/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.commons.lang;

/**
 * <p>Operations on char primitives and Character objects.</p>
 *
 * <p>This class tries to handle <code>null</code> input gracefully.
 * An exception will not be thrown for a <code>null</code> input.
 * Each method documents its behaviour in more detail.</p>
 * 
 * <p>#ThreadSafe#</p>
 * @author Apache Software Foundation
 * @since 2.1
 * @version $Id$
 */
public class CharUtils {
    
    private static final String CHAR_STRING = 
        "\u0000\u0001\u0002\u0003\u0004\u0005\u0006\u0007" +
        "\b\t\n\u000b\f\r\u000e\u000f" +
        "\u0010\u0011\u0012\u0013\u0014\u0015\u0016\u0017" +
        "\u0018\u0019\u001a\u001b\u001c\u001d\u001e\u001f" +
        "\u0020\u0021\"\u0023\u0024\u0025\u0026\u0027" +
        "\u0028\u0029\u002a\u002b\u002c\u002d\u002e\u002f" +
        "\u0030\u0031\u0032\u0033\u0034\u0035\u0036\u0037" +
        "\u0038\u0039\u003a\u003b\u003c\u003d\u003e\u003f" +
        "\u0040\u0041\u0042\u0043\u0044\u0045\u0046\u0047" +
        "\u0048\u0049\u004a\u004b\u004c\u004d\u004e\u004f" +
        "\u0050\u0051\u0052\u0053\u0054\u0055\u0056\u0057" +
        "\u0058\u0059\u005a\u005b\\\u005d\u005e\u005f" +
        "\u0060\u0061\u0062\u0063\u0064\u0065\u0066\u0067" +
        "\u0068\u0069\u006a\u006b\u006c\u006d\u006e\u006f" +
        "\u0070\u0071\u0072\u0073\u0074\u0075\u0076\u0077" +
        "\u0078\u0079\u007a\u007b\u007c\u007d\u007e\u007f";
    
    private static final String[] CHAR_STRING_ARRAY = new String[128];
    private static final Character[] CHAR_ARRAY = new Character[128];
    
    /**
     * <code>\u000a</code> linefeed LF ('\n').
     * 
     * @see <a href="http://java.sun.com/docs/books/jls/third_edition/html/lexical.html#101089">JLF: Escape Sequences
     *      for Character and String Literals</a>
     * @since 2.2
     */
    public static final char LF = '\n';

    /**
     * <code>\u000d</code> carriage return CR ('\r').
     * 
     * @see <a href="http://java.sun.com/docs/books/jls/third_edition/html/lexical.html#101089">JLF: Escape Sequences
     *      for Character and String Literals</a>
     * @since 2.2
     */
    public static final char CR = '\r';
    

    static {
        for (int i = 127; i >= 0; i--) {
            CHAR_STRING_ARRAY[i] = CHAR_STRING.substring(i, i + 1);
            CHAR_ARRAY[i] = new Character((char) i);
        }
    }

    /**
     * <p><code>CharUtils</code> instances should NOT be constructed in standard programming.
     * Instead, the class should be used as <code>CharUtils.toString('c');</code>.</p>
     *
     * <p>This constructor is public to permit tools that require a JavaBean instance
     * to operate.</p>
     */
    public CharUtils() {
      super();
    }

    //-----------------------------------------------------------------------
    /**
     * <p>Converts the character to a Character.</p>
     * 
     * <p>For ASCII 7 bit characters, this uses a cache that will return the
     * same Character object each time.</p>
     *
     * <pre>
     *   CharUtils.toCharacterObject(' ')  = ' '
     *   CharUtils.toCharacterObject('A')  = 'A'
     * </pre>
     *
     * @param ch  the character to convert
     * @return a Character of the specified character
     */
    public static Character toCharacterObject(char ch) {
        if (ch < CHAR_ARRAY.length) {
            return CHAR_ARRAY[ch];
        }
        return new Character(ch);
    }
    
    /**
     * <p>Converts the String to a Character using the first character, returning
     * null for empty Strings.</p>
     * 
     * <p>For ASCII 7 bit characters, this uses a cache that will return the
     * same Character object each time.</p>
     * 
     * <pre>
     *   CharUtils.toCharacterObject(null) = null
     *   CharUtils.toCharacterObject("")   = null
     *   CharUtils.toCharacterObject("A")  = 'A'
     *   CharUtils.toCharacterObject("BA") = 'B'
     * </pre>
     *
     * @param str  the character to convert
     * @return the Character value of the first letter of the String
     */
    public static Character toCharacterObject(String str) {
        if (StringUtils.isEmpty(str)) {
            return null;
        }
        return toCharacterObject(str.charAt(0));
    }
    
    //-----------------------------------------------------------------------
    /**
     * <p>Converts the Character to a char throwing an exception for <code>null</code>.</p>
     * 
     * <pre>
     *   CharUtils.toChar(null) = IllegalArgumentException
     *   CharUtils.toChar(' ')  = ' '
     *   CharUtils.toChar('A')  = 'A'
     * </pre>
     *
     * @param ch  the character to convert
     * @return the char value of the Character
     * @throws IllegalArgumentException if the Character is null
     */
    public static char toChar(Character ch) {
        if (ch == null) {
            throw new IllegalArgumentException("The Character must not be null");
        }
        return ch.charValue();
    }
    
    /**
     * <p>Converts the Character to a char handling <code>null</code>.</p>
     * 
     * <pre>
     *   CharUtils.toChar(null, 'X') = 'X'
     *   CharUtils.toChar(' ', 'X')  = ' '
     *   CharUtils.toChar('A', 'X')  = 'A'
     * </pre>
     *
     * @param ch  the character to convert
     * @param defaultValue  the value to use if the  Character is null
     * @return the char value of the Character or the default if null
     */
    public static char toChar(Character ch, char defaultValue) {
        if (ch == null) {
            return defaultValue;
        }
        return ch.charValue();
    }
    
    //-----------------------------------------------------------------------
    /**
     * <p>Converts the String to a char using the first character, throwing
     * an exception on empty Strings.</p>
     * 
     * <pre>
     *   CharUtils.toChar(null) = IllegalArgumentException
     *   CharUtils.toChar("")   = IllegalArgumentException
     *   CharUtils.toChar("A")  = 'A'
     *   CharUtils.toChar("BA") = 'B'
     * </pre>
     *
     * @param str  the character to convert
     * @return the char value of the first letter of the String
     * @throws IllegalArgumentException if the String is empty
     */
    public static char toChar(String str) {
        if (StringUtils.isEmpty(str)) {
            throw new IllegalArgumentException("The String must not be empty");
        }
        return str.charAt(0);
    }
    
    /**
     * <p>Converts the String to a char using the first character, defaulting
     * the value on empty Strings.</p>
     * 
     * <pre>
     *   CharUtils.toChar(null, 'X') = 'X'
     *   CharUtils.toChar("", 'X')   = 'X'
     *   CharUtils.toChar("A", 'X')  = 'A'
     *   CharUtils.toChar("BA", 'X') = 'B'
     * </pre>
     *
     * @param str  the character to convert
     * @param defaultValue  the value to use if the  Character is null
     * @return the char value of the first letter of the String or the default if null
     */
    public static char toChar(String str, char defaultValue) {
        if (StringUtils.isEmpty(str)) {
            return defaultValue;
        }
        return str.charAt(0);
    }
    
    //-----------------------------------------------------------------------
    /**
     * <p>Converts the character to the Integer it represents, throwing an
     * exception if the character is not numeric.</p>
     * 
     * <p>This method coverts the char '1' to the int 1 and so on.</p>
     *
     * <pre>
     *   CharUtils.toIntValue('3')  = 3
     *   CharUtils.toIntValue('A')  = IllegalArgumentException
     * </pre>
     *
     * @param ch  the character to convert
     * @return the int value of the character
     * @throws IllegalArgumentException if the character is not ASCII numeric
     */
    public static int toIntValue(char ch) {
        if (isAsciiNumeric(ch) == false) {
            throw new IllegalArgumentException("The character " + ch + " is not in the range '0' - '9'");
        }
        return ch - 48;
    }
    
    /**
     * <p>Converts the character to the Integer it represents, throwing an
     * exception if the character is not numeric.</p>
     * 
     * <p>This method coverts the char '1' to the int 1 and so on.</p>
     *
     * <pre>
     *   CharUtils.toIntValue('3', -1)  = 3
     *   CharUtils.toIntValue('A', -1)  = -1
     * </pre>
     *
     * @param ch  the character to convert
     * @param defaultValue  the default value to use if the character is not numeric
     * @return the int value of the character
     */
    public static int toIntValue(char ch, int defaultValue) {
        if (isAsciiNumeric(ch) == false) {
            return defaultValue;
        }
        return ch - 48;
    }
    
    /**
     * <p>Converts the character to the Integer it represents, throwing an
     * exception if the character is not numeric.</p>
     * 
     * <p>This method coverts the char '1' to the int 1 and so on.</p>
     *
     * <pre>
     *   CharUtils.toIntValue(null) = IllegalArgumentException
     *   CharUtils.toIntValue('3')  = 3
     *   CharUtils.toIntValue('A')  = IllegalArgumentException
     * </pre>
     *
     * @param ch  the character to convert, not null
     * @return the int value of the character
     * @throws IllegalArgumentException if the Character is not ASCII numeric or is null
     */
    public static int toIntValue(Character ch) {
        if (ch == null) {
            throw new IllegalArgumentException("The character must not be null");
        }
        return toIntValue(ch.charValue());
    }
    
    /**
     * <p>Converts the character to the Integer it represents, throwing an
     * exception if the character is not numeric.</p>
     * 
     * <p>This method coverts the char '1' to the int 1 and so on.</p>
     *
     * <pre>
     *   CharUtils.toIntValue(null, -1) = -1
     *   CharUtils.toIntValue('3', -1)  = 3
     *   CharUtils.toIntValue('A', -1)  = -1
     * </pre>
     *
     * @param ch  the character to convert
     * @param defaultValue  the default value to use if the character is not numeric
     * @return the int value of the character
     */
    public static int toIntValue(Character ch, int defaultValue) {
        if (ch == null) {
            return defaultValue;
        }
        return toIntValue(ch.charValue(), defaultValue);
    }
    
    //-----------------------------------------------------------------------
    /**
     * <p>Converts the character to a String that contains the one character.</p>
     * 
     * <p>For ASCII 7 bit characters, this uses a cache that will return the
     * same String object each time.</p>
     *
     * <pre>
     *   CharUtils.toString(' ')  = " "
     *   CharUtils.toString('A')  = "A"
     * </pre>
     *
     * @param ch  the character to convert
     * @return a String containing the one specified character
     */
    public static String toString(char ch) {
        if (ch < 128) {
            return CHAR_STRING_ARRAY[ch];
        }
        return new String(new char[] {ch});
    }
    
    /**
     * <p>Converts the character to a String that contains the one character.</p>
     * 
     * <p>For ASCII 7 bit characters, this uses a cache that will return the
     * same String object each time.</p>
     * 
     * <p>If <code>null</code> is passed in, <code>null</code> will be returned.</p>
     *
     * <pre>
     *   CharUtils.toString(null) = null
     *   CharUtils.toString(' ')  = " "
     *   CharUtils.toString('A')  = "A"
     * </pre>
     *
     * @param ch  the character to convert
     * @return a String containing the one specified character
     */
    public static String toString(Character ch) {
        if (ch == null) {
            return null;
        }
        return toString(ch.charValue());
    }
    
    //--------------------------------------------------------------------------
    /**
     * <p>Converts the string to the unicode format '\u0020'.</p>
     * 
     * <p>This format is the Java source code format.</p>
     *
     * <pre>
     *   CharUtils.unicodeEscaped(' ') = "\u0020"
     *   CharUtils.unicodeEscaped('A') = "\u0041"
     * </pre>
     * 
     * @param ch  the character to convert
     * @return the escaped unicode string
     */
    public static String unicodeEscaped(char ch) {
        if (ch < 0x10) {
            return "\\u000" + Integer.toHexString(ch);
        } else if (ch < 0x100) {
            return "\\u00" + Integer.toHexString(ch);
        } else if (ch < 0x1000) {
            return "\\u0" + Integer.toHexString(ch);
        }
        return "\\u" + Integer.toHexString(ch);
    }
    
    /**
     * <p>Converts the string to the unicode format '\u0020'.</p>
     * 
     * <p>This format is the Java source code format.</p>
     * 
     * <p>If <code>null</code> is passed in, <code>null</code> will be returned.</p>
     *
     * <pre>
     *   CharUtils.unicodeEscaped(null) = null
     *   CharUtils.unicodeEscaped(' ')  = "\u0020"
     *   CharUtils.unicodeEscaped('A')  = "\u0041"
     * </pre>
     * 
     * @param ch  the character to convert, may be null
     * @return the escaped unicode string, null if null input
     */
    public static String unicodeEscaped(Character ch) {
        if (ch == null) {
            return null;
        }
        return unicodeEscaped(ch.charValue());
    }
    
    //--------------------------------------------------------------------------
    /**
     * <p>Checks whether the character is ASCII 7 bit.</p>
     *
     * <pre>
     *   CharUtils.isAscii('a')  = true
     *   CharUtils.isAscii('A')  = true
     *   CharUtils.isAscii('3')  = true
     *   CharUtils.isAscii('-')  = true
     *   CharUtils.isAscii('\n') = true
     *   CharUtils.isAscii('&copy;') = false
     * </pre>
     * 
     * @param ch  the character to check
     * @return true if less than 128
     */
    public static boolean isAscii(char ch) {
        return ch < 128;
    }
    
    /**
     * <p>Checks whether the character is ASCII 7 bit printable.</p>
     *
     * <pre>
     *   CharUtils.isAsciiPrintable('a')  = true
     *   CharUtils.isAsciiPrintable('A')  = true
     *   CharUtils.isAsciiPrintable('3')  = true
     *   CharUtils.isAsciiPrintable('-')  = true
     *   CharUtils.isAsciiPrintable('\n') = false
     *   CharUtils.isAsciiPrintable('&copy;') = false
     * </pre>
     * 
     * @param ch  the character to check
     * @return true if between 32 and 126 inclusive
     */
    public static boolean isAsciiPrintable(char ch) {
        return ch >= 32 && ch < 127;
    }
    
    /**
     * <p>Checks whether the character is ASCII 7 bit control.</p>
     *
     * <pre>
     *   CharUtils.isAsciiControl('a')  = false
     *   CharUtils.isAsciiControl('A')  = false
     *   CharUtils.isAsciiControl('3')  = false
     *   CharUtils.isAsciiControl('-')  = false
     *   CharUtils.isAsciiControl('\n') = true
     *   CharUtils.isAsciiControl('&copy;') = false
     * </pre>
     * 
     * @param ch  the character to check
     * @return true if less than 32 or equals 127
     */
    public static boolean isAsciiControl(char ch) {
        return ch < 32 || ch == 127;
    }
    
    /**
     * <p>Checks whether the character is ASCII 7 bit alphabetic.</p>
     *
     * <pre>
     *   CharUtils.isAsciiAlpha('a')  = true
     *   CharUtils.isAsciiAlpha('A')  = true
     *   CharUtils.isAsciiAlpha('3')  = false
     *   CharUtils.isAsciiAlpha('-')  = false
     *   CharUtils.isAsciiAlpha('\n') = false
     *   CharUtils.isAsciiAlpha('&copy;') = false
     * </pre>
     * 
     * @param ch  the character to check
     * @return true if between 65 and 90 or 97 and 122 inclusive
     */
    public static boolean isAsciiAlpha(char ch) {
        return (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z');
    }
    
    /**
     * <p>Checks whether the character is ASCII 7 bit alphabetic upper case.</p>
     *
     * <pre>
     *   CharUtils.isAsciiAlphaUpper('a')  = false
     *   CharUtils.isAsciiAlphaUpper('A')  = true
     *   CharUtils.isAsciiAlphaUpper('3')  = false
     *   CharUtils.isAsciiAlphaUpper('-')  = false
     *   CharUtils.isAsciiAlphaUpper('\n') = false
     *   CharUtils.isAsciiAlphaUpper('&copy;') = false
     * </pre>
     * 
     * @param ch  the character to check
     * @return true if between 65 and 90 inclusive
     */
    public static boolean isAsciiAlphaUpper(char ch) {
        return ch >= 'A' && ch <= 'Z';
    }
    
    /**
     * <p>Checks whether the character is ASCII 7 bit alphabetic lower case.</p>
     *
     * <pre>
     *   CharUtils.isAsciiAlphaLower('a')  = true
     *   CharUtils.isAsciiAlphaLower('A')  = false
     *   CharUtils.isAsciiAlphaLower('3')  = false
     *   CharUtils.isAsciiAlphaLower('-')  = false
     *   CharUtils.isAsciiAlphaLower('\n') = false
     *   CharUtils.isAsciiAlphaLower('&copy;') = false
     * </pre>
     * 
     * @param ch  the character to check
     * @return true if between 97 and 122 inclusive
     */
    public static boolean isAsciiAlphaLower(char ch) {
        return ch >= 'a' && ch <= 'z';
    }
    
    /**
     * <p>Checks whether the character is ASCII 7 bit numeric.</p>
     *
     * <pre>
     *   CharUtils.isAsciiNumeric('a')  = false
     *   CharUtils.isAsciiNumeric('A')  = false
     *   CharUtils.isAsciiNumeric('3')  = true
     *   CharUtils.isAsciiNumeric('-')  = false
     *   CharUtils.isAsciiNumeric('\n') = false
     *   CharUtils.isAsciiNumeric('&copy;') = false
     * </pre>
     * 
     * @param ch  the character to check
     * @return true if between 48 and 57 inclusive
     */
    public static boolean isAsciiNumeric(char ch) {
        return ch >= '0' && ch <= '9';
    }
    
    /**
     * <p>Checks whether the character is ASCII 7 bit numeric.</p>
     *
     * <pre>
     *   CharUtils.isAsciiAlphanumeric('a')  = true
     *   CharUtils.isAsciiAlphanumeric('A')  = true
     *   CharUtils.isAsciiAlphanumeric('3')  = true
     *   CharUtils.isAsciiAlphanumeric('-')  = false
     *   CharUtils.isAsciiAlphanumeric('\n') = false
     *   CharUtils.isAsciiAlphanumeric('&copy;') = false
     * </pre>
     * 
     * @param ch  the character to check
     * @return true if between 48 and 57 or 65 and 90 or 97 and 122 inclusive
     */
    public static boolean isAsciiAlphanumeric(char ch) {
        return (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z') || (ch >= '0' && ch <= '9');
    }

    // ----------------- Following code copied from Apache Harmony (Character class)
    /**
     * Indicates whether {@code ch} is a high- (or leading-) surrogate code unit
     * that is used for representing supplementary characters in UTF-16
     * encoding.
     *
     * @param ch
     *            the character to test.
     * @return {@code true} if {@code ch} is a high-surrogate code unit;
     *         {@code false} otherwise.
     */
    static boolean isHighSurrogate(char ch) {
        return ('\uD800' <= ch && '\uDBFF' >= ch);
    }
    
}