/*
    * This file is part of ***  M y C o R e  ***
    * See http://www.mycore.de/ for details.
    *
    * MyCoRe is free software: you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    *
   * MyCoRe is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with MyCoRe.  If not, see <http://www.gnu.org/licenses/>.
   */
  package org.mycore.access.facts;
  
  import java.util.Collection;
  import java.util.HashSet;
  import java.util.Optional;
  import java.util.Set;
  import java.util.StringJoiner;
  
  import org.mycore.access.facts.model.MCRFact;
  import org.mycore.access.facts.model.MCRFactComputable;
  
  /**
   * This class holds all facts which are validated as 'true'
   * If an identical fact is request again during the rules processing
   * the result is taken from here and won't be calculated again.
   * 
   * Internally it also stores the fact computers, for easier access.
   * Fact computers are usually the conditions parsed from the rules.xml.
   *  
   * @author Robert Stephan
   *
   */
  public class MCRFactsHolder {
  
      private Collection<MCRFactComputable<MCRFact<?>>> computers;
  
      private final Set<MCRFact<?>> facts = new HashSet<MCRFact<?>>();
  
      public MCRFactsHolder(Collection<MCRFactComputable<MCRFact<?>>> computers) {
          this.computers = computers;
      }
  
      public void add(MCRFact<?> fact) {
          facts.add(fact);
      }
  
      public boolean isFact(String factName, String term) {
          Optional<MCRFact<?>> osc = facts.stream()
              .filter(f -> factName.equals(f.getName()))
              .filter(f -> term.equals(f.getTerm()))
              .findFirst();
          return osc.isPresent();
      }
  
      public Optional<MCRFact<?>> require(String factName, MCRFactComputable<MCRFact<?>> factComputer) {
          Optional<MCRFact<?>> osc = facts.stream().filter(f -> factName.equals(f.getName())).findFirst();
          if (osc.isPresent()) {
              return osc;
          } else {
              Optional<MCRFact<?>> fact = factComputer.computeFact(this);
              if (fact.isPresent()) {
                  facts.add(fact.get());
                  return fact;
              }
          }
          return Optional.empty();
      }
  
      @SuppressWarnings("unchecked")
      public <F extends MCRFact<?>> Optional<F> require(String factName) {
          Optional<F> osc = (Optional<F>) facts.stream().filter(f -> factName.equals(f.getName())).findFirst();
          if (osc.isPresent()) {
              return osc;
          } else {
              Optional<MCRFactComputable<MCRFact<?>>> theComputer = computers.stream()
                  .filter(c -> factName.equals(c.getFactName())).findFirst();
              if (theComputer.isPresent()) {
                  Optional<MCRFact<?>> fact = theComputer.get().computeFact(this);
                  if (fact.isPresent()) {
                      facts.add(fact.get());
                      return (Optional<F>) fact;
                  }
              }
          }
          return Optional.empty();
      }
  
      @Override
      public String toString() {
          StringJoiner sj = new StringJoiner(" & ");
          facts.stream().forEach(f -> sj.add(f.toString()));
          return sj.toString();
     }
 }