package edu.neu.ccs.evergreen.model;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;

/**
 * Tracks all of the variables in the system.
 * 
 */
public class Variables {
	private List<List<Constraint>> foundIn;

	private List<Constraint> constraints = new LinkedList<Constraint>();
	
	private int maximumVariable;

	/**
	 * Create a new instance which supports the given number of variables.
	 * 
	 * @param maximumVariable
	 *            Maximum variable
	 */
	public Variables(int maximumVariable) {
		this.maximumVariable = maximumVariable;
		foundIn = new ArrayList<List<Constraint>>(maximumVariable + 1);
		for (int i = 0; i <= maximumVariable; i++) {
			foundIn.add(new ArrayList<Constraint>());
		}
	}

	/**
	 * Add a link between the constraint and the variables in it.
	 * 
	 * @param constraint
	 *            Constraint
	 */
	public void addConstraint(Constraint constraint) {
		constraints.add(constraint);
		for (int i = 0; i < constraint.getRank(); i++) {
			int variable = constraint.getVariable(i);
			if (variable > maximumVariable) {
				for (int j = maximumVariable + 1; j <= variable; j++) {
					foundIn.add(new ArrayList<Constraint>());
				}
				maximumVariable = variable;
			}
			List<Constraint> relations = foundIn.get(variable);
			relations.add(constraint);
		}
	}

	/**
	 * Return the maximum variable seen so far.
	 * 
	 * @return Maximum variable
	 */
	public int getMaximumVariable() {
		return maximumVariable;
	}

	/**
	 * Return a list of constraints that the given variable is in.
	 * 
	 * @param variable
	 *            Variable
	 * @return List of constraints
	 */
	public List<Constraint> getConstraints(int variable) {
		return foundIn.get(variable);
	}
	
	/**
	 * Return all of the constraints in the system.
	 * @return List of constraints
	 */
	public List<Constraint> getConstraints() {
		return constraints;
	}
}