/* ComplexNumTester.java
** 
** Author: R. McCloskey
** Date: Feb. 2022
** Adapted from Fraction2Tester 
**
** Java application that is for the purpose of testing the ComplexNumber class.
** An input line can have any of eight forms, as exemplified by the following:
**
** Form 1: Q          (quit: terminates execution)
** Form 2: H          (help: displays examples of commands)
** Form 3: C          (displays the "current" complex number)
** Form 4: 3.2 8.7    (sets the current complex number to 3.2 + 8.7i) 
** Form 5: + 5 9      (adds 5 + 9i to the current complex number)
** Form 6: - 13 4     (subtracts 13 + 4i from the current complex number)
** Form 7: * 2 -7     (multiplies the current complex number by 2 - 7i)
** Form 8: / 1 3      (divides the current complex number by 1 + 3i)
**
** That is, an input of 'Q' (or 'q') causes the program to terminate,
** 'C' (or 'c') causes the current complex number to be displayed,
** 'H' (or 'h') causes example commands to be displayed,
** a pair (a,b) of numbers results in the "current" complex number being
** set to a + bi.
** a pair (a,b) of numbers preceded by an operator (any of +, -, *, or /) 
** results in the current complex number being modified in the specified 
** way (using a mutator method) and its updated value displayed.
*/

import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;

public class ComplexNumTester {

   private static ComplexNumber x;  // the "current" complex number

   public static void main(String[] args) throws FileNotFoundException {
      String QUIT = "Q";
      String HELP = "H";
      String CURRENT  = "C";

      Scanner input; // for reading input data
      boolean echo;  // true iff inputs are to be printed

      if (args.length == 0) {  // no command line arg, so input is from keyboard
         echo = false;
         input = new Scanner(System.in); 
      }
      else {  // args[0] is name of input file
         echo = true;
         input = new Scanner(new File(args[0]));
      }

      println("Welcome to the Complex Number Tester Program.");

      // initialize current complex number to 0 + 0i
      x = new ComplexNumber();

      boolean keepGoing = true;
      while (keepGoing) {
         System.out.print("\n> ");
         String line = input.nextLine().trim();
         if (echo) { println(line); }

         if (line.length() == 0) {
            // ignore a blank line
         }
         else if (line.toUpperCase().equals(QUIT)) {
            keepGoing = false;
         }
         else if (line.toUpperCase().equals(HELP)) {
            printHelp();
         }
         else if (line.toUpperCase().equals(CURRENT)) {
            println(x.toString());
         }
         else {  // carry out the command
            try {
               doCommand(line);
            }
            catch (Exception e) {
               e.printStackTrace(System.out);
            }
         }
      }
      println("Goodbye.");
   }


   /* Carries out the specified command.
   */
   private static void doCommand(String command) {

      String[] tokens = command.split("\\s+");
      if (tokens.length == 1  ||  tokens.length > 3) {
         println("Ignoring unknown command");
      }
      else if (tokens.length == 2) {  
          // Command should be a pair (a,b) of numbers. 
          // Set x to a + bi.
          double a = Double.parseDouble(tokens[0]);
          double b = Double.parseDouble(tokens[1]);
          x = new ComplexNumber(a, b);
          println(x.toString());
      }
      else {    // tokens.length == 3
         // tokens[0] should be an operator
         char operator = tokens[0].charAt(0);

         // tokens[1] and tokens[2] should be a pair (a,b) of numbers 
         // describing complex number a + bi
         double a = Double.parseDouble(tokens[1]);
         double b = Double.parseDouble(tokens[2]);
         ComplexNumber y = new ComplexNumber(a,b);

         // Set x's new value to x op y by calling appropriate mutator method 
         applyMutator(operator, x, y);
         println(x.toString());
      }
   }

   // Symbolic constants used in the following methods.
   // -------------------------------------------------
   private static final char ADD_OP = '+';
   private static final char SUBTRACT_OP = '-';
   private static final char MULTIPLY_OP = '*';
   private static final char DIVIDE_OP = '/';

   /* Applies to one given complex number the mutator method indicated by
   ** the given operator, passing the other given complex number as the 
   ** argument to that method.
   */
   private static void applyMutator(char operator, 
                                    ComplexNumber left, 
                                    ComplexNumber right) {

      if (operator == ADD_OP)           { left.addTo(right); }
      else if (operator == SUBTRACT_OP) { left.subtractFrom(right); }
      else if (operator == MULTIPLY_OP) { left.multiplyBy(right); }
      else if (operator == DIVIDE_OP)   { left.divideBy(right); }
      else { 
         throw new IllegalArgumentException(operator + " is invalid operator");
      }
   }


   /* Prints an example of each kind of command.
   */
   private static void printHelp() {
      println("Examples of commands:");
      println("Q        (quit)");
      println("H        (print this help info)");
      println("C        (print current complex number)");
      println("4.5 -2.8 (set current complex number to 4.5 - 2.8i)");
      println("+ 1 5    (add 1 + 5i to current complex number)");
      println("- 7 4    (subtract 7 + 4i from current complex number)");
      println("* 2 9    (multiply current complex number by 2 + 9i)");
      println("/ 11 -4  (divide current complex number by 11 - 4i)");
   }

   /* Surrogate for System.out.println().
   */
   private static void println(String s) { System.out.println(s); }

}