/**
 * This class contains numerous static methods for manipulating Strings.
 * 
 * @author Dave Reed
 * @version 11/1/09
 */
public class StringUtils {
    /**
     * Reverses a string.
     *   @param str the string to be reversed
     *   @return a copy of str with the order of the characters reversed
     */
    public static String reverse(String str) {
        String copy = "";
        for (int i = 0; i < str.length(); i++) {
            copy = str.charAt(i) + copy;
        }
        return copy;
    }
    
    /**
     * Strips all spaces out of a string.
     *   @param str the string to be stripped
     *   @return a copy of str with each space removed
     */    
    public static String stripSpaces(String str) {
        return stripAllOf(" ", str);
    }
    
    /**
     * Censors a string by replacing all vowels with asterisks.
     *   @param str the string to be censored
     *   @return a copy of str with each vowel replaced by an asterisk
     */    
    public static String censor(String str) {
        
        String copy = "";
        for (int i = 0; i < str.length(); i++) {
            if (isVowel(str.charAt(i))) {
                copy += '*'; 
            }
            else {
                copy += str.charAt(i);
            }
        }
        return copy;
    }

    /**
     * Capitalizes the first letter in the string.
     *   @param str the string to be capitalized
     *   @return a copy of str with the first letter capitalized
     */     
    public static String capitalize(String str) {
        return Character.toUpperCase(str.charAt(0)) + str.substring(1, str.length());
    }
    
    /**
     * Translates a string into Pig Latin
     *   @param str the string to be translated
     *   @return a copy of str translated into Pig Latin
     */     
    public static String pigLatin(String str) {
        int firstVowel = findVowel(str);
        
        if (firstVowel <= 0) {
            return str + "way";
        }
        else {
            return str.substring(firstVowel, str.length()) + 
                   str.substring(0,firstVowel) + "ay";
        }
    }
    
    /**
     * Removes all non-letters from a string.
     *   @param str the string to be stripped
     *   @return a copy of str with all non-letters removed
     */
    public static String stripNonLetters(String str) {
        String copy = "";
        for (int i = 0; i < str.length(); i++) {
            if (Character.isLetter(str.charAt(i))) {
                copy += str.charAt(i);
            }
        }
        return copy;    
    }
 
    /**
     * Determines if a character is a vowel (either upper or lower case).
     *   @param ch the character to be tested
     *   @return true if ch is a vowel, else false
     */
    public static boolean isVowel(char ch) {
        return isOneOf(ch, "aeiouAEIOU");
    }
 
    /**
     * Finds the first occurrence of a vowel in a string.
     *   @param str the string to be searched
     *   @return the index where the first vowel in str occurs (-1 if no vowel)
     */
    public static int findVowel(String str)  {
        return findOneOf("aeiouAEIOU", str);
    }
    
    /**
     * Determines whether a character is contained in a string.
     *   @param ch the character to be searched for
     *   @param str the string to be searched
     *   @return true if ch is contained in str
     */
    public static boolean isOneOf(char ch, String str) {
        return str.indexOf(ch) != -1;
    }
    
    /**
     * Finds the first occurrence of a character in a string
     *   @param str the string to be searched
     *   @param seq the sequence of characters to be searched for
     *   @return the index of the first occurrence of a char from seq
     */
     public static int findOneOf(String seq, String str) {
        for (int i = 0; i < str.length(); i++) {
            if (isOneOf(str.charAt(i), seq)) {
                return i;
            }
        }
        return -1;
    }
    
    /**
     * Removes all occurrences of select letters from a string.
     *   @param str the string to be searched and modified
     *   @param seq the sequence of characters to be removed
     *   @return a copy of str with all chars from seq removed
     */
     public static String stripAllOf(String seq, String str) {
        String copy = "";
        for (int i = 0; i < str.length(); i++) {
            if (!isOneOf(str.charAt(i), seq)) {
                copy += str.charAt(i);
            }
        }
        return copy;
    }
}