/*
    * 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.polyfill;
  
  import java.io.IOException;
  import java.nio.charset.StandardCharsets;
  import java.util.HashMap;
  import java.util.Map;
  
  import org.apache.commons.io.IOUtils;
  import org.htmlunit.corejs.javascript.Context;
  import org.htmlunit.corejs.javascript.Script;
  import org.htmlunit.corejs.javascript.Scriptable;
  import org.htmlunit.corejs.javascript.VarScope;
  
  /**
   * Support to use polyfills for js features not implemented so far
   * (idea from Colin Alworth).
   *
   * @author Ronald Brill
   */
  public class Polyfill {
  
      private static final Map<String, Polyfill> CACHE = new HashMap<>();
  
      private String url_;
      private String source_;
      private Script script_;
  
      /**
       * Returns the build in fetch polyfill.
       *
       * @return the build in fetch polyfill
       * @throws IOException in case of error
       */
      public static Polyfill getFetchPolyfill() throws IOException {
          return getPolyfill("fetch/fetch.umd.js");
      }
  
      private static Polyfill getPolyfill(final String resouceName) throws IOException {
          Polyfill poly = CACHE.get(resouceName);
          if (poly != null) {
              return poly;
          }
  
          poly = new Polyfill();
          poly.source_ = IOUtils.toString(poly.getClass().getResourceAsStream(resouceName), StandardCharsets.UTF_8);
          poly.url_ = poly.getClass().getResource(resouceName).toExternalForm();
  
          CACHE.put(resouceName, poly);
          return poly;
      }
  
      /**
       * Compile the script if needed and exec to setup the context.
       *
       * @param context the context
       * @param scope the scope to execute relative to
       * @param thisObject the value "this" should be set to
       */
      public void apply(final Context context, final VarScope scope, final Scriptable thisObject) {
          if (script_ == null) {
              script_ = context.compileString(source_, url_, 0, null);
          }
  
          if (script_ != null) {
              script_.exec(context, scope, thisObject);
          }
      }
  }