/*
    * 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 java.io.Serializable;
  import java.util.AbstractList;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.List;
  import java.util.RandomAccess;
  
  /**
   * Static utility methods pertaining to {@code byte} primitives, that are not
   * already found in either {@link Byte} or {@link Arrays}, <i>and interpret
   * bytes as neither signed nor unsigned</i>. The methods which specifically
   * treat bytes as signed or unsigned are found in {@link SignedBytes} and {@link
   * UnsignedBytes}.
   *
   * <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
   */
  // TODO(kevinb): how to prevent warning on UnsignedBytes when building GWT
  // javadoc?
  @GwtCompatible
  public final class Bytes {
    private Bytes() {}
  
    /**
     * Returns a hash code for {@code value}; equal to the result of invoking
     * {@code ((Byte) value).hashCode()}.
     *
     * @param value a primitive {@code byte} value
     * @return a hash code for the value
     */
    public static int hashCode(byte value) {
      return value;
    }
  
    /**
     * Returns {@code true} if {@code target} is present as an element anywhere in
     * {@code array}.
     *
     * @param array an array of {@code byte} values, possibly empty
     * @param target a primitive {@code byte} value
     * @return {@code true} if {@code array[i] == target} for some value of {@code
     *     i}
     */
    public static boolean contains(byte[] array, byte target) {
      for (byte 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 byte} values, possibly empty
     * @param target a primitive {@code byte} 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(byte[] array, byte target) {
      return indexOf(array, target, 0, array.length);
    }
  
    // TODO(kevinb): consider making this public
    private static int indexOf(
        byte[] array, byte 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(byte[] array, byte[] 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 byte} values, possibly empty
    * @param target a primitive {@code byte} 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(byte[] array, byte target) {
     return lastIndexOf(array, target, 0, array.length);
   }
 
   // TODO(kevinb): consider making this public
   private static int lastIndexOf(
       byte[] array, byte target, int start, int end) {
     for (int i = end - 1; i >= start; i--) {
       if (array[i] == target) {
         return i;
       }
     }
     return -1;
   }
 
   /**
    * Returns the values from each provided array combined into a single array.
    * For example, {@code concat(new byte[] {a, b}, new byte[] {}, new
    * byte[] {c}} returns the array {@code {a, b, c}}.
    *
    * @param arrays zero or more {@code byte} arrays
    * @return a single array containing all the values from the source arrays, in
    *     order
    */
   public static byte[] concat(byte[]... arrays) {
     int length = 0;
     for (byte[] array : arrays) {
       length += array.length;
     }
     byte[] result = new byte[length];
     int pos = 0;
     for (byte[] array : arrays) {
       System.arraycopy(array, 0, result, pos, array.length);
       pos += array.length;
     }
     return result;
   }
 
   /**
    * 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 byte[] ensureCapacity(
       byte[] 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 byte[] copyOf(byte[] original, int length) {
     byte[] copy = new byte[length];
     System.arraycopy(original, 0, copy, 0, Math.min(original.length, length));
     return copy;
   }
 
   /**
    * Returns an array containing each value of {@code collection}, converted to
    * a {@code byte} value in the manner of {@link Number#byteValue}.
    *
    * <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<Byte>} before 12.0)
    */
   public static byte[] toArray(Collection<? extends Number> collection) {
     if (collection instanceof ByteArrayAsList) {
       return ((ByteArrayAsList) collection).toByteArray();
     }
 
     Object[] boxedArray = collection.toArray();
     int len = boxedArray.length;
     byte[] array = new byte[len];
     for (int i = 0; i < len; i++) {
       // checkNotNull for GWT (do not optimize)
       array[i] = ((Number) checkNotNull(boxedArray[i])).byteValue();
     }
     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 Byte} 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<Byte> asList(byte... backingArray) {
     if (backingArray.length == 0) {
       return Collections.emptyList();
     }
     return new ByteArrayAsList(backingArray);
   }
 
   @GwtCompatible
   private static class ByteArrayAsList extends AbstractList<Byte>
       implements RandomAccess, Serializable {
     final byte[] array;
     final int start;
     final int end;
 
     ByteArrayAsList(byte[] array) {
       this(array, 0, array.length);
     }
 
     ByteArrayAsList(byte[] 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 Byte 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 Byte)
           && Bytes.indexOf(array, (Byte) target, start, end) != -1;
     }
 
     @Override public int indexOf(Object target) {
       // Overridden to prevent a ton of boxing
       if (target instanceof Byte) {
         int i = Bytes.indexOf(array, (Byte) 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 Byte) {
         int i = Bytes.lastIndexOf(array, (Byte) target, start, end);
         if (i >= 0) {
           return i - start;
         }
       }
       return -1;
     }
 
     @Override public Byte set(int index, Byte element) {
       checkElementIndex(index, size());
       byte oldValue = array[start + index];
       // checkNotNull for GWT (do not optimize)
       array[start + index] = checkNotNull(element);
       return oldValue;
     }
 
     @Override public List<Byte> subList(int fromIndex, int toIndex) {
       int size = size();
       checkPositionIndexes(fromIndex, toIndex, size);
       if (fromIndex == toIndex) {
         return Collections.emptyList();
       }
       return new ByteArrayAsList(array, start + fromIndex, start + toIndex);
     }
 
     @Override public boolean equals(Object object) {
       if (object == this) {
         return true;
       }
       if (object instanceof ByteArrayAsList) {
         ByteArrayAsList that = (ByteArrayAsList) 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 + Bytes.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();
     }
 
     byte[] toByteArray() {
       // Arrays.copyOfRange() is not available under GWT
       int size = size();
       byte[] result = new byte[size];
       System.arraycopy(array, start, result, 0, size);
       return result;
     }
 
     private static final long serialVersionUID = 0;
   }
 }