/*
    * 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}.
   */
  public class ExpressionPath extends Path {
  
      private final Expression expression;
      private final Expression[] predicates;
      private boolean basicKnown;
      private boolean basic;
  
      /**
       * Constructs a new ExpressionPath.
       *
       * @param expression Expression
       * @param predicates to execute
       * @param steps      navigation
       */
      public ExpressionPath(final Expression expression, final Expression[] predicates, final Step[] steps) {
          super(steps);
          this.expression = expression;
          this.predicates = predicates;
      }
  
      @Override
      public Object compute(final EvalContext context) {
          return expressionPath(context, false);
      }
  
      /**
       * Returns true if the root expression or any of the predicates or the path steps are context dependent.
       *
       * @return boolean
       */
      @Override
      public boolean computeContextDependent() {
          if (expression.isContextDependent()) {
              return true;
          }
          if (predicates != null) {
              for (final Expression predicate : predicates) {
                  if (predicate.isContextDependent()) {
                      return true;
                  }
              }
          }
          return super.computeContextDependent();
      }
  
      @Override
      public Object computeValue(final 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(final EvalContext evalContext, final boolean firstMatch) {
          final 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)) {
             final EvalContext ctx = context;
             final 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);
     }
 
     /**
      * Gets 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;
     }
 
     /**
      * Recognized paths formatted as {@code $x[3]/foo[2]}. 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;
     }
 
     @Override
     public String toString() {
         final StringBuilder buffer = new StringBuilder();
         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 (final Expression predicate : predicates) {
                 buffer.append('[');
                 buffer.append(predicate);
                 buffer.append(']');
             }
         }
         final Step[] steps = getSteps();
         if (steps != null) {
             for (final Step step : steps) {
                 buffer.append("/");
                 buffer.append(step);
             }
         }
         return buffer.toString();
     }
 }