/*
 * Copyright (c) 2001 Matthew Feldt. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided the copyright notice above is
 * retained.
 *
 * THIS SOFTWARE IS PROVIDED ''AS IS'' AND WITHOUT ANY EXPRESSED OR
 * IMPLIED WARRANTIES.
 */

/**
 * Assignment.java
 *
 * Java Examples In A Nutshell Copyright (c) 2000 David Flanagan
 * Exercise 8-3:
 * Define a class named Assignment that is modeled on the Command class shown
 * in Example 8-2. Instead of invoking a named method, as Command does,
 * Assignment should assign a value to a named field of an object. Give your
 * class a constructor with the following signature:
 *
 *     public Assignment(Object target, Field field, Object value);
 *
 * Also give it an assign() method that, when invoked, assigns the specified
 * value to the specified field of the specified object. Assignment should
 * implement ActionListerner and define an actionPerformed() method that also
 * performs the assignment. Write a static parse() method for Assignment that is
 * similar to the parse() method of Command. It should parse strings of the form
 * fieldname=value and be able to parse boolean, numeric and string values.
 *
 * @author Matthew Feldt <developer@feldt.com>
 * @version 1.0, 04/18/2001 23:35
 */

package com.feldt.examples.reflect;
import java.awt.event.*;
import java.lang.reflect.*;
import java.io.*;
import java.util.*;

/** test class with some fields to work with */
class TestAssignment {
	public boolean b;
	protected int i;
	protected double d;
	protected String s;

	public TestAssignment(boolean b, int i, double d, String s) {
		this.b = b; this.i = i;
		this.d = d;	this.s = s;
	}

	public String toString() {
		return b + ":" + i + ":" + d + ":" + s;
	}
}

public class Assignment implements ActionListener {
	Object target;
	Field field;
	Object value;

	public Assignment(Object target, Field field, Object value) {
		this.target = target;
		this.field = field;
		this.value = value;
	}

	// throws IllegalAccessException if attempting to assign values to
	// private fields
	private void assign() throws IllegalAccessException {
		field.set(target, value);
	}

	public void actionPerformed(ActionEvent e) {
		try {
			assign();
		} catch(IllegalAccessException ex) {
			throw new RuntimeException("Assign: " + ex.toString());
		}
	}

	public static Assignment parse(Object target, String text)
			throws IOException, NoSuchFieldException {
		String fieldName = null;
		Field field = null;
		Object value = null;

		// convert string to stream and use StreamTokenizer to parse out tokens
		StreamTokenizer t = new StreamTokenizer(new StringReader(text));

		// parse the fieldname
		if (t.nextToken() != t.TT_WORD)
			throw new IOException("Missing fieldname");
		field = target.getClass().getDeclaredField(t.sval);

		// parse the fieldname value seperator character '='
		if (t.nextToken() != '=')
			throw new IOException("Missing fieldname value seperator '='.");

		// parse the value and determine its type
		int type = t.nextToken();

		// if TT_WORD value must be Boolean or String
		if (type == t.TT_WORD) {
			if (t.sval.equals("true")) {
				value = new Boolean(true);
			} else if (t.sval.equals("false")) {
				value = new Boolean(false);
			} else {
				value = new String(t.sval);
			}
		// if TT_NUMBER value must be an Integer or Double
		} else if (type == t.TT_NUMBER) {
			if ((int)t.nval == t.nval) { // x.0 and true integers evaluate as Integer
				value = new Integer((int)t.nval);
			} else {
				value = new Double(t.nval);
			}
		// if single or double quote value must be a quoted string
		} else if (type == '\'' || type == '"') {
			value = new String(t.sval);
		} else { // anything else would be an error
			throw new IOException("Assignment.parse() unexpected token: " + t.sval);
		}

		return new Assignment(target, field, value);
	}

	/** test class */
	static class Test {
		public static void main(String[] args) {
			// create a TestAssignment object to play with
			TestAssignment t = new TestAssignment(true, 0, 1.25, "hello world");
			System.out.println(t);

			try {
				// create Assignment object through constructor and modify
				// TestAssignment String field 's'
				Field f = t.getClass().getDeclaredField("s");
				Assignment a1 = new Assignment(t, f, "you say goodbye");
				a1.assign();
				System.out.println(t);

				// create Assignment object through static parse method and
				// modify TestAssignment boolean field 'b'
				Assignment a2 = Assignment.parse(t, "b=false");
				a2.assign();
				System.out.println(t);

				Assignment a3 = Assignment.parse(t,
					"s=\"double quote bounded string\"");
				a3.assign();
				System.out.println(t);

				Assignment a4 = Assignment.parse(t,
					"s=\'single quote bounded string\'");
				a4.assign();
				System.out.println(t);

				Assignment a5 = Assignment.parse(t, "d=2.125");
				a5.assign();
				System.out.println(t);

				f = t.getClass().getDeclaredField("i");
				Assignment a6 = new Assignment(t, f, new Integer(44));
				a6.assign();
				System.out.println(t);

			} catch(IllegalAccessException e) {
				System.out.println(e);
			} catch(IOException e) {
				System.out.println(e);
			} catch(NoSuchFieldException e) {
				System.out.println(e);
			}
		}
	}
}