/*
    * Copyright (C) 2008 The Guava Authors
    *
    * 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.
   */
  
  package com.google.common.primitives;
  
  import static com.google.common.base.Preconditions.checkArgument;
  import static com.google.common.base.Preconditions.checkElementIndex;
  import static com.google.common.base.Preconditions.checkNotNull;
  import static com.google.common.base.Preconditions.checkPositionIndexes;
  import static java.lang.Double.NEGATIVE_INFINITY;
  import static java.lang.Double.POSITIVE_INFINITY;
  
  import com.google.common.annotations.Beta;
  import com.google.common.annotations.GwtCompatible;
  import com.google.common.annotations.GwtIncompatible;
  import com.google.common.base.Converter;
  
  import java.io.Serializable;
  import java.util.AbstractList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Comparator;
  import java.util.List;
  import java.util.RandomAccess;
  import java.util.regex.Pattern;
  
  import javax.annotation.Nullable;
  
  /**
   * Static utility methods pertaining to {@code double} primitives, that are not
   * already found in either {@link Double} or {@link Arrays}.
   *
   * <p>See the Guava User Guide article on <a href=
   * "http://code.google.com/p/guava-libraries/wiki/PrimitivesExplained">
   * primitive utilities</a>.
   *
   * @author Kevin Bourrillion
   * @since 1.0
   */
  @GwtCompatible(emulated = true)
  public final class Doubles {
    private Doubles() {}
  
    /**
     * The number of bytes required to represent a primitive {@code double}
     * value.
     *
     * @since 10.0
     */
    public static final int BYTES = Double.SIZE / Byte.SIZE;
  
    /**
     * Returns a hash code for {@code value}; equal to the result of invoking
     * {@code ((Double) value).hashCode()}.
     *
     * @param value a primitive {@code double} value
     * @return a hash code for the value
     */
    public static int hashCode(double value) {
      return ((Double) value).hashCode();
      // TODO(kevinb): do it this way when we can (GWT problem):
      // long bits = Double.doubleToLongBits(value);
      // return (int) (bits ^ (bits >>> 32));
    }
  
    /**
     * Compares the two specified {@code double} values. The sign of the value
     * returned is the same as that of <code>((Double) a).{@linkplain
     * Double#compareTo compareTo}(b)</code>. As with that method, {@code NaN} is
     * treated as greater than all other values, and {@code 0.0 > -0.0}.
     *
     * <p><b>Note:</b> this method simply delegates to the JDK method {@link
     * Double#compare}. It is provided for consistency with the other primitive
     * types, whose compare methods were not added to the JDK until JDK 7.
     *
     * @param a the first {@code double} to compare
     * @param b the second {@code double} to compare
     * @return a negative value if {@code a} is less than {@code b}; a positive
     *     value if {@code a} is greater than {@code b}; or zero if they are equal
     */
    public static int compare(double a, double b) {
      return Double.compare(a, b);
    }
  
    /**
    * Returns {@code true} if {@code value} represents a real number. This is
    * equivalent to, but not necessarily implemented as,
    * {@code !(Double.isInfinite(value) || Double.isNaN(value))}.
    *
    * @since 10.0
    */
   public static boolean isFinite(double value) {
     return NEGATIVE_INFINITY < value & value < POSITIVE_INFINITY;
   }
 
   /**
    * Returns {@code true} if {@code target} is present as an element anywhere in
    * {@code array}. Note that this always returns {@code false} when {@code
    * target} is {@code NaN}.
    *
    * @param array an array of {@code double} values, possibly empty
    * @param target a primitive {@code double} value
    * @return {@code true} if {@code array[i] == target} for some value of {@code
    *     i}
    */
   public static boolean contains(double[] array, double target) {
     for (double value : array) {
       if (value == target) {
         return true;
       }
     }
     return false;
   }
 
   /**
    * Returns the index of the first appearance of the value {@code target} in
    * {@code array}. Note that this always returns {@code -1} when {@code target}
    * is {@code NaN}.
    *
    * @param array an array of {@code double} values, possibly empty
    * @param target a primitive {@code double} value
    * @return the least index {@code i} for which {@code array[i] == target}, or
    *     {@code -1} if no such index exists.
    */
   public static int indexOf(double[] array, double target) {
     return indexOf(array, target, 0, array.length);
   }
 
   // TODO(kevinb): consider making this public
   private static int indexOf(
       double[] array, double target, int start, int end) {
     for (int i = start; i < end; i++) {
       if (array[i] == target) {
         return i;
       }
     }
     return -1;
   }
 
   /**
    * Returns the start position of the first occurrence of the specified {@code
    * target} within {@code array}, or {@code -1} if there is no such occurrence.
    *
    * <p>More formally, returns the lowest index {@code i} such that {@code
    * java.util.Arrays.copyOfRange(array, i, i + target.length)} contains exactly
    * the same elements as {@code target}.
    *
    * <p>Note that this always returns {@code -1} when {@code target} contains
    * {@code NaN}.
    *
    * @param array the array to search for the sequence {@code target}
    * @param target the array to search for as a sub-sequence of {@code array}
    */
   public static int indexOf(double[] array, double[] target) {
     checkNotNull(array, "array");
     checkNotNull(target, "target");
     if (target.length == 0) {
       return 0;
     }
 
     outer:
     for (int i = 0; i < array.length - target.length + 1; i++) {
       for (int j = 0; j < target.length; j++) {
         if (array[i + j] != target[j]) {
           continue outer;
         }
       }
       return i;
     }
     return -1;
   }
 
   /**
    * Returns the index of the last appearance of the value {@code target} in
    * {@code array}. Note that this always returns {@code -1} when {@code target}
    * is {@code NaN}.
    *
    * @param array an array of {@code double} values, possibly empty
    * @param target a primitive {@code double} value
    * @return the greatest index {@code i} for which {@code array[i] == target},
    *     or {@code -1} if no such index exists.
    */
   public static int lastIndexOf(double[] array, double target) {
     return lastIndexOf(array, target, 0, array.length);
   }
 
   // TODO(kevinb): consider making this public
   private static int lastIndexOf(
       double[] array, double target, int start, int end) {
     for (int i = end - 1; i >= start; i--) {
       if (array[i] == target) {
         return i;
       }
     }
     return -1;
   }
 
   /**
    * Returns the least value present in {@code array}, using the same rules of
    * comparison as {@link Math#min(double, double)}.
    *
    * @param array a <i>nonempty</i> array of {@code double} values
    * @return the value present in {@code array} that is less than or equal to
    *     every other value in the array
    * @throws IllegalArgumentException if {@code array} is empty
    */
   public static double min(double... array) {
     checkArgument(array.length > 0);
     double min = array[0];
     for (int i = 1; i < array.length; i++) {
       min = Math.min(min, array[i]);
     }
     return min;
   }
 
   /**
    * Returns the greatest value present in {@code array}, using the same rules
    * of comparison as {@link Math#max(double, double)}.
    *
    * @param array a <i>nonempty</i> array of {@code double} values
    * @return the value present in {@code array} that is greater than or equal to
    *     every other value in the array
    * @throws IllegalArgumentException if {@code array} is empty
    */
   public static double max(double... array) {
     checkArgument(array.length > 0);
     double max = array[0];
     for (int i = 1; i < array.length; i++) {
       max = Math.max(max, array[i]);
     }
     return max;
   }
 
   /**
    * Returns the values from each provided array combined into a single array.
    * For example, {@code concat(new double[] {a, b}, new double[] {}, new
    * double[] {c}} returns the array {@code {a, b, c}}.
    *
    * @param arrays zero or more {@code double} arrays
    * @return a single array containing all the values from the source arrays, in
    *     order
    */
   public static double[] concat(double[]... arrays) {
     int length = 0;
     for (double[] array : arrays) {
       length += array.length;
     }
     double[] result = new double[length];
     int pos = 0;
     for (double[] array : arrays) {
       System.arraycopy(array, 0, result, pos, array.length);
       pos += array.length;
     }
     return result;
   }
 
   private static final class DoubleConverter
       extends Converter<String, Double> implements Serializable {
     static final DoubleConverter INSTANCE = new DoubleConverter();
 
     @Override
     protected Double doForward(String value) {
       return Double.valueOf(value);
     }
 
     @Override
     protected String doBackward(Double value) {
       return value.toString();
     }
 
     @Override
     public String toString() {
       return "Doubles.stringConverter()";
     }
 
     private Object readResolve() {
       return INSTANCE;
     }
     private static final long serialVersionUID = 1;
   }
 
   /**
    * Returns a serializable converter object that converts between strings and
    * doubles using {@link Double#valueOf} and {@link Double#toString()}.
    *
    * @since 16.0
    */
   @Beta
   public static Converter<String, Double> stringConverter() {
     return DoubleConverter.INSTANCE;
   }
 
   /**
    * Returns an array containing the same values as {@code array}, but
    * guaranteed to be of a specified minimum length. If {@code array} already
    * has a length of at least {@code minLength}, it is returned directly.
    * Otherwise, a new array of size {@code minLength + padding} is returned,
    * containing the values of {@code array}, and zeroes in the remaining places.
    *
    * @param array the source array
    * @param minLength the minimum length the returned array must guarantee
    * @param padding an extra amount to "grow" the array by if growth is
    *     necessary
    * @throws IllegalArgumentException if {@code minLength} or {@code padding} is
    *     negative
    * @return an array containing the values of {@code array}, with guaranteed
    *     minimum length {@code minLength}
    */
   public static double[] ensureCapacity(
       double[] array, int minLength, int padding) {
     checkArgument(minLength >= 0, "Invalid minLength: %s", minLength);
     checkArgument(padding >= 0, "Invalid padding: %s", padding);
     return (array.length < minLength)
         ? copyOf(array, minLength + padding)
         : array;
   }
 
   // Arrays.copyOf() requires Java 6
   private static double[] copyOf(double[] original, int length) {
     double[] copy = new double[length];
     System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
     return copy;
   }
 
   /**
    * Returns a string containing the supplied {@code double} values, converted
    * to strings as specified by {@link Double#toString(double)}, and separated
    * by {@code separator}. For example, {@code join("-", 1.0, 2.0, 3.0)} returns
    * the string {@code "1.0-2.0-3.0"}.
    *
    * <p>Note that {@link Double#toString(double)} formats {@code double}
    * differently in GWT sometimes.  In the previous example, it returns the
    * string {@code "1-2-3"}.
    *
    * @param separator the text that should appear between consecutive values in
    *     the resulting string (but not at the start or end)
    * @param array an array of {@code double} values, possibly empty
    */
   public static String join(String separator, double... array) {
     checkNotNull(separator);
     if (array.length == 0) {
       return "";
     }
 
     // For pre-sizing a builder, just get the right order of magnitude
     StringBuilder builder = new StringBuilder(array.length * 12);
     builder.append(array[0]);
     for (int i = 1; i < array.length; i++) {
       builder.append(separator).append(array[i]);
     }
     return builder.toString();
   }
 
   /**
    * Returns a comparator that compares two {@code double} arrays
    * lexicographically. That is, it compares, using {@link
    * #compare(double, double)}), the first pair of values that follow any
    * common prefix, or when one array is a prefix of the other, treats the
    * shorter array as the lesser. For example,
    * {@code [] < [1.0] < [1.0, 2.0] < [2.0]}.
    *
    * <p>The returned comparator is inconsistent with {@link
    * Object#equals(Object)} (since arrays support only identity equality), but
    * it is consistent with {@link Arrays#equals(double[], double[])}.
    *
    * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
    *     Lexicographical order article at Wikipedia</a>
    * @since 2.0
    */
   public static Comparator<double[]> lexicographicalComparator() {
     return LexicographicalComparator.INSTANCE;
   }
 
   private enum LexicographicalComparator implements Comparator<double[]> {
     INSTANCE;
 
     @Override
     public int compare(double[] left, double[] right) {
       int minLength = Math.min(left.length, right.length);
       for (int i = 0; i < minLength; i++) {
         int result = Doubles.compare(left[i], right[i]);
         if (result != 0) {
           return result;
         }
       }
       return left.length - right.length;
     }
   }
 
   /**
    * Returns an array containing each value of {@code collection}, converted to
    * a {@code double} value in the manner of {@link Number#doubleValue}.
    *
    * <p>Elements are copied from the argument collection as if by {@code
    * collection.toArray()}.  Calling this method is as thread-safe as calling
    * that method.
    *
    * @param collection a collection of {@code Number} instances
    * @return an array containing the same values as {@code collection}, in the
    *     same order, converted to primitives
    * @throws NullPointerException if {@code collection} or any of its elements
    *     is null
    * @since 1.0 (parameter was {@code Collection<Double>} before 12.0)
    */
   public static double[] toArray(Collection<? extends Number> collection) {
     if (collection instanceof DoubleArrayAsList) {
       return ((DoubleArrayAsList) collection).toDoubleArray();
     }
 
     Object[] boxedArray = collection.toArray();
     int len = boxedArray.length;
     double[] array = new double[len];
     for (int i = 0; i < len; i++) {
       // checkNotNull for GWT (do not optimize)
       array[i] = ((Number) checkNotNull(boxedArray[i])).doubleValue();
     }
     return array;
   }
 
   /**
    * Returns a fixed-size list backed by the specified array, similar to {@link
    * Arrays#asList(Object[])}. The list supports {@link List#set(int, Object)},
    * but any attempt to set a value to {@code null} will result in a {@link
    * NullPointerException}.
    *
    * <p>The returned list maintains the values, but not the identities, of
    * {@code Double} objects written to or read from it.  For example, whether
    * {@code list.get(0) == list.get(0)} is true for the returned list is
    * unspecified.
    *
    * <p>The returned list may have unexpected behavior if it contains {@code
    * NaN}, or if {@code NaN} is used as a parameter to any of its methods.
    *
    * @param backingArray the array to back the list
    * @return a list view of the array
    */
   public static List<Double> asList(double... backingArray) {
     if (backingArray.length == 0) {
       return Collections.emptyList();
     }
     return new DoubleArrayAsList(backingArray);
   }
 
   @GwtCompatible
   private static class DoubleArrayAsList extends AbstractList<Double>
       implements RandomAccess, Serializable {
     final double[] array;
     final int start;
     final int end;
 
     DoubleArrayAsList(double[] array) {
       this(array, 0, array.length);
     }
 
     DoubleArrayAsList(double[] array, int start, int end) {
       this.array = array;
       this.start = start;
       this.end = end;
     }
 
     @Override public int size() {
       return end - start;
     }
 
     @Override public boolean isEmpty() {
       return false;
     }
 
     @Override public Double get(int index) {
       checkElementIndex(index, size());
       return array[start + index];
     }
 
     @Override public boolean contains(Object target) {
       // Overridden to prevent a ton of boxing
       return (target instanceof Double)
           && Doubles.indexOf(array, (Double) target, start, end) != -1;
     }
 
     @Override public int indexOf(Object target) {
       // Overridden to prevent a ton of boxing
       if (target instanceof Double) {
         int i = Doubles.indexOf(array, (Double) target, start, end);
         if (i >= 0) {
           return i - start;
         }
       }
       return -1;
     }
 
     @Override public int lastIndexOf(Object target) {
       // Overridden to prevent a ton of boxing
       if (target instanceof Double) {
         int i = Doubles.lastIndexOf(array, (Double) target, start, end);
         if (i >= 0) {
           return i - start;
         }
       }
       return -1;
     }
 
     @Override public Double set(int index, Double element) {
       checkElementIndex(index, size());
       double oldValue = array[start + index];
       // checkNotNull for GWT (do not optimize)
       array[start + index] = checkNotNull(element);
       return oldValue;
     }
 
     @Override public List<Double> subList(int fromIndex, int toIndex) {
       int size = size();
       checkPositionIndexes(fromIndex, toIndex, size);
       if (fromIndex == toIndex) {
         return Collections.emptyList();
       }
       return new DoubleArrayAsList(array, start + fromIndex, start + toIndex);
     }
 
     @Override public boolean equals(Object object) {
       if (object == this) {
         return true;
       }
       if (object instanceof DoubleArrayAsList) {
         DoubleArrayAsList that = (DoubleArrayAsList) object;
         int size = size();
         if (that.size() != size) {
           return false;
         }
         for (int i = 0; i < size; i++) {
           if (array[start + i] != that.array[that.start + i]) {
             return false;
           }
         }
         return true;
       }
       return super.equals(object);
     }
 
     @Override public int hashCode() {
       int result = 1;
       for (int i = start; i < end; i++) {
         result = 31 * result + Doubles.hashCode(array[i]);
       }
       return result;
     }
 
     @Override public String toString() {
       StringBuilder builder = new StringBuilder(size() * 12);
       builder.append('[').append(array[start]);
       for (int i = start + 1; i < end; i++) {
         builder.append(", ").append(array[i]);
       }
       return builder.append(']').toString();
     }
 
     double[] toDoubleArray() {
       // Arrays.copyOfRange() is not available under GWT
       int size = size();
       double[] result = new double[size];
       System.arraycopy(array, start, result, 0, size);
       return result;
     }
 
     private static final long serialVersionUID = 0;
   }
 
   /**
    * This is adapted from the regex suggested by {@link Double#valueOf(String)}
    * for prevalidating inputs.  All valid inputs must pass this regex, but it's
    * semantically fine if not all inputs that pass this regex are valid --
    * only a performance hit is incurred, not a semantics bug.
    */
   @GwtIncompatible("regular expressions")
   static final Pattern FLOATING_POINT_PATTERN = fpPattern();
 
   @GwtIncompatible("regular expressions")
   private static Pattern fpPattern() {
     String decimal = "(?:\\d++(?:\\.\\d*+)?|\\.\\d++)";
     String completeDec = decimal + "(?:[eE][+-]?\\d++)?[fFdD]?";
     String hex = "(?:\\p{XDigit}++(?:\\.\\p{XDigit}*+)?|\\.\\p{XDigit}++)";
     String completeHex = "0[xX]" + hex + "[pP][+-]?\\d++[fFdD]?";
     String fpPattern = "[+-]?(?:NaN|Infinity|" + completeDec + "|" + completeHex + ")";
     return Pattern.compile(fpPattern);
   }
 
   /**
    * Parses the specified string as a double-precision floating point value.
    * The ASCII character {@code '-'} (<code>'&#92;u002D'</code>) is recognized
    * as the minus sign.
    *
    * <p>Unlike {@link Double#parseDouble(String)}, this method returns
    * {@code null} instead of throwing an exception if parsing fails.
    * Valid inputs are exactly those accepted by {@link Double#valueOf(String)},
    * except that leading and trailing whitespace is not permitted.
    *
    * <p>This implementation is likely to be faster than {@code
    * Double.parseDouble} if many failures are expected.
    *
    * @param string the string representation of a {@code double} value
    * @return the floating point value represented by {@code string}, or
    *     {@code null} if {@code string} has a length of zero or cannot be
    *     parsed as a {@code double} value
    * @since 14.0
    */
   @GwtIncompatible("regular expressions")
   @Nullable
   @Beta
   public static Double tryParse(String string) {
     if (FLOATING_POINT_PATTERN.matcher(string).matches()) {
       // TODO(user): could be potentially optimized, but only with
       // extensive testing
       try {
         return Double.parseDouble(string);
       } catch (NumberFormatException e) {
         // Double.parseDouble has changed specs several times, so fall through
         // gracefully
       }
     }
     return null;
   }
 }