/*
 * 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.activemq.artemis.selector.filter;

import java.util.ArrayList;
import java.util.List;

/**
 * A sequence of expressions, to be combined with OR or AND conjunctions.
 *
 */
public abstract class LogicExpression implements BooleanExpression {

   protected final List<BooleanExpression> expressions = new ArrayList<>(2);

   private LogicExpression(BooleanExpression lvalue, BooleanExpression rvalue) {
      expressions.add(lvalue);
      expressions.add(rvalue);
   }

   protected void addExpression(BooleanExpression expression) {
      expressions.add(expression);
   }

   public BooleanExpression getLeft() {
      if (expressions.size() == 2) {
         return expressions.get(0);
      }
      throw new IllegalStateException("This expression is not binary: " + this);
   }

   public BooleanExpression getRight() {
      if (expressions.size() == 2) {
         return expressions.get(1);
      }
      throw new IllegalStateException("This expression is not binary: " + this);
   }

   /**
    * Returns the symbol that represents this binary expression.  For example, addition is
    * represented by "+"
    *
    * @return
    */
   public abstract String getExpressionSymbol();

   @Override
   public String toString() {
      if (expressions.size() == 2) {
         return "( " + expressions.get(0) + " " + getExpressionSymbol() + " " + expressions.get(1) + " )";
      }
      StringBuilder result = new StringBuilder("(");
      int count = 0;
      for (BooleanExpression expression : expressions) {
         if (count++ > 0) {
            result.append(" " + getExpressionSymbol() + " ");
         }
         result.append(expression.toString());
      }
      result.append(")");
      return result.toString();
   }

   public static BooleanExpression createOR(BooleanExpression lvalue, BooleanExpression rvalue) {
      if (lvalue instanceof ORExpression) {
         ORExpression orExpression = (ORExpression) lvalue;
         orExpression.addExpression(rvalue);
         return orExpression;
      } else {
         return new ORExpression(lvalue, rvalue);
      }
   }

   public static BooleanExpression createAND(BooleanExpression lvalue, BooleanExpression rvalue) {
      if (lvalue instanceof ANDExpression) {
         ANDExpression orExpression = (ANDExpression) lvalue;
         orExpression.addExpression(rvalue);
         return orExpression;
      } else {
         return new ANDExpression(lvalue, rvalue);
      }
   }

   @Override
   public abstract Object evaluate(Filterable message) throws FilterException;

   @Override
   public abstract boolean matches(Filterable message) throws FilterException;

   private static class ORExpression extends LogicExpression {

      ORExpression(BooleanExpression lvalue, BooleanExpression rvalue) {
         super(lvalue, rvalue);
      }

      @Override
      public Object evaluate(Filterable message) throws FilterException {
         boolean someNulls = false;
         for (BooleanExpression expression : expressions) {
            Boolean lv = (Boolean)expression.evaluate(message);
            if (lv != null && lv.booleanValue()) {
               return Boolean.TRUE;
            }
            if (lv == null) {
               someNulls = true;
            }
         }
         if (someNulls) {
            return null;
         }
         return Boolean.FALSE;
      }

      @Override
      public boolean matches(Filterable message) throws FilterException {
         for (BooleanExpression expression : expressions) {
            boolean lv = expression.matches(message);
            if (lv) {
               return true;
            }
         }
         return false;
      }

      @Override
      public String getExpressionSymbol() {
         return "OR";
      }
   }

   private static class ANDExpression extends LogicExpression {

      ANDExpression(BooleanExpression lvalue, BooleanExpression rvalue) {
         super(lvalue, rvalue);
      }

      @Override
      public Object evaluate(Filterable message) throws FilterException {
         boolean someNulls = false;
         for (BooleanExpression expression : expressions) {
            Boolean lv = (Boolean)expression.evaluate(message);
            if (lv != null && !lv.booleanValue()) {
               return Boolean.FALSE;
            }
            if (lv == null) {
               someNulls = true;
            }
         }
         if (someNulls) {
            return null;
         }
         return Boolean.TRUE;
      }

      @Override
      public boolean matches(Filterable message) throws FilterException {
         for (BooleanExpression expression : expressions) {
            boolean lv = expression.matches(message);
            if (!lv) {
               return false;
            }
         }
         return true;
      }

      @Override
      public String getExpressionSymbol() {
         return "AND";
      }
   }
}
