/**
 * Copyright (C) 2011 - present by OpenGamma Inc. and the OpenGamma group of companies
 *
 * Please see distribution for license.
 */
package com.opengamma.core.position.impl;

import java.util.Collection;

import com.opengamma.core.position.PortfolioNode;
import com.opengamma.core.position.Position;
import com.opengamma.util.ArgumentChecker;

/**
 * Implementation of {@code PortfolioNodeTraversalCallback} that collects values from a portfolio.
 * <p>
 * A {@link PortfolioMapperFunction} is used at each node in the portfolio, and the return value from its apply()
 * method is stored. Any null values generated by the mapper function are ignored.
 *
 * @param <T>  the type that is collected
 * @param <V>  the collection type into which the values are collected
 */
/*package*/ class MappingCallback<T, V extends Collection<T>> extends AbstractPortfolioNodeTraversalCallback {

  /**
   * The collected values
   */
  private final V _values;
  /**
   * The mapper function which generates the values
   */
  private final PortfolioMapperFunction<T> _fn;

  /**
   * Constructs an instance.
   *
   * @param fn  the function that generates values for the portfolio's nodes, not null
   * @param resultCollection  the collection instance to which the results will be added, not null
   */
  public MappingCallback(final PortfolioMapperFunction<T> fn, final V resultCollection) {
    ArgumentChecker.notNull(fn, "fn");
    ArgumentChecker.notNull(resultCollection, "resultCollection");
    _fn = fn;
    _values = resultCollection;
  }

  @Override
  public void preOrderOperation(final PortfolioNode portfolioNode) {
    final T result = _fn.apply(portfolioNode);
    if (result != null) {
      _values.add(result);
    }
  }

  @Override
  public void preOrderOperation(final PortfolioNode parentNode, final Position position) {
    final T result = _fn.apply(parentNode, position);
    if (result != null) {
      _values.add(result);
    }
  }

  /** @return The values generated by the mapper function */
  public V getValues() {
    return _values;
  }

}