/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.jxpath.ri.compiler;
  
  import org.apache.commons.jxpath.ri.EvalContext;
  import org.apache.commons.jxpath.ri.axes.InitialContext;
  import org.apache.commons.jxpath.ri.axes.NodeSetContext;
  import org.apache.commons.jxpath.ri.axes.PredicateContext;
  import org.apache.commons.jxpath.ri.axes.SimplePathInterpreter;
  import org.apache.commons.jxpath.ri.axes.UnionContext;
  import org.apache.commons.jxpath.ri.model.NodePointer;
  
  /**
   * An  element of the parse tree that represents an expression path, which is a
   * path that starts with an expression like a function call: <code>getFoo(.)
   * /bar</code>.
   *
   * @author Dmitri Plotnikov
   * @version $Revision: 652845 $ $Date: 2008-05-02 19:46:46 +0200 (Fr, 02 Mai 2008) $
   */
  public class ExpressionPath extends Path {
  
      private Expression expression;
      private Expression[] predicates;
  
      private boolean basicKnown = false;
      private boolean basic;
  
      /**
       * Create a new ExpressionPath.
       * @param expression Expression
       * @param predicates to execute
       * @param steps navigation
       */
      public ExpressionPath(Expression expression, Expression[] predicates,
              Step[] steps) {
          super(steps);
          this.expression = expression;
          this.predicates = predicates;
      }
  
      /**
       * Get the expression.
       * @return Expression
       */
      public Expression getExpression() {
          return expression;
      }
  
      /**
       * Predicates are the expressions in brackets that may follow
       * the root expression of the path.
       * @return Expression[]
       */
      public Expression[] getPredicates() {
          return predicates;
      }
  
      /**
       * Returns true if the root expression or any of the
       * predicates or the path steps are context dependent.
       * @return boolean
       */
      public boolean computeContextDependent() {
          if (expression.isContextDependent()) {
              return true;
          }
          if (predicates != null) {
              for (int i = 0; i < predicates.length; i++) {
                  if (predicates[i].isContextDependent()) {
                      return true;
                  }
              }
          }
          return super.computeContextDependent();
      }
  
      /**
       * Recognized paths formatted as <code>$x[3]/foo[2]</code>.  The
       * evaluation of such "simple" paths is optimized and streamlined.
       * @return boolean
       */
      public synchronized boolean isSimpleExpressionPath() {
          if (!basicKnown) {
              basicKnown = true;
             basic = isSimplePath() && areBasicPredicates(getPredicates());
         }
         return basic;
     }
 
     public String toString() {
         StringBuffer buffer = new StringBuffer();
         if (expression instanceof CoreOperation
             || expression instanceof ExpressionPath
             || expression instanceof LocationPath) {
             buffer.append('(');
             buffer.append(expression);
             buffer.append(')');
         }
         else {
             buffer.append(expression);
         }
         if (predicates != null) {
             for (int i = 0; i < predicates.length; i++) {
                 buffer.append('[');
                 buffer.append(predicates[i]);
                 buffer.append(']');
             }
         }
 
         Step[] steps = getSteps();
         if (steps != null) {
             for (int i = 0; i < steps.length; i++) {
                 buffer.append("/");
                 buffer.append(steps[i]);
             }
         }
         return buffer.toString();
     }
 
     public Object compute(EvalContext context) {
         return expressionPath(context, false);
     }
 
     public Object computeValue(EvalContext context) {
         return expressionPath(context, true);
     }
 
     /**
      * Walks an expression path (a path that starts with an expression)
      * @param evalContext base context
      * @param firstMatch whether to return the first match found
      * @return Object found
      */
     protected Object expressionPath(EvalContext evalContext, boolean firstMatch) {
         Object value = expression.compute(evalContext);
         EvalContext context;
         if (value instanceof InitialContext) {
             // This is an optimization. We can avoid iterating through a
             // collection if the context bean is in fact one.
             context = (InitialContext) value;
         }
         else if (value instanceof EvalContext) {
             // UnionContext will collect all values from the "value" context
             // and treat the whole thing as a big collection.
             context =
                 new UnionContext(
                     evalContext,
                     new EvalContext[] {(EvalContext) value });
         }
         else {
             context = evalContext.getRootContext().getConstantContext(value);
         }
 
         if (firstMatch
             && isSimpleExpressionPath()
             && !(context instanceof NodeSetContext)) {
             EvalContext ctx = context;
             NodePointer ptr = (NodePointer) ctx.getSingleNodePointer();
             if (ptr != null
                 && (ptr.getIndex() == NodePointer.WHOLE_COLLECTION
                     || predicates == null
                     || predicates.length == 0)) {
                 return SimplePathInterpreter.interpretSimpleExpressionPath(
                     evalContext,
                     ptr,
                     predicates,
                     getSteps());
             }
         }
         if (predicates != null) {
             for (int j = 0; j < predicates.length; j++) {
                 if (j != 0) {
                     context = new UnionContext(context, new EvalContext[]{context});
                 }
                 context = new PredicateContext(context, predicates[j]);
             }
         }
         return firstMatch ? (Object) getSingleNodePointerForSteps(context)
                 : evalSteps(context);
     }
 }