package edu.neu.ccs.evergreen.visitor;

import java.util.Date;
import java.util.LinkedList;

import org.apache.log4j.Logger;

import edu.neu.ccs.demeter.dj.Visitor;
import edu.neu.ccs.evergreen.demeterj.Constraint;
import edu.neu.ccs.evergreen.demeterj.Variable;
import edu.neu.ccs.evergreen.model.ConstraintFactory;
import edu.neu.ccs.evergreen.model.Variables;
import edu.neu.ccs.evergreen.model.Weights;

/**
 * Convert the generic parsed problem into custom objects.
 */
public class Preprocessor extends Visitor {
	private static final Logger LOGGER = Logger.getLogger(Preprocessor.class);

	/**
	 * Variables in the problem.
	 */
	public Variables variables;

	/**
	 * Weights of the problem.
	 */
	public Weights weights = new Weights();

	/**
	 * Number of constraints in the problem.
	 */
	public int constraintCount;

	private LinkedList<Integer> constraintVariables;

	private int maxVariable;

	/**
	 * Create a new pre preprocessor.
	 * 
	 * @param maxVariable
	 *            Maximum variable
	 */
	public Preprocessor(int maxVariable) {
		this.maxVariable = maxVariable;
		variables = new Variables(maxVariable);
	}

	/**
	 * @see edu.neu.ccs.demeter.dj.Visitor#start()
	 */
	@Override
	public void start() {
		LOGGER.info("Starting preprocessor at: " + new Date());
		constraintCount = 0;
		super.start();
	}

	/**
	 * Run before each constraint in the problem.
	 * 
	 * @param constraint
	 *            Constraint
	 */
	public void before(Constraint constraint) {
		constraintVariables = new LinkedList<Integer>();
	}

	/**
	 * Make sure the variable is valid.
	 * 
	 * @param variable
	 *            Variable to check
	 */
	private void checkVariable(int variable) {
		if (variable == 0) {
			throw new IllegalArgumentException("Variable can not equal to 0");
		}
		if (variable > maxVariable) {
			throw new IllegalArgumentException(
					"Variable can not be greater than " + maxVariable);
		}
	}

	/**
	 * Run before each variable.
	 * 
	 * @param variable
	 *            Variable
	 */
	public void before(Variable variable) {
		checkVariable(variable.get_variable());
		constraintVariables.addFirst(variable.get_variable());
	}

	/**
	 * Run after each constraint.
	 * 
	 * @param constraint
	 *            Constraint
	 */
	public void after(Constraint constraint) {
		if (constraintVariables.size() == 0) {
			throw new IllegalArgumentException("No variables given");
		}
		int createVariables[] = new int[constraintVariables.size()];
		int i = 0;
		for (Integer variable : constraintVariables) {
			createVariables[i] = variable;
			i++;
		}
		int weight = 1;
		if (constraint.get_weight() != null)
		{
			weight = constraint.getWeight();
		}
		addConstraint(constraint.getRelationNumber(), createVariables, weight);
	}

	/**
	 * Add a constraint to the system.
	 * 
	 * @param relationNumber
	 *            Relation number for the constraint
	 * @param createVariables
	 *            Variables
	 * @param weight
	 *            Weight
	 */
	private void addConstraint(int relationNumber, int createVariables[],
			int weight) {
		edu.neu.ccs.evergreen.model.Constraint constraint = ConstraintFactory
				.createConstraint(constraintCount, relationNumber,
						createVariables, weight);
		variables.addConstraint(constraint);
		weights.addWeight(constraint.getRelationNumber(), weight);
		constraintCount++;
		if (constraintCount % 1000 == 0) {
			LOGGER.debug("Processed " + constraintCount);
		}
	}

	/**
	 * @see edu.neu.ccs.demeter.dj.Visitor#finish()
	 */
	@Override
	public void finish() {
		LOGGER.info("Preprocessor finished at: " + new Date());
		super.finish();
	}
}