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

/* Java application for the purpose of illustrating how to make use
** of instances of classes that implement the Comparator and ArraySorter
** interfaces to sort an array.
*/

public class SelSortTester {

   private static String inputFileName;

   public static void main(String[] args) {  //throws FileNotFoundException {
      
      // The first command line argument is taken to be the name of the
      // file from which input is to be read.
      inputFileName = args[0];

      // Call method that reads a bunch of points into an array, sorts the
      // array with the help of a comparator based on distance-to-origin,
      // and prints the resulting array.
      readSortPrint(inputFileName, new DistToOrigComparator());

   }

   private static void readSortPrint(String fileName, 
                                     Comparator<PointIn2Space> comp) {
      Scanner input = null;

      // Establish a scanner to read data from the file whose name was given.
      try {
         input = new Scanner(new File(fileName));
      }
      catch (FileNotFoundException e) {
         e.printStackTrace();
         System.out.println("\nProgram aborting...");
         System.exit(0);
      }

      // Establish an array containing the points described in the input file
      PointIn2Space[] points = readPoints(input);

      // Display the array
      System.out.println("Array established:");
      System.out.println(Arrays.toString(points));

      // Establish an object that can sort an array into ascending order
      // in accord with the given Comparator.
      SelectionSorter sorter = new SelectionSorter(comp);

      // Sort the array
      sorter.sort(points);

      // Print the resulting array
      System.out.println("After sorting, the array contains");
      System.out.println(Arrays.toString(points));
   }

   /* Returns a new array containing the points described by the input
   ** accessible to the given scanner, which assumes that the first token
   ** is on a line by itself and indicates how many points are subsequently
   ** described.
   */
   private static PointIn2Space[] readPoints(Scanner input) {
      final int N = input.nextInt();  input.nextLine();
      PointIn2Space[] result = new PointIn2Space[N];
      for (int i=0; i != N; i++) {
         double x = input.nextDouble();
         double y = input.nextDouble();
         result[i] = new PointIn2Space(x,y);
      }
      return result;
   }
}