/*
    * 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.GwtCompatible;
  import com.google.common.annotations.GwtIncompatible;
  
  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;
  
  /**
   * Static utility methods pertaining to {@code char} primitives, that are not
   * already found in either {@link Character} or {@link Arrays}.
   *
   * <p>All the operations in this class treat {@code char} values strictly
   * numerically; they are neither Unicode-aware nor locale-dependent.
   *
   * <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 Chars {
    private Chars() {}
  
    /**
     * The number of bytes required to represent a primitive {@code char}
     * value.
     */
    public static final int BYTES = Character.SIZE / Byte.SIZE;
  
    /**
     * Returns a hash code for {@code value}; equal to the result of invoking
     * {@code ((Character) value).hashCode()}.
     *
     * @param value a primitive {@code char} value
     * @return a hash code for the value
     */
    public static int hashCode(char value) {
      return value;
    }
  
    /**
     * Returns the {@code char} value that is equal to {@code value}, if possible.
     *
     * @param value any value in the range of the {@code char} type
     * @return the {@code char} value that equals {@code value}
     * @throws IllegalArgumentException if {@code value} is greater than {@link
     *     Character#MAX_VALUE} or less than {@link Character#MIN_VALUE}
     */
    public static char checkedCast(long value) {
      char result = (char) value;
      if (result != value) {
        // don't use checkArgument here, to avoid boxing
        throw new IllegalArgumentException("Out of range: " + value);
      }
      return result;
    }
  
    /**
     * Returns the {@code char} nearest in value to {@code value}.
     *
     * @param value any {@code long} value
     * @return the same value cast to {@code char} if it is in the range of the
     *     {@code char} type, {@link Character#MAX_VALUE} if it is too large,
     *     or {@link Character#MIN_VALUE} if it is too small
     */
    public static char saturatedCast(long value) {
      if (value > Character.MAX_VALUE) {
        return Character.MAX_VALUE;
      }
     if (value < Character.MIN_VALUE) {
       return Character.MIN_VALUE;
     }
     return (char) value;
   }
 
   /**
    * Compares the two specified {@code char} values. The sign of the value
    * returned is the same as that of {@code ((Character) a).compareTo(b)}.
    *
    * <p><b>Note for Java 7 and later:</b> this method should be treated as
    * deprecated; use the equivalent {@link Character#compare} method instead.
    *
    * @param a the first {@code char} to compare
    * @param b the second {@code char} 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(char a, char b) {
     return a - b; // safe due to restricted range
   }
 
   /**
    * Returns {@code true} if {@code target} is present as an element anywhere in
    * {@code array}.
    *
    * @param array an array of {@code char} values, possibly empty
    * @param target a primitive {@code char} value
    * @return {@code true} if {@code array[i] == target} for some value of {@code
    *     i}
    */
   public static boolean contains(char[] array, char target) {
     for (char 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 char} values, possibly empty
    * @param target a primitive {@code char} 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(char[] array, char target) {
     return indexOf(array, target, 0, array.length);
   }
 
   // TODO(kevinb): consider making this public
   private static int indexOf(
       char[] array, char 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(char[] array, char[] 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 char} values, possibly empty
    * @param target a primitive {@code char} 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(char[] array, char target) {
     return lastIndexOf(array, target, 0, array.length);
   }
 
   // TODO(kevinb): consider making this public
   private static int lastIndexOf(
       char[] array, char 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 char} 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 char min(char... array) {
     checkArgument(array.length > 0);
     char 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 char} 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 char max(char... array) {
     checkArgument(array.length > 0);
     char 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 char[] {a, b}, new char[] {}, new
    * char[] {c}} returns the array {@code {a, b, c}}.
    *
    * @param arrays zero or more {@code char} arrays
    * @return a single array containing all the values from the source arrays, in
    *     order
    */
   public static char[] concat(char[]... arrays) {
     int length = 0;
     for (char[] array : arrays) {
       length += array.length;
     }
     char[] result = new char[length];
     int pos = 0;
     for (char[] 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 2-element byte
    * array; equivalent to {@code
    * ByteBuffer.allocate(2).putChar(value).array()}.  For example, the input
    * value {@code '\\u5432'} would yield the byte array {@code {0x54, 0x32}}.
    *
    * <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(char value) {
     return new byte[] {
         (byte) (value >> 8),
         (byte) value};
   }
 
   /**
    * Returns the {@code char} value whose big-endian representation is
    * stored in the first 2 bytes of {@code bytes}; equivalent to {@code
    * ByteBuffer.wrap(bytes).getChar()}. For example, the input byte array
    * {@code {0x54, 0x32}} would yield the {@code char} value {@code '\\u5432'}.
    *
    * <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 2
    *     elements
    */
   @GwtIncompatible("doesn't work")
   public static char fromByteArray(byte[] bytes) {
     checkArgument(bytes.length >= BYTES,
         "array too small: %s < %s", bytes.length, BYTES);
     return fromBytes(bytes[0], bytes[1]);
   }
 
   /**
    * Returns the {@code char} value whose byte representation is the given 2
    * bytes, in big-endian order; equivalent to {@code Chars.fromByteArray(new
    * byte[] {b1, b2})}.
    *
    * @since 7.0
    */
   @GwtIncompatible("doesn't work")
   public static char fromBytes(byte b1, byte b2) {
     return (char) ((b1 << 8) | (b2 & 0xFF));
   }
 
   /**
    * 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 char[] ensureCapacity(
       char[] 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 char[] copyOf(char[] original, int length) {
     char[] copy = new char[length];
     System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
     return copy;
   }
 
   /**
    * Returns a string containing the supplied {@code char} 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 char} values, possibly empty
    */
   public static String join(String separator, char... array) {
     checkNotNull(separator);
     int len = array.length;
     if (len == 0) {
       return "";
     }
 
     StringBuilder builder
         = new StringBuilder(len + separator.length() * (len - 1));
     builder.append(array[0]);
     for (int i = 1; i < len; i++) {
       builder.append(separator).append(array[i]);
     }
     return builder.toString();
   }
 
   /**
    * Returns a comparator that compares two {@code char} arrays
    * lexicographically. That is, it compares, using {@link
    * #compare(char, char)}), 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 [] < ['a'] < ['a', 'b'] < ['b']}.
    *
    * <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(char[], char[])}.
    *
    * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
    *     Lexicographical order article at Wikipedia</a>
    * @since 2.0
    */
   public static Comparator<char[]> lexicographicalComparator() {
     return LexicographicalComparator.INSTANCE;
   }
 
   private enum LexicographicalComparator implements Comparator<char[]> {
     INSTANCE;
 
     @Override
     public int compare(char[] left, char[] right) {
       int minLength = Math.min(left.length, right.length);
       for (int i = 0; i < minLength; i++) {
         int result = Chars.compare(left[i], right[i]);
         if (result != 0) {
           return result;
         }
       }
       return left.length - right.length;
     }
   }
 
   /**
    * Copies a collection of {@code Character} instances into a new array of
    * primitive {@code char} values.
    *
    * <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 Character} objects
    * @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
    */
   public static char[] toArray(Collection<Character> collection) {
     if (collection instanceof CharArrayAsList) {
       return ((CharArrayAsList) collection).toCharArray();
     }
 
     Object[] boxedArray = collection.toArray();
     int len = boxedArray.length;
     char[] array = new char[len];
     for (int i = 0; i < len; i++) {
       // checkNotNull for GWT (do not optimize)
       array[i] = (Character) checkNotNull(boxedArray[i]);
     }
     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 Character} 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<Character> asList(char... backingArray) {
     if (backingArray.length == 0) {
       return Collections.emptyList();
     }
     return new CharArrayAsList(backingArray);
   }
 
   @GwtCompatible
   private static class CharArrayAsList extends AbstractList<Character>
       implements RandomAccess, Serializable {
     final char[] array;
     final int start;
     final int end;
 
     CharArrayAsList(char[] array) {
       this(array, 0, array.length);
     }
 
     CharArrayAsList(char[] 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 Character 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 Character)
           && Chars.indexOf(array, (Character) target, start, end) != -1;
     }
 
     @Override public int indexOf(Object target) {
       // Overridden to prevent a ton of boxing
       if (target instanceof Character) {
         int i = Chars.indexOf(array, (Character) 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 Character) {
         int i = Chars.lastIndexOf(array, (Character) target, start, end);
         if (i >= 0) {
           return i - start;
         }
       }
       return -1;
     }
 
     @Override public Character set(int index, Character element) {
       checkElementIndex(index, size());
       char oldValue = array[start + index];
       // checkNotNull for GWT (do not optimize)
       array[start + index] = checkNotNull(element);
       return oldValue;
     }
 
     @Override public List<Character> subList(int fromIndex, int toIndex) {
       int size = size();
       checkPositionIndexes(fromIndex, toIndex, size);
       if (fromIndex == toIndex) {
         return Collections.emptyList();
       }
       return new CharArrayAsList(array, start + fromIndex, start + toIndex);
     }
 
     @Override public boolean equals(Object object) {
       if (object == this) {
         return true;
       }
       if (object instanceof CharArrayAsList) {
         CharArrayAsList that = (CharArrayAsList) 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 + Chars.hashCode(array[i]);
       }
       return result;
     }
 
     @Override public String toString() {
       StringBuilder builder = new StringBuilder(size() * 3);
       builder.append('[').append(array[start]);
       for (int i = start + 1; i < end; i++) {
         builder.append(", ").append(array[i]);
       }
       return builder.append(']').toString();
     }
 
     char[] toCharArray() {
       // Arrays.copyOfRange() is not available under GWT
       int size = size();
       char[] result = new char[size];
       System.arraycopy(array, start, result, 0, size);
       return result;
     }
 
     private static final long serialVersionUID = 0;
   }
 }