package grading;

import java.util.*;

/**
 * An implementation GradingStrategy that applies weights to specific grade keys and weighs each
 * grade before summing a total.
 */
public class WeightedTotalStrategy implements GradingStrategy
{
  private Map<String, Double> weights;

  /**
   * Creates a new instance WeightedTotalStrategy.
   */
  public WeightedTotalStrategy()
  {
  }

  /**
   * Creates a new instance WeightedTotalStrategy.
   * 
   * @param weights
   *          A map of keys and weights to be applied to the grades during calculation.
   */
  public WeightedTotalStrategy(final Map<String, Double> weights)
  {
    this.weights = weights;
  }

  /**
   * @param key
   *          The key of the final totaled grade
   * @param grades
   *          The list of grades to calculate the final total grade from
   * @return A new grade representing the total of the weighted grades
   */
  public Grade calculate(final String key, final List<Grade> grades) throws SizeException
  {
    if (grades == null || grades.isEmpty())
    {
      throw new SizeException();
    }

    Double total = 0.0;

    for (Grade grade : grades)
    {
      Double weight = 1.0;
      if (weights != null && weights.containsKey(grade.getKey()))
      {
        Double mapWeight = weights.get(grade.getKey());
        weight = Math.max(mapWeight, 0.0);
      }

      total += Missing.doubleValue(grade.getValue()) * weight;
    }

    return new LeafGrade(key, total);
  }
}