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Hyperledger Fabric Java Chaincode Shim
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/*
Copyright IBM Corp. All Rights Reserved.

SPDX-License-Identifier: Apache-2.0
*/

package org.hyperledger.fabric.shim.ledger;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import static java.util.stream.Collectors.joining;

public class CompositeKey {

    private static final String DELIMITER = new String(Character.toChars(Character.MIN_CODE_POINT));
    public static final String NAMESPACE = DELIMITER;
    private static final String INVALID_SEGMENT_CHAR = new String(Character.toChars(Character.MAX_CODE_POINT));
    private static final String INVALID_SEGMENT_PATTERN = String.format("(?:%s|%s)", INVALID_SEGMENT_CHAR, DELIMITER);

    final String objectType;
    final List attributes;
    final String compositeKey;

    public CompositeKey(String objectType, String... attributes) {
        this(objectType, attributes == null ? Collections.emptyList() : Arrays.asList(attributes));
    }

    public CompositeKey(String objectType, List attributes) {
        if (objectType == null) throw new NullPointerException("objectType cannot be null");
        this.objectType = objectType;
        this.attributes = attributes;
        this.compositeKey = generateCompositeKeyString(objectType, attributes);
    }

    public String getObjectType() {
        return objectType;
    }

    public List getAttributes() {
        return attributes;
    }

    @Override
    public String toString() {
        return compositeKey;
    }

    public static CompositeKey parseCompositeKey(String compositeKey) {
        if (compositeKey == null) return null;
        if (!compositeKey.startsWith(NAMESPACE))
            throw CompositeKeyFormatException.forInputString(compositeKey, compositeKey, 0);
        // relying on the fact that NAMESPACE == DELIMETER
        final String[] segments = compositeKey.split(DELIMITER, 0);
        return new CompositeKey(segments[1], Arrays.stream(segments).skip(2).toArray(String[]::new));
    }

    /**
     * To ensure that simple keys do not go into composite key namespace,
     * we validate simple key to check whether the key starts with 0x00 (which
     * is the namespace for compositeKey). This helps in avoding simple/composite
     * key collisions.
     *
     * @param keys the list of simple keys
     * @throws CompositeKeyFormatException if First character of the key
     */
    public static void validateSimpleKeys(String... keys) {
        for (String key : keys) {
            if (!key.isEmpty() && key.startsWith(NAMESPACE)) {
                throw CompositeKeyFormatException.forSimpleKey(key);
            }
        }
    }

    private String generateCompositeKeyString(String objectType, List attributes) {

        // object type must be a valid composite key segment
        validateCompositeKeySegment(objectType);

        if (attributes == null || attributes.isEmpty()) {
            return NAMESPACE + objectType + DELIMITER;
        }
        // the attributes must be valid composite key segments
        attributes.forEach(this::validateCompositeKeySegment);

        // return NAMESPACE + objectType + DELIMITER + (attribute + DELIMITER)*
        return attributes.stream().collect(joining(DELIMITER, NAMESPACE + objectType + DELIMITER, DELIMITER));

    }

    private void validateCompositeKeySegment(String segment) {
        final Matcher matcher = Pattern.compile(INVALID_SEGMENT_PATTERN).matcher(segment);
        if (matcher.find()) {
            throw CompositeKeyFormatException.forInputString(segment, matcher.group(), matcher.start());
        }
    }

}