import java.text.DecimalFormat;
import java.util.Scanner;

/* For the purpose of testing the Polynomial class.
**
** Author: R. McCloskey (last modified October 2022)
*/

public class PolynomialTester {

   private static Scanner keyboard = new Scanner(System.in);

   // for formatting real numbers when they are displayed
   private static DecimalFormat df = new DecimalFormat("#####0.0########");


   public static void main(String[] args) {
      System.out.println("Welcome to the Polynomial Tester Program!");
      boolean keepGoing = true;
      while (keepGoing) {
         System.out.println();
         System.out.println("1: Test Evaluate");
         System.out.println("2: Test Root Find");
         System.out.println("3: Test Arithmetic");
         System.out.println("4: Quit");
         System.out.println();

         System.out.print("Enter choice: ");
         String responseStr = keyboard.nextLine().trim();
         int response;
         try {
            response = Integer.parseInt(responseStr);
         }
         catch (Exception e) {
            response = -1;
         }
      
         if (response == 1) { 
            try { testValueAt(); }
            catch (Exception e) { e.printStackTrace(System.out); }
         }
         else if (response == 2) { 
            try { testRootFind(); }
            catch (Exception e) { e.printStackTrace(System.out); }
         }
         else if (response == 3) { 
            try { testArithmetic(); }
            catch (Exception e) { e.printStackTrace(System.out); }
         }
         else if (response == 4) { keepGoing = false; }
         else { System.out.println("Invalid response, moron!"); }
      }
      System.out.println("Goodbye");
   }


   /* Tests the methods that do polynomial arithmetic: sum(), difference(), 
   ** product(). 
   */
   private static void testArithmetic() {
      // Create polynomial p.
      Polynomial p = makePoly("p");

      // Display p (which tests the toString() method).
      System.out.println("p, of degree " + p.degreeOf() + ", is " + p);

      System.out.println();

      // Now create polynomial q.
      Polynomial q = makePoly("q");

      // Display q (which tests the toString() method).
      System.out.println("q, of degree " + q.degreeOf() + ", is " + q);

      // Make clones of p and q.
      Polynomial pClone = p.clone();
      Polynomial qClone = q.clone();

      // Compute and display the sum, difference, and product of p and q, and
      // each time check to see that neither p's nor q's state has changed.

      System.out.println();

      Polynomial sumPQ = p.sum(q);
      System.out.println("p+q is " + sumPQ);

      checkEquals(p, pClone, "p", "pClone");
      checkEquals(q, qClone, "q", "qClone");

      Polynomial diffPQ = p.difference(q);
      System.out.println("p-q is " + diffPQ);

      checkEquals(p, pClone, "p", "pClone");
      checkEquals(q, qClone, "q", "qClone");

      Polynomial prodPQ = p.product(q);
      System.out.println("p*q is " + prodPQ);

      checkEquals(p, pClone, "p", "pClone");
      checkEquals(q, qClone, "q", "qClone");

      System.out.println();
   }


   /* Tests the valueAt() method.
   */
   private static void testValueAt() {
      Polynomial p = makePoly("p");
      boolean keepGoing = true;
      while (keepGoing) {
         System.out.println();
         System.out.println("Polynomial p = " + p);
         System.out.print("Enter value at which to evaluate p " +
                          "(empty string to exit): ");
         String line = keyboard.nextLine().trim();
         if (line.length() == 0) {
            keepGoing = false;
         }
         else {
            double x = Double.parseDouble(line);
            double pAtX = p.valueAt(x);
            System.out.println("p(" + df.format(x) + ") = " + df.format(pAtX));
         }
      }
   }


   /* Tests the rootOf() method.
   */
   private static void testRootFind() {
      Polynomial p = makePoly("p");

      boolean keepGoing = true;
      while (keepGoing) {
         System.out.println();
         System.out.println("Polynomial p = " + p);
         System.out.print("Enter endpoints of interval " +
                          "in which to search for a root " +
                          "(empty string to exit): ");
         String response = keyboard.nextLine().trim();
         if (response.length() == 0) {
            keepGoing = false;
         } 
         else {
            Scanner s = new Scanner(response);
            double xLow = s.nextDouble();
            double xHigh = s.nextDouble();
            double eps = 0.000005;  // for epsilon

            try {
               // Search for root and display result.
               double z = p.rootOf(xLow, xHigh, eps);
               System.out.print("Root found at z = " + df.format(z));
               double pAtZ = p.valueAt(z);
               System.out.println("; p(z) = " + df.format(pAtZ));
               if (Math.abs(pAtZ) > 0.0005) {
                  System.out.println("WARNING: p(z) seems too far " + 
                                     "from zero for z to be a root");
               }
            }
            catch (Exception e) {
               e.printStackTrace(System.out);
            }
         }
      }
   }


   /* If the two given polynomials (s and t) are not equal, displays an
   *  error message indicating that the polynomials with the given names
   *  (sName and tName) are not equal.  Otherwise does nothing.
   */
   private static void checkEquals(Polynomial s, Polynomial t, 
                                   String sName, String tName) {
      if (!s.equals(t)) {
         System.out.println("ERROR: polynomial " + sName + 
                            " is not equal to " + tName);
      }
   }

   /* Makes a polynomial corresponding to the coefficients entered at the
   *  keyboard in response to a prompt.
   */
   private static Polynomial makePoly(String name)
   {
      System.out.print("Enter the coefficients for polynomial " + name + ": ");
      return new Polynomial(getCoeffs());
   }

   /* Reads a line of text entered at the keyboard that is expected to be
   ** a sequence of integers; returns an array containing those integers.
   */
   private static int[] getCoeffs() {
      String line = keyboard.nextLine();
      String[] tokens = line.split(" +");
      int[] result = new int[tokens.length];
      for (int i=0; i != result.length; i++) { 
         result[i] = Integer.parseInt(tokens[i]);
      }
      return result;
   }

}