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   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
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   *
   *   http://www.apache.org/licenses/LICENSE-2.0
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  package org.apache.asterix.optimizer.rules;
  
  import java.util.HashMap;
  import java.util.Map;
  
  import org.apache.commons.lang3.mutable.Mutable;
  import org.apache.commons.lang3.mutable.MutableObject;
  import org.apache.hyracks.algebricks.common.exceptions.AlgebricksException;
  import org.apache.hyracks.algebricks.core.algebra.base.EquivalenceClass;
  import org.apache.hyracks.algebricks.core.algebra.base.ILogicalExpression;
  import org.apache.hyracks.algebricks.core.algebra.base.ILogicalOperator;
  import org.apache.hyracks.algebricks.core.algebra.base.IOptimizationContext;
  import org.apache.hyracks.algebricks.core.algebra.base.LogicalExpressionTag;
  import org.apache.hyracks.algebricks.core.algebra.base.LogicalOperatorTag;
  import org.apache.hyracks.algebricks.core.algebra.base.LogicalVariable;
  import org.apache.hyracks.algebricks.core.algebra.expressions.AbstractFunctionCallExpression;
  import org.apache.hyracks.algebricks.core.algebra.expressions.VariableReferenceExpression;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.AbstractBinaryJoinOperator;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.visitors.FDsAndEquivClassesVisitor;
  import org.apache.hyracks.algebricks.core.algebra.operators.logical.visitors.VariableUtilities;
  
  public class RemoveRedundantBooleanExpressionsInJoinRule extends InlineAndRemoveRedundantBooleanExpressionsRule {
      private final FDsAndEquivClassesVisitor visitor = new FDsAndEquivClassesVisitor();
      private final Map<LogicalVariable, LogicalVariable> normalizedVariables = new HashMap<>();
  
      @Override
      public boolean rewritePre(Mutable<ILogicalOperator> opRef, IOptimizationContext context)
              throws AlgebricksException {
          return false;
      }
  
      @Override
      public boolean rewritePost(Mutable<ILogicalOperator> opRef, IOptimizationContext context)
              throws AlgebricksException {
          ILogicalOperator op = opRef.getValue();
          LogicalOperatorTag opTag = op.getOperatorTag();
  
          if (context.checkIfInDontApplySet(this, op)) {
              return false;
          }
  
          if (opTag != LogicalOperatorTag.INNERJOIN && opTag != LogicalOperatorTag.LEFTOUTERJOIN) {
              // TODO FDsAndEquivClassesVisitor alters the distinct variables? We have seen bugs with distinct
              // not sure if that related
              if (op.getOperatorTag() != LogicalOperatorTag.DISTINCT) {
                  // Compute the equivalent classes for op
                  op.accept(visitor, context);
              }
              context.addToDontApplySet(this, op);
              return false;
          }
  
          boolean changed = normalize(context, op);
          // compute equivalent classes for the join op
          op.accept(visitor, context);
          context.addToDontApplySet(this, op);
          return changed;
      }
  
      private boolean normalize(IOptimizationContext context, ILogicalOperator op) {
          AbstractBinaryJoinOperator joinOp = (AbstractBinaryJoinOperator) op;
          ILogicalOperator leftOp = joinOp.getInputs().get(0).getValue();
          ILogicalOperator rightOp = joinOp.getInputs().get(1).getValue();
  
          Map<LogicalVariable, EquivalenceClass> leftEqMap = context.getEquivalenceClassMap(leftOp);
          Map<LogicalVariable, EquivalenceClass> rightEqMap = context.getEquivalenceClassMap(rightOp);
  
          normalizedVariables.clear();
  
          Mutable<ILogicalExpression> joinCondRef = joinOp.getCondition();
          Mutable<ILogicalExpression> clonedCondition = new MutableObject<>(joinCondRef.getValue().cloneExpression());
  
          if (normalizeVariables(leftEqMap, rightEqMap, clonedCondition) && transform(clonedCondition)) {
              // replace the join condition iff the normalization led to a minimized circuit
              joinCondRef.setValue(clonedCondition.getValue());
              return true;
          }
  
          return false;
      }
  
      private boolean normalizeVariables(Map<LogicalVariable, EquivalenceClass> leftEqMap,
              Map<LogicalVariable, EquivalenceClass> rightEqMap, Mutable<ILogicalExpression> exprRef) {
          ILogicalExpression expr = exprRef.getValue();
          if (expr.getExpressionTag() == LogicalExpressionTag.FUNCTION_CALL) {
              return processFunction(leftEqMap, rightEqMap, (AbstractFunctionCallExpression) expr);
          } else if (expr.getExpressionTag() == LogicalExpressionTag.CONSTANT) {
              // TODO is this possible in joins?
              return false;
          }
  
          LogicalVariable toNormalizeVariable = VariableUtilities.getVariable(expr);
          LogicalVariable normalized =
                  getNormalizedVariableAndSetEquivalentsIfAny(leftEqMap, rightEqMap, toNormalizeVariable);
  
          if (normalized == toNormalizeVariable) {
              // both are the same, do nothing
              return false;
          }
  
          // we need to replace the variable expression using the normalized expression
          exprRef.setValue(new VariableReferenceExpression(normalized));
          return true;
      }
  
      private LogicalVariable getNormalizedVariableAndSetEquivalentsIfAny(
              Map<LogicalVariable, EquivalenceClass> leftEqMap, Map<LogicalVariable, EquivalenceClass> rightEqMap,
              LogicalVariable toNormalizeVariable) {
          if (normalizedVariables.containsKey(toNormalizeVariable)) {
              // get the normalized variable
              return normalizedVariables.get(toNormalizeVariable);
          } else if (leftEqMap != null && leftEqMap.containsKey(toNormalizeVariable)) {
              setNormalizedVariables(toNormalizeVariable, leftEqMap.get(toNormalizeVariable));
          } else if (rightEqMap != null && rightEqMap.containsKey(toNormalizeVariable)) {
              setNormalizedVariables(toNormalizeVariable, rightEqMap.get(toNormalizeVariable));
          }
  
          return toNormalizeVariable;
      }
  
      private void setNormalizedVariables(LogicalVariable toNormalizeVariable, EquivalenceClass equivalenceClass) {
          for (LogicalVariable eqVar : equivalenceClass.getMembers()) {
              normalizedVariables.put(eqVar, toNormalizeVariable);
          }
      }
  
      private boolean processFunction(Map<LogicalVariable, EquivalenceClass> leftEqMap,
              Map<LogicalVariable, EquivalenceClass> rightEqMap, AbstractFunctionCallExpression funcExpr) {
  
          boolean changed = false;
          for (Mutable<ILogicalExpression> argRef : funcExpr.getArguments()) {
              changed |= normalizeVariables(leftEqMap, rightEqMap, argRef);
          }
  
          return changed;
      }
  }
  