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

/* Java application for testing instances of the SubSeqSumSolver class.
**
** Author: R. McCloskey
** Date: November 2022
*/

public class SubSeqSumApp {

   public static void main(String[] args) throws FileNotFoundException {
      // From the file whose name was provided via command line argument,
      // read the elements of the sequence that will be the subject of
      // subsequent queries and place them into an an array.
      int[] ary = readArray(args[0]);

      // Display the array and create a new SubSeqSumSolver object having 
      // it as its "resident" array.
      System.out.printf("Array is %s\n", Arrays.toString(ary));
      SubSeqSumSolver ssss = new SubSeqSumSolver(ary, System.out);

      // Read inputs from the user, each of which is a target value to test.
      // An input of -1 signals the desire to quit.  An input less than -1
      // is a request to display the resident array. 
      // For each target value entered, call the observer methods of the
      // SubSeqSumSolver object and report the results.
      Scanner input = new Scanner(System.in);
      boolean keepGoing = true;
      while (keepGoing) {
         System.out.print("\nEnter target value (-1 to quit): ");
         int target = input.nextInt();
         if (target == -1)
            { keepGoing = false; }
         else if (target < 0) {
            System.out.println(Arrays.toString(ary));
         }
         else {
            testExists(ssss, target);
            testNumberOf(ssss, target);
            testEnumerate(ssss, target);
         }
      }
      System.out.println("Goodbye.");
   }

   /* Invokes the exists() method on the given SubSeqSumSolver object to 
   ** determine whether there are any ways to choose elements from its
   ** resident array to achieve a sum equal to 'target'.
   */
   private static void testExists(SubSeqSumSolver solver, int target) {
      System.out.printf("\nexists(%d) yields %b\n", 
                        target, solver.exists(target));
   }

   /* Invokes the numberOf() method on the given SubSeqSumSolver object to 
   ** determine how many ways there are to choose elements from its resident
   ** array to achieve a sum equal to 'target'.
   */
   private static void testNumberOf(SubSeqSumSolver solver, int target) {
      System.out.printf("\nnumberOf(%d) yields %d\n", 
                        target, solver.numberOf(target));
   }

   /* Invokes the enumerate() method on the given SubSeqSumSolver object to 
   ** print (a String representing) every one of the ways to choose elements
   ** from its resident array to achieve a sum equal to 'target'.
   */
   private static void testEnumerate(SubSeqSumSolver solver, int target) {
      System.out.printf("\nenumerate(%d) yields:\n", target);
      solver.enumerate(target);
   }


   /* Returns a new array of type int[] containing the sequence of integers
   ** described in the file with the given name.  The assumed format of data
   ** in that file is exemplified by  "7 4 6 1 34 23 5 2".
   ** The first number, n, indicates the length of the sequence.
   ** The n numbers that follow are the elements in the sequence.
   */
   private static int[] readArray(String fileName) throws FileNotFoundException {
      Scanner input = new Scanner(new File(fileName));

      // the first input is the length of the sequence/array.
      final int N = input.nextInt(); 
      int[] result = new int[N];

      // The remaining inputs are the elements of the sequence.
      for (int i=0; i != N; i++) {
         result[i] = input.nextInt();
      }

      return result;
   }

}