package ca.uhn.fhir.jpa.model.util;

/*-
 * #%L
 * HAPI FHIR JPA Model
 * %%
 * Copyright (C) 2014 - 2021 Smile CDR, Inc.
 * %%
 * 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.
 * #L%
 */

import ca.uhn.fhir.util.UrlUtil;
import com.google.common.base.Charsets;
import com.google.common.hash.HashCode;
import com.google.common.hash.HashFunction;
import com.google.common.hash.Hasher;
import com.google.common.hash.Hashing;

public class CodeSystemHash {
    private static final HashFunction HASH_FUNCTION = Hashing.murmur3_128(0);
    private static final byte[] DELIMITER_BYTES = "|".getBytes(Charsets.UTF_8);

    static public long hashCodeSystem( String system, String code ) {
        Hasher hasher = HASH_FUNCTION.newHasher();
        addStringToHasher(hasher, system);
        addStringToHasher(hasher, code);

        HashCode hashCode = hasher.hash();
        return hashCode.asLong();
    }

    static private void addStringToHasher(Hasher hasher, String next) {
        if (next == null) {
            hasher.putByte((byte) 0);
        } else {
            next = UrlUtil.escapeUrlParam(next);
            byte[] bytes = next.getBytes(Charsets.UTF_8);
            hasher.putBytes(bytes);
        }
        hasher.putBytes(DELIMITER_BYTES);
    }
}
