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A record-oriented layer built for FoundationDB (proto2).
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/*
 * NestingKeyExpression.java
 *
 * This source file is part of the FoundationDB open source project
 *
 * Copyright 2015-2018 Apple Inc. and the FoundationDB project authors
 *
 * 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.apple.foundationdb.record.metadata.expressions;

import com.apple.foundationdb.annotation.API;
import com.apple.foundationdb.record.RecordMetaDataProto;
import com.apple.foundationdb.record.metadata.Key;
import com.apple.foundationdb.record.provider.foundationdb.FDBRecord;
import com.google.protobuf.Descriptors;
import com.google.protobuf.Message;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;

/**
 * A key expression within a nested subrecord.
 * If the parent field is repeated, then the parent field must have fan type FanType.FanOut.
 * In that case, this will return the nested expression evaluated against every subrecord (possibly returning
 * no Key.Evaluateds if the parent field is empty). If the parent field is not repeated and not set,
 * then this will evaluate the nested expression on the null record. This should return the same
 * result as if the field were set to the empty message. If this expression is evaluated on the null
 * record, then it will evaluate the same as if the parent field is unset or empty (depending on the fan type).
 */
@API(API.Status.MAINTAINED)
public class NestingKeyExpression extends BaseKeyExpression implements KeyExpressionWithChild, AtomKeyExpression {
    @Nonnull
    private final FieldKeyExpression parent;
    @Nonnull
    private final KeyExpression child;

    public NestingKeyExpression(@Nonnull FieldKeyExpression parent, @Nonnull KeyExpression child) {
        this.parent = parent;
        this.child = child;
    }

    public NestingKeyExpression(@Nonnull RecordMetaDataProto.Nesting nesting) throws DeserializationException {
        if (!nesting.hasParent()) {
            throw new DeserializationException("Serialized Nesting is missing parent");
        }
        parent = new FieldKeyExpression(nesting.getParent());
        child = KeyExpression.fromProto(nesting.getChild());
    }

    @Nonnull
    @Override
    public  List evaluateMessage(@Nullable FDBRecord record, @Nullable Message message) {
        final List parentKeys = parent.evaluateMessage(record, message);
        List result = new ArrayList<>();
        // TODO make this more type safe. But those components should always be single messages
        for (Key.Evaluated value : parentKeys) {
            final Message submessage = (Message) value.toList().get(0);
            result.addAll(getChild().evaluateMessage(record, submessage));
        }
        validateColumnCounts(result);
        return result;
    }

    @Override
    public boolean createsDuplicates() {
        return parent.createsDuplicates() || getChild().createsDuplicates();
    }

    @Override
    public List validate(@Nonnull Descriptors.Descriptor descriptor) {
        parent.validate(descriptor, true);
        return getChild().validate(parent.getDescriptor(descriptor));
    }

    @Override
    public int getColumnSize() {
        return getChild().getColumnSize();
    }

    @Nonnull
    @Override
    public RecordMetaDataProto.Nesting toProto() throws SerializationException {
        final RecordMetaDataProto.Nesting.Builder builder = RecordMetaDataProto.Nesting.newBuilder();
        builder.setParent(parent.toProto());
        builder.setChild(getChild().toKeyExpression());
        return builder.build();
    }

    @Nonnull
    @Override
    public RecordMetaDataProto.KeyExpression toKeyExpression() {
        return RecordMetaDataProto.KeyExpression.newBuilder().setNesting(toProto()).build();
    }

    @Nonnull
    @Override
    public List normalizeKeyForPositions() {
        return getChild().normalizeKeyForPositions()
                .stream().map(normalizedChild -> new NestingKeyExpression(parent, normalizedChild))
                .collect(Collectors.toList());
    }

    @Override
    public int versionColumns() {
        return getChild().versionColumns();
    }

    @Override
    public boolean hasRecordTypeKey() {
        return getChild().hasRecordTypeKey();
    }

    @Override
    public KeyExpression getSubKeyImpl(int start, int end) {
        KeyExpression childKey = getChild().getSubKey(start, end);
        return new NestingKeyExpression(parent, childKey);
    }

    @Nonnull
    public FieldKeyExpression getParent() {
        return parent;
    }

    @Override
    @Nonnull
    public KeyExpression getChild() {
        return child;
    }

    /**
     * Get this nesting as a group without any grouping keys.
     * @return this nesting without any grouping keys
     */
    @Nonnull
    public GroupingKeyExpression ungrouped() {
        return new GroupingKeyExpression(this, getColumnSize());
    }

    @Nonnull
    public GroupingKeyExpression groupBy(@Nonnull KeyExpression groupByFirst, @Nonnull KeyExpression... groupByRest) {
        return GroupingKeyExpression.of(this, groupByFirst, groupByRest);
    }

    @Override
    public String toString() {
        return parent + "/" + getChild();
    }

    @Override
    public boolean equals(Object o) {
        if (o == this) {
            return true;
        }

        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        NestingKeyExpression that = (NestingKeyExpression)o;
        return this.parent.equals(that.parent) && this.getChild().equals(that.getChild());
    }

    @Override
    public int hashCode() {
        return parent.hashCode() + getChild().hashCode();
    }

    @Override
    public int planHash() {
        return parent.planHash() + getChild().planHash();
    }

    @Override
    public boolean equalsAtomic(AtomKeyExpression other) {
        return this.getClass() == other.getClass() && parent.equals(((NestingKeyExpression) other).parent);
    }
}