, String>)obj;
                } else {
                    output.println("Previous DB map not right type!");

                    db = new HashMap<String, String>();
                }
            }
            catch(Exception ex)
            {
                fis.close();
                output.println(ex.getMessage());
                output.println("Could not read in previous DB map.");

                db = new HashMap<String, String>();
            }
        }
        catch(Exception ex)
        {
            output.printf("Could not open \"%s\".\n", DB);

            db = new HashMap<String, String>();
        }

        // Read in commands and values from the terminal.
        output.println("Command:");
        while (input.hasNextLine()) {
            String line = input.nextLine();

            String cmd = line.replaceFirst("^([^ ]+).*$", "$1");
            String key = line.replaceFirst("^[^ ]+[ ]*([^ ]*).*$", "$1");
            String val = line.replaceFirst(
                    "^[^ ]+[ ]*[^ ]*[ ]*([^ ]*).*$", "$1");

            if (cmd.equals("put"))
            {
                db.put(key, val);

                output.printf("Added\n");
                output.printf("    key = %s\n", key);
                output.printf("    val = %s\n", val);
            } else if (cmd.equals("get"))
            {
                val = db.get(key);
                if (val != null)
                {
                    output.printf("Retrieved for \"%s\"\n", key);
                    output.printf("    val = %s\n", val);
                } else 
                {
                    output.printf("Nothing stored for \"%s\"\n", key);
                }
            } else if (cmd.equals("clear"))
            {
                db.clear();
                output.printf("Map cleared.\n");
            } else
            {
                output.printf("Say what?\n");
            }

            output.println("");
            output.println("Command:");
        }

        // Print out the contents of the map.
        Iterator<String> keys = db.keySet().iterator();
        String key;
        for (; keys.hasNext();)
        {
            key = keys.next();
            output.printf("key = %s    ", key);
            output.printf("val = %s\n", db.get(key));
        }

        // Try saving DB from this run.
        try
        {
            ObjectOutputStream outStr =
                new ObjectOutputStream(new FileOutputStream(DB));
            outStr.writeObject(db);
            outStr.flush();
            outStr.close();
        }
        catch(IOException ioe)
        {
            output.println(ioe.getMessage());
            output.println("Could not save current DB.");
        }
    }
}