// POINTREADER.JAVA
// Read a series of points from a file.  The first line of the file gives
// the number of points, while each subsequent line contains
// X- and Y-coordinates for one point.
//
import java.io.*;

public class PointReader {
    // Extract an integer from a string, which may contain whitespace
    static int parseInteger(String s)
    {
	int x = 0;
	
	try {
	    x = Integer.parseInt(s.trim());
	} catch (NumberFormatException e) {
	    System.out.println("Cannot parse integer from string \"" +
			       s + "\"\n" + e);
	}
	
	return x;
    }
    
    // Extract a pair of integers from a string, which may contain whitespace.
    // Treat the pair as x,y coordinates for a point.
    static XYPoint parsePoint(String s)
    {
	int x, y;
	
	s = s.trim().replace('\t', ' ');
	int firstSpaceIdx = s.indexOf(' ');
	String sx = s.substring(0, firstSpaceIdx);
	String sy = s.substring(firstSpaceIdx).trim();
	
	x = parseInteger(sx);
	y = parseInteger(sy);
	
	return new XYPoint(x,y);
    }
    
    // Read a collection of points from a file.
    public static XYPoint [] readXYPoints(String fileName)
    {
        XYPoint points [] = null;
	BufferedReader r;
	int nPoints;
	
        // Create a reader for the file
        //
        try {
            InputStream is = new FileInputStream(fileName);
            r = new BufferedReader(new InputStreamReader(is));
        }
        catch (IOException e) {
            System.out.println("IOException while opening " +
                               fileName + "\n" + e);
            return points;
        }
	
	try {
	    String nextline = r.readLine();
	    if (nextline == null) // end of file
		{
		    System.out.println("Error: point file " +
				       fileName + " is empty!\n");
		    return points;
		}
	    
	    nPoints = parseInteger(nextline);
		
	} catch (IOException e) {
            System.out.println("IOException while getting # of points from " +
                               fileName + "\n" + e);
            return points;
        }
	    
	
	points = new XYPoint [nPoints];
	
	for (int j = 0; j < nPoints; j++)
	    {
		try {
		    String nextline = r.readLine();
		    if (nextline == null) // end of file
			{
			    System.out.println("Error: point file ends " +
					       "after " + j + " points\n" +
					       " (expected " + nPoints + 
					       ")\n");
			    return points;
			}
		    
		    points[j] = parsePoint(nextline);
		    
		} catch (IOException e) {
		    System.out.println("IOException while reading line " +
				       j+2 + " from " + fileName + "\n" + e);
		    return points;
		}
	    }
	
	return points;
    }
}