/*
 *   This program 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.
 *
 *   This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 *    Instance.java
 *    Copyright (C) 1999-2012 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.core;

import java.util.Enumeration;

/**
 * Interface representing an instance. All values (numeric, date, nominal,
 * string or relational) are internally stored as floating-point numbers in the
 * original concrete class implementations (now called DenseInstance.java and
 * SparseInstance.java), and the methods in this interface reflect this. If an
 * attribute is nominal (or a string or relational), the stored value is the
 * index of the corresponding nominal (or string or relational) value in the
 * attribute's definition. We have chosen this approach in favor of a more
 * elegant object-oriented approach because it is much faster.
 * <p>
 * 
 * Typical usage (code from the main() method of this class):
 * <p>
 * 
 * <code>
 * ... <br>
 *      
 * // Create empty instance with three attribute values <br>
 * Instance inst = new DenseInstance(3); <br><br>
 *     
 * // Set instance's values for the attributes "length", "weight", and "position"<br>
 * inst.setValue(length, 5.3); <br>
 * inst.setValue(weight, 300); <br>
 * inst.setValue(position, "first"); <br><br>
 *   
 * // Set instance's dataset to be the dataset "race" <br>
 * inst.setDataset(race); <br><br>
 *   
 * // Print the instance <br>
 * System.out.println("The instance: " + inst); <br>
 * 
 * ... <br>
 * </code>
 * <p>
 * 
 * All methods that change an instance's attribute values must be safe, ie. a
 * change of an instance's attribute values must not affect any other instances.
 * 
 * @author Eibe Frank (eibe@cs.waikato.ac.nz)
 * @version $Revision: 9028 $
 */
public interface Instance extends Copyable {

  /**
   * Returns the attribute with the given index.
   * 
   * @param index the attribute's index
   * @return the attribute at the given position
   * @throws UnassignedDatasetException if instance doesn't have access to a
   *           dataset
   */
  public Attribute attribute(int index);

  /**
   * Returns the attribute with the given index in the sparse representation.
   * Same as attribute(int) for a DenseInstance.
   * 
   * @param indexOfIndex the index of the attribute's index
   * @return the attribute at the given position
   * @throws UnassignedDatasetException if instance doesn't have access to a
   *           dataset
   */
  public Attribute attributeSparse(int indexOfIndex);

  /**
   * Returns class attribute.
   * 
   * @return the class attribute
   * @throws UnassignedDatasetException if the class is not set or the instance
   *           doesn't have access to a dataset
   */
  public Attribute classAttribute();

  /**
   * Returns the class attribute's index.
   * 
   * @return the class index as an integer
   * @throws UnassignedDatasetException if instance doesn't have access to a
   *           dataset
   */
  public int classIndex();

  /**
   * Tests if an instance's class is missing.
   * 
   * @return true if the instance's class is missing
   * @throws UnassignedClassException if the class is not set or the instance
   *           doesn't have access to a dataset
   */
  public boolean classIsMissing();

  /**
   * Returns an instance's class value as a floating-point number.
   * 
   * @return the corresponding value as a double (If the corresponding attribute
   *         is nominal (or a string) then it returns the value's index as a
   *         double).
   * @throws UnassignedClassException if the class is not set or the instance
   *           doesn't have access to a dataset
   */
  public double classValue();

  /**
   * Returns the dataset this instance has access to. (ie. obtains information
   * about attribute types from) Null if the instance doesn't have access to a
   * dataset.
   * 
   * @return the dataset the instance has accesss to
   */
  public Instances dataset();

  /**
   * Deletes an attribute at the given position (0 to numAttributes() - 1). Only
   * succeeds if the instance does not have access to any dataset because
   * otherwise inconsistencies could be introduced.
   * 
   * @param position the attribute's position
   * @throws RuntimeException if the instance has access to a dataset
   */
  public void deleteAttributeAt(int position);

  /**
   * Returns an enumeration of all the attributes.
   * 
   * @return enumeration of all the attributes
   * @throws UnassignedDatasetException if the instance doesn't have access to a
   *           dataset
   */
  public Enumeration enumerateAttributes();

  /**
   * Tests if the headers of two instances are equivalent.
   * 
   * @param inst another instance
   * @return true if the header of the given instance is equivalent to this
   *         instance's header
   * @throws UnassignedDatasetException if instance doesn't have access to any
   *           dataset
   */
  public boolean equalHeaders(Instance inst);

  /**
   * Checks if the headers of two instances are equivalent. If not, then returns
   * a message why they differ.
   * 
   * @param dataset another instance
   * @return null if the header of the given instance is equivalent to this
   *         instance's header, otherwise a message with details on why they
   *         differ
   */
  public String equalHeadersMsg(Instance inst);

  /**
   * Tests whether an instance has a missing value. Skips the class attribute if
   * set.
   * 
   * @return true if instance has a missing value.
   * @throws UnassignedDatasetException if instance doesn't have access to any
   *           dataset
   */
  public boolean hasMissingValue();

  /**
   * Returns the index of the attribute stored at the given position in the
   * sparse representation. Identify function for an instance of type
   * DenseInstance.
   * 
   * @param position the position
   * @return the index of the attribute stored at the given position
   */
  public int index(int position);

  /**
   * Inserts an attribute at the given position (0 to numAttributes()). Only
   * succeeds if the instance does not have access to any dataset because
   * otherwise inconsistencies could be introduced.
   * 
   * @param position the attribute's position
   * @throws RuntimeException if the instance has accesss to a dataset
   * @throws IllegalArgumentException if the position is out of range
   */
  public void insertAttributeAt(int position);

  /**
   * Tests if a specific value is "missing".
   * 
   * @param attIndex the attribute's index
   * @return true if the value is "missing"
   */
  public boolean isMissing(int attIndex);

  /**
   * Tests if a specific value is "missing" in the sparse representation. Samse
   * as isMissing(int) for a DenseInstance.
   * 
   * @param indexOfIndex the index of the attribute's index
   * @return true if the value is "missing"
   */
  public boolean isMissingSparse(int indexOfIndex);

  /**
   * Tests if a specific value is "missing". The given attribute has to belong
   * to a dataset.
   * 
   * @param att the attribute
   * @return true if the value is "missing"
   */
  public boolean isMissing(Attribute att);

  /**
   * Merges this instance with the given instance and returns the result.
   * Dataset is set to null. The returned instance is of the same type as this
   * instance.
   * 
   * @param inst the instance to be merged with this one
   * @return the merged instances
   */
  public Instance mergeInstance(Instance inst);

  /**
   * Returns the number of attributes.
   * 
   * @return the number of attributes as an integer
   */
  public int numAttributes();

  /**
   * Returns the number of class labels.
   * 
   * @return the number of class labels as an integer if the class attribute is
   *         nominal, 1 otherwise.
   * @throws UnassignedDatasetException if instance doesn't have access to any
   *           dataset
   */
  public int numClasses();

  /**
   * Returns the number of values present in a sparse representation.
   * 
   * @return the number of values
   */
  public int numValues();

  /**
   * Replaces all missing values in the instance with the values contained in
   * the given array. A deep copy of the vector of attribute values is performed
   * before the values are replaced.
   * 
   * @param array containing the means and modes
   * @throws IllegalArgumentException if numbers of attributes are unequal
   */
  public void replaceMissingValues(double[] array);

  /**
   * Sets the class value of an instance to be "missing". A deep copy of the
   * vector of attribute values is performed before the value is set to be
   * missing.
   * 
   * @throws UnassignedClassException if the class is not set
   * @throws UnassignedDatasetException if the instance doesn't have access to a
   *           dataset
   */
  public void setClassMissing();

  /**
   * Sets the class value of an instance to the given value (internal
   * floating-point format). A deep copy of the vector of attribute values is
   * performed before the value is set.
   * 
   * @param value the new attribute value (If the corresponding attribute is
   *          nominal (or a string) then this is the new value's index as a
   *          double).
   * @throws UnassignedClassException if the class is not set
   * @throws UnaddignedDatasetException if the instance doesn't have access to a
   *           dataset
   */
  public void setClassValue(double value);

  /**
   * Sets the class value of an instance to the given value. A deep copy of the
   * vector of attribute values is performed before the value is set.
   * 
   * @param value the new class value (If the class is a string attribute and
   *          the value can't be found, the value is added to the attribute).
   * @throws UnassignedClassException if the class is not set
   * @throws UnassignedDatasetException if the dataset is not set
   * @throws IllegalArgumentException if the attribute is not nominal or a
   *           string, or the value couldn't be found for a nominal attribute
   */
  public void setClassValue(String value);

  /**
   * Sets the reference to the dataset. Does not check if the instance is
   * compatible with the dataset. Note: the dataset does not know about this
   * instance. If the structure of the dataset's header gets changed, this
   * instance will not be adjusted automatically.
   * 
   * @param instances the reference to the dataset
   */
  public void setDataset(Instances instances);

  /**
   * Sets a specific value to be "missing". Performs a deep copy of the vector
   * of attribute values before the value is set to be missing.
   * 
   * @param attIndex the attribute's index
   */
  public void setMissing(int attIndex);

  /**
   * Sets a specific value to be "missing". Performs a deep copy of the vector
   * of attribute values before the value is set to be missing. The given
   * attribute has to belong to a dataset.
   * 
   * @param att the attribute
   */
  public void setMissing(Attribute att);

  /**
   * Sets a specific value in the instance to the given value (internal
   * floating-point format). Performs a deep copy of the vector of attribute
   * values before the value is set.
   * 
   * @param attIndex the attribute's index
   * @param value the new attribute value (If the corresponding attribute is
   *          nominal (or a string) then this is the new value's index as a
   *          double).
   */
  public void setValue(int attIndex, double value);

  /**
   * Sets a specific value in the instance to the given value (internal
   * floating-point format), given an index into the sparse representation.
   * Performs a deep copy of the vector of attribute values before the value is
   * set. Same as setValue(int, double) for a DenseInstance.
   * 
   * @param indexOfIndex the index of the attribute's index
   * @param value the new attribute value (If the corresponding attribute is
   *          nominal (or a string) then this is the new value's index as a
   *          double).
   */
  public void setValueSparse(int indexOfIndex, double value);

  /**
   * Sets a value of a nominal or string attribute to the given value. Performs
   * a deep copy of the vector of attribute values before the value is set.
   * 
   * @param attIndex the attribute's index
   * @param value the new attribute value (If the attribute is a string
   *          attribute and the value can't be found, the value is added to the
   *          attribute).
   * @throws UnassignedDatasetException if the dataset is not set
   * @throws IllegalArgumentException if the selected attribute is not nominal
   *           or a string, or the supplied value couldn't be found for a
   *           nominal attribute
   */
  public void setValue(int attIndex, String value);

  /**
   * Sets a specific value in the instance to the given value (internal
   * floating-point format). Performs a deep copy of the vector of attribute
   * values before the value is set, so if you are planning on calling setValue
   * many times it may be faster to create a new instance using toDoubleArray.
   * The given attribute has to belong to a dataset.
   * 
   * @param att the attribute
   * @param value the new attribute value (If the corresponding attribute is
   *          nominal (or a string) then this is the new value's index as a
   *          double).
   */
  public void setValue(Attribute att, double value);

  /**
   * Sets a value of an nominal or string attribute to the given value. Performs
   * a deep copy of the vector of attribute values before the value is set, so
   * if you are planning on calling setValue many times it may be faster to
   * create a new instance using toDoubleArray. The given attribute has to
   * belong to a dataset.
   * 
   * @param att the attribute
   * @param value the new attribute value (If the attribute is a string
   *          attribute and the value can't be found, the value is added to the
   *          attribute).
   * @throws IllegalArgumentException if the the attribute is not nominal or a
   *           string, or the value couldn't be found for a nominal attribute
   */
  public void setValue(Attribute att, String value);

  /**
   * Sets the weight of an instance.
   * 
   * @param weight the weight
   */
  public void setWeight(double weight);

  /**
   * Returns the relational value of a relational attribute.
   * 
   * @param attIndex the attribute's index
   * @return the corresponding relation as an Instances object
   * @throws IllegalArgumentException if the attribute is not a relation-valued
   *           attribute
   * @throws UnassignedDatasetException if the instance doesn't belong to a
   *           dataset.
   */
  public Instances relationalValue(int attIndex);

  /**
   * Returns the relational value of a relational attribute.
   * 
   * @param att the attribute
   * @return the corresponding relation as an Instances object
   * @throws IllegalArgumentException if the attribute is not a relation-valued
   *           attribute
   * @throws UnassignedDatasetException if the instance doesn't belong to a
   *           dataset.
   */
  public Instances relationalValue(Attribute att);

  /**
   * Returns the value of a nominal, string, date, or relational attribute for
   * the instance as a string.
   * 
   * @param attIndex the attribute's index
   * @return the value as a string
   * @throws IllegalArgumentException if the attribute is not a nominal, string,
   *           date, or relation-valued attribute.
   * @throws UnassignedDatasetException if the instance doesn't belong to a
   *           dataset.
   */
  public String stringValue(int attIndex);

  /**
   * Returns the value of a nominal, string, date, or relational attribute for
   * the instance as a string.
   * 
   * @param att the attribute
   * @return the value as a string
   * @throws IllegalArgumentException if the attribute is not a nominal, string,
   *           date, or relation-valued attribute.
   * @throws UnassignedDatasetException if the instance doesn't belong to a
   *           dataset.
   */
  public String stringValue(Attribute att);

  /**
   * Returns the values of each attribute as an array of doubles.
   * 
   * @return an array containing all the instance attribute values
   */
  public double[] toDoubleArray();

  /**
   * Returns the description of one instance (without weight appended). If the
   * instance doesn't have access to a dataset, it returns the internal
   * floating-point values. Quotes string values that contain whitespace
   * characters.
   * 
   * This method is used by getRandomNumberGenerator() in Instances.java in
   * order to maintain backwards compatibility with weka 3.4.
   * 
   * @param afterDecimalPoint maximum number of digits after the decimal point
   *          for numeric values
   * 
   * @return the instance's description as a string
   */
  public String toStringNoWeight(int afterDecimalPoint);

  /**
   * Returns the description of one instance (without weight appended). If the
   * instance doesn't have access to a dataset, it returns the internal
   * floating-point values. Quotes string values that contain whitespace
   * characters.
   * 
   * This method is used by getRandomNumberGenerator() in Instances.java in
   * order to maintain backwards compatibility with weka 3.4.
   * 
   * @return the instance's description as a string
   */
  public String toStringNoWeight();

  /**
   * Returns the description of one instance with any numeric values printed at
   * the supplied maximum number of decimal places. If the instance doesn't have
   * access to a dataset, it returns the internal floating-point values. Quotes
   * string values that contain whitespace characters.
   * 
   * @param afterDecimalPoint the maximum number of digits permitted after the
   *          decimal point for a numeric value
   * 
   * @return the instance's description as a string
   */
  public String toStringMaxDecimalDigits(int afterDecimalPoint);

  /**
   * Returns the description of one value of the instance as a string. If the
   * instance doesn't have access to a dataset, it returns the internal
   * floating-point value. Quotes string values that contain whitespace
   * characters, or if they are a question mark.
   * 
   * @param attIndex the attribute's index
   * @param afterDecimalPoint the maximum number of digits permitted after the
   *          decimal point for numeric values
   * @return the value's description as a string
   */
  public String toString(int attIndex, int afterDecimalPoint);

  /**
   * Returns the description of one value of the instance as a string. If the
   * instance doesn't have access to a dataset, it returns the internal
   * floating-point value. Quotes string values that contain whitespace
   * characters, or if they are a question mark.
   * 
   * @param attIndex the attribute's index
   * @return the value's description as a string
   */
  public String toString(int attIndex);

  /**
   * Returns the description of one value of the instance as a string. If the
   * instance doesn't have access to a dataset it returns the internal
   * floating-point value. Quotes string values that contain whitespace
   * characters, or if they are a question mark. The given attribute has to
   * belong to a dataset.
   * 
   * @param att the attribute
   * @param afterDecimalPoint the maximum number of decimal places to print
   * @return the value's description as a string
   */
  public String toString(Attribute att, int afterDecimalPoint);

  /**
   * Returns the description of one value of the instance as a string. If the
   * instance doesn't have access to a dataset it returns the internal
   * floating-point value. Quotes string values that contain whitespace
   * characters, or if they are a question mark. The given attribute has to
   * belong to a dataset.
   * 
   * @param att the attribute
   * @return the value's description as a string
   */
  public String toString(Attribute att);

  /**
   * Returns an instance's attribute value in internal format.
   * 
   * @param attIndex the attribute's index
   * @return the specified value as a double (If the corresponding attribute is
   *         nominal (or a string) then it returns the value's index as a
   *         double).
   */
  public double value(int attIndex);

  /**
   * Returns an instance's attribute value in internal format, given an index in
   * the sparse representation. Same as value(int) for a DenseInstance.
   * 
   * @param indexOfIndex the index of the attribute's index
   * @return the specified value as a double (If the corresponding attribute is
   *         nominal (or a string) then it returns the value's index as a
   *         double).
   */
  public double valueSparse(int indexOfIndex);

  /**
   * Returns an instance's attribute value in internal format. The given
   * attribute has to belong to a dataset.
   * 
   * @param att the attribute
   * @return the specified value as a double (If the corresponding attribute is
   *         nominal (or a string) then it returns the value's index as a
   *         double).
   */
  public double value(Attribute att);

  /**
   * Returns the instance's weight.
   * 
   * @return the instance's weight as a double
   */
  public double weight();
}
