import textio.TextIO;

/** 
 * This program will convert measurements expressed in inches,
 * feet, yards, or miles into each of the possible units of
 * measure.  The measurement is input by the user, followed by
 * the unit of measure.  For example:  "17 feet", "1 inch",
 * "2.73 mi".  Several measurements can be combined on
 * one line of input.  For example:  "2 miles 5 yards 1 inch".
 * In this case, the measurements are combined into one total.
 * Abbreviations in, ft, yd, and mi are accepted.  Negative 
 * measurements are not allowed.
 * 
 * The program will continue to read and convert measurements
 * until the user enters an empty line.
 * 
 * This version of the program uses exception handling.
 */
public class LengthConverter3 {

    /**
     * This nested class is used to represent errors in the user's input.
     */
    static class ParseError extends Exception {
        ParseError(String message) {
            super(message);
        }
    }

    public static void main(String[] args) {

        double inches, feet, yards, miles;  // Measurement expressed in each
                                            //   possible unit of measure.

        System.out.println("Enter measurements in inches, feet, yards, or miles.");
        System.out.println("For example:  1 inch   17 feet   2.73 miles");
        System.out.println("You can use abbreviations:   in   ft  yd   mi");
        System.out.println("You can combine measurements, as in:  1 mile 270 yards 17 inches");
        System.out.println("I will convert your input into each of the four units of measure.");

        while (true) {

            /* Get the user's input, and convert it to inches. */

            System.out.println();
            System.out.println();
            System.out.println("Enter your measurement, or press return to end:");

            skipBlanks();  

            if (TextIO.peek() == '\n')  // End if there is nothing on the line.
                break;

            try {
                inches = readMeasurement();
            }
            catch (ParseError e) {
                System.out.println( "Error:  " + e.getMessage() );
                TextIO.getln();  // Discard the rest of the input line.
                continue;  // jump back to the start of the while loop
            }

            /* Convert the measurement in inches to feet, yards, and miles. */

            feet = inches / 12;
            yards = inches / 36;
            miles = inches / (12*5280);

            /* Output the measurement in terms of each unit of measure. */

            System.out.println();
            System.out.println("That's equivalent to:");
            System.out.printf("%12.5g", inches);
            System.out.println(" inches");
            System.out.printf("%12.5g", feet);
            System.out.println(" feet");
            System.out.printf("%12.5g", yards);
            System.out.println(" yards");
            System.out.printf("%12.5g", miles);
            System.out.println(" miles");

            TextIO.getln();  // Discard the rest of the input line before
                             // getting the next line.

        } // end while

        System.out.println();
        System.out.println("OK!  Bye for now.");

    } // end main()


    /**
     * Reads past any blanks and tabs in the input.
     * Postcondition:  The next character in the input is an
     *                 end-of-line or a non-blank character.
     */
    static void skipBlanks() {
        char ch;
        ch = TextIO.peek();
        while (ch == ' ' || ch == '\t') {
            ch = TextIO.getAnyChar();
            ch = TextIO.peek();
        }
    }


    /**
     * Reads the user's input measurement from one line of input.
     * Precondition:  The input line is not empty.
     * Postcondition:  If the user's input is legal, the measurement
     *                 is converted to inches and returned. 
     * @throws ParseError if the user's input is not legal.
     */
    static double readMeasurement() throws ParseError {

        double inches;  // Total number of inches in user's measurement.

        double measurement;  // One measurement, such as the 12 in "12 miles"
        String units;   // The units specified for the measurement, such as "miles"

        char ch;  // Used to peek at next character in the user's input.

        inches = 0;  // No inches have yet been read.

        skipBlanks();
        ch = TextIO.peek();

        /* As long as there is more input on the line, read a measurement and
             add the equivalent number of inches to the variable, inches.  If an
             error is detected during the loop, end the subroutine immediately
             by throwing a ParseError. */

        while (ch != '\n') {

            /* Get the next measurement and the units.  Before reading
                 anything, make sure that a legal value is there to read. */

            if ( ! Character.isDigit(ch) ) {
                throw new ParseError("Expected to find a number, but found " + ch);
            }
            measurement = TextIO.getDouble();
            skipBlanks();
            if (TextIO.peek() == '\n') {
                throw new ParseError("Missing unit of measure at end of line.");
            }
            units = TextIO.getWord();
            units = units.toLowerCase();

            /* Convert the measurement to inches and add it to the total. */

            if (units.equals("inch") || units.equals("inches") || units.equals("in"))
                inches += measurement;
            else if (units.equals("foot") || units.equals("feet") || units.equals("ft"))
                inches += measurement * 12;
            else if (units.equals("yard") || units.equals("yards") || units.equals("yd"))
                inches += measurement * 36;
            else if (units.equals("mile") || units.equals("miles") || units.equals("mi"))
                inches += measurement * 12 * 5280;
            else {
                throw new ParseError("\"" + units + "\" is not a legal unit of measure.");
            }

            /* Look ahead to see whether the next thing on the line is the end-of-line. */

            skipBlanks();
            ch = TextIO.peek();

        }  // end while

        return inches;

    } // end readMeasurement()


} // end class LengthConverter3