/*******************************************************************************
    * 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.InputStream;
  import java.io.PrintWriter;
  import java.io.Serializable;
  
  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;
  
  	/**
  	 * @since 2.1
  	 */
  	protected EfficientScanner scanner;
  
  	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.
  	 * @since 2.1
 	 */
 	protected void skipComments() throws IOException {
 		scanner.skipComments();
 	}
 
 	/**
 	 * @param in
 	 *            the input stream
 	 * @throws IOException
 	 *             iff an IO occurs
 	 * @throws ParseFormatException
 	 *             if the input stream does not comply with the DIMACS format.
 	 * @since 2.1
 	 */
 	protected void readProblemLine() throws IOException, ParseFormatException {
 
 		String line = scanner.nextLine().trim();
 
 		if (line == null) {
 			throw new ParseFormatException(
 					"premature end of file: <p cnf ...> expected");
 		}
 		String[] tokens = line.split("\\s+");
 		if (tokens.length < 4 || !"p".equals(tokens[0])
 				|| !formatString.equals(tokens[1])) {
 			throw new ParseFormatException("problem line expected (p cnf ...)");
 		}
 
 		int vars;
 
 		// reads the max var id
 		vars = Integer.parseInt(tokens[2]);
 		assert vars > 0;
 		solver.newVar(vars);
 		// reads the number of clauses
 		expectedNbOfConstr = Integer.parseInt(tokens[3]);
 		assert expectedNbOfConstr > 0;
 		solver.setExpectedNumberOfClauses(expectedNbOfConstr);
 	}
 
 	/**
 	 * @since 2.1
 	 */
 	protected IVecInt literals = new VecInt();
 
 	/**
 	 * @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.
 	 * @since 2.1
 	 */
 	protected void readConstrs() throws IOException, ParseFormatException,
 			ContradictionException {
 		int realNbOfConstr = 0;
 
 		literals.clear();
 		boolean needToContinue = true;
 
 		while (needToContinue) {
 			boolean added = false;
 			if (scanner.eof()) {
 				// end of file
 				if (literals.size() > 0) {
 					// no 0 end the last clause
 					flushConstraint();
 					added = true;
 				}
 				needToContinue = false;
 			} else {
 				if (scanner.currentChar() == 'c') {
 					// ignore comment line
 					scanner.skipRestOfLine();
 					continue;
 				}
 				if (scanner.currentChar() == '%'
 						&& expectedNbOfConstr == realNbOfConstr) {
 					if (solver.isVerbose()) {
 						System.out
 								.println("Ignoring the rest of the file (SATLIB format");
 					}
 					break;
 				}
 				added = handleLine();
 			}
 			if (added) {
 				realNbOfConstr++;
 			}
 		}
 		if (checkConstrNb && expectedNbOfConstr != realNbOfConstr) {
 			throw new ParseFormatException("wrong nbclauses parameter. Found "
 					+ realNbOfConstr + ", " + expectedNbOfConstr + " expected");
 		}
 	}
 
 	/**
 	 * 
 	 * @throws ContradictionException
 	 * @since 2.1
 	 */
 	protected void flushConstraint() throws ContradictionException {
 		try {
 			solver.addClause(literals);
 		} catch (IllegalArgumentException ex) {
 			if (isVerbose()) {
 				System.err.println("c Skipping constraint " + literals);
 			}
 		}
 	}
 
 	/**
 	 * @since 2.1
 	 */
 	protected boolean handleLine() throws ContradictionException, IOException,
 			ParseFormatException {
 		int lit;
 		boolean added = false;
 		while (!scanner.eof()) {
 			lit = scanner.nextInt();
 			if (lit == 0) {
 				if (literals.size() > 0) {
 					flushConstraint();
 					literals.clear();
 					added = true;
 				}
 				break;
 			}
 			literals.push(lit);
 		}
 		return added;
 	}
 
 	@Override
 	public IProblem parseInstance(InputStream in) throws ParseFormatException,
 			ContradictionException, IOException {
 		scanner = new EfficientScanner(in);
 		return parseInstance();
 	}
 
 	/**
 	 * @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() throws ParseFormatException,
 			ContradictionException {
 		solver.reset();
 		try {
 			skipComments();
 			readProblemLine();
 			readConstrs();
 			scanner.close();
 			return solver;
 		} catch (IOException e) {
 			throw new ParseFormatException(e);
 		} catch (NumberFormatException e) {
 			throw new ParseFormatException("integer value expected ");
 		}
 	}
 
 	@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;
 	}
 }