/*
    * Copyright (C) 2009 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.checkNotNull;
  
  import com.google.common.annotations.GwtCompatible;
  
  import java.util.Comparator;
  
  /**
   * Static utility methods pertaining to {@code byte} primitives that
   * interpret values as signed. The corresponding methods that treat the values
   * as unsigned are found in {@link UnsignedBytes}, and the methods for which
   * signedness is not an issue are in {@link Bytes}.
   * 
   * <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 SignedBytes {
    private SignedBytes() {}
  
    /**
     * The largest power of two that can be represented as a signed {@code byte}. 
     *
     * @since 10.0
     */
    public static final byte MAX_POWER_OF_TWO = 1 << 6;
    
    /**
     * Returns the {@code byte} value that is equal to {@code value}, if possible.
     *
     * @param value any value in the range of the {@code byte} type
     * @return the {@code byte} value that equals {@code value}
     * @throws IllegalArgumentException if {@code value} is greater than {@link
     *     Byte#MAX_VALUE} or less than {@link Byte#MIN_VALUE}
     */
    public static byte checkedCast(long value) {
      byte result = (byte) value;
      if (result != value) {
        // don't use checkArgument here, to avoid boxing
        throw new IllegalArgumentException("Out of range: " + value);
      }
      return result;
    }
  
    /**
     * Returns the {@code byte} nearest in value to {@code value}.
     *
     * @param value any {@code long} value
     * @return the same value cast to {@code byte} if it is in the range of the
     *     {@code byte} type, {@link Byte#MAX_VALUE} if it is too large,
     *     or {@link Byte#MIN_VALUE} if it is too small
     */
    public static byte saturatedCast(long value) {
      if (value > Byte.MAX_VALUE) {
        return Byte.MAX_VALUE;
      }
      if (value < Byte.MIN_VALUE) {
        return Byte.MIN_VALUE;
      }
      return (byte) value;
    }
  
    /**
     * Compares the two specified {@code byte} values. The sign of the value
     * returned is the same as that of {@code ((Byte) a).compareTo(b)}.
     *
     * <p><b>Note:</b> this method behaves identically to the JDK 7 method {@link
     * Byte#compare}.
     *
     * @param a the first {@code byte} to compare
     * @param b the second {@code byte} 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
     */
    // TODO(kevinb): if Ints.compare etc. are ever removed, *maybe* remove this
   // one too, which would leave compare methods only on the Unsigned* classes.
   public static int compare(byte a, byte b) {
     return a - b; // safe due to restricted range
   }
 
   /**
    * Returns the least value present in {@code array}.
    *
    * @param array a <i>nonempty</i> array of {@code byte} 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 byte min(byte... array) {
     checkArgument(array.length > 0);
     byte 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 byte} 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 byte max(byte... array) {
     checkArgument(array.length > 0);
     byte max = array[0];
     for (int i = 1; i < array.length; i++) {
       if (array[i] > max) {
         max = array[i];
       }
     }
     return max;
   }
 
   /**
    * Returns a string containing the supplied {@code byte} values separated
    * by {@code separator}. For example, {@code join(":", 0x01, 0x02, -0x01)}
    * returns the string {@code "1:2:-1"}.
    *
    * @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 byte} values, possibly empty
    */
   public static String join(String separator, byte... 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 byte} arrays
    * lexicographically. That is, it compares, using {@link
    * #compare(byte, byte)}), 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 [] < [0x01] < [0x01, 0x80] <
    * [0x01, 0x7F] < [0x02]}. Values are treated as signed.
    *
    * <p>The returned comparator is inconsistent with {@link
    * Object#equals(Object)} (since arrays support only identity equality), but
    * it is consistent with {@link java.util.Arrays#equals(byte[], byte[])}.
    *
    * @see <a href="http://en.wikipedia.org/wiki/Lexicographical_order">
    *     Lexicographical order article at Wikipedia</a>
    * @since 2.0
    */
   public static Comparator<byte[]> lexicographicalComparator() {
     return LexicographicalComparator.INSTANCE;
   }
 
   private enum LexicographicalComparator implements Comparator<byte[]> {
     INSTANCE;
 
     @Override
     public int compare(byte[] left, byte[] right) {
       int minLength = Math.min(left.length, right.length);
       for (int i = 0; i < minLength; i++) {
         int result = SignedBytes.compare(left[i], right[i]);
         if (result != 0) {
           return result;
         }
       }
       return left.length - right.length;
     }
   }
 }