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/*
 * The MIT License
 *
 *  Copyright (c) 2022, Mahmoud Ben Hassine ([email protected])
 *
 *  Permission is hereby granted, free of charge, to any person obtaining a copy
 *  of this software and associated documentation files (the "Software"), to deal
 *  in the Software without restriction, including without limitation the rights
 *  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 *  copies of the Software, and to permit persons to whom the Software is
 *  furnished to do so, subject to the following conditions:
 *
 *  The above copyright notice and this permission notice shall be included in
 *  all copies or substantial portions of the Software.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 *  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 *  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 *  THE SOFTWARE.
 */
package org.jeasy.rules.api;

import java.util.Objects;

/**
 * A class representing a named fact. Facts have unique names within a {@link Facts} instance.
 *
 * @param  type of the fact
 * @author Mahmoud Ben Hassine
 */
public class Fact {

  private final String name;
  private final T value;

  /**
   * Create a new fact.
   *
   * @param name of the fact
   * @param value of the fact
   */
  public Fact(String name, T value) {
    Objects.requireNonNull(name, "name must not be null");
    Objects.requireNonNull(value, "value must not be null");
    this.name = name;
    this.value = value;
  }

  /**
   * Get the fact name.
   *
   * @return fact name
   */
  public String getName() {
    return name;
  }

  /**
   * Get the fact value.
   *
   * @return fact value
   */
  public T getValue() {
    return value;
  }

  @Override
  public String toString() {
    return "Fact{" + "name='" + name + '\'' + ", value=" + value + '}';
  }

  /*
   * The Facts API represents a namespace for facts where each fact has a unique name.
   * Hence, equals/hashcode are deliberately calculated only on the fact name.
   */

  @Override
  public boolean equals(Object o) {
    if (this == o) return true;
    if (o == null || getClass() != o.getClass()) return false;
    Fact fact = (Fact) o;
    return name.equals(fact.name);
  }

  @Override
  public int hashCode() {
    return Objects.hash(name);
  }
}