/*******************************************************************************
   * 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.
  *******************************************************************************/
  package org.sat4j.csp;
  
  import java.io.FileNotFoundException;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.net.URL;
  import java.util.HashMap;
  import java.util.Map;
  
  import org.mozilla.javascript.Context;
  import org.mozilla.javascript.Script;
  import org.mozilla.javascript.Scriptable;
  import org.sat4j.core.Vec;
  import org.sat4j.csp.encodings.BinarySupportEncoding;
  import org.sat4j.csp.encodings.DirectEncoding;
  import org.sat4j.specs.ContradictionException;
  import org.sat4j.specs.ISolver;
  import org.sat4j.specs.IVec;
  
  /**
   * A predicate is a formula given in intension.
   * 
   * @author daniel
   */
  public class Predicate implements Clausifiable {
  
      private String expr;
  
      private Encoding encoding;
  
      private final IVec<String> variables = new Vec<String>();
  
      private static Context cx;
  
      private static Scriptable scope;
  
      static {
          cx = Context.enter(); 
          scope = cx.initStandardObjects();
          try {
              URL url = Predicate.class.getResource("predefinedfunctions.js");
              cx.evaluateReader(scope, new InputStreamReader(url.openStream()),
                      "predefinedfunctions.js", 1, null);
  
          } catch (FileNotFoundException e) {
              e.printStackTrace();
          } catch (IOException e) {
              e.printStackTrace();
          }
      }
  
      public Predicate() {
      }
  
      public void setExpression(String expr) {
          this.expr = expr.replaceAll("if\\(", "ite(");
      }
  
      public void addVariable(String name) {
          variables.push(name);
      }
  
      private boolean evaluate(int[] values) {
          assert values.length == variables.size();
          for (int i = 0; i < variables.size(); i++) {
              scope.put(variables.get(i), scope, values[i]);
          }
          Object result = myscript.exec(cx, scope);
          return Context.toBoolean(result);
      }
  
      public void toClause(ISolver solver, IVec<Var> vscope, IVec<Evaluable> vars)
              throws ContradictionException {
          if (myscript == null) {
              myscript = cx.compileString(expr, "rhino.log", 1, null);
          }
          if (vscope.size() == 2) {
              encoding = BinarySupportEncoding.instance();
          } else {
              encoding = DirectEncoding.instance();
          }
         encoding.onInit(solver, vscope);
         int[] tuple = new int[vars.size()];
         valuemapping.clear();
         find(tuple, 0, vscope, vars, solver);
         encoding.onFinish(solver, vscope);
     }
 
     private final Map<Evaluable, Integer> valuemapping = new HashMap<Evaluable, Integer>();
 
     private Script myscript;
 
     private void find(int[] tuple, int n, IVec<Var> theScope,
             IVec<Evaluable> vars, ISolver solver) throws ContradictionException {
         if (valuemapping.size() == theScope.size()) {
             for (int i = 0; i < tuple.length; i++) {
                 Evaluable ev = vars.get(i);
                 Integer value = valuemapping.get(ev);
                 if (value == null) {
                     tuple[i] = ev.domain().get(0);
                 } else {
                     tuple[i] = value;
                 }
             }
             if (evaluate(tuple)) {
                 encoding.onSupport(solver, theScope, valuemapping);
             } else {
                 encoding.onNogood(solver, theScope, valuemapping);
             }
         } else {
             Var var = theScope.get(n);
             Domain domain = var.domain();
             for (int i = 0; i < domain.size(); i++) {
                 valuemapping.put(var, domain.get(i));
                 find(tuple, n + 1, theScope, vars, solver);
             }
             valuemapping.remove(var);
         }
     }
 }