/*******************************************************************************
   * SAT4J: a SATisfiability library for Java Copyright (C) 2004-2008 Daniel Le Berre
   *
   * All rights reserved. This program and the accompanying materials
   * are made available under the terms of the Eclipse Public License v1.0
   * which accompanies this distribution, and is available at
   * http://www.eclipse.org/legal/epl-v10.html
   *
   * Alternatively, the contents of this file may be used under the terms of
  * either the GNU Lesser General Public License Version 2.1 or later (the
  * "LGPL"), in which case the provisions of the LGPL are applicable instead
  * of those above. If you wish to allow use of your version of this file only
  * under the terms of the LGPL, and not to allow others to use your version of
  * this file under the terms of the EPL, indicate your decision by deleting
  * the provisions above and replace them with the notice and other provisions
  * required by the LGPL. If you do not delete the provisions above, a recipient
  * may use your version of this file under the terms of the EPL or the LGPL.
  * 
  * Based on the original MiniSat specification from:
  * 
  * An extensible SAT solver. Niklas Een and Niklas Sorensson. Proceedings of the
  * Sixth International Conference on Theory and Applications of Satisfiability
  * Testing, LNCS 2919, pp 502-518, 2003.
  *
  * See www.minisat.se for the original solver in C++.
  * 
  *******************************************************************************/
  package org.sat4j.reader;
  
  import java.io.IOException;
  import java.io.LineNumberReader;
  import java.io.PrintWriter;
  import java.io.Serializable;
  import java.util.Scanner;
  import java.util.StringTokenizer;
  
  import org.sat4j.core.VecInt;
  import org.sat4j.specs.ContradictionException;
  import org.sat4j.specs.IProblem;
  import org.sat4j.specs.ISolver;
  import org.sat4j.specs.IVecInt;
  
  /**
   * Very simple Dimacs file parser. Allow solvers to read the constraints from a
   * Dimacs formatted file. It should be used that way:
   * 
   * <pre>
   * DimacsReader solver = new DimacsReader(SolverFactory.OneSolver());
   * solver.readInstance(&quot;mybench.cnf&quot;);
   * if (solver.isSatisfiable()) {
   *     // SAT case
   * } else {
   *     // UNSAT case
   * }
   * </pre>
   * 
   * That parser is not used for efficiency reasons. It will be updated with Java
   * 1.5 scanner feature.
   * 
   * @version 1.0
   * @author dlb
   * @author or
   */
  public class DimacsReader extends Reader implements Serializable {
  
      private static final long serialVersionUID = 1L;
  
      protected int expectedNbOfConstr; // as announced on the p cnf line
  
      protected final ISolver solver;
  
      private boolean checkConstrNb = true;
  
      protected final String formatString;
  
      public DimacsReader(ISolver solver) {
          this(solver, "cnf");
      }
  
      public DimacsReader(ISolver solver, String format) {
          this.solver = solver;
          formatString = format;
      }
  
      public void disableNumberOfConstraintCheck() {
          checkConstrNb = false;
      }
  
      /**
       * Skip comments at the beginning of the input stream.
       * 
       * @param in
       *            the input stream
       * @throws IOException
       *             if an IO problem occurs.
       */
      protected void skipComments(final LineNumberReader in) throws IOException {
          int c;
  
         do {
             in.mark(4);
             c = in.read();
             if (c == 'c') {
                 in.readLine();
             } else {
                 in.reset();
             }
         } while (c == 'c');
     }
 
     /**
      * @param in
      *            the input stream
      * @throws IOException
      *             iff an IO occurs
      * @throws ParseFormatException
      *             if the input stream does not comply with the DIMACS format.
      */
     protected void readProblemLine(LineNumberReader in) throws IOException,
             ParseFormatException {
 
         String line = in.readLine();
 
         if (line == null) {
             throw new ParseFormatException(
                     "premature end of file: <p cnf ...> expected  on line "
                             + in.getLineNumber());
         }
         StringTokenizer stk = new StringTokenizer(line);
 
         if (!(stk.hasMoreTokens() && stk.nextToken().equals("p")
                 && stk.hasMoreTokens() && stk.nextToken().equals(formatString))) {
             throw new ParseFormatException(
                     "problem line expected (p cnf ...) on line "
                             + in.getLineNumber());
         }
 
         int vars;
 
         // reads the max var id
         vars = Integer.parseInt(stk.nextToken());
         assert vars > 0;
         solver.newVar(vars);
         // reads the number of clauses
         expectedNbOfConstr = Integer.parseInt(stk.nextToken());
         assert expectedNbOfConstr > 0;
         solver.setExpectedNumberOfClauses(expectedNbOfConstr);
     }
 
     /**
      * @param in
      *            the input stream
      * @throws IOException
      *             iff an IO problems occurs
      * @throws ParseFormatException
      *             if the input stream does not comply with the DIMACS format.
      * @throws ContradictionException
      *             si le probl?me est trivialement inconsistant.
      */
     protected void readConstrs(LineNumberReader in) throws IOException,
             ParseFormatException, ContradictionException {
         String line;
 
         int realNbOfConstr = 0;
 
         IVecInt literals = new VecInt();
 
         while (true) {
             line = in.readLine();
 
             if (line == null) {
                 // end of file
                 if (literals.size() > 0) {
                     // no 0 end the last clause
                     solver.addClause(literals);
                     realNbOfConstr++;
                 }
 
                 break;
             }
 
             if (line.startsWith("c ")) {
                 // ignore comment line
                 continue;
             }
             if (line.startsWith("%") && expectedNbOfConstr == realNbOfConstr) {
                 System.out
                         .println("Ignoring the rest of the file (SATLIB format");
                 break;
             }
             boolean added = handleConstr(line, literals);
             if (added) {
                 realNbOfConstr++;
             }
         }
         if (checkConstrNb && expectedNbOfConstr != realNbOfConstr) {
             throw new ParseFormatException("wrong nbclauses parameter. Found "
                     + realNbOfConstr + ", " + expectedNbOfConstr + " expected");
         }
     }
 
     protected boolean handleConstr(String line, IVecInt literals)
             throws ContradictionException {
         int lit;
         boolean added = false;
         Scanner scan;
         scan = new Scanner(line);
         while (scan.hasNext()) {
             lit = scan.nextInt();
 
             if (lit == 0) {
                 if (literals.size() > 0) {
                     solver.addClause(literals);
                     literals.clear();
                     added = true;
                 }
             } else {
                 literals.push(lit);
             }
         }
         return added;
     }
 
     @Override
     public final IProblem parseInstance(final java.io.Reader in)
             throws ParseFormatException, ContradictionException, IOException {
         return parseInstance(new LineNumberReader(in));
 
     }
 
     /**
      * @param in
      *            the input stream
      * @throws ParseFormatException
      *             if the input stream does not comply with the DIMACS format.
      * @throws ContradictionException
      *             si le probl?me est trivialement inconsitant
      */
     private IProblem parseInstance(LineNumberReader in)
             throws ParseFormatException, ContradictionException {
         solver.reset();
         try {
             skipComments(in);
             readProblemLine(in);
             readConstrs(in);
             return solver;
         } catch (IOException e) {
             throw new ParseFormatException(e);
         } catch (NumberFormatException e) {
             throw new ParseFormatException("integer value expected on line "
                     + in.getLineNumber(), e);
         }
     }
 
     @Override
     public String decode(int[] model) {
         StringBuffer stb = new StringBuffer();
         for (int i = 0; i < model.length; i++) {
             stb.append(model[i]);
             stb.append(" ");
         }
         stb.append("0");
         return stb.toString();
     }
 
     @Override
     public void decode(int[] model, PrintWriter out) {
         for (int i = 0; i < model.length; i++) {
             out.print(model[i]);
             out.print(" ");
         }
         out.print("0");
     }
 
     protected ISolver getSolver() {
         return solver;
     }
 }