/*
    * 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 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 javax.annotation.CheckForNull;
  
  /**
   * Static utility methods pertaining to {@code int} primitives, that are not
   * already found in either {@link Integer} 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 Ints {
    private Ints() {}
  
    /**
     * The number of bytes required to represent a primitive {@code int}
     * value.
     */
    public static final int BYTES = Integer.SIZE / Byte.SIZE;
  
    /**
     * The largest power of two that can be represented as an {@code int}.
     *
     * @since 10.0
     */
    public static final int MAX_POWER_OF_TWO = 1 << (Integer.SIZE - 2);
  
    /**
     * Returns a hash code for {@code value}; equal to the result of invoking
     * {@code ((Integer) value).hashCode()}.
     *
     * @param value a primitive {@code int} value
     * @return a hash code for the value
     */
    public static int hashCode(int value) {
      return value;
    }
  
    /**
     * Returns the {@code int} value that is equal to {@code value}, if possible.
     *
     * @param value any value in the range of the {@code int} type
     * @return the {@code int} value that equals {@code value}
     * @throws IllegalArgumentException if {@code value} is greater than {@link
     *     Integer#MAX_VALUE} or less than {@link Integer#MIN_VALUE}
     */
    public static int checkedCast(long value) {
      int result = (int) value;
      if (result != value) {
        // don't use checkArgument here, to avoid boxing
        throw new IllegalArgumentException("Out of range: " + value);
      }
      return result;
    }
  
    /**
     * Returns the {@code int} nearest in value to {@code value}.
     *
     * @param value any {@code long} value
    * @return the same value cast to {@code int} if it is in the range of the
    *     {@code int} type, {@link Integer#MAX_VALUE} if it is too large,
    *     or {@link Integer#MIN_VALUE} if it is too small
    */
   public static int saturatedCast(long value) {
     if (value > Integer.MAX_VALUE) {
       return Integer.MAX_VALUE;
     }
     if (value < Integer.MIN_VALUE) {
       return Integer.MIN_VALUE;
     }
     return (int) value;
   }
 
   /**
    * Compares the two specified {@code int} values. The sign of the value
    * returned is the same as that of {@code ((Integer) a).compareTo(b)}.
    *
    * <p><b>Note:</b> projects using JDK 7 or later should use the equivalent
    * {@link Integer#compare} method instead.
    *
    * @param a the first {@code int} to compare
    * @param b the second {@code int} 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(int a, int b) {
     return (a < b) ? -1 : ((a > b) ? 1 : 0);
   }
 
   /**
    * Returns {@code true} if {@code target} is present as an element anywhere in
    * {@code array}.
    *
    * @param array an array of {@code int} values, possibly empty
    * @param target a primitive {@code int} value
    * @return {@code true} if {@code array[i] == target} for some value of {@code
    *     i}
    */
   public static boolean contains(int[] array, int target) {
     for (int value : array) {
       if (value == target) {
         return true;
       }
     }
     return false;
   }
 
   /**
    * Returns the index of the first appearance of the value {@code target} in
    * {@code array}.
    *
    * @param array an array of {@code int} values, possibly empty
    * @param target a primitive {@code int} 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(int[] array, int target) {
     return indexOf(array, target, 0, array.length);
   }
 
   // TODO(kevinb): consider making this public
   private static int indexOf(
       int[] array, int 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}.
    *
    * @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(int[] array, int[] 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}.
    *
    * @param array an array of {@code int} values, possibly empty
    * @param target a primitive {@code int} 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(int[] array, int target) {
     return lastIndexOf(array, target, 0, array.length);
   }
 
   // TODO(kevinb): consider making this public
   private static int lastIndexOf(
       int[] array, int 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}.
    *
    * @param array a <i>nonempty</i> array of {@code int} 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 int min(int... array) {
     checkArgument(array.length > 0);
     int min = array[0];
     for (int i = 1; i < array.length; i++) {
       if (array[i] < min) {
         min = array[i];
       }
     }
     return min;
   }
 
   /**
    * Returns the greatest value present in {@code array}.
    *
    * @param array a <i>nonempty</i> array of {@code int} 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 int max(int... array) {
     checkArgument(array.length > 0);
     int max = array[0];
     for (int i = 1; i < array.length; i++) {
       if (array[i] > max) {
         max = array[i];
       }
     }
     return max;
   }
 
   /**
    * Returns the values from each provided array combined into a single array.
    * For example, {@code concat(new int[] {a, b}, new int[] {}, new
    * int[] {c}} returns the array {@code {a, b, c}}.
    *
    * @param arrays zero or more {@code int} arrays
    * @return a single array containing all the values from the source arrays, in
    *     order
    */
   public static int[] concat(int[]... arrays) {
     int length = 0;
     for (int[] array : arrays) {
       length += array.length;
     }
     int[] result = new int[length];
     int pos = 0;
     for (int[] array : arrays) {
       System.arraycopy(array, 0, result, pos, array.length);
       pos += array.length;
     }
     return result;
   }
 
   /**
    * Returns a big-endian representation of {@code value} in a 4-element byte
    * array; equivalent to {@code ByteBuffer.allocate(4).putInt(value).array()}.
    * For example, the input value {@code 0x12131415} would yield the byte array
    * {@code {0x12, 0x13, 0x14, 0x15}}.
    *
    * <p>If you need to convert and concatenate several values (possibly even of
    * different types), use a shared {@link java.nio.ByteBuffer} instance, or use
    * {@link com.google.common.io.ByteStreams#newDataOutput()} to get a growable
    * buffer.
    */
   @GwtIncompatible("doesn't work")
   public static byte[] toByteArray(int value) {
     return new byte[] {
         (byte) (value >> 24),
         (byte) (value >> 16),
         (byte) (value >> 8),
         (byte) value};
   }
 
   /**
    * Returns the {@code int} value whose big-endian representation is stored in
    * the first 4 bytes of {@code bytes}; equivalent to {@code
    * ByteBuffer.wrap(bytes).getInt()}. For example, the input byte array {@code
    * {0x12, 0x13, 0x14, 0x15, 0x33}} would yield the {@code int} value {@code
    * 0x12131415}.
    *
    * <p>Arguably, it's preferable to use {@link java.nio.ByteBuffer}; that
    * library exposes much more flexibility at little cost in readability.
    *
    * @throws IllegalArgumentException if {@code bytes} has fewer than 4 elements
    */
   @GwtIncompatible("doesn't work")
   public static int fromByteArray(byte[] bytes) {
     checkArgument(bytes.length >= BYTES,
         "array too small: %s < %s", bytes.length, BYTES);
     return fromBytes(bytes[0], bytes[1], bytes[2], bytes[3]);
   }
 
   /**
    * Returns the {@code int} value whose byte representation is the given 4
    * bytes, in big-endian order; equivalent to {@code Ints.fromByteArray(new
    * byte[] {b1, b2, b3, b4})}.
    *
    * @since 7.0
    */
   @GwtIncompatible("doesn't work")
   public static int fromBytes(byte b1, byte b2, byte b3, byte b4) {
     return b1 << 24 | (b2 & 0xFF) << 16 | (b3 & 0xFF) << 8 | (b4 & 0xFF);
   }
 
   private static final class IntConverter
       extends Converter<String, Integer> implements Serializable {
     static final IntConverter INSTANCE = new IntConverter();
 
     @Override
     protected Integer doForward(String value) {
       return Integer.decode(value);
     }
 
     @Override
     protected String doBackward(Integer value) {
       return value.toString();
     }
 
     @Override
     public String toString() {
       return "Ints.stringConverter()";
     }
 
     private Object readResolve() {
       return INSTANCE;
     }
     private static final long serialVersionUID = 1;
   }
 
   /**
    * Returns a serializable converter object that converts between strings and
    * integers using {@link Integer#decode} and {@link Integer#toString()}.
    *
    * @since 16.0
    */
   @Beta
   public static Converter<String, Integer> stringConverter() {
     return IntConverter.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 int[] ensureCapacity(
       int[] 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 int[] copyOf(int[] original, int length) {
     int[] copy = new int[length];
     System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
     return copy;
   }
 
   /**
    * Returns a string containing the supplied {@code int} values separated
    * by {@code separator}. For example, {@code join("-", 1, 2, 3)} 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 int} values, possibly empty
    */
   public static String join(String separator, int... 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 * 5);
     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 int} arrays
    * lexicographically. That is, it compares, using {@link
    * #compare(int, int)}), 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] < [1, 2] < [2]}.
    *
    * <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(int[], int[])}.
    *
    * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
    *     Lexicographical order article at Wikipedia</a>
    * @since 2.0
    */
   public static Comparator<int[]> lexicographicalComparator() {
     return LexicographicalComparator.INSTANCE;
   }
 
   private enum LexicographicalComparator implements Comparator<int[]> {
     INSTANCE;
 
     @Override
     public int compare(int[] left, int[] right) {
       int minLength = Math.min(left.length, right.length);
       for (int i = 0; i < minLength; i++) {
         int result = Ints.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 int} value in the manner of {@link Number#intValue}.
    *
    * <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<Integer>} before 12.0)
    */
   public static int[] toArray(Collection<? extends Number> collection) {
     if (collection instanceof IntArrayAsList) {
       return ((IntArrayAsList) collection).toIntArray();
     }
 
     Object[] boxedArray = collection.toArray();
     int len = boxedArray.length;
     int[] array = new int[len];
     for (int i = 0; i < len; i++) {
       // checkNotNull for GWT (do not optimize)
       array[i] = ((Number) checkNotNull(boxedArray[i])).intValue();
     }
     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 Integer} 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.
    *
    * @param backingArray the array to back the list
    * @return a list view of the array
    */
   public static List<Integer> asList(int... backingArray) {
     if (backingArray.length == 0) {
       return Collections.emptyList();
     }
     return new IntArrayAsList(backingArray);
   }
 
   @GwtCompatible
   private static class IntArrayAsList extends AbstractList<Integer>
       implements RandomAccess, Serializable {
     final int[] array;
     final int start;
     final int end;
 
     IntArrayAsList(int[] array) {
       this(array, 0, array.length);
     }
 
     IntArrayAsList(int[] 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 Integer 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 Integer)
           && Ints.indexOf(array, (Integer) target, start, end) != -1;
     }
 
     @Override public int indexOf(Object target) {
       // Overridden to prevent a ton of boxing
       if (target instanceof Integer) {
         int i = Ints.indexOf(array, (Integer) 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 Integer) {
         int i = Ints.lastIndexOf(array, (Integer) target, start, end);
         if (i >= 0) {
           return i - start;
         }
       }
       return -1;
     }
 
     @Override public Integer set(int index, Integer element) {
       checkElementIndex(index, size());
       int oldValue = array[start + index];
       // checkNotNull for GWT (do not optimize)
       array[start + index] = checkNotNull(element);
       return oldValue;
     }
 
     @Override public List<Integer> subList(int fromIndex, int toIndex) {
       int size = size();
       checkPositionIndexes(fromIndex, toIndex, size);
       if (fromIndex == toIndex) {
         return Collections.emptyList();
       }
       return new IntArrayAsList(array, start + fromIndex, start + toIndex);
     }
 
     @Override public boolean equals(Object object) {
       if (object == this) {
         return true;
       }
       if (object instanceof IntArrayAsList) {
         IntArrayAsList that = (IntArrayAsList) 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 + Ints.hashCode(array[i]);
       }
       return result;
     }
 
     @Override public String toString() {
       StringBuilder builder = new StringBuilder(size() * 5);
       builder.append('[').append(array[start]);
       for (int i = start + 1; i < end; i++) {
         builder.append(", ").append(array[i]);
       }
       return builder.append(']').toString();
     }
 
     int[] toIntArray() {
       // Arrays.copyOfRange() is not available under GWT
       int size = size();
       int[] result = new int[size];
       System.arraycopy(array, start, result, 0, size);
       return result;
     }
 
     private static final long serialVersionUID = 0;
   }
 
   private static final byte[] asciiDigits = new byte[128];
 
   static {
     Arrays.fill(asciiDigits, (byte) -1);
     for (int i = 0; i <= 9; i++) {
       asciiDigits['0' + i] = (byte) i;
     }
     for (int i = 0; i <= 26; i++) {
       asciiDigits['A' + i] = (byte) (10 + i);
       asciiDigits['a' + i] = (byte) (10 + i);
     }
   }
 
   private static int digit(char c) {
     return (c < 128) ? asciiDigits[c] : -1;
   }
 
   /**
    * Parses the specified string as a signed decimal integer value. The ASCII
    * character {@code '-'} (<code>'&#92;u002D'</code>) is recognized as the
    * minus sign.
    *
    * <p>Unlike {@link Integer#parseInt(String)}, this method returns
    * {@code null} instead of throwing an exception if parsing fails.
    * Additionally, this method only accepts ASCII digits, and returns
    * {@code null} if non-ASCII digits are present in the string.
    *
    * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even
    * under JDK 7, despite the change to {@link Integer#parseInt(String)} for
    * that version.
    *
    * @param string the string representation of an integer value
    * @return the integer value represented by {@code string}, or {@code null} if
    *     {@code string} has a length of zero or cannot be parsed as an integer
    *     value
    * @since 11.0
    */
   @Beta
   @CheckForNull
   @GwtIncompatible("TODO")
   public static Integer tryParse(String string) {
     return tryParse(string, 10);
   }
 
   /**
    * Parses the specified string as a signed integer value using the specified
    * radix. The ASCII character {@code '-'} (<code>'&#92;u002D'</code>) is
    * recognized as the minus sign.
    *
    * <p>Unlike {@link Integer#parseInt(String, int)}, this method returns
    * {@code null} instead of throwing an exception if parsing fails.
    * Additionally, this method only accepts ASCII digits, and returns
    * {@code null} if non-ASCII digits are present in the string.
    *
    * <p>Note that strings prefixed with ASCII {@code '+'} are rejected, even
    * under JDK 7, despite the change to {@link Integer#parseInt(String, int)}
    * for that version.
    *
    * @param string the string representation of an integer value
    * @param radix the radix to use when parsing
    * @return the integer value represented by {@code string} using
    *     {@code radix}, or {@code null} if {@code string} has a length of zero
    *     or cannot be parsed as an integer value
    * @throws IllegalArgumentException if {@code radix < Character.MIN_RADIX} or
    *     {@code radix > Character.MAX_RADIX}
    */
   @CheckForNull
   @GwtIncompatible("TODO") static Integer tryParse(
       String string, int radix) {
     if (checkNotNull(string).isEmpty()) {
       return null;
     }
     if (radix < Character.MIN_RADIX || radix > Character.MAX_RADIX) {
       throw new IllegalArgumentException(
           "radix must be between MIN_RADIX and MAX_RADIX but was " + radix);
     }
     boolean negative = string.charAt(0) == '-';
     int index = negative ? 1 : 0;
     if (index == string.length()) {
       return null;
     }
     int digit = digit(string.charAt(index++));
     if (digit < 0 || digit >= radix) {
       return null;
     }
     int accum = -digit;
 
     int cap = Integer.MIN_VALUE / radix;
 
     while (index < string.length()) {
       digit = digit(string.charAt(index++));
       if (digit < 0 || digit >= radix || accum < cap) {
         return null;
       }
       accum *= radix;
       if (accum < Integer.MIN_VALUE + digit) {
         return null;
       }
       accum -= digit;
     }
 
     if (negative) {
       return accum;
     } else if (accum == Integer.MIN_VALUE) {
       return null;
     } else {
       return -accum;
     }
   }
 }