/*
    * Licensed to the Apache Software Foundation (ASF) under one
    * or more contributor license agreements.  See the NOTICE file
    * distributed with this work for additional information
    * regarding copyright ownership.  The ASF licenses this file
    * to you 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 org.apache.maven.doxia.module.markdown;
  
  import java.util.HashSet;
  import java.util.Set;
  import java.util.regex.Matcher;
  import java.util.regex.Pattern;
  
  import com.vladsch.flexmark.ext.wikilink.internal.WikiLinkLinkResolver;
  import com.vladsch.flexmark.html.IndependentLinkResolverFactory;
  import com.vladsch.flexmark.html.LinkResolver;
  import com.vladsch.flexmark.html.renderer.LinkResolverBasicContext;
  import com.vladsch.flexmark.html.renderer.LinkStatus;
  import com.vladsch.flexmark.html.renderer.LinkType;
  import com.vladsch.flexmark.html.renderer.ResolvedLink;
  import com.vladsch.flexmark.util.ast.Node;
  import org.jetbrains.annotations.NotNull;
  import org.jetbrains.annotations.Nullable;
  
  /**
   * The FlexmarkDoxiaLinkResolver rewrites the md, markdown links to html.
   *
   * Sample links it rewrites:
   * - doc.md to doc.html
   * - doc.markdown to doc.html
   * - doc.md#anchor to doc.html#anchor
   * - doc.markdown#anchor to doc.html#anchor
   * - ../doc.markdown#anchor to ../doc.html#anchor
   * - :doc.md to :doc.html
   * - :doc.markdown to :doc.html
   *
   * Sample links it leaves untouched:
   * - http://doc.md
   * - https://doc.markdown
   * - doc.md.badformat
   * - doc.md#bad#format
   * - doc.md#bad.format
   */
  public class FlexmarkDoxiaLinkResolver implements LinkResolver {
      final Pattern pattern;
  
      /**
       * <p>Constructor for FlexmarkDoxiaLinkResolver.</p>
       *
       */
      public FlexmarkDoxiaLinkResolver() {
          this.pattern = Pattern.compile("^(?![^:]+:)((?:\\./)?(?:\\.\\./)*[^\\.]+).(?:"
                  + MarkdownParserModule.FILE_EXTENSION
                  + "|"
                  + MarkdownParserModule.ALTERNATE_FILE_EXTENSION
                  + ")(#[^#\\.]*){0,1}$");
      }
  
      @Override
      public @NotNull ResolvedLink resolveLink(
              @NotNull Node node, @NotNull LinkResolverBasicContext context, @NotNull ResolvedLink link) {
          if (link.getLinkType() == LinkType.LINK) {
              Matcher matcher = this.pattern.matcher(link.getUrl());
              if (matcher.matches()) {
                  return link.withStatus(LinkStatus.VALID).withUrl(matcher.replaceAll("$1.html$2"));
              }
          }
  
          return link;
      }
  
      /**
       * Factory that creates FlexmarkDoxiaLinkResolver objects.
       */
      public static class Factory extends IndependentLinkResolverFactory {
          @Override
          public @Nullable Set<Class<?>> getBeforeDependents() {
              Set<Class<?>> set = new HashSet<>();
              set.add(WikiLinkLinkResolver.Factory.class);
              return set;
          }
  
          @Override
          public @NotNull LinkResolver apply(@NotNull LinkResolverBasicContext context) {
              return new FlexmarkDoxiaLinkResolver();
          }
      }
 }