/*
    * Copyright (c) 2002-2026 Gargoyle Software Inc.
    *
    * 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
    * https://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 org.htmlunit.javascript.host.crypto;
  
  import java.security.SecureRandom;
  import java.util.Locale;
  
  import org.htmlunit.corejs.javascript.typedarrays.NativeTypedArrayView;
  import org.htmlunit.javascript.HtmlUnitScriptable;
  import org.htmlunit.javascript.JavaScriptEngine;
  import org.htmlunit.javascript.configuration.JsxClass;
  import org.htmlunit.javascript.configuration.JsxConstructor;
  import org.htmlunit.javascript.configuration.JsxFunction;
  import org.htmlunit.javascript.configuration.JsxGetter;
  import org.htmlunit.javascript.host.Window;
  import org.htmlunit.javascript.host.dom.DOMException;
  
  /**
   * A JavaScript object for {@code Crypto}.
   *
   * @author Ahmed Ashour
   * @author Marc Guillemot
   * @author Ronald Brill
   *
   * @see <a href="https://developer.mozilla.org/en-US/docs/Web/API/Crypto">MDN Documentation</a>
   */
  @JsxClass
  public class Crypto extends HtmlUnitScriptable {
  
      static final SecureRandom RANDOM = new SecureRandom();
      private SubtleCrypto subtle_;
  
      /**
       * Creates an instance.
       */
      public Crypto() {
          super();
      }
  
      /**
       * Creates an instance.
       */
      @JsxConstructor
      public void jsConstructor() {
          throw JavaScriptEngine.typeErrorIllegalConstructor();
      }
  
      /**
       * Facility constructor.
       * @param window the owning window
       */
      public Crypto(final Window window) {
          this();
          setParentScope(getTopLevelScope(window.getParentScope()));
          setPrototype(window.getPrototype(Crypto.class));
      }
  
      /**
       * Fills array with random values.
       * @param array the array to fill
       * @return the modified array
       * @see <a href="https://developer.mozilla.org/en-US/docs/Web/API/RandomSource/getRandomValues">MDN Doc</a>
       */
      @JsxFunction
      public NativeTypedArrayView<?> getRandomValues(final NativeTypedArrayView<?> array) {
          if (array == null) {
              throw JavaScriptEngine.typeError("Argument 1 of Crypto.getRandomValues is not an object.");
          }
          if (array.getByteLength() > 65_536) {
              throw JavaScriptEngine.asJavaScriptException(
                      getWindow(),
                      "Error: Failed to execute 'getRandomValues' on 'Crypto': "
                              + "The ArrayBufferView's byte length "
                              + "(" + array.getByteLength() + ") exceeds the number of bytes "
                              + "of entropy available via this API (65536).",
                      DOMException.QUOTA_EXCEEDED_ERR);
          }
  
          final int length = array.getByteLength() / array.getBytesPerElement();
          for (int i = 0; i < length; i++) {
              array.put(i, array, RANDOM.nextInt());
          }
          return array;
      }
  
      /**
       * Returns the {@code subtle} property.
      * @return the {@code subtle} property
      */
     @JsxGetter
     public SubtleCrypto getSubtle() {
         if (subtle_ != null) {
             return subtle_;
         }
         final SubtleCrypto subtle = new SubtleCrypto();
         subtle.setParentScope(getParentScope());
         subtle.setPrototype(getWindow().getPrototype(SubtleCrypto.class));
         subtle_ = subtle;
         return subtle_;
     }
 
     /**
      * Generates a random UUID.
      * @return a v4 UUID generated using a cryptographically secure random number generator
      */
     @JsxFunction
     public String randomUUID() {
         // Let bytes be a byte sequence of length 16.
         // Fill bytes with cryptographically secure random bytes.
         final byte[] bytes = new byte[16];
         RANDOM.nextBytes(bytes);
 
         // Set the 4 most significant bits of bytes[6], which represent the UUID version, to 0100.
         bytes[6] = (byte) (bytes[6] | 0b01000000);
         bytes[6] = (byte) (bytes[6] & 0b01001111);
         // Set the 2 most significant bits of bytes[8], which represent the UUID variant, to 10.
         bytes[8] = (byte) (bytes[8] | 0b10000000);
         bytes[8] = (byte) (bytes[8] & 0b10111111);
 
         final StringBuilder result = new StringBuilder()
                                             .append(toHex(bytes[0]))
                                             .append(toHex(bytes[1]))
                                             .append(toHex(bytes[2]))
                                             .append(toHex(bytes[3]))
                                             .append('-')
                                             .append(toHex(bytes[4]))
                                             .append(toHex(bytes[5]))
                                             .append('-')
                                             .append(toHex(bytes[6]))
                                             .append(toHex(bytes[7]))
                                             .append('-')
                                             .append(toHex(bytes[8]))
                                             .append(toHex(bytes[9]))
                                             .append('-')
                                             .append(toHex(bytes[10]))
                                             .append(toHex(bytes[11]))
                                             .append(toHex(bytes[12]))
                                             .append(toHex(bytes[13]))
                                             .append(toHex(bytes[14]))
                                             .append(toHex(bytes[15]));
         return result.toString();
     }
 
     private static String toHex(final byte b) {
         return "%02X ".formatted(b).trim().toLowerCase(Locale.ROOT);
     }
 }