/** 
 * This class contains static methods used to anglicize integers in the 
 * range 1..999,999. Method anglicize contains the solution.
 * 
 * This is great class to see how preconditions work.
 */
public class Anglicize {
    
    /**
     * Returns: English equivalent of n.
     * Precondition: 0 < n < 1,000,000.
     * Examples:
     * 		3:      "three"
     * 		45:     "forty five"
     * 		100:    "one hundred"
     * 		127:    "one hunded twenty seven"
     * 		1001:   "one thousand one"
     * 		999099: "nine hundred ninety thousand ninety nine
     */
    public static String anglicize(int n) {
        if (n < 1000) {
            return anglicize1000(n) ;
        }
        
        // n >= 1000
        return anglicize1000(n/1000) + " thousand"+ 
            (n % 1000 == 0 ? "" : " " + anglicize1000(n % 1000));
    } 

    /** 
     * Yields: English equiv of n.
     * Precondition: n in 1..999 
     */
    public static String anglicize1000(int n) {
        if (n < 20) {
            return anglicize1to19(n);
        }
        
        // n >= 20
        if (n < 100) {
            return anglicize20to99(n) ;
        }
        
        // n >= 100
        return anglicize100to999(n) ;
    } 
        
    /** 
     * Returns: English equiv of n.
     * Precondition: n in 1..19 
     */
    public static String anglicize1to19(int n) {
        if (n == 1) { return "one";   }
        if (n == 2) { return "two";   }
        if (n == 3) { return "three"; }
        if (n == 4) { return "four";  }
        if (n == 5) { return "five";  }
        if (n == 6) { return "six";   }
        if (n == 7) { return "seven"; }
        if (n == 8) { return "eight"; }
        if (n == 9) { return "nine";  }
        if (n == 10) { return "ten";  }
        if (n == 11) { return "eleven";   }
        if (n == 12) { return "twelve";   }
        if (n == 13) { return "thirteen"; }
        if (n == 14) { return "fourteen"; }
        if (n == 15) { return "fifteen";  }
        if (n == 16) { return "sixteen";  }
        if (n == 17) { return "seventeen";}
        if (n == 18) { return "eighteen"; }
        return "nineteen";
    }
    
    /** 
     * Returns: English equiv of n.
     * Precondition: n in 20..99 
     */
    public static String anglicize20to99(int n) {
        return tens(n/10) + (n % 10 == 0 ? "" : " " +  anglicize1to19(n % 10));
    }
    
    /** 
     * Returns: English equiv of n.
     * Precondition: n in 100..999
     */
    public static String anglicize100to999(int n) {
        // Anglicize the first three digits
        int hundreds = n % 100;
        String suffix = "";
        if (hundreds > 0 && hundreds < 20) {
            suffix = " "+anglicize1to19(hundreds);
        } 
        if (hundreds > 20) {
            suffix = " "+anglicize20to99(hundreds);                
        }
        
        return anglicize1to19(n/100) + " hundred" + suffix;
    }
    
    /** 
     * Returns: tens-word for n 
     * Precondition: n in 2..9 
     */
    public static String tens(int n) {
        if (n == 2) { return "twenty"; }
        if (n == 3) { return "thirty"; }
        if (n == 4) { return "forty";  }
        if (n == 5) { return "fifty";  }
        if (n == 6) { return "sixty";  }
        if (n == 7) { return "seventy";}
        if (n == 8) { return "eighty"; }
        return "ninety";  
    }
    
}