001// --------------------------------------------------------------------------------
002// Copyright 2002-2025 Echo Three, LLC
003//
004// Licensed under the Apache License, Version 2.0 (the "License");
005// you may not use this file except in compliance with the License.
006// You may obtain a copy of the License at
007//
008//     http://www.apache.org/licenses/LICENSE-2.0
009//
010// Unless required by applicable law or agreed to in writing, software
011// distributed under the License is distributed on an "AS IS" BASIS,
012// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013// See the License for the specific language governing permissions and
014// limitations under the License.
015// --------------------------------------------------------------------------------
016
017package com.echothree.model.control.item.server.logic.checksum;
018
019import com.echothree.util.common.message.ExecutionErrors;
020import com.echothree.util.server.message.ExecutionErrorAccumulator;
021import javax.enterprise.context.ApplicationScoped;
022import javax.enterprise.inject.spi.CDI;
023
024@ApplicationScoped
025public class Gtin13ChecksumLogic
026        extends BaseChecksumLogic
027        implements ItemAliasChecksumInterface {
028
029    protected Gtin13ChecksumLogic() {
030        super();
031    }
032
033    public static Gtin13ChecksumLogic getInstance() {
034        return CDI.current().select(Gtin13ChecksumLogic.class).get();
035    }
036
037    @Override
038    public void checkChecksum(final ExecutionErrorAccumulator eea, final String alias) {
039        if(alias.length() == 13) {
040            var hasCharacterError = false;
041            var checksum = 0;
042
043            for(int i = 0; i < 12; i++) {
044                int d = getDigit(alias, i);
045
046                if(d == -1) {
047                    hasCharacterError = true;
048                    break;
049                }
050
051                // https://www.gs1.org/services/how-calculate-check-digit-manually
052                checksum += i % 2 == 0 ? d : (3 * d);
053            }
054
055            if(!hasCharacterError) {
056                var checkDigit = getDigit(alias, 12);
057
058                hasCharacterError = checkDigit == -1;
059
060                if(!hasCharacterError) {
061                    var intermediate = (10 - (checksum % 10)) % 10;
062
063                    if(intermediate != checkDigit) {
064                        eea.addExecutionError(ExecutionErrors.IncorrectGtin13Checksum.name(), alias);
065                    }
066                }
067            }
068
069            if(hasCharacterError) {
070                eea.addExecutionError(ExecutionErrors.IncorrectGtin13Character.name(), alias);
071            }
072        } else {
073            eea.addExecutionError(ExecutionErrors.IncorrectGtin13Length.name(), alias);
074        }
075    }
076
077}