/** 
 * 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) {
            TextIO.putln( "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 LengthConverter