/*
 * Licensed 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 com.facebook.presto.sql.planner.iterative.rule;

import com.facebook.presto.sql.planner.PlanNodeIdAllocator;
import com.facebook.presto.sql.planner.Symbol;
import com.facebook.presto.sql.planner.SymbolAllocator;
import com.facebook.presto.sql.planner.iterative.Lookup;
import com.facebook.presto.sql.planner.iterative.Rule;
import com.facebook.presto.sql.planner.plan.PlanNode;
import com.facebook.presto.sql.planner.plan.ProjectNode;
import com.facebook.presto.sql.planner.plan.ValuesNode;
import com.facebook.presto.sql.tree.Expression;
import com.google.common.collect.ImmutableList;

import java.util.Arrays;
import java.util.List;
import java.util.Optional;
import java.util.stream.Collectors;

import static com.facebook.presto.sql.planner.iterative.rule.Util.pruneInputs;

public class PruneValuesColumns
        implements Rule
{
    @Override
    public Optional<PlanNode> apply(PlanNode node, Lookup lookup, PlanNodeIdAllocator idAllocator, SymbolAllocator symbolAllocator)
    {
        if (!(node instanceof ProjectNode)) {
            return Optional.empty();
        }

        ProjectNode parent = (ProjectNode) node;

        PlanNode child = lookup.resolve(parent.getSource());
        if (!(child instanceof ValuesNode)) {
            return Optional.empty();
        }

        ValuesNode values = (ValuesNode) child;

        Optional<List<Symbol>> dependencies = pruneInputs(child.getOutputSymbols(), parent.getAssignments().getExpressions());
        if (!dependencies.isPresent()) {
            return Optional.empty();
        }

        List<Symbol> newOutputs = dependencies.get();

        // for each output of project, the corresponding column in the values node
        int[] mapping = new int[newOutputs.size()];
        for (int i = 0; i < mapping.length; i++) {
            mapping[i] = values.getOutputSymbols().indexOf(newOutputs.get(i));
        }

        ImmutableList.Builder<List<Expression>> rowsBuilder = ImmutableList.builder();
        for (List<Expression> row : values.getRows()) {
            rowsBuilder.add(Arrays.stream(mapping)
                    .mapToObj(row::get)
                    .collect(Collectors.toList()));
        }

        return Optional.of(
                new ProjectNode(
                        parent.getId(),
                        new ValuesNode(values.getId(), newOutputs, rowsBuilder.build()),
                        parent.getAssignments()));
    }
}

@@ -1341,16 +1341,71 @@
 eInputs;
+%0Aimport static com.facebook.presto.util.Optionals.cast;
 %0A%0Apublic
@@ -1620,29 +1620,25 @@
     
-if (!(node instanceof
+return cast(node,
  Pro
@@ -1641,28 +1641,31 @@
  ProjectNode
-)) %7B
+.class)
 %0A           
@@ -1669,118 +1669,40 @@
     
-return Optional.empty();%0A        %7D%0A%0A        ProjectNode parent = (ProjectNode) node;%0A%0A        PlanNode child =
+.flatMap((ProjectNode parent) -%3E
  loo
@@ -1735,41 +1735,9 @@
 ce()
-);%0A        if (!(child instanceof
+,
  Val
@@ -1743,20 +1743,23 @@
 luesNode
-)) %7B
+.class)
 %0A       
@@ -1767,72 +1767,17 @@
     
-return Optional.empty();%0A        %7D%0A%0A        ValuesNode values = 
+.flatMap(
 (Val
@@ -1787,63 +1787,18 @@
 Node
-)
  child
-;%0A%0A        Optional%3CList%3CSymbol%3E%3E dependencies =
+) -%3E
  pru
@@ -1873,17 +1873,16 @@
 sions())
-;
 %0A       
@@ -1886,96 +1886,307 @@
     
-if (!dependencies.isPresent()) %7B%0A            return Optional.empty();%0A        %7D%0A%0A       
+    .map((List%3CSymbol%3E dependencies) -%3E%0A                        new ProjectNode(parent.getId(),%0A                                createNewValuesNode(child, dependencies),%0A                                parent.getAssignments()))));%0A    %7D%0A%0A    private ValuesNode createNewValuesNode(ValuesNode values,
  Lis
@@ -2209,31 +2209,15 @@
 puts
- = dependencies.get();%0A
+)%0A    %7B
 %0A   
@@ -2805,118 +2805,8 @@
 urn 
-Optional.of(%0A                new ProjectNode(%0A                        parent.getId(),%0A                        
 new 
@@ -2868,59 +2868,8 @@
 d())
-,%0A                        parent.getAssignments()))
 ;%0A  

Refactor PruneValuesColumns to leverage Optional's methods