001/*-
002 * #%L
003 * HAPI FHIR Storage api
004 * %%
005 * Copyright (C) 2014 - 2025 Smile CDR, Inc.
006 * %%
007 * Licensed under the Apache License, Version 2.0 (the "License");
008 * you may not use this file except in compliance with the License.
009 * You may obtain a copy of the License at
010 *
011 *      http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing, software
014 * distributed under the License is distributed on an "AS IS" BASIS,
015 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
016 * See the License for the specific language governing permissions and
017 * limitations under the License.
018 * #L%
019 */
020package ca.uhn.fhir.jpa.util;
021
022import java.security.SecureRandom;
023
024public class RandomTextUtils {
025
026        private static final SecureRandom ourRandom = new SecureRandom();
027        private static final String ALPHANUMERIC_CHARS = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
028
029        /**
030         * Creates a new string using randomly selected characters (using a secure random
031         * PRNG) containing letters (mixed case) and numbers.
032         */
033        public static String newSecureRandomAlphaNumericString(int theLength) {
034                StringBuilder b = new StringBuilder();
035                for (int i = 0; i < theLength; i++) {
036                        int nextInt = Math.abs(ourRandom.nextInt());
037                        b.append(ALPHANUMERIC_CHARS.charAt(nextInt % ALPHANUMERIC_CHARS.length()));
038                }
039                return b.toString();
040        }
041
042        /**
043         * Finds the matching ")" for a "(" at the given starting index.
044         * @param theStartIndex the index of the "(" being matched
045         * @param theStr the string to find matches in
046         * @return the index of the matching closing brace, or -1 if none found
047         */
048        public static int findMatchingClosingBrace(int theStartIndex, String theStr) {
049                return findMatchingClosingBrace(theStartIndex, theStr, '(', ')');
050        }
051
052        /**
053         * Finds the matching "closing" value given both the index of the "opening" value and what the value is.
054         * -
055         * If none found, it will return -1.
056         */
057        public static int findMatchingClosingBrace(
058                        int theStartIndex, String theStr, char theOpenBrace, char theClosingBrace) {
059                int len = theStr.length();
060                assert theStartIndex >= 0;
061                assert theStartIndex < len;
062
063                int balance = 0;
064                for (int i = theStartIndex; i < len; i++) {
065                        char next = theStr.charAt(i);
066                        if (next == theClosingBrace) {
067                                balance--;
068                        } else if (next == theOpenBrace) {
069                                balance++;
070                        }
071
072                        if (balance == 0) {
073                                return i;
074                        }
075                }
076                // no closing brace found to match
077                return -1;
078        }
079}