/*
 * 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.Beta;

/**
 * Static utility methods pertaining to {@code byte} primitives that interpret
 * values as <i>unsigned</i> (that is, any negative value {@code b} is treated
 * as the positive value {@code 256 + b}). The corresponding methods that treat
 * the values as signed are found in {@link SignedBytes}, 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
 * @author Martin Buchholz
 * @author Hiroshi Yamauchi
 * @author Louis Wasserman
 * @since 1.0
 */
public final class UnsignedBytes {
	private UnsignedBytes() {
	}

	/**
	 * The largest power of two that can be represented as an unsigned {@code
	 * byte}.
	 *
	 * @since 10.0
	 */
	public static final byte MAX_POWER_OF_TWO = (byte) 0x80;

	/**
	 * The largest value that fits into an unsigned byte.
	 *
	 * @since 13.0
	 */
	public static final byte MAX_VALUE = (byte) 0xFF;

	private static final int UNSIGNED_MASK = 0xFF;

	/**
	 * Returns the value of the given byte as an integer, when treated as unsigned.
	 * That is, returns {@code value + 256} if {@code value} is negative;
	 * {@code value} itself otherwise.
	 *
	 * @since 6.0
	 */
	public static int toInt(byte value) {
		return value & UNSIGNED_MASK;
	}

	/**
	 * Returns the {@code byte} value that, when treated as unsigned, is equal to
	 * {@code value}, if possible.
	 *
	 * @param value a value between 0 and 255 inclusive
	 * @return the {@code byte} value that, when treated as unsigned, equals
	 *         {@code value}
	 * @throws IllegalArgumentException if {@code value} is negative or greater than
	 *                                  255
	 */
	public static byte checkedCast(long value) {
		if ((value >> Byte.SIZE) != 0) {
			// don't use checkArgument here, to avoid boxing
			throw new IllegalArgumentException("Out of range: " + value);
		}
		return (byte) value;
	}

	/**
	 * Returns the {@code byte} value that, when treated as unsigned, is nearest in
	 * value to {@code value}.
	 *
	 * @param value any {@code long} value
	 * @return {@code (byte) 255} if {@code value >= 255}, {@code (byte) 0} if
	 *         {@code value <= 0}, and {@code value} cast to {@code byte} otherwise
	 */
	public static byte saturatedCast(long value) {
		if (value > toInt(MAX_VALUE)) {
			return MAX_VALUE; // -1
		}
		if (value < 0) {
			return (byte) 0;
		}
		return (byte) value;
	}

	/**
	 * Compares the two specified {@code byte} values, treating them as unsigned
	 * values between 0 and 255 inclusive. For example, {@code (byte) -127} is
	 * considered greater than {@code (byte) 127} because it is seen as having the
	 * value of positive {@code 129}.
	 *
	 * @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
	 */
	public static int compare(byte a, byte b) {
		return toInt(a) - toInt(b);
	}

	/**
	 * 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);
		int min = toInt(array[0]);
		for (int i = 1; i < array.length; i++) {
			int next = toInt(array[i]);
			if (next < min) {
				min = next;
			}
		}
		return (byte) 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);
		int max = toInt(array[0]);
		for (int i = 1; i < array.length; i++) {
			int next = toInt(array[i]);
			if (next > max) {
				max = next;
			}
		}
		return (byte) max;
	}

	/**
	 * Returns a string representation of x, where x is treated as unsigned.
	 *
	 * @since 13.0
	 */
	@Beta
	public static String toString(byte x) {
		return toString(x, 10);
	}

	/**
	 * Returns a string representation of {@code x} for the given radix, where
	 * {@code x} is treated as unsigned.
	 *
	 * @param x     the value to convert to a string.
	 * @param radix the radix to use while working with {@code x}
	 * @throws IllegalArgumentException if {@code radix} is not between
	 *                                  {@link Character#MIN_RADIX} and
	 *                                  {@link Character#MAX_RADIX}.
	 * @since 13.0
	 */
	@Beta
	public static String toString(byte x, int radix) {
		checkArgument(radix >= Character.MIN_RADIX && radix <= Character.MAX_RADIX,
				"radix (%s) must be between Character.MIN_RADIX and Character.MAX_RADIX", radix);
		// Benchmarks indicate this is probably not worth optimizing.
		return Integer.toString(toInt(x), radix);
	}

	/**
	 * Returns the unsigned {@code byte} value represented by the given decimal
	 * string.
	 *
	 * @throws NumberFormatException if the string does not contain a valid unsigned
	 *                               {@code byte} value
	 * @throws NullPointerException  if {@code s} is null (in contrast to
	 *                               {@link Byte#parseByte(String)})
	 * @since 13.0
	 */
	@Beta
	public static byte parseUnsignedByte(String string) {
		return parseUnsignedByte(string, 10);
	}

	/**
	 * Returns the unsigned {@code byte} value represented by a string with the
	 * given radix.
	 *
	 * @param string the string containing the unsigned {@code byte} representation
	 *               to be parsed.
	 * @param radix  the radix to use while parsing {@code string}
	 * @throws NumberFormatException if the string does not contain a valid unsigned
	 *                               {@code byte} with the given radix, or if
	 *                               {@code radix} is not between
	 *                               {@link Character#MIN_RADIX} and
	 *                               {@link Character#MAX_RADIX}.
	 * @throws NullPointerException  if {@code s} is null (in contrast to
	 *                               {@link Byte#parseByte(String)})
	 * @since 13.0
	 */
	@Beta
	public static byte parseUnsignedByte(String string, int radix) {
		int parse = Integer.parseInt(checkNotNull(string), radix);
		// We need to throw a NumberFormatException, so we have to duplicate
		// checkedCast. =(
		if (parse >> Byte.SIZE == 0) {
			return (byte) parse;
		} else {
			throw new NumberFormatException("out of range: " + parse);
		}
	}

	/**
	 * Returns a string containing the supplied {@code byte} values separated by
	 * {@code separator}. For example, {@code join(":", (byte) 1, (byte) 2,
	 * (byte) 255)} returns the string {@code "1:2:255"}.
	 *
	 * @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 * (3 + separator.length()));
		builder.append(toInt(array[0]));
		for (int i = 1; i < array.length; i++) {
			builder.append(separator).append(toString(array[i]));
		}
		return builder.toString();
	}

}