feat(simple-jwt): Create a random secret with specified requirements.

simple-jwt-facade/src/main/java/cn/org/codecrafters/simplejwt/SecretCreator.java

@@ -0,0 +1,154 @@
+/*
+ * Copyright (C) 2023 CodeCraftersCN.
+ *
+ * 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.
+ */
+
+package cn.org.codecrafters.simplejwt;
+
+import cn.org.codecrafters.simplejwt.exceptions.WeakSecretException;
+
+import java.util.Random;
+
+/**
+ * SecretCreator is a utility class that provides methods to generate secure
+ * secret strings. The generated secrets can be used as cryptographic keys or
+ * passwords for various security-sensitive purposes.
+ *
+ * @author Zihlu Wang
+ * @version 1.0.0
+ * @since 1.0.0
+ */
+public final class SecretCreator {
+
+    /**
+     * Private constructor to prevent instantiation
+     */
+    private SecretCreator() {
+    }
+
+    /**
+     * The string containing all lowercase characters that can be used to
+     * generate the secret.
+     */
+    private static final String LOWERCASE_CHARACTERS = "abcdefghijklmnopqrstuvwxyz";
+
+    /**
+     * The string containing all uppercase characters that can be used to
+     * generate the secret.
+     */
+    private static final String UPPERCASE_CHARACTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+
+    /**
+     * The string containing all digit characters that can be used to generate
+     * the secret.
+     */
+    private static final String DIGITS = "0123456789";
+
+    /**
+     * The string containing all special sign characters that can be used to
+     * generate the secret.
+     */
+    private static final String SPECIAL_SIGNS = "!@#$%^&,*()_+-=,[]{}|;:,'\",.<>/?";
+
+    /**
+     * Generates a secure secret with the specified length and character sets.
+     *
+     * @param length               the length of the secret to be generated
+     * @param isContainCapital     flag indicating if the secret should contain
+     *                             uppercase letters
+     * @param isContainDigital     flag indicating if the secret should contain
+     *                             digits
+     * @param isContainSpecialSign flag indicating if the secret should contain
+     *                             special sign characters
+     * @return the generated secure secret
+     * @throws WeakSecretException if the requested secret length is less than
+     *                             32 characters
+     */
+    public static String createSecret(int length,
+                                      boolean isContainCapital,
+                                      boolean isContainDigital,
+                                      boolean isContainSpecialSign) {
+        if (length < 32) {
+            throw new WeakSecretException("""
+                    The requested secret, which is only %d characters long, is too weak. \
+                    Please replace it with a stronger secret.
+                    """.formatted(length));
+        }
+
+        final var randomizer = new Random();
+        var charset = new StringBuilder(LOWERCASE_CHARACTERS);
+
+        if (isContainCapital) charset.append(UPPERCASE_CHARACTERS);
+        if (isContainDigital) charset.append(DIGITS);
+        if (isContainSpecialSign) charset.append(SPECIAL_SIGNS);
+
+        var password = new StringBuilder();
+        var charsetSize = charset.length();
+        for (var i = 0; i < length; ++i) {
+            password.append(charset.charAt(randomizer.nextInt(charsetSize)));
+        }
+
+        return password.toString();
+    }
+
+    /**
+     * Generates a secure secret with the specified length, containing
+     * uppercase letters and digits.
+     *
+     * @param length           the length of the secret to be generated
+     * @param isContainCapital flag indicating if the secret should contain
+     *                         uppercase letters
+     * @param isContainDigital flag indicating if the secret should contain
+     *                         digits
+     * @return the generated secure secret
+     * @throws WeakSecretException if the requested secret length is less than
+     *                             32 characters
+     */
+    public static String createSecret(int length,
+                                      boolean isContainCapital,
+                                      boolean isContainDigital) {
+        return createSecret(length, isContainCapital, isContainDigital, false);
+    }
+
+    /**
+     * Generates a secure secret with the specified length, containing
+     * uppercase letters.
+     *
+     * @param length           the length of the secret to be generated
+     * @param isContainCapital flag indicating if the secret should contain
+     *                         uppercase letters
+     * @return the generated secure secret
+     * @throws WeakSecretException if the requested secret length is less than
+     *                             32 characters
+     */
+    public static String createSecret(int length,
+                                      boolean isContainCapital) {
+        return createSecret(length, isContainCapital, false, false);
+    }
+
+    /**
+     * Generates a secure secret with the specified length, containing
+     * lowercase letters.
+     *
+     * @param length the length of the secret to be generated
+     * @return the generated secure secret
+     * @throws WeakSecretException if the requested secret length is less than
+     *                             32 characters
+     */
+    public static String createSecret(int length) {
+        return createSecret(length, false, false, false);
+    }
+
+}