/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You 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.
   */
  package org.apache.commons.math4.legacy.linear;
  
  import java.io.Serializable;
  
  import org.apache.commons.math4.legacy.exception.DimensionMismatchException;
  import org.apache.commons.math4.legacy.exception.MathArithmeticException;
  import org.apache.commons.math4.legacy.exception.NotPositiveException;
  import org.apache.commons.math4.legacy.exception.OutOfRangeException;
  import org.apache.commons.math4.legacy.exception.util.LocalizedFormats;
  import org.apache.commons.math4.core.jdkmath.JdkMath;
  import org.apache.commons.math4.legacy.linear.OpenIntToDoubleHashMap.Iterator;
  
  /**
   * This class implements the {@link RealVector} interface with a
   * {@link OpenIntToDoubleHashMap} backing store.
   * <p>
   *  Caveat: This implementation assumes that, for any {@code x},
   *  the equality {@code x * 0d == 0d} holds. But it is is not true for
   *  {@code NaN}. Moreover, zero entries will lose their sign.
   *  Some operations (that involve {@code NaN} and/or infinities) may
   *  thus give incorrect results, like multiplications, divisions or
   *  functions mapping.
   * </p>
   * @since 2.0
   */
  public class OpenMapRealVector extends SparseRealVector
      implements Serializable {
      /** Default Tolerance for having a value considered zero. */
      public static final double DEFAULT_ZERO_TOLERANCE = 1.0e-12;
      /** Serializable version identifier. */
      private static final long serialVersionUID = 8772222695580707260L;
      /** Entries of the vector. */
      private final OpenIntToDoubleHashMap entries;
      /** Dimension of the vector. */
      private final int virtualSize;
      /** Tolerance for having a value considered zero. */
      private final double epsilon;
  
      /**
       * Build a 0-length vector.
       * Zero-length vectors may be used to initialized construction of vectors
       * by data gathering. We start with zero-length and use either the {@link
       * #OpenMapRealVector(OpenMapRealVector, int)} constructor
       * or one of the {@code append} method ({@link #append(double)},
       * {@link #append(RealVector)}) to gather data into this vector.
       */
      public OpenMapRealVector() {
          this(0, DEFAULT_ZERO_TOLERANCE);
      }
  
      /**
       * Construct a vector of zeroes.
       *
       * @param dimension Size of the vector.
       */
      public OpenMapRealVector(int dimension) {
          this(dimension, DEFAULT_ZERO_TOLERANCE);
      }
  
      /**
       * Construct a vector of zeroes, specifying zero tolerance.
       *
       * @param dimension Size of the vector.
       * @param epsilon Tolerance below which a value considered zero.
       */
      public OpenMapRealVector(int dimension, double epsilon) {
          virtualSize = dimension;
          entries = new OpenIntToDoubleHashMap(0.0);
          this.epsilon = epsilon;
      }
  
      /**
       * Build a resized vector, for use with append.
       *
       * @param v Original vector.
       * @param resize Amount to add.
       */
      protected OpenMapRealVector(OpenMapRealVector v, int resize) {
          virtualSize = v.getDimension() + resize;
          entries = new OpenIntToDoubleHashMap(v.entries);
          epsilon = v.epsilon;
      }
  
     /**
      * Build a vector with known the sparseness (for advanced use only).
      *
      * @param dimension Size of the vector.
      * @param expectedSize The expected number of non-zero entries.
      */
     public OpenMapRealVector(int dimension, int expectedSize) {
         this(dimension, expectedSize, DEFAULT_ZERO_TOLERANCE);
     }
 
     /**
      * Build a vector with known the sparseness and zero tolerance
      * setting (for advanced use only).
      *
      * @param dimension Size of the vector.
      * @param expectedSize Expected number of non-zero entries.
      * @param epsilon Tolerance below which a value is considered zero.
      */
     public OpenMapRealVector(int dimension, int expectedSize, double epsilon) {
         virtualSize = dimension;
         entries = new OpenIntToDoubleHashMap(expectedSize, 0.0);
         this.epsilon = epsilon;
     }
 
     /**
      * Create from an array.
      * Only non-zero entries will be stored.
      *
      * @param values Set of values to create from.
      */
     public OpenMapRealVector(double[] values) {
         this(values, DEFAULT_ZERO_TOLERANCE);
     }
 
     /**
      * Create from an array, specifying zero tolerance.
      * Only non-zero entries will be stored.
      *
      * @param values Set of values to create from.
      * @param epsilon Tolerance below which a value is considered zero.
      */
     public OpenMapRealVector(double[] values, double epsilon) {
         virtualSize = values.length;
         entries = new OpenIntToDoubleHashMap(0.0);
         this.epsilon = epsilon;
         for (int key = 0; key < values.length; key++) {
             double value = values[key];
             if (!isDefaultValue(value)) {
                 entries.put(key, value);
             }
         }
     }
 
     /**
      * Create from an array.
      * Only non-zero entries will be stored.
      *
      * @param values The set of values to create from
      */
     public OpenMapRealVector(Double[] values) {
         this(values, DEFAULT_ZERO_TOLERANCE);
     }
 
     /**
      * Create from an array.
      * Only non-zero entries will be stored.
      *
      * @param values Set of values to create from.
      * @param epsilon Tolerance below which a value is considered zero.
      */
     public OpenMapRealVector(Double[] values, double epsilon) {
         virtualSize = values.length;
         entries = new OpenIntToDoubleHashMap(0.0);
         this.epsilon = epsilon;
         for (int key = 0; key < values.length; key++) {
             double value = values[key].doubleValue();
             if (!isDefaultValue(value)) {
                 entries.put(key, value);
             }
         }
     }
 
     /**
      * Copy constructor.
      *
      * @param v Instance to copy from.
      */
     public OpenMapRealVector(OpenMapRealVector v) {
         virtualSize = v.getDimension();
         entries = new OpenIntToDoubleHashMap(v.getEntries());
         epsilon = v.epsilon;
     }
 
     /**
      * Generic copy constructor.
      *
      * @param v Instance to copy from.
      */
     public OpenMapRealVector(RealVector v) {
         virtualSize = v.getDimension();
         entries = new OpenIntToDoubleHashMap(0.0);
         epsilon = DEFAULT_ZERO_TOLERANCE;
         for (int key = 0; key < virtualSize; key++) {
             double value = v.getEntry(key);
             if (!isDefaultValue(value)) {
                 entries.put(key, value);
             }
         }
     }
 
     /**
      * Get the entries of this instance.
      *
      * @return the entries of this instance.
      */
     private OpenIntToDoubleHashMap getEntries() {
         return entries;
     }
 
     /**
      * Determine if this value is within epsilon of zero.
      *
      * @param value Value to test
      * @return {@code true} if this value is within epsilon to zero,
      * {@code false} otherwise.
      * @since 2.1
      */
     protected boolean isDefaultValue(double value) {
         return JdkMath.abs(value) < epsilon;
     }
 
     /** {@inheritDoc} */
     @Override
     public RealVector add(RealVector v)
         throws DimensionMismatchException {
         checkVectorDimensions(v.getDimension());
         if (v instanceof OpenMapRealVector) {
             return add((OpenMapRealVector) v);
         } else {
             return super.add(v);
         }
     }
 
     /**
      * Optimized method to add two OpenMapRealVectors.
      * It copies the larger vector, then iterates over the smaller.
      *
      * @param v Vector to add.
      * @return the sum of {@code this} and {@code v}.
      * @throws DimensionMismatchException if the dimensions do not match.
      */
     public OpenMapRealVector add(OpenMapRealVector v)
         throws DimensionMismatchException {
         checkVectorDimensions(v.getDimension());
         boolean copyThis = entries.size() > v.entries.size();
         OpenMapRealVector res = copyThis ? this.copy() : v.copy();
         Iterator iter = copyThis ? v.entries.iterator() : entries.iterator();
         OpenIntToDoubleHashMap randomAccess = copyThis ? entries : v.entries;
         while (iter.hasNext()) {
             iter.advance();
             int key = iter.key();
             if (randomAccess.containsKey(key)) {
                 res.setEntry(key, randomAccess.get(key) + iter.value());
             } else {
                 res.setEntry(key, iter.value());
             }
         }
         return res;
     }
 
     /**
      * Optimized method to append a OpenMapRealVector.
      * @param v vector to append
      * @return The result of appending {@code v} to self
      */
     public OpenMapRealVector append(OpenMapRealVector v) {
         OpenMapRealVector res = new OpenMapRealVector(this, v.getDimension());
         Iterator iter = v.entries.iterator();
         while (iter.hasNext()) {
             iter.advance();
             res.setEntry(iter.key() + virtualSize, iter.value());
         }
         return res;
     }
 
     /** {@inheritDoc} */
     @Override
     public OpenMapRealVector append(RealVector v) {
         if (v instanceof OpenMapRealVector) {
             return append((OpenMapRealVector) v);
         } else {
             final OpenMapRealVector res = new OpenMapRealVector(this, v.getDimension());
             for (int i = 0; i < v.getDimension(); i++) {
                 res.setEntry(i + virtualSize, v.getEntry(i));
             }
             return res;
         }
     }
 
     /** {@inheritDoc} */
     @Override
     public OpenMapRealVector append(double d) {
         OpenMapRealVector res = new OpenMapRealVector(this, 1);
         res.setEntry(virtualSize, d);
         return res;
     }
 
     /**
      * {@inheritDoc}
      * @since 2.1
      */
     @Override
     public OpenMapRealVector copy() {
         return new OpenMapRealVector(this);
     }
 
     /** {@inheritDoc} */
     @Override
     public OpenMapRealVector ebeDivide(RealVector v)
         throws DimensionMismatchException {
         checkVectorDimensions(v.getDimension());
         OpenMapRealVector res = new OpenMapRealVector(this);
         /*
          * MATH-803: it is not sufficient to loop through non zero entries of
          * this only. Indeed, if this[i] = 0d and v[i] = 0d, then
          * this[i] / v[i] = NaN, and not 0d.
          */
         final int n = getDimension();
         for (int i = 0; i < n; i++) {
             res.setEntry(i, this.getEntry(i) / v.getEntry(i));
         }
         return res;
     }
 
     /** {@inheritDoc} */
     @Override
     public OpenMapRealVector ebeMultiply(RealVector v)
         throws DimensionMismatchException {
         checkVectorDimensions(v.getDimension());
         OpenMapRealVector res = new OpenMapRealVector(this);
         Iterator iter = entries.iterator();
         while (iter.hasNext()) {
             iter.advance();
             res.setEntry(iter.key(), iter.value() * v.getEntry(iter.key()));
         }
         return res;
     }
 
     /** {@inheritDoc} */
     @Override
     public OpenMapRealVector getSubVector(int index, int n)
         throws NotPositiveException, OutOfRangeException {
         checkIndex(index);
         if (n < 0) {
             throw new NotPositiveException(LocalizedFormats.NUMBER_OF_ELEMENTS_SHOULD_BE_POSITIVE, n);
         }
         checkIndex(index + n - 1);
         OpenMapRealVector res = new OpenMapRealVector(n);
         int end = index + n;
         Iterator iter = entries.iterator();
         while (iter.hasNext()) {
             iter.advance();
             int key = iter.key();
             if (key >= index && key < end) {
                 res.setEntry(key - index, iter.value());
             }
         }
         return res;
     }
 
     /** {@inheritDoc} */
     @Override
     public int getDimension() {
         return virtualSize;
     }
 
     /**
      * Optimized method to compute distance.
      *
      * @param v Vector to compute distance to.
      * @return the distance from {@code this} and {@code v}.
      * @throws DimensionMismatchException if the dimensions do not match.
      */
     public double getDistance(OpenMapRealVector v)
         throws DimensionMismatchException {
         checkVectorDimensions(v.getDimension());
         Iterator iter = entries.iterator();
         double res = 0;
         while (iter.hasNext()) {
             iter.advance();
             int key = iter.key();
             double delta;
             delta = iter.value() - v.getEntry(key);
             res += delta * delta;
         }
         iter = v.getEntries().iterator();
         while (iter.hasNext()) {
             iter.advance();
             int key = iter.key();
             if (!entries.containsKey(key)) {
                 final double value = iter.value();
                 res += value * value;
             }
         }
         return JdkMath.sqrt(res);
     }
 
     /** {@inheritDoc} */
     @Override
     public double getDistance(RealVector v) throws DimensionMismatchException {
         checkVectorDimensions(v.getDimension());
         if (v instanceof OpenMapRealVector) {
             return getDistance((OpenMapRealVector) v);
         } else {
             return super.getDistance(v);
         }
     }
 
     /** {@inheritDoc} */
     @Override
     public double getEntry(int index) throws OutOfRangeException {
         checkIndex(index);
         return entries.get(index);
     }
 
     /**
      * Distance between two vectors.
      * This method computes the distance consistent with
      * L<sub>1</sub> norm, i.e. the sum of the absolute values of
      * elements differences.
      *
      * @param v Vector to which distance is requested.
      * @return distance between this vector and {@code v}.
      * @throws DimensionMismatchException if the dimensions do not match.
      */
     public double getL1Distance(OpenMapRealVector v)
         throws DimensionMismatchException {
         checkVectorDimensions(v.getDimension());
         double max = 0;
         Iterator iter = entries.iterator();
         while (iter.hasNext()) {
             iter.advance();
             double delta = JdkMath.abs(iter.value() - v.getEntry(iter.key()));
             max += delta;
         }
         iter = v.getEntries().iterator();
         while (iter.hasNext()) {
             iter.advance();
             int key = iter.key();
             if (!entries.containsKey(key)) {
                 double delta = JdkMath.abs(iter.value());
                 max +=  JdkMath.abs(delta);
             }
         }
         return max;
     }
 
     /** {@inheritDoc} */
     @Override
     public double getL1Distance(RealVector v)
         throws DimensionMismatchException {
         checkVectorDimensions(v.getDimension());
         if (v instanceof OpenMapRealVector) {
             return getL1Distance((OpenMapRealVector) v);
         } else {
             return super.getL1Distance(v);
         }
     }
 
     /**
      * Optimized method to compute LInfDistance.
      *
      * @param v Vector to compute distance from.
      * @return the LInfDistance.
      * @throws DimensionMismatchException if the dimensions do not match.
      */
     private double getLInfDistance(OpenMapRealVector v)
         throws DimensionMismatchException {
         checkVectorDimensions(v.getDimension());
         double max = 0;
         Iterator iter = entries.iterator();
         while (iter.hasNext()) {
             iter.advance();
             double delta = JdkMath.abs(iter.value() - v.getEntry(iter.key()));
             if (delta > max) {
                 max = delta;
             }
         }
         iter = v.getEntries().iterator();
         while (iter.hasNext()) {
             iter.advance();
             int key = iter.key();
             if (!entries.containsKey(key) && iter.value() > max) {
                 max = iter.value();
             }
         }
         return max;
     }
 
     /** {@inheritDoc} */
     @Override
     public double getLInfDistance(RealVector v)
         throws DimensionMismatchException {
         checkVectorDimensions(v.getDimension());
         if (v instanceof OpenMapRealVector) {
             return getLInfDistance((OpenMapRealVector) v);
         } else {
             return super.getLInfDistance(v);
         }
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean isInfinite() {
         boolean infiniteFound = false;
         Iterator iter = entries.iterator();
         while (iter.hasNext()) {
             iter.advance();
             final double value = iter.value();
             if (Double.isNaN(value)) {
                 return false;
             }
             if (Double.isInfinite(value)) {
                 infiniteFound = true;
             }
         }
         return infiniteFound;
     }
 
     /** {@inheritDoc} */
     @Override
     public boolean isNaN() {
         Iterator iter = entries.iterator();
         while (iter.hasNext()) {
             iter.advance();
             if (Double.isNaN(iter.value())) {
                 return true;
             }
         }
         return false;
     }
 
     /** {@inheritDoc} */
     @Override
     public OpenMapRealVector mapAdd(double d) {
         return copy().mapAddToSelf(d);
     }
 
     /** {@inheritDoc} */
     @Override
     public OpenMapRealVector mapAddToSelf(double d) {
         for (int i = 0; i < virtualSize; i++) {
             setEntry(i, getEntry(i) + d);
         }
         return this;
     }
 
     /** {@inheritDoc} */
     @Override
     public void setEntry(int index, double value)
         throws OutOfRangeException {
         checkIndex(index);
         if (!isDefaultValue(value)) {
             entries.put(index, value);
         } else if (entries.containsKey(index)) {
             entries.remove(index);
         }
     }
 
     /** {@inheritDoc} */
     @Override
     public void setSubVector(int index, RealVector v)
         throws OutOfRangeException {
         checkIndex(index);
         checkIndex(index + v.getDimension() - 1);
         for (int i = 0; i < v.getDimension(); i++) {
             setEntry(i + index, v.getEntry(i));
         }
     }
 
     /** {@inheritDoc} */
     @Override
     public void set(double value) {
         for (int i = 0; i < virtualSize; i++) {
             setEntry(i, value);
         }
     }
 
     /**
      * Optimized method to subtract OpenMapRealVectors.
      *
      * @param v Vector to subtract from {@code this}.
      * @return the difference of {@code this} and {@code v}.
      * @throws DimensionMismatchException if the dimensions do not match.
      */
     public OpenMapRealVector subtract(OpenMapRealVector v)
         throws DimensionMismatchException {
         checkVectorDimensions(v.getDimension());
         OpenMapRealVector res = copy();
         Iterator iter = v.getEntries().iterator();
         while (iter.hasNext()) {
             iter.advance();
             int key = iter.key();
             if (entries.containsKey(key)) {
                 res.setEntry(key, entries.get(key) - iter.value());
             } else {
                 res.setEntry(key, -iter.value());
             }
         }
         return res;
     }
 
     /** {@inheritDoc} */
     @Override
     public RealVector subtract(RealVector v)
         throws DimensionMismatchException {
         checkVectorDimensions(v.getDimension());
         if (v instanceof OpenMapRealVector) {
             return subtract((OpenMapRealVector) v);
         } else {
             return super.subtract(v);
         }
     }
 
     /** {@inheritDoc} */
     @Override
     public OpenMapRealVector unitVector() throws MathArithmeticException {
         OpenMapRealVector res = copy();
         res.unitize();
         return res;
     }
 
     /** {@inheritDoc} */
     @Override
     public void unitize() throws MathArithmeticException {
         double norm = getNorm();
         if (isDefaultValue(norm)) {
             throw new MathArithmeticException(LocalizedFormats.ZERO_NORM);
         }
         Iterator iter = entries.iterator();
         while (iter.hasNext()) {
             iter.advance();
             entries.put(iter.key(), iter.value() / norm);
         }
     }
 
     /** {@inheritDoc} */
     @Override
     public double[] toArray() {
         double[] res = new double[virtualSize];
         Iterator iter = entries.iterator();
         while (iter.hasNext()) {
             iter.advance();
             res[iter.key()] = iter.value();
         }
         return res;
     }
 
     /**
      * {@inheritDoc}
      * Implementation Note: This works on exact values, and as a result
      * it is possible for {@code a.subtract(b)} to be the zero vector, while
      * {@code a.hashCode() != b.hashCode()}.
      */
     @Override
     public int hashCode() {
         final int prime = 31;
         int result = 1;
         long temp;
         temp = Double.doubleToLongBits(epsilon);
         result = prime * result + (int) (temp ^ (temp >>> 32));
         result = prime * result + virtualSize;
         Iterator iter = entries.iterator();
         while (iter.hasNext()) {
             iter.advance();
             temp = Double.doubleToLongBits(iter.value());
             result = prime * result + (int) (temp ^ (temp >>32));
         }
         return result;
     }
 
     /**
      * {@inheritDoc}
      * Implementation Note: This performs an exact comparison, and as a result
      * it is possible for {@code a.subtract(b}} to be the zero vector, while
      * {@code  a.equals(b) == false}.
      */
     @Override
     public boolean equals(Object obj) {
         if (this == obj) {
             return true;
         }
         if (!(obj instanceof OpenMapRealVector)) {
             return false;
         }
         OpenMapRealVector other = (OpenMapRealVector) obj;
         if (virtualSize != other.virtualSize) {
             return false;
         }
         if (Double.doubleToLongBits(epsilon) !=
             Double.doubleToLongBits(other.epsilon)) {
             return false;
         }
         Iterator iter = entries.iterator();
         while (iter.hasNext()) {
             iter.advance();
             double test = other.getEntry(iter.key());
             if (Double.doubleToLongBits(test) != Double.doubleToLongBits(iter.value())) {
                 return false;
             }
         }
         iter = other.getEntries().iterator();
         while (iter.hasNext()) {
             iter.advance();
             double test = iter.value();
             if (Double.doubleToLongBits(test) != Double.doubleToLongBits(getEntry(iter.key()))) {
                 return false;
             }
         }
         return true;
     }
 
     /**
      *
      * @return the percentage of none zero elements as a decimal percent.
      * @since 2.2
      */
     public double getSparsity() {
         return (double)entries.size()/(double)getDimension();
     }
 
     /** {@inheritDoc} */
     @Override
     public java.util.Iterator<Entry> sparseIterator() {
         return new OpenMapSparseIterator();
     }
 
     /**
      * Implementation of {@code Entry} optimized for OpenMap.
      * This implementation does not allow arbitrary calls to {@code setIndex}
      * since the order in which entries are returned is undefined.
      */
     protected class OpenMapEntry extends Entry {
         /** Iterator pointing to the entry. */
         private final Iterator iter;
 
         /**
          * Build an entry from an iterator point to an element.
          *
          * @param iter Iterator pointing to the entry.
          */
         protected OpenMapEntry(Iterator iter) {
             this.iter = iter;
         }
 
         /** {@inheritDoc} */
         @Override
         public double getValue() {
             return iter.value();
         }
 
         /** {@inheritDoc} */
         @Override
         public void setValue(double value) {
             entries.put(iter.key(), value);
         }
 
         /** {@inheritDoc} */
         @Override
         public int getIndex() {
             return iter.key();
         }
     }
 
     /**
      * Iterator class to do iteration over just the non-zero elements.
      * This implementation is fail-fast, so cannot be used to modify
      * any zero element.
      */
     protected class OpenMapSparseIterator implements java.util.Iterator<Entry> {
         /** Underlying iterator. */
         private final Iterator iter;
         /** Current entry. */
         private final Entry current;
 
         /** Simple constructor. */
         protected OpenMapSparseIterator() {
             iter = entries.iterator();
             current = new OpenMapEntry(iter);
         }
 
         /** {@inheritDoc} */
         @Override
         public boolean hasNext() {
             return iter.hasNext();
         }
 
         /** {@inheritDoc} */
         @Override
         public Entry next() {
             iter.advance();
             return current;
         }
 
         /** {@inheritDoc} */
         @Override
         public void remove() {
             throw new UnsupportedOperationException("Not supported");
         }
     }
 }