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AIMA-Java Core Algorithms from the book Artificial Intelligence a Modern Approach 3rd Ed.
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package aima.core.search.online;

import aima.core.search.framework.problem.ActionsFunction;
import aima.core.search.framework.problem.DefaultStepCostFunction;
import aima.core.search.framework.problem.GoalTest;
import aima.core.search.framework.problem.StepCostFunction;

/**
 * Artificial Intelligence A Modern Approach (3rd Edition): page 147.

 * 

 * An online search problem must be solved by an agent executing actions, rather
 * than by pure computation. We assume a deterministic and fully observable
 * environment (Chapter 17 relaxes these assumptions), but we stipulate that the
 * agent knows only the following: 

 * 
 * ACTIONS(s), which returns a list of actions allowed in state s;
 * The step-cost function c(s, a, s') - note that this cannot be used until
 * the agent knows that s' is the outcome; and
 * GOAL-TEST(s).
 * 
 * 
 * @author Ciaran O'Reilly
 * @author Mike Stampone
 */
public class OnlineSearchProblem {

	protected ActionsFunction actionsFunction;

	protected StepCostFunction stepCostFunction;

	protected GoalTest goalTest;

	/**
	 * Constructs an online search problem with the specified action function,
	 * goal test, and a default step cost function.
	 * 
	 * @param actionsFunction
	 *            ACTIONS(s), which returns a list of actions allowed in state s
	 * @param goalTest
	 *            GOAL-TEST(s), which the agent can apply to a single state
	 *            description to determine if it is a goal state
	 */
	public OnlineSearchProblem(ActionsFunction actionsFunction,
			GoalTest goalTest) {
		this(actionsFunction, goalTest, new DefaultStepCostFunction());
	}

	/**
	 * Constructs an online search problem with the specified action function,
	 * goal test, and a default step cost function.
	 * 
	 * @param actionsFunction
	 *            ACTIONS(s), which returns a list of actions allowed in state s
	 * @param goalTest
	 *            GOAL-TEST(s), which the agent can apply to a single state
	 *            description to determine if it is a goal state
	 * @param stepCostFunction
	 *            the step-cost function c(s, a, s') - note that this cannot be
	 *            used until the agent knows that s' is the outcome
	 */
	public OnlineSearchProblem(ActionsFunction actionsFunction,
			GoalTest goalTest, StepCostFunction stepCostFunction) {
		this.actionsFunction = actionsFunction;
		this.goalTest = goalTest;
		this.stepCostFunction = stepCostFunction;
	}

	/**
	 * Returns the action function of this online search problem.
	 * 
	 * @return the action function of this online search problem.
	 */
	public ActionsFunction getActionsFunction() {
		return actionsFunction;
	}

	/**
	 * Returns true if the given state is a goal state.
	 * 
	 * @param state
	 *            an object representing a state
	 * 
	 * @return true if the given state is a goal state.
	 */
	public boolean isGoalState(Object state) {

		return goalTest.isGoalState(state);
	}

	/**
	 * Returns the step cost function of this online search problem.
	 * 
	 * @return the step cost function of this online search problem.
	 */
	public StepCostFunction getStepCostFunction() {
		return stepCostFunction;
	}

	//
	// PROTECTED METHODS
	//
	protected OnlineSearchProblem() {
	}
}