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/*
 * (c) Copyright 2018 Palantir Technologies Inc. All rights reserved.
 *
 * 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.palantir.atlasdb.keyvalue.api;

import com.google.common.hash.HashFunction;
import com.google.common.hash.Hashing;
import org.immutables.value.Value;

@Value.Immutable
public abstract class CellReference {
    private static final HashFunction rowHash = Hashing.murmur3_32(0);
    private static final HashFunction colHash = Hashing.murmur3_32(1);

    public abstract TableReference tableRef();

    public abstract Cell cell();

    /**
     * {@link Cell#hashCode()} implementation has a rather unfortunate case where it is always 0 if the row name and
     * the column name match. We did not want to change it to keep backwards compatibility, but we need a uniform
     * distribution here for all reasonable patterns.
     */
    public int goodHash() {
        int hash = 5381;
        hash = hash * 1439 + tableRef().hashCode();
        hash = hash * 1439 + rowHash.hashBytes(cell().getRowName()).asInt();
        hash = hash * 1439 + colHash.hashBytes(cell().getColumnName()).asInt();
        return hash;
    }

    public static CellReference of(TableReference tableRef, Cell cell) {
        return ImmutableCellReference.builder().tableRef(tableRef).cell(cell).build();
    }

    static CellReference of(TableReference tableRef, byte[] row, byte[] col) {
        return ImmutableCellReference.builder()
                .tableRef(tableRef)
                .cell(Cell.create(row, col))
                .build();
    }
}