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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.environment.map;

import java.util.ArrayList;
import java.util.List;
import java.util.Set;

import aima.core.agent.Action;
import aima.core.agent.EnvironmentViewNotifier;
import aima.core.agent.Percept;
import aima.core.agent.State;
import aima.core.agent.impl.DynamicPercept;
import aima.core.agent.impl.DynamicState;
import aima.core.search.framework.ProblemSolvingAgent;
import aima.core.search.framework.SearchForActions;
import aima.core.search.framework.evalfunc.EvaluationFunction;
import aima.core.search.framework.evalfunc.HeuristicFunctionFactory;
import aima.core.search.framework.problem.Problem;
import aima.core.search.informed.BestFirstSearch;
import aima.core.search.informed.HeuristicEvaluationFunction;
import aima.core.search.informed.RecursiveBestFirstSearch;

/**
 * Variant of {@link aima.core.environment.map.SimpleMapAgent} which works
 * correctly also for A* and other best-first search implementations. It can be
 * extended also for scenarios, in which the agent faces unforeseen events. When
 * using informed search and more then one goal, make sure, that a heuristic
 * function factory is provided!
 * 
 * @author Ruediger Lunde
 *
 */
public class MapAgent extends ProblemSolvingAgent {

	protected final Map map;
	protected final DynamicState state = new DynamicState();
	protected final List goals = new ArrayList();
	protected int currGoalIdx = -1;

	// possibly null...
	protected EnvironmentViewNotifier notifier = null;
	private SearchForActions search = null;
	private HeuristicFunctionFactory hfFactory;

	public MapAgent(Map map, SearchForActions search, String goal) {
		this.map = map;
		this.search = search;
		goals.add(goal);
	}

	public MapAgent(Map map, SearchForActions search, String goal, EnvironmentViewNotifier notifier) {
		this(map, search, goal);
		this.notifier = notifier;
	}

	public MapAgent(Map map, SearchForActions search, List goals) {
		this.map = map;
		this.search = search;
		this.goals.addAll(goals);
	}

	public MapAgent(Map map, SearchForActions search, List goals, EnvironmentViewNotifier notifier) {
		this(map, search, goals);
		this.notifier = notifier;
	}

	public MapAgent(Map map, SearchForActions search, List goals, EnvironmentViewNotifier notifier,
			HeuristicFunctionFactory hfFactory) {
		this(map, search, goals, notifier);
		this.hfFactory = hfFactory;
	}

	//
	// PROTECTED METHODS
	//
	@Override
	protected State updateState(Percept p) {
		DynamicPercept dp = (DynamicPercept) p;
		state.setAttribute(DynAttributeNames.AGENT_LOCATION, dp.getAttribute(DynAttributeNames.PERCEPT_IN));
		return state;
	}

	@Override
	protected Object formulateGoal() {
		Object goal = null;
		if (currGoalIdx < goals.size() - 1) {
			goal = goals.get(++currGoalIdx);
			if (notifier != null)
				notifier.notifyViews("CurrentLocation=In(" + state.getAttribute(DynAttributeNames.AGENT_LOCATION)
						+ "), Goal=In(" + goal + ")");
			modifyHeuristicFunction(goal);
		}
		return goal;
	}

	@Override
	protected Problem formulateProblem(Object goal) {
		return new BidirectionalMapProblem(map, (String) state.getAttribute(DynAttributeNames.AGENT_LOCATION),
				(String) goal);
	}

	@Override
	protected List search(Problem problem) {
		List result = new ArrayList();
		try {
			result.addAll(search.findActions(problem));
		} catch (Exception ex) {
			ex.printStackTrace();
		}
		notifyViewOfMetrics();
		return result;
	}

	protected void notifyViewOfMetrics() {
		if (notifier != null) {
			Set keys = search.getMetrics().keySet();
			for (String key : keys) {
				notifier.notifyViews("METRIC[" + key + "]=" + search.getMetrics().get(key));
			}
		}
	}

	private void modifyHeuristicFunction(Object goal) {
		if (hfFactory != null) {
			EvaluationFunction ef = null;
			if (search instanceof BestFirstSearch)
				ef = ((BestFirstSearch) search).getEvaluationFunction();
			else if (search instanceof RecursiveBestFirstSearch)
				ef = ((RecursiveBestFirstSearch) search).getEvaluationFunction();
			if (ef instanceof HeuristicEvaluationFunction)
				((HeuristicEvaluationFunction) ef).setHeuristicFunction(hfFactory.createHeuristicFunction(goal));
		}
	}
}