package edu.neu.ccs.evergreen.model;

import edu.neu.ccs.evergreen.util.AppMean;
import edu.neu.ccs.evergreen.util.AppSAT;
import edu.neu.ccs.evergreen.util.Polynomial;

/**
 * Tracks the weight of the system.
 * 
 */
public class Weights {
	private int weights[] = new int[256];

	private int total;

	private Polynomial polynomial;

	/**
	 * @see java.lang.Object#clone()
	 */
	public Weights clone() {
		Weights newWeights = new Weights();
		System.arraycopy(weights, 0, newWeights.weights, 0, weights.length);
		newWeights.total = total;
		newWeights.polynomial = polynomial;
		return newWeights;
	}

	/**
	 * Add the given weight to the relation number.
	 * 
	 * @param relationNumber
	 *            Relation number
	 * @param weight
	 *            Weight
	 */
	public void addWeight(int relationNumber, int weight) {
		weights[relationNumber] += weight;
		total += weight;
		if (polynomial != null) {
			polynomial = polynomial.add(AppSAT.appSAT(relationNumber).multiply(
					weight));
		}
	}

	/**
	 * Subtract the given weight from the relation number.
	 * 
	 * @param relationNumber
	 *            Relation number
	 * @param weight
	 *            Weight
	 */
	public void subtractWeight(int relationNumber, int weight) {
		weights[relationNumber] -= weight;
		total -= weight;
		if (polynomial != null) {
			polynomial = polynomial.subtract(AppSAT.appSAT(relationNumber)
					.multiply(weight));
		}
	}

	/**
	 * Change the weight from the old relation number to the new relation
	 * number.
	 * 
	 * @param oldRelationNumber
	 *            Old relation number
	 * @param newRelationNumber
	 *            New relation number
	 * @param weight
	 *            Weight
	 */
	public void switchWeight(int oldRelationNumber, int newRelationNumber,
			int weight) {
		subtractWeight(oldRelationNumber, weight);
		addWeight(newRelationNumber, weight);
	}

	/**
	 * Get the total weight.
	 * 
	 * @return Total weight
	 */
	public int getTotal() {
		return total;
	}

	/**
	 * Internal method to get the polynomial used for calculations.
	 * 
	 * @return Polynomial
	 */
	public Polynomial getPolynomial() {
		if (polynomial == null) {
			createPolynomial();
		}
		return polynomial.multiply(1.0 / (double) total);
	}

	/**
	 * Solve the polynomial given by this weight.
	 * 
	 * @return Y value at maximum X
	 */
	public double solve() {
		Polynomial temp = getPolynomial();
		return temp.eval(AppMean.maxX0To1(temp));
	}

	/**
	 * Determine max bias based on the weights.
	 * 
	 * @return Maximum X
	 */
	public double maxBias() {
		return AppMean.maxX0To1(getPolynomial());
	}

	/**
	 * Create the initial polynomial.
	 */
	private void createPolynomial() {
		polynomial = null;
		for (int relationNumber = 0; relationNumber < weights.length; relationNumber++) {
			if (weights[relationNumber] > 0) {
				Polynomial temp = AppSAT.appSAT(relationNumber);
				temp = temp.multiply(weights[relationNumber]);
				if (polynomial == null) {
					polynomial = temp;
				} else {
					polynomial = polynomial.add(temp);
				}
			}
		}
	}

	/**
	 * @see java.lang.Object#toString()
	 */
	@Override
	public String toString() {
		StringBuffer result = new StringBuffer();
		for (int relationNumber = 0; relationNumber < weights.length; relationNumber++) {
			if (weights[relationNumber] > 0) {
				if (result.length() > 0) {
					result.append(", ");
				}
				result.append(relationNumber);
				result.append("=");
				result.append(weights[relationNumber]);
			}
		}
		return result.toString();
	}

	/**
	 * Calculate the number of clauses satisfied for the given bias.
	 * 
	 * @param bias
	 *            Bias
	 * @return Percentage of clauses satisfied
	 */
	public double satisfiedPercentage(double bias) {
		return getPolynomial().eval(bias);
	}
}