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.sequence.server.logic.checksum;
018
019import com.echothree.model.control.sequence.server.logic.SequenceGeneratorLogic;
020import java.nio.charset.StandardCharsets;
021import javax.enterprise.context.ApplicationScoped;
022import javax.enterprise.inject.spi.CDI;
023
024@ApplicationScoped
025public class Mod10SequenceChecksum
026        implements SequenceChecksum {
027
028    protected Mod10SequenceChecksum() {
029        super();
030    }
031
032    public static Mod10SequenceChecksum getInstance() {
033        return CDI.current().select(Mod10SequenceChecksum.class).get();
034    }
035
036    @Override
037    public String calculate(String value) {
038        var bytes = value.getBytes(StandardCharsets.UTF_8);
039        var sum = 0;
040
041        for(var i = 0; i < bytes.length; i++) {
042            sum += (bytes [i] * (i + 1));
043        }
044
045        var modCharacter = new char[]{SequenceGeneratorLogic.NUMERIC_VALUES.charAt(sum % SequenceGeneratorLogic.NUMERIC_MAX_INDEX)};
046        return new String(modCharacter);
047    }
048
049    @Override
050    public String regexp() {
051        return "[\\p{Digit}]";
052    }
053
054    @Override
055    public boolean verify(String value) {
056        var codePoints = value.codePoints().toArray();
057        var length = codePoints.length;
058        var valueWithoutChecksum = new String(codePoints, 0, length - 1);
059        var checksumFromValue = new String(codePoints, length - 1, 1);
060        var checksum = calculate(valueWithoutChecksum);
061
062        return checksumFromValue.equals(checksum);
063    }
064
065}