// simple command-line tool for adding and looking up names in a phone book
//
// to build:
//      javac -source 1.4 Phones.java
// to run:
//      java -ea Phones add zoe 555-9876
//      java -ea Phones get zoe
//      java -ea Phones get rich
//

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

// java Phones add [name] [number]
// java Phones get [name]

public class Phones
{
   public static void main(String[] args)
   {
      // echoArgs(args);           // for debugging

      PhoneBook book;

      if ( args.length < 2 )
         post_usage("Missing add or get command and name");
      String name = args[1];

      book = load("phone-book.dat");
      if ( book == null ) // no file, create object
         book = new PhoneBook();

      String cmd = args[0];
      if ( cmd.equals("add") )
      {
         if ( args.length < 3 )
            post_usage("Missing phone number");
         String phone = args[2];
         if ( book.contains(name) )
            book.changeEntry(name, phone);
         else
            book.addEntry(new PhoneEntry(name, phone));
         save(book, "phone-book.dat");
      }
      else if( cmd.equals("get") )
      {
         String phone = book.lookupNumber(name);
         if ( phone == null )
         {
            System.out.println("No phone entry for " + name);
            System.exit(1);
         }
         else
            System.out.println("Phone # for " + name + ": " + phone);
      }
      else
         post_usage("First argument must be add or get; got " + cmd);
   }

   protected static void post_usage(String msg)
   {
      System.out.println("Usage: java Phones add|get name [number]");
      System.out.println(msg);
      System.exit(1);
   }

   protected static PhoneBook load(String filename)
   {
      PhoneBook bk = null;
      try
      {
         FileInputStream istream = new FileInputStream(filename);
         ObjectInputStream p = new ObjectInputStream(istream);
         
         bk = (PhoneBook)p.readObject();
         
         istream.close();
      }
      catch ( IOException e )
      {
         // file not found, just return a null
         return null;
      }
      catch ( ClassNotFoundException e )
      {
         System.err.println("Data file " + filename
                            + " contains wrong class.");
         System.exit(1);
      }
      return bk;
   }

   protected static void save(PhoneBook bk, String filename)
   {
      try
      {
         FileOutputStream ostream = new FileOutputStream(filename);
         ObjectOutputStream p = new ObjectOutputStream(ostream);
         
         p.writeObject(bk);
         
         p.flush();
         ostream.close();
      }
      catch ( IOException e )
      {
         System.err.println("Could not save phone book to " + filename);
      }
   }

   protected static void echoArgs(String[] args)
   {
      System.out.println("Number of command-line arguments: " + args.length);
      for(int i = 0; i < args.length; ++i)
         System.out.println("args[" + i + "] = " + args[i]);
   }
}