/*
    * 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.jexl3.internal;
  
  import java.util.Collections;
  import java.util.EnumSet;
  import java.util.Set;
  import java.util.function.Consumer;
  
  import org.apache.commons.jexl3.JexlArithmetic;
  import org.apache.commons.jexl3.JexlCache;
  import org.apache.commons.jexl3.JexlEngine;
  import org.apache.commons.jexl3.JexlException;
  import org.apache.commons.jexl3.JexlOperator;
  import org.apache.commons.jexl3.internal.introspection.MethodExecutor;
  import org.apache.commons.jexl3.internal.introspection.MethodKey;
  import org.apache.commons.jexl3.introspection.JexlMethod;
  import org.apache.commons.jexl3.introspection.JexlUberspect;
  import org.apache.commons.jexl3.parser.JexlNode;
  
  /**
   * Helper class to deal with operator overloading and specifics.
   * @since 3.0
   */
  public final class Operator implements JexlOperator.Uberspect {
      private static final String METHOD_IS_EMPTY = "isEmpty";
      private static final String METHOD_SIZE = "size";
      private static final String METHOD_CONTAINS = "contains";
      private static final String METHOD_STARTS_WITH = "startsWith";
      private static final String METHOD_ENDS_WITH = "endsWith";
  
      /**
       * The comparison operators.
       * <p>Used to determine if a compare method overload might be used.</p>
       */
      private static final Set<JexlOperator> CMP_OPS =
              EnumSet.of(JexlOperator.GT, JexlOperator.LT, JexlOperator.EQ, JexlOperator.GTE, JexlOperator.LTE);
  
      /**
       * The postfix operators.
       * <p>Used to determine the returned value in assignment.</p>
       */
      private static final Set<JexlOperator> POSTFIX_OPS =
              EnumSet.of(JexlOperator.GET_AND_INCREMENT, JexlOperator.GET_AND_DECREMENT);
  
      /** The uberspect. */
      private final JexlUberspect uberspect;
      /** The arithmetic instance being analyzed. */
      private final JexlArithmetic arithmetic;
      /** The set of overloaded operators. */
      private final Set<JexlOperator> overloads;
      /** The delegate if built as a 3.4 legacy. */
      private final JexlArithmetic.Uberspect delegate;
      /** Caching state: -1 unknown, 0 false, 1 true. */
      private volatile int caching = -1;
  
      /**
       * Creates an instance.
       * <p>Mostly used as a compatibility measure by delegating instead of extending.</p>
       *
       * @param theUberspect  the uberspect instance
       * @param theArithmetic the arithmetic instance used to delegate operator overloads
       */
      public Operator(final JexlUberspect theUberspect, final JexlArithmetic theArithmetic) {
          this.uberspect = theUberspect;
          this.arithmetic = theArithmetic;
          this.overloads = Collections.emptySet();
          this.delegate = theUberspect.getArithmetic(theArithmetic);
      }
  
      /**
       * Creates an instance.
       * @param theUberspect the uberspect instance
       * @param theArithmetic the arithmetic instance
       * @param theOverloads  the overloaded operators
       */
      public Operator(final JexlUberspect theUberspect,
                      final JexlArithmetic theArithmetic,
                      final Set<JexlOperator> theOverloads) {
          this(theUberspect, theArithmetic, theOverloads, -1);
      }
  
      /**
       * Creates an instance.
       * @param theUberspect the uberspect instance
      * @param theArithmetic the arithmetic instance
      * @param theOverloads  the overloaded operators
      * @param theCache the caching state
      */
     public Operator(final JexlUberspect theUberspect,
                     final JexlArithmetic theArithmetic,
                     final Set<JexlOperator> theOverloads,
                     final int theCache) {
         this.uberspect = theUberspect;
         this.arithmetic = theArithmetic;
         this.overloads = theOverloads;
         this.delegate = null;
         this.caching = theCache;
     }
 
     @Override
     public JexlMethod getOperator(final JexlOperator operator, final Object... args) {
         if (delegate != null) {
             return delegate.getOperator(operator, args);
         }
         if (overloads.contains(operator) && args != null && args.length == operator.getArity()) {
             return uberspectOperator(arithmetic, operator, args);
         }
         return null;
     }
 
     @Override
     public boolean overloads(final JexlOperator operator) {
         return delegate != null
             ? delegate.overloads(operator)
             : overloads.contains(operator);
     }
 
     /**
      * @return whether caching is enabled in the engine
      */
     private boolean isCaching() {
         int c = caching;
         if (c < 0) {
             synchronized(this) {
                 c = caching;
                 if (c < 0) {
                     JexlEngine jexl = JexlEngine.getThreadEngine();
                     caching = c = (jexl instanceof Engine) && ((Engine) jexl).cache != null ? 1 : 0;
                 }
             }
         }
         return c > 0;
     }
 
     /**
      * Tidy arguments based on operator arity.
      * <p>The interpreter may add a null to the arguments of operator expecting only one parameter.</p>
      * @param operator the operator
      * @param args the arguments (as seen by the interpreter)
      * @return the tidied arguments
      */
     private Object[] arguments(final JexlOperator operator, final Object...args) {
         return operator.getArity() == 1 && args.length > 1 ? new Object[]{args[0]} : args;
     }
 
     /**
      * Attempts finding a method in left and eventually narrowing right.
      * @param methodName the method name
      * @param right the left argument in the operator
      * @param left the right argument in the operator
      * @return a boolean is call was possible, null otherwise
      * @throws Exception if invocation fails
      */
     private Boolean booleanDuckCall(final String methodName, final Object left, final Object right) throws Exception {
         JexlMethod vm = uberspect.getMethod(left, methodName, right);
         if (returnsBoolean(vm)) {
             return (Boolean) vm.invoke(left, right);
         }
         final Object[] argv = { right };
         if (arithmetic.narrowArguments(argv)) {
             vm = uberspect.getMethod(left, methodName, argv);
             if (returnsBoolean(vm)) {
                 return (Boolean) vm.invoke(left, argv);
             }
         }
         return null;
     }
 
     /**
      * Throw a NPE if operator is strict and one of the arguments is null.
      * @param arithmetic the JEXL arithmetic instance
      * @param operator the operator to check
      * @param args the operands
      * @throws JexlArithmetic.NullOperand if operator is strict and an operand is null
      */
      private void controlNullOperands(final JexlArithmetic arithmetic, final JexlOperator operator, final Object...args) {
         for (final Object arg : args) {
             // only check operator if necessary
             if (arg == null) {
                 // check operator only once if it is not strict
                 if (arithmetic.isStrict(operator)) {
                     throw new JexlArithmetic.NullOperand();
                 }
                 break;
             }
         }
     }
 
     /**
      * Triggered when an operator fails.
      * @param ref     the node where the error originated from
      * @param operator the operator symbol
      * @param cause    the cause of error (if any)
      * @param alt      what to return if not strict
      * @param <T>      the return type
      * @return throws JexlException if strict and not silent, null otherwise
      */
     private <T> T operatorError(final JexlCache.Reference ref, final JexlOperator operator, final Throwable cause, T alt) {
         JexlNode node = (ref instanceof JexlNode) ? (JexlNode) ref : null;
         Engine engine = (Engine) JexlEngine.getThreadEngine();
         if (engine == null || engine.isStrict()) {
             throw new JexlException.Operator(node, operator.getOperatorSymbol(), cause);
         }
         if (engine.logger.isDebugEnabled()) {
             engine.logger.debug(JexlException.operatorError(node, operator.getOperatorSymbol()), cause);
         }
         return alt;
     }
 
     /**
      * Seeks an implementation of an operator method in an arithmetic instance.
      * <p>Method must <em><>not/em belong to JexlArithmetic</p>
      * @param arithmetic the arithmetic instance
      * @param operator the operator
      * @param args the arguments
      * @return a JexlMethod instance or null
      */
     private JexlMethod uberspectOperator(final JexlArithmetic arithmetic,
                                        final JexlOperator operator,
                                        final Object... args) {
         final JexlMethod me = uberspect.getMethod(arithmetic, operator.getMethodName(), args);
         if (!(me instanceof MethodExecutor) ||
             !JexlArithmetic.class.equals(((MethodExecutor) me).getMethod().getDeclaringClass())) {
             return me;
         }
         return null;
     }
 
     /**
      * Checks whether a method returns a boolean or a Boolean.
      * @param vm the JexlMethod (can be null)
      * @return true of false
      */
     private boolean returnsBoolean(final JexlMethod vm) {
         if (vm != null) {
             final Class<?> rc = vm.getReturnType();
             return Boolean.TYPE.equals(rc) || Boolean.class.equals(rc);
         }
         return false;
     }
 
     /**
      * Checks whether a method returns an int or an Integer.
      * @param vm the JexlMethod (can be null)
      * @return true of false
      */
     private boolean returnsInteger(final JexlMethod vm) {
         if (vm != null) {
             final Class<?> rc = vm.getReturnType();
             return Integer.TYPE.equals(rc) || Integer.class.equals(rc);
         }
         return false;
     }
 
     @Override
     public Object empty(final JexlCache.Reference node, final Object object) {
         if (object == null) {
             return true;
         }
         Object result = overloads(JexlOperator.EMPTY)
                 ? tryOverload(node, JexlOperator.EMPTY, object)
                 : JexlEngine.TRY_FAILED;
         if (result == JexlEngine.TRY_FAILED) {
             result = arithmetic.isEmpty(object, null);
             if (result == null) {
                 result = false;
                 // check if there is an isEmpty method on the object that returns a
                 // boolean and if so, just use it
                 final JexlMethod vm = uberspect.getMethod(object, METHOD_IS_EMPTY, InterpreterBase.EMPTY_PARAMS);
                 if (returnsBoolean(vm)) {
                     try {
                         result = vm.invoke(object, InterpreterBase.EMPTY_PARAMS);
                     } catch (final Exception any) {
                         return operatorError(node, JexlOperator.EMPTY, any, false);
                     }
                 }
             }
         }
         return result;
     }
 
     @Override
     public Object size(final JexlCache.Reference node, final Object object) {
         if (object == null) {
             return 0;
         }
         Object result = overloads(JexlOperator.SIZE)
                 ? tryOverload(node, JexlOperator.SIZE, object)
                 : JexlEngine.TRY_FAILED;
         if (result == JexlEngine.TRY_FAILED) {
             result = arithmetic.size(object, null);
             if (result == null) {
                 // check if there is a size method on the object that returns an
                 // integer and if so, just use it
                 final JexlMethod vm = uberspect.getMethod(object, METHOD_SIZE, InterpreterBase.EMPTY_PARAMS);
                 if (returnsInteger(vm)) {
                     try {
                         result = vm.invoke(object, InterpreterBase.EMPTY_PARAMS);
                     } catch (final Exception any) {
                         return operatorError(node, JexlOperator.SIZE, any, 0);
                     }
                 }
             }
         }
         return result instanceof Number ? ((Number) result).intValue() : 0;
     }
 
     @Override
     public boolean contains(final JexlCache.Reference node, final JexlOperator operator, final Object left, final Object right) {
         final boolean contained;
         try {
             // try operator overload
             final Object result = overloads(JexlOperator.CONTAINS)
                     ? tryOverload(node, JexlOperator.CONTAINS, left, right)
                     : null;
             if (result instanceof Boolean) {
                 contained = (Boolean) result;
             } else {
                 // use arithmetic / pattern matching ?
                 final Boolean matched = arithmetic.contains(left, right);
                 if (matched != null) {
                     contained = matched;
                 } else {
                     // try a left.contains(right) method
                     final Boolean duck = booleanDuckCall(METHOD_CONTAINS, left, right);
                     if (duck != null) {
                         contained = duck;
                     } else {
                         // defaults to equal
                         contained = arithmetic.equals(left, right);
                     }
                 }
             }
             // not-contains is !contains
             return (JexlOperator.CONTAINS == operator) == contained;
         } catch (final Exception any) {
             return operatorError(node, operator, any, false);
         }
     }
 
     @Override
     public boolean startsWith(final JexlCache.Reference node, final JexlOperator operator, final Object left, final Object right) {
         final boolean starts;
         try {
             // try operator overload
             final Object result = overloads(JexlOperator.STARTSWITH)
                     ? tryOverload(node, JexlOperator.STARTSWITH, left, right)
                     : null;
             if (result instanceof Boolean) {
                 starts = (Boolean) result;
             } else {
                 // use arithmetic / pattern matching ?
                 final Boolean matched = arithmetic.startsWith(left, right);
                 if (matched != null) {
                     starts = matched;
                 } else {
                     // try a left.startsWith(right) method
                     final Boolean duck = booleanDuckCall(METHOD_STARTS_WITH, left, right);
                     if (duck != null) {
                         starts = duck;
                     } else {
                         // defaults to equal
                         starts = arithmetic.equals(left, right);
                     }
                 }
             }
             // not-startswith is !starts-with
             return (JexlOperator.STARTSWITH == operator) == starts;
         } catch (final Exception any) {
             return operatorError(node, operator, any, false);
         }
     }
 
     @Override
     public boolean endsWith(final JexlCache.Reference node, final JexlOperator operator, final Object left, final Object right) {
         try {
             final boolean ends;
             // try operator overload
             final Object result = overloads(JexlOperator.ENDSWITH)
                 ? tryOverload(node, JexlOperator.ENDSWITH, left, right)
                 : null;
             if (result instanceof Boolean) {
                 ends = (Boolean) result;
             } else {
                 // use arithmetic / pattern matching ?
                 final Boolean matched = arithmetic.endsWith(left, right);
                 if (matched != null) {
                     ends = matched;
                 } else {
                     // try a left.endsWith(right) method
                     final Boolean duck = booleanDuckCall(METHOD_ENDS_WITH, left, right);
                     if (duck != null) {
                         ends = duck;
                     } else {
                         // defaults to equal
                         ends = arithmetic.equals(left, right);
                     }
                 }
             }
             // not-endswith is !ends-with
             return (JexlOperator.ENDSWITH == operator) == ends;
         } catch (final Exception any) {
             return operatorError(node, operator, any, false);
         }
     }
 
     @Override
     public Object tryAssignOverload(final JexlCache.Reference node,
                              final JexlOperator operator,
                              final Consumer<Object> assignFun,
                              final Object... args) {
         if (args.length < operator.getArity()) {
             return JexlEngine.TRY_FAILED;
         }
         Object result = JexlEngine.TRY_FAILED;
         try {
             // if the operator is strict, the left-hand side can not be null
             controlNullOperands(arithmetic, operator, args[0]);
             // attempt assignment operator overload
             if (overloads(operator)) {
                 result = tryOverload(node, operator, arguments(operator, args));
                 if (result != JexlEngine.TRY_FAILED) {
                     return result;
                 }
             }
             // let's attempt base operator overload
             final JexlOperator base = operator.getBaseOperator();
             if (base != null && overloads(base)) {
                 result = tryOverload(node, base, arguments(base, args));
             }
             // no overload or overload failed, use base operator
             if (result == JexlEngine.TRY_FAILED) {
                 result = performBaseOperation(operator, args);
             }
             // on success, assign value
             if (result != JexlEngine.TRY_FAILED) {
                 assignFun.accept(result);
                 // postfix implies return initial argument value
                 if (POSTFIX_OPS.contains(operator)) {
                     result = args[0];
                 }
             }
             return result;
         } catch (final Exception any) {
             return operatorError(node, operator, any, JexlEngine.TRY_FAILED);
         }
     }
 
     /**
      * Performs the base operation of an assignment.
      * @param operator the operator
      * @param args the arguments
      * @return the result
      */
     private Object performBaseOperation(final JexlOperator operator, final Object... args) {
         switch (operator) {
             case SELF_ADD: return arithmetic.add(args[0], args[1]);
             case SELF_SUBTRACT: return arithmetic.subtract(args[0], args[1]);
             case SELF_MULTIPLY: return arithmetic.multiply(args[0], args[1]);
             case SELF_DIVIDE: return arithmetic.divide(args[0], args[1]);
             case SELF_MOD: return arithmetic.mod(args[0], args[1]);
             case SELF_AND: return arithmetic.and(args[0], args[1]);
             case SELF_OR: return arithmetic.or(args[0], args[1]);
             case SELF_XOR: return arithmetic.xor(args[0], args[1]);
             case SELF_SHIFTLEFT: return arithmetic.shiftLeft(args[0], args[1]);
             case SELF_SHIFTRIGHT: return arithmetic.shiftRight(args[0], args[1]);
             case SELF_SHIFTRIGHTU: return arithmetic.shiftRightUnsigned(args[0], args[1]);
             case INCREMENT_AND_GET:
             case GET_AND_INCREMENT:
                 return arithmetic.increment(args[0]);
             case DECREMENT_AND_GET:
             case GET_AND_DECREMENT:
                 return arithmetic.decrement(args[0]);
             default:
                 throw new UnsupportedOperationException(operator.getOperatorSymbol());
         }
     }
 
     @Override
     public Object tryOverload(final JexlCache.Reference node, final JexlOperator operator, final Object... args) {
         controlNullOperands(arithmetic, operator, args);
         try {
             return tryEval(isCaching() ? node : null, operator, args);
         } catch (final Exception any) {
             // ignore return if lenient, will return try_failed
             return operatorError(node, operator, any, JexlEngine.TRY_FAILED);
         }
     }
 
     /**
      * Tries operator evaluation, handles method resolution caching.
      * @param node the node
      * @param operator the operator
      * @param args the operator arguments
      * @return the operator evaluation result or TRY_FAILED
      */
     private Object tryEval(final JexlCache.Reference node, final JexlOperator operator, final Object...args) {
         if (node != null) {
             final Object cached = node.getCache();
             if (cached instanceof JexlMethod) {
                 // we found a method on previous call; try and reuse it (*1)
                 final JexlMethod me = (JexlMethod) cached;
                 final Object eval = me.tryInvoke(operator.getMethodName(), arithmetic, args);
                 if (!me.tryFailed(eval)) {
                     return eval;
                 }
             } else if (cached instanceof MethodKey) {
                 // check for a fail-fast, we tried to find an overload before but could not (*2)
                 final MethodKey cachedKey = (MethodKey) cached;
                 final MethodKey key = new MethodKey(operator.getMethodName(), args);
                 if (key.equals(cachedKey)) {
                     return JexlEngine.TRY_FAILED;
                 }
             }
         }
         // trying to find an operator overload
         JexlMethod vm = getOperator(operator, args);
         // no direct overload, any special case ?
         if (vm == null) {
             vm = getAlternateOverload(operator, args);
         }
         // *1: found a method, try it and cache it if successful
         if (vm != null) {
             final Object result = vm.tryInvoke(operator.getMethodName(), arithmetic, args);
             if (node != null && !vm.tryFailed(result)) {
                 node.setCache(vm);
             }
             return result;
         }
         if (node != null) {
             // *2: could not find an overload for this operator and arguments, keep track of the fail
             MethodKey key = new MethodKey(operator.getMethodName(), args);
             node.setCache(key);
         }
         return JexlEngine.TRY_FAILED;
     }
 
     /**
      * Special handling of overloads where another attempt at finding a method may be attempted.
      * <p>As of 3.5.0, only the comparison operators attempting to use compare() are handled.</p>
      * @param operator the operator
      * @param args the arguments
      * @return an instance or null
      */
     private JexlMethod getAlternateOverload(final JexlOperator operator, final Object... args) {
         // comparison operators may use the compare overload in derived arithmetic
         if (CMP_OPS.contains(operator) && args.length == 2) {
             JexlMethod cmp = getOperator(JexlOperator.COMPARE, args);
             if (cmp != null) {
                 return new Operator.CompareMethod(operator, cmp);
             }
             cmp = getOperator(JexlOperator.COMPARE, args[1], args[0]);
             if (cmp != null) {
                 return new Operator.AntiCompareMethod(operator, cmp);
             }
         }
         return null;
     }
 
     /**
      * Delegates a comparison operator to a compare method.
      * The expected signature of the derived JexlArithmetic method is:
      * int compare(L left, R right);
      */
     private static class CompareMethod implements JexlMethod {
         protected final JexlOperator operator;
         protected final JexlMethod compare;
 
         CompareMethod(final JexlOperator op, final JexlMethod m) {
             operator = op;
             compare = m;
         }
 
         @Override
         public Class<?> getReturnType() {
             return Boolean.TYPE;
         }
 
         @Override
         public Object invoke(Object arithmetic, Object... params) throws Exception {
             return operate((int) compare.invoke(arithmetic, params));
         }
 
         @Override
         public boolean isCacheable() {
             return true;
         }
 
         @Override
         public boolean tryFailed(Object rval) {
             return rval == JexlEngine.TRY_FAILED;
         }
 
         @Override
         public Object tryInvoke(String name, Object arithmetic, Object... params) throws JexlException.TryFailed {
             final Object cmp = compare.tryInvoke(JexlOperator.COMPARE.getMethodName(), arithmetic, params);
             return cmp instanceof Integer? operate((int) cmp) : JexlEngine.TRY_FAILED;
         }
 
         /**
          * From compare() int result to operator boolean result.
          * @param cmp the compare result
          * @return the operator applied
          */
         protected boolean operate(final int cmp) {
             switch(operator) {
                 case EQ: return cmp == 0;
                 case LT: return cmp < 0;
                 case LTE: return cmp <= 0;
                 case GT: return cmp > 0;
                 case GTE: return cmp >= 0;
                 default:
                     throw new ArithmeticException("unexpected operator " + operator);
             }
         }
     }
 
     /**
      * The reverse compare swaps left and right arguments and exploits the symmetry
      * of compare as in: compare(a, b) &lt=&gt -compare(b, a)
      */
     private static class AntiCompareMethod extends CompareMethod {
         AntiCompareMethod(final JexlOperator op, final JexlMethod m) {
             super(op, m);
         }
 
         @Override
         public Object invoke(Object arithmetic, Object... params) throws Exception {
             return operate(-(int) compare.invoke(arithmetic, params[1], params[0]));
         }
 
         @Override
         public Object tryInvoke(String name, Object arithmetic, Object... params) throws JexlException.TryFailed {
             final Object cmp = compare.tryInvoke(JexlOperator.COMPARE.getMethodName(), arithmetic, params[1], params[0]);
             return cmp instanceof Integer? operate(-Integer.signum((Integer) cmp)) : JexlEngine.TRY_FAILED;
         }
     }
 }