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

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

public class Phones
{
    public static void main(String[] args)
    {
        // debug code to print the command-line arguments:
        // echoArgs(args);

        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 ( ObjectInputStream p =
              new ObjectInputStream(new FileInputStream(filename)) ) {
            
            bk = (PhoneBook)p.readObject();

        }
        catch ( IOException e )
        {
            // file not found, just return a null so that the application
            // creates the file for future runs
            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( ObjectOutputStream p 
             = new ObjectOutputStream(new FileOutputStream(filename)) ) {
            p.writeObject(bk);
        }
        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]);
    }
}