/*
    * 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.util.Set;
  
  import org.htmlunit.corejs.javascript.Scriptable;
  import org.htmlunit.corejs.javascript.ScriptableObject;
  import org.htmlunit.corejs.javascript.VarScope;
  import org.htmlunit.javascript.JavaScriptEngine;
  
  /**
   * Internal helper representing HMAC key algorithm parameters.
   * Used by {@link SubtleCrypto} for HMAC key operations.
   *
   * @author Lai Quang Duong
   * @author Ronald Brill
   */
  final class HmacKeyAlgorithm implements KeyAlgorithm {
  
      static final Set<String> SUPPORTED_HASH_ALGORITHMS = Set.of("SHA-1", "SHA-256", "SHA-384", "SHA-512");
  
      private final String hash_;
      private final int length_;
  
      HmacKeyAlgorithm(final String hash, final int length) {
          if (!SUPPORTED_HASH_ALGORITHMS.contains(hash)) {
              throw new UnsupportedOperationException("HMAC " + hash);
          }
          hash_ = hash;
          length_ = length;
      }
  
      /**
       * Parses HMAC key algorithm parameters from a JS object.
       *
       * @param keyGenParams the JS algorithm parameters object
       * @return the parsed HmacKeyAlgorithm
       */
      static HmacKeyAlgorithm from(final Scriptable keyGenParams) {
          return from(keyGenParams, null);
      }
  
      /**
       * Parses HMAC key algorithm parameters from a JS object, with an optional fallback length.
       *
       * @param keyGenParams the JS algorithm parameters object
       * @param fallbackLength optional length to use when not specified in params;
       *     if null, defaults to the hash block size
       * @return the parsed HmacKeyAlgorithm
       */
      static HmacKeyAlgorithm from(final Scriptable keyGenParams, final Integer fallbackLength) {
          final String hash = SubtleCrypto.resolveAlgorithmName(SubtleCrypto.getRequiredMember(keyGenParams, "hash"));
  
          final int length;
          final Object lengthProp = ScriptableObject.getProperty(keyGenParams, "length");
          if (lengthProp == Scriptable.NOT_FOUND || JavaScriptEngine.isUndefined(lengthProp)) {
              if (fallbackLength != null) {
                  length = fallbackLength;
              }
              else {
                  // default to the block size of the hash algorithm
                  length = switch (hash) {
                      case "SHA-1", "SHA-256" -> 512;
                      case "SHA-384", "SHA-512" -> 1024;
                      default -> throw new UnsupportedOperationException("HMAC " + hash);
                  };
              }
          }
          else {
              length = (int) SubtleCrypto.getRequiredNumber(keyGenParams, "length");
          }
  
          return new HmacKeyAlgorithm(hash, length);
      }
  
      @Override
      public String getName() {
          return "HMAC";
      }
  
      String getHash() {
          return hash_;
      }
  
      int getLength() {
          return length_;
     }
 
     /**
      * Returns the Java algorithm name for {@link javax.crypto.Mac} (e.g. "HmacSHA256").
      *
      * @return the Java algorithm name for {@link javax.crypto.Mac} (e.g. "HmacSHA256")
      */
     String getJavaName() {
         return "Hmac" + hash_.replace("-", "");
     }
 
     /**
      * Converts to a JS object matching the {@code HmacKeyAlgorithm} dictionary:
      * {@code {name: "HMAC", hash: {name: "SHA-256"}, length: N}}.
      *
      * @param scope the JS scope for prototype/parent setup
      * @return the JS algorithm object
      */
     @Override
     public Scriptable toScriptableObject(final VarScope scope) {
         final Scriptable hashObj = JavaScriptEngine.newObject(scope);
         ScriptableObject.putProperty(hashObj, "name", getHash());
 
         final Scriptable algorithm = JavaScriptEngine.newObject(scope);
         ScriptableObject.putProperty(algorithm, "name", getName());
         ScriptableObject.putProperty(algorithm, "hash", hashObj);
         ScriptableObject.putProperty(algorithm, "length", getLength());
         return algorithm;
     }
 }