/*
 *  JFLAP - Formal Languages and Automata Package
 * 
 * 
 *  Susan H. Rodger
 *  Computer Science Department
 *  Duke University
 *  August 27, 2009

 *  Copyright (c) 2002-2009
 *  All rights reserved.

 *  JFLAP is open source software. Please see the LICENSE for terms.
 *
 */





package automata.pda;

import java.util.ArrayList;

import automata.Automaton;
import automata.ClosureTaker;
import automata.Configuration;
import automata.State;
import automata.Transition;

public class PDAStepWithClosureSimulator extends PDAStepByStateSimulator {

	public PDAStepWithClosureSimulator(Automaton automaton) {
		super(automaton);
	}

	/**
	 * Returns a PDAConfiguration array that represents the initial
	 * configuration of the PDA, before any input has been processed. It returns
	 * an array of length one.
	 * 
	 * @param input
	 *            the input string.
	 */
	public Configuration[] getInitialConfigurations(String input) {
		/** The stack should contain the bottom of stack marker. */
		State init = myAutomaton.getInitialState();
		State[] closure = ClosureTaker.getClosure(init, myAutomaton);
		Configuration[] configs = new Configuration[closure.length];
		for (int k = 0; k < closure.length; k++) {
			CharacterStack stack = new CharacterStack();
			stack.push("Z");
			configs[k] = new PDAConfiguration(closure[k], null, input, input,
					stack, myAcceptance);
		}
		return configs;
	}

	/**
	 * Simulates one step for a particular configuration, adding all possible
	 * configurations reachable in one step to set of possible configurations.
	 * 
	 * @param config
	 *            the configuration to simulate the one step on
	 */
	public ArrayList stepConfiguration(Configuration config) {
		ArrayList list = new ArrayList();
		PDAConfiguration configuration = (PDAConfiguration) config;
		/** get all information from configuration. */
		String unprocessedInput = configuration.getUnprocessedInput();
		String totalInput = configuration.getInput();
		State currentState = configuration.getCurrentState();
		Transition[] transitions = myAutomaton
				.getTransitionsFromState(currentState);
		for (int k = 0; k < transitions.length; k++) {
			PDATransition transition = (PDATransition) transitions[k];
			/** get all information from transition. */
			String inputToRead = transition.getInputToRead();
			String stringToPop = transition.getStringToPop();
			CharacterStack tempStack = configuration.getStack();
			/** copy stack object so as to not alter original. */
			CharacterStack stack = new CharacterStack(tempStack);
			String stackContents = stack.pop(stringToPop.length());
			if (unprocessedInput.startsWith(inputToRead)
					&& stringToPop.equals(stackContents)) {
				String input = "";
				if (inputToRead.length() < unprocessedInput.length()) {
					input = unprocessedInput.substring(inputToRead.length());
				}
				State toState = transition.getToState();
				stack.push(transition.getStringToPush());
				State[] closure = ClosureTaker.getClosure(toState, myAutomaton);
				for (int i = 0; i < closure.length; i++) {
					CharacterStack cstack = new CharacterStack(stack);
					PDAConfiguration configurationToAdd = new PDAConfiguration(
							closure[i], configuration, totalInput, input,
							cstack, myAcceptance);
					list.add(configurationToAdd);
				}

			}
		}
		return list;
	}

}