package org.apache.samoa.moa.classifiers;

/*
 * #%L
 * SAMOA
 * %%
 * Copyright (C) 2014 - 2015 Apache Software Foundation
 * %%
 * 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.
 * #L%
 */

import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
import java.util.Random;

import org.apache.samoa.instances.Instance;
import org.apache.samoa.instances.InstancesHeader;
import org.apache.samoa.moa.MOAObject;
import org.apache.samoa.moa.core.Example;
import org.apache.samoa.moa.core.Measurement;
import org.apache.samoa.moa.core.ObjectRepository;
import org.apache.samoa.moa.core.StringUtils;
import org.apache.samoa.moa.core.Utils;
import org.apache.samoa.moa.learners.Learner;
import org.apache.samoa.moa.options.AbstractOptionHandler;
import org.apache.samoa.moa.tasks.TaskMonitor;

import com.github.javacliparser.IntOption;

public abstract class AbstractClassifier extends AbstractOptionHandler implements Classifier {

  @Override
  public String getPurposeString() {
    return "MOA Classifier: " + getClass().getCanonicalName();
  }

  /** Header of the instances of the data stream */
  protected InstancesHeader modelContext;

  /** Sum of the weights of the instances trained by this model */
  protected double trainingWeightSeenByModel = 0.0;

  /** Random seed used in randomizable learners */
  protected int randomSeed = 1;

  /** Option for randomizable learners to change the random seed */
  protected IntOption randomSeedOption;

  /** Random Generator used in randomizable learners */
  public Random classifierRandom;

  /**
   * Creates an classifier and setups the random seed option if the classifier is randomizable.
   */
  public AbstractClassifier() {
    if (isRandomizable()) {
      this.randomSeedOption = new IntOption("randomSeed", 'r',
          "Seed for random behaviour of the classifier.", 1);
    }
  }

  @Override
  public void prepareForUseImpl(TaskMonitor monitor,
      ObjectRepository repository) {
    if (this.randomSeedOption != null) {
      this.randomSeed = this.randomSeedOption.getValue();
    }
    if (!trainingHasStarted()) {
      resetLearning();
    }
  }

  @Override
  public double[] getVotesForInstance(Example<Instance> example) {
    return getVotesForInstance(example.getData());
  }

  @Override
  public abstract double[] getVotesForInstance(Instance inst);

  @Override
  public void setModelContext(InstancesHeader ih) {
    if ((ih != null) && (ih.classIndex() < 0)) {
      throw new IllegalArgumentException(
          "Context for a classifier must include a class to learn");
    }
    if (trainingHasStarted()
        && (this.modelContext != null)
        && ((ih == null) || !contextIsCompatible(this.modelContext, ih))) {
      throw new IllegalArgumentException(
          "New context is not compatible with existing model");
    }
    this.modelContext = ih;
  }

  @Override
  public InstancesHeader getModelContext() {
    return this.modelContext;
  }

  @Override
  public void setRandomSeed(int s) {
    this.randomSeed = s;
    if (this.randomSeedOption != null) {
      // keep option consistent
      this.randomSeedOption.setValue(s);
    }
  }

  @Override
  public boolean trainingHasStarted() {
    return this.trainingWeightSeenByModel > 0.0;
  }

  @Override
  public double trainingWeightSeenByModel() {
    return this.trainingWeightSeenByModel;
  }

  @Override
  public void resetLearning() {
    this.trainingWeightSeenByModel = 0.0;
    if (isRandomizable()) {
      this.classifierRandom = new Random(this.randomSeed);
    }
    resetLearningImpl();
  }

  @Override
  public void trainOnInstance(Instance inst) {
    if (inst.weight() > 0.0) {
      this.trainingWeightSeenByModel += inst.weight();
      trainOnInstanceImpl(inst);
    }
  }

  @Override
  public Measurement[] getModelMeasurements() {
    List<Measurement> measurementList = new LinkedList<>();
    measurementList.add(new Measurement("model training instances",
        trainingWeightSeenByModel()));
    measurementList.add(new Measurement("model serialized size (bytes)",
        measureByteSize()));
    Measurement[] modelMeasurements = getModelMeasurementsImpl();
    if (modelMeasurements != null) {
      measurementList.addAll(Arrays.asList(modelMeasurements));
    }
    // add average of sub-model measurements
    Learner[] subModels = getSublearners();
    if ((subModels != null) && (subModels.length > 0)) {
      List<Measurement[]> subMeasurements = new LinkedList<>();
      for (Learner subModel : subModels) {
        if (subModel != null) {
          subMeasurements.add(subModel.getModelMeasurements());
        }
      }
      Measurement[] avgMeasurements = Measurement.averageMeasurements(subMeasurements
          .toArray(new Measurement[subMeasurements.size()][]));
      measurementList.addAll(Arrays.asList(avgMeasurements));
    }
    return measurementList.toArray(new Measurement[measurementList.size()]);
  }

  @Override
  public void getDescription(StringBuilder out, int indent) {
    StringUtils.appendIndented(out, indent, "Model type: ");
    out.append(this.getClass().getName());
    StringUtils.appendNewline(out);
    Measurement.getMeasurementsDescription(getModelMeasurements(), out,
        indent);
    StringUtils.appendNewlineIndented(out, indent, "Model description:");
    StringUtils.appendNewline(out);
    if (trainingHasStarted()) {
      getModelDescription(out, indent);
    } else {
      StringUtils.appendIndented(out, indent,
          "Model has not been trained.");
    }
  }

  @Override
  public Learner[] getSublearners() {
    return null;
  }

  @Override
  public Classifier[] getSubClassifiers() {
    return null;
  }

  @Override
  public Classifier copy() {
    return (Classifier) super.copy();
  }

  @Override
  public MOAObject getModel() {
    return this;
  }

  @Override
  public void trainOnInstance(Example<Instance> example) {
    trainOnInstance(example.getData());
  }

  @Override
  public boolean correctlyClassifies(Instance inst) {
    return Utils.maxIndex(getVotesForInstance(inst)) == (int) inst.classValue();
  }

  /**
   * Gets the name of the attribute of the class from the header.
   * 
   * @return the string with name of the attribute of the class
   */
  public String getClassNameString() {
    return InstancesHeader.getClassNameString(this.modelContext);
  }

  /**
   * Gets the name of a label of the class from the header.
   * 
   * @param classLabelIndex
   *          the label index
   * @return the name of the label of the class
   */
  public String getClassLabelString(int classLabelIndex) {
    return InstancesHeader.getClassLabelString(this.modelContext,
        classLabelIndex);
  }

  /**
   * Gets the name of an attribute from the header.
   * 
   * @param attIndex
   *          the attribute index
   * @return the name of the attribute
   */
  public String getAttributeNameString(int attIndex) {
    return InstancesHeader.getAttributeNameString(this.modelContext, attIndex);
  }

  /**
   * Gets the name of a value of an attribute from the header.
   * 
   * @param attIndex
   *          the attribute index
   * @param valIndex
   *          the value of the attribute
   * @return the name of the value of the attribute
   */
  public String getNominalValueString(int attIndex, int valIndex) {
    return InstancesHeader.getNominalValueString(this.modelContext, attIndex, valIndex);
  }

  /**
   * Returns if two contexts or headers of instances are compatible.<br>
   * <br>
   * 
   * Two contexts are compatible if they follow the following rules:<br>
   * Rule 1: num classes can increase but never decrease<br>
   * Rule 2: num attributes can increase but never decrease<br>
   * Rule 3: num nominal attribute values can increase but never decrease<br>
   * Rule 4: attribute types must stay in the same order (although class can move; is always skipped over)<br>
   * <br>
   * 
   * Attribute names are free to change, but should always still represent the original attributes.
   * 
   * @param originalContext
   *          the first context to compare
   * @param newContext
   *          the second context to compare
   * @return true if the two contexts are compatible.
   */
  public static boolean contextIsCompatible(InstancesHeader originalContext,
      InstancesHeader newContext) {

    if (newContext.numClasses() < originalContext.numClasses()) {
      return false; // rule 1
    }
    if (newContext.numAttributes() < originalContext.numAttributes()) {
      return false; // rule 2
    }
    int oPos = 0;
    int nPos = 0;
    while (oPos < originalContext.numAttributes()) {
      if (oPos == originalContext.classIndex()) {
        oPos++;
        if (!(oPos < originalContext.numAttributes())) {
          break;
        }
      }
      if (nPos == newContext.classIndex()) {
        nPos++;
      }
      if (originalContext.attribute(oPos).isNominal()) {
        if (!newContext.attribute(nPos).isNominal()) {
          return false; // rule 4
        }
        if (newContext.attribute(nPos).numValues() < originalContext.attribute(oPos).numValues()) {
          return false; // rule 3
        }
      } else {
        assert (originalContext.attribute(oPos).isNumeric());
        if (!newContext.attribute(nPos).isNumeric()) {
          return false; // rule 4
        }
      }
      oPos++;
      nPos++;
    }
    return true; // all checks clear
  }

  /**
   * Resets this classifier. It must be similar to starting a new classifier from scratch. <br>
   * <br>
   * 
   * The reason for ...Impl methods: ease programmer burden by not requiring them to remember calls to super in
   * overridden methods. Note that this will produce compiler errors if not overridden.
   */
  public abstract void resetLearningImpl();

  /**
   * Trains this classifier incrementally using the given instance.<br>
   * <br>
   * 
   * The reason for ...Impl methods: ease programmer burden by not requiring them to remember calls to super in
   * overridden methods. Note that this will produce compiler errors if not overridden.
   * 
   * @param inst
   *          the instance to be used for training
   */
  public abstract void trainOnInstanceImpl(Instance inst);

  /**
   * Gets the current measurements of this classifier.<br>
   * <br>
   * 
   * The reason for ...Impl methods: ease programmer burden by not requiring them to remember calls to super in
   * overridden methods. Note that this will produce compiler errors if not overridden.
   * 
   * @return an array of measurements to be used in evaluation tasks
   */
  protected abstract Measurement[] getModelMeasurementsImpl();

  /**
   * Returns a string representation of the model.
   * 
   * @param out
   *          the stringbuilder to add the description
   * @param indent
   *          the number of characters to indent
   */
  public abstract void getModelDescription(StringBuilder out, int indent);

  /**
   * Gets the index of the attribute in the instance, given the index of the attribute in the learner.
   * 
   * @param index
   *          the index of the attribute in the learner
   * @return the index in the instance
   */
  protected static int modelAttIndexToInstanceAttIndex(int index) {
    return index; // inst.classIndex() > index ? index : index + 1;
  }
}