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package de.gurkenlabs.litiengine.attributes;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * An attribute is a numerical representation of a property that can be adjusted using {@link AttributeModifier}s.
 * 
 * It typically doesn't adjust the raw base value (unless explicitly requested) and instead adjusts the value by
 * registered modifications. This is e.g. useful when a property might only be changed for a certain period of time or
 * we need to know the original value of a property.
 * 
 * 
 * 
 *  An example use-case are player stats that might be affected throughout the game (e.g. via certain skills,
 * upgrades or level-ups). 
 * 
 *
 * @param 
 *          The type of the attribute value.
 */
public class Attribute {

  private final List> modifiers;

  private T baseValue;

  /**
   * Initializes a new instance of the {@code Attribute} class.
   *
   * @param initialValue
   *          The initial value
   */
  public Attribute(final T initialValue) {
    this.modifiers = new ArrayList<>();
    this.baseValue = initialValue;
  }

  /**
   * Adds the specified modifier to this attribute.
   * 
   * @param modifier
   *          The modifier to be added to this instance.
   */
  public void addModifier(final AttributeModifier modifier) {
    if (this.getModifiers().contains(modifier)) {
      return;
    }

    this.getModifiers().add(modifier);
    Collections.sort(this.getModifiers());
  }

  /**
   * Removes the specified modifier from this attribute.
   * 
   * @param modifier
   *          The modifier to be removed from this instance.
   */
  public void removeModifier(final AttributeModifier modifier) {
    this.getModifiers().remove(modifier);
    Collections.sort(this.getModifiers());
  }

  /**
   * Gets the current value of this attribute, respecting all the registered {@code AttributeModifier}s.
   * 
   * @return The current value of this attribute.
   */
  public T get() {
    return this.applyModifiers(this.getBase());
  }

  /**
   * Gets the raw base value of this attribute without applying any modifications.
   * 
   * @return The raw base value of this attribute.
   */
  public T getBase() {
    return this.baseValue;
  }

  /**
   * Gets all modifiers added to this instance.
   * 
   * @return All modifiers added to this instance.
   */
  public List> getModifiers() {
    return this.modifiers;
  }

  /**
   * Determines whether the specified modifier instance is added to this attribute instance.
   * 
   * @param modifier
   *          The modifier to check for.
   * @return True if the modifier was added to this attribute instance; otherwise false.
   */
  public boolean isModifierApplied(final AttributeModifier modifier) {
    return this.getModifiers().contains(modifier);
  }

  /**
   * Adjusts the base value of this attribute once with the specified modifier.
   * 
   * @param modifier
   *          The modifier used to adjust this attribute's base value.
   * 
   * @see #getBase()
   * @see #setBaseValue(Number)
   */
  public void modifyBaseValue(final AttributeModifier modifier) {
    this.baseValue = modifier.modify(this.getBase());
  }

  /**
   * Adjusts the base value of this attribute once with the specified modifier.
   *
   * @param modification
   *          The modification type.
   * @param value
   *          The modification value to be applied.
   */
  public void modifyBaseValue(final Modification modification, double value) {
    this.baseValue = new AttributeModifier(modification, value).modify(this.getBase());
  }

  /**
   * Sets the base value of this attribute.
   * 
   * @param baseValue
   *          The base value to be set.
   */
  public void setBaseValue(final T baseValue) {
    this.baseValue = baseValue;
  }

  /**
   * Apply modifiers.
   *
   * @param baseValue
   *          the base value
   * @return the t
   */
  protected T applyModifiers(final T baseValue) {
    T currentValue = baseValue;
    for (final AttributeModifier modifier : this.getModifiers()) {
      currentValue = modifier.modify(currentValue);
    }

    return currentValue;
  }

  @Override
  public String toString() {
    return this.get() == null ? null : this.get().toString();
  }
}