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Basics3 is a collection of Java classes used by the YAGO project.
There is a newer version: 1.1
package basics;

import java.util.Objects;
import java.util.regex.Pattern;

import javatools.administrative.D;

/**
Copyright 2016 Fabian M. Suchanek

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

This class represents a fact for YAGO. Convention: all fact
components must be the output of a method of the class FactComponent.
 */
public class Fact {

  /** Use this to annotate hacks that are needed to make YAGO work*/
  public @interface ImplementationNote {

    String value();
  }

  /** ID (or NULL) */
  private String id;

  /** Argument 1 */
  protected final String subject;

  /** Relation */
  protected final String relation;

  /** Argument 2 */
  protected final String object;

  /** Hash code */
  protected final int hashCode;

  /**
   * All fact components must be the output of a method of the class
   * FactComponent!
   */
  public Fact(String id, String arg1, String relation, String object) {
    this.subject = arg1;
    this.relation = relation;
    this.object = object;
    if (id != null) {
      this.id = id;
    }
    this.hashCode = Objects.hash(arg1, relation, object);
  }

  /**
   * All fact components must be the output of a method of the class
   * FactComponent!
   */
  public Fact(String arg1, String relation, String arg2withDataType) {
    this(null, arg1, relation, arg2withDataType);
  }

  /** Creates a copy of the fact */
  public Fact(Fact copy) {
    this.subject = copy.subject;
    this.object = copy.object;
    this.relation = copy.relation;
    this.id = copy.getId();
    this.hashCode = copy.hashCode;
  }

  @Override
  public int hashCode() {
    return (hashCode);
  }

  @Override
  public boolean equals(Object obj) {
    if (!(obj instanceof Fact)) return (false);
    Fact f = (Fact) obj;
    return (D.equal(id, f.id) && subject.equals(f.subject) && relation.equals(f.relation) && object.equals(f.object));
  }

  /** Returns arg n as a Java string */
  public String getArgJavaString(int a) {
    return (FactComponent.asJavaString(a == 1 ? subject : object));
  }

  /** Returns object as a Java string */
  public String getObjectAsJavaString() {
    return (FactComponent.asJavaString(object));
  }

  /** Returns arg n, strips quotes, compiles a case-insensitive pattern */
  public Pattern getArgPattern(int a) {
    return (Pattern.compile(getArgJavaString(a), Pattern.CASE_INSENSITIVE));
  }

  /** Gets subject */
  public String getSubject() {
    return (subject);
  }

  /** Gets object with data type */
  public String getObject() {
    return (object);
  }

  /** Gets argument 1 or 2 */
  public String getArg(int a) {
    return (a == 1 ? getSubject() : getObject());
  }

  /** returns the relation */
  public String getRelation() {
    return (relation);
  }

  /** returns the datatype of the second argument */
  public String getDataType() {
    return (FactComponent.getDatatype(object));
  }

  @Override
  public String toString() {
    return (getId() == null ? "" : getId() + " ") + subject + " " + relation + " " + object;
  }

  /**
   * Makes (and sets) the id, which depends on the fact components, 1+6+3+6=16
   * chars long, MIGHT HAVE DUPS, but the chances are # facts with id / 2
   * billion
   */
  public String makeId() {
    if (id != null) return (id);
    id = "id_";
    id += FactComponent.hashEntity(subject);
    id += "_" + FactComponent.hashRelation(relation);
    id += "_" + FactComponent.hashLiteralOrEntity(object);
    id = FactComponent.forYagoEntity(id);
    return (id);
  }

  /** returns the id */
  public String getId() {
    return id;
  }

  /** returns a TSV line */
  public String toTsvLine(boolean withValue) {
    if (withValue && FactComponent.isLiteral(object)) {
      String val = getValue();
      if (val == null) val = "";
      return ((id == null ? "" : id) + "\t" + getArg(1) + "\t" + getRelation() + "\t" + getArg(2) + "\t" + val + "\n");
    } else {
      return ((id == null ? "" : id) + "\t" + getArg(1) + "\t" + getRelation() + "\t" + getArg(2) + (withValue ? "\t\n" : "\n"));
    }
  }

  public String getValue() {
    String val = null;
    if (FactComponent.isLiteral(object)) {
      String datatype = getDataType();
      if (datatype != null && datatype.equals("xsd:date")) {
        String[] split = getObjectAsJavaString().split("-");
        if (split.length == 3) {
          for (int i = 0; i < 3; i++) {
            split[i] = split[i].replace('#', '0');
            while (split[i].length() < 2)
              split[i] = "0" + split[i];
          }
          val = split[0] + "." + split[1] + split[2];
        }
      } else if (datatype != null) {
        String object = getObjectAsJavaString();
        if (FactComponent.javaStringIsFloat(object)) val = object;
      }
    }
    return val;
  }

  /** returns a TSV line */
  public String toTsvLine() {
    return toTsvLine(false);
  }

  /** Creates a meta fact for this fact (generates an id if necessary) */
  public Fact metaFact(String relation, String arg2withdatatype) {
    if (getId() == null) makeId();
    return (new Fact(getId(), relation, arg2withdatatype));
  }
}