content: /*
   * 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.asterix.optimizer.rules;
  
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  import org.apache.asterix.dataflow.data.common.TypeResolverUtil;
  import org.apache.asterix.lang.common.util.FunctionUtil;
  import org.apache.asterix.om.functions.BuiltinFunctions;
  import org.apache.asterix.om.typecomputer.base.TypeCastUtils;
  import org.apache.asterix.om.typecomputer.impl.TypeComputeUtils;
  import org.apache.asterix.om.types.IAType;
  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.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.expressions.AbstractFunctionCallExpression;
  import org.apache.hyracks.algebricks.core.algebra.expressions.IVariableTypeEnvironment;
  import org.apache.hyracks.algebricks.core.algebra.expressions.ScalarFunctionCallExpression;
  import org.apache.hyracks.algebricks.core.algebra.functions.FunctionIdentifier;
  import org.apache.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule;
  
  /**
   * This rule injects casts for function parameters if they have heterogeneous return types:
   * <ul>
   *     <li>for "THEN" and "ELSE" branches of a switch-case function</li>
   *     <li>for parameters of "if missing/null" functions  (if-missing(), if-null(), if-missing-or-null())</li>
   * </ul>
   */
  public class InjectTypeCastForFunctionArgumentsRule implements IAlgebraicRewriteRule {
  
      private static final Map<FunctionIdentifier, BiIntPredicate> FUN_TO_ARG_CHECKER = new HashMap<>();
  
      static {
          addFunctionAndArgChecker(BuiltinFunctions.SWITCH_CASE, InjectTypeCastForFunctionArgumentsRule::switchResultArg);
          addFunctionAndArgChecker(BuiltinFunctions.IF_MISSING, null);
          addFunctionAndArgChecker(BuiltinFunctions.IF_NULL, null);
          addFunctionAndArgChecker(BuiltinFunctions.IF_MISSING_OR_NULL, null);
          addFunctionAndArgChecker(BuiltinFunctions.IF_SYSTEM_NULL, null);
          addFunctionAndArgChecker(BuiltinFunctions.IF_ERROR, null);
      }
  
      // allows the rule to check other functions in addition to the ones specified here
      public static void addFunctionAndArgChecker(FunctionIdentifier function, BiIntPredicate argChecker) {
          FUN_TO_ARG_CHECKER.put(function, argChecker);
      }
  
      @Override
      public boolean rewritePost(Mutable<ILogicalOperator> opRef, IOptimizationContext context)
              throws AlgebricksException {
          ILogicalOperator op = opRef.getValue();
          if (op.getInputs().isEmpty()) {
              return false;
          }
          // Populates the latest type information.
          context.computeAndSetTypeEnvironmentForOperator(op);
          if (op.acceptExpressionTransform(exprRef -> injectTypeCast(op, exprRef, context))) {
              // Generates the up-to-date type information.
              context.computeAndSetTypeEnvironmentForOperator(op);
              return true;
          }
          return false;
      }
  
      // Injects type casts to cast return expressions' return types to a generalized type that conforms to every
      // return type.
      private static boolean injectTypeCast(ILogicalOperator op, Mutable<ILogicalExpression> exprRef,
              IOptimizationContext context) throws AlgebricksException {
          ILogicalExpression expr = exprRef.getValue();
          if (expr.getExpressionTag() != LogicalExpressionTag.FUNCTION_CALL) {
              return false;
          }
          boolean rewritten = false;
          AbstractFunctionCallExpression func = (AbstractFunctionCallExpression) expr;
          for (Mutable<ILogicalExpression> argRef : func.getArguments()) {
              // Recursively rewrites arguments.
              if (injectTypeCast(op, argRef, context)) {
                  context.computeAndSetTypeEnvironmentForOperator(op);
                  rewritten = true;
              }
          }
          FunctionIdentifier funcId = func.getFunctionIdentifier();
          if (FUN_TO_ARG_CHECKER.containsKey(funcId)) {
              rewritten |= rewriteFunction(op, func, FUN_TO_ARG_CHECKER.get(funcId), context);
          }
          return rewritten;
      }
  
      // Injects casts that cast types for all function parameters
      private static boolean rewriteFunction(ILogicalOperator op, AbstractFunctionCallExpression func,
              BiIntPredicate argChecker, IOptimizationContext context) throws AlgebricksException {
          IVariableTypeEnvironment env = op.computeInputTypeEnvironment(context);
          IAType producedType = (IAType) env.getType(func);
          List<Mutable<ILogicalExpression>> argRefs = func.getArguments();
          int argSize = argRefs.size();
          boolean rewritten = false;
          for (int argIndex = 0; argIndex < argSize; argIndex++) {
              if (argChecker == null || argChecker.test(argIndex, argSize)) {
                  rewritten |= rewriteFunctionArgument(argRefs.get(argIndex), producedType, env);
              }
          }
          return rewritten;
      }
  
      private static boolean rewriteFunctionArgument(Mutable<ILogicalExpression> argRef, IAType funcOutputType,
              IVariableTypeEnvironment env) throws AlgebricksException {
          ILogicalExpression argExpr = argRef.getValue();
          IAType type = (IAType) env.getType(argExpr);
          if (TypeResolverUtil.needsCast(funcOutputType, type)) {
              // Injects a cast call to cast the data type to the produced type of the function call.
              ScalarFunctionCallExpression castFunc =
                      new ScalarFunctionCallExpression(FunctionUtil.getFunctionInfo(BuiltinFunctions.CAST_TYPE),
                              new ArrayList<>(Collections.singletonList(new MutableObject<>(argExpr))));
              castFunc.setSourceLocation(argExpr.getSourceLocation());
              IAType funcOutputPrimeType = TypeComputeUtils.getActualType(funcOutputType);
              TypeCastUtils.setRequiredAndInputTypes(castFunc, funcOutputPrimeType, type, false);
              argRef.setValue(castFunc);
              return true;
          }
          return false;
      }
  
      public static boolean switchResultArg(int argIdx, int numArguments) {
          // e.g. switch(cond, exp1, res1, exp2, res2, def_res)
          return argIdx > 1 && (argIdx % 2 == 0 || argIdx == numArguments - 1);
      }
  
      @FunctionalInterface
      public interface BiIntPredicate {
          boolean test(int argIndex, int numArguments);
      }
  }
  