import java.io.*;
import java.util.*;

/**
 * FileManager is a simple class designed to read
 * files formatted for the SAT1 program.  The format
 * of the file must comply to these rules:<br><br>
 * 1) comments start at the beginning of the file only
 *    and are denoted by a 'c'.<br><br>
 * 2) there may be zero or more lines of comments followed
 *    immediately by the line p cnf num_vars num_clauses
 *    where num_vars and num_clauses are integers and
 *    match the correct number of variables and clauses
 *    appearing in the formula file.<br><br>
 * 3) the remainder of the file is comprised of num_clauses
 *    number of lines containing only the numbers from 1-num_vars,
 *    that correspond to their correct boolean variable, and their
 *    negatives (to negate the boolean variables).  Every line ends
 *    with the number 0 so the FileManager will know that the clause
 *    has been completely read.<br><br>
 *
 * To use this class, prepFile() must be called first so the FileManager
 * will be able to access the appropriate file.  The parse() method will
 * return the formula contained in the file as a byte matrix.
 * 
 * @author Andrew J. Fabian
 * @version 01/31/07
 */
public class FileManager
{
  private Scanner reader;

  /**
   * Initialize the Scanner to read from the appropriate file.
   *
   * @param filename The name of the file to be accessed.
   * @return true if the load was successful.
   */
  public boolean prepFile(String filename)
  {
    boolean success = true;
    try
    {
      reader = new Scanner(new File(filename));
    }
    catch(FileNotFoundException fnfe)
    {
      success = false;
    }
    return success;
  }

  /**
   * This method must be called after prepFile()
   * has been successful.  This method will parse
   * the file as described in the FileManager class
   * javadoc. It will then return a byte matrix
   * representation of the SAT formula contained
   * in the file.
   *
   * @return a byte matrix representation of the formula
   * @throws IOException if the file is improperly formatted
   */
  public byte[][] parse() throws IOException
  {
    int x, y; //x=num of variables, y=num of clauses
    byte[][] formula = null;
    try
    {
      while(reader.next().equals("c")) //skip comments
        reader.nextLine();
      reader.next(); //skip to parameters
      x = reader.nextInt(); //read number of variables
      y = reader.nextInt(); //read number of clauses

      //initialize formula byte matrix
      formula = new byte[x][y];
      for(int i=0; i<x; i++)
        for(int j=0; j<y; j++)
          formula[i][j] = 0;

      //read formula into byte matrix
      for(int i=0; i<y; i++)
      {
        int element = reader.nextInt();
        while(element != 0)
        {
          if(element < 0)
          {
            //True or False is always True, so the
            //variable does not matter in this case.
            if(formula[Math.abs(element)-1][i] == 1)
              formula[Math.abs(element)-1][i] = 0;
            else
              formula[Math.abs(element)-1][i] = -1;
          }
          if(element > 0)
          {
            if(formula[element-1][i] == -1)
              formula[Math.abs(element)-1][i] = 0;
            else
              formula[element-1][i] = 1;
          }
          element = reader.nextInt();
        }
      }
    }
    catch(InputMismatchException ime)
    {
      throw new IOException("Bad input file format!");
    }
    catch(NoSuchElementException nsee)
    {
      throw new IOException("Bad input file format!");
    }
    return formula;
  }
}