/*
 * 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.plan;

import com.facebook.presto.sql.planner.Symbol;
import com.facebook.presto.sql.tree.Expression;
import com.facebook.presto.sql.tree.SymbolReference;
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;

import javax.annotation.concurrent.Immutable;

import java.util.List;
import java.util.Map;

import static java.util.Objects.requireNonNull;

@Immutable
public class ProjectNode
        extends PlanNode
{
    private final PlanNode source;
    private final Assignments assignments;

    // TODO: pass in the "assignments" and the "outputs" separately (i.e., get rid if the symbol := symbol idiom)
    @JsonCreator
    public ProjectNode(@JsonProperty("id") PlanNodeId id,
            @JsonProperty("source") PlanNode source,
            @JsonProperty("assignments") Assignments assignments)
    {
        super(id);

        requireNonNull(source, "source is null");
        requireNonNull(assignments, "assignments is null");

        this.source = source;
        this.assignments = assignments;
    }

    @Override
    public List<Symbol> getOutputSymbols()
    {
        return assignments.getOutputs();
    }

    @JsonProperty
    public Assignments getAssignments()
    {
        return assignments;
    }

    @Override
    public List<PlanNode> getSources()
    {
        return ImmutableList.of(source);
    }

    @JsonProperty
    public PlanNode getSource()
    {
        return source;
    }

    public boolean isIdentity()
    {
        for (Map.Entry<Symbol, Expression> entry : assignments.entrySet()) {
            Expression expression = entry.getValue();
            Symbol symbol = entry.getKey();
            if (!(expression instanceof SymbolReference && ((SymbolReference) expression).getName().equals(symbol.getName()))) {
                return false;
            }
        }
        return true;
    }

    @Override
    public <C, R> R accept(PlanVisitor<C, R> visitor, C context)
    {
        return visitor.visitProject(this, context);
    }

    @Override
    public PlanNode replaceChildren(List<PlanNode> newChildren)
    {
        return new ProjectNode(getId(), Iterables.getOnlyElement(newChildren), assignments);
    }
}