/*
    * 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.siterenderer.sink;
  
  import java.io.StringWriter;
  import java.io.Writer;
  import java.util.ArrayList;
  import java.util.List;
  
  import org.apache.maven.doxia.markup.HtmlMarkup;
  import org.apache.maven.doxia.module.xhtml5.Xhtml5Sink;
  import org.apache.maven.doxia.sink.SinkEventAttributes;
  import org.apache.maven.doxia.sink.impl.SinkEventAttributeSet;
  import org.apache.maven.doxia.sink.impl.SinkUtils;
  import org.apache.maven.doxia.site.MermaidConfiguration;
  import org.apache.maven.doxia.siterenderer.DefaultSiteRenderer;
  import org.apache.maven.doxia.siterenderer.DocumentContent;
  import org.apache.maven.doxia.siterenderer.DocumentRenderingContext;
  
  /**
   * Sink for site rendering of a document, to allow later merge document's output with a template.
   * During raw Doxia rendering, content is stored in multiple fields for later use when incorporating
   * into skin or template: title, date, authors, head, body
   *
   * @author <a href="mailto:evenisse@codehaus.org">Emmanuel Venisse</a>
   */
  @SuppressWarnings("checkstyle:methodname")
  public class SiteRendererSink extends Xhtml5Sink implements DocumentContent {
      private String date;
  
      private String title;
  
      private List<String> authors = new ArrayList<>();
  
      private final StringWriter headWriter;
  
      /** Buffer inside verbatim elements to potentially remove enclosed code elements for Mermaid diagrams */
      private StringBuilder verbatimBuffer;
  
      private final Writer writer;
  
      private final MermaidConfiguration mermaidConfig;
  
      private DocumentRenderingContext docRenderingContext;
  
      private boolean containsMermaidDiagram = false;
  
      private boolean insideMermaidCodeElement = false;
      /**
       * Construct a new SiteRendererSink for a document.
       *
       * @param docRenderingContext the document's rendering context.
       */
      public SiteRendererSink(DocumentRenderingContext docRenderingContext) {
          this(docRenderingContext, null);
      }
  
      public SiteRendererSink(DocumentRenderingContext docRenderingContext, MermaidConfiguration mermaid) {
          this(new StringWriter(), docRenderingContext, mermaid);
      }
  
      private SiteRendererSink(
              StringWriter writer, DocumentRenderingContext docRenderingContext, MermaidConfiguration mermaid) {
          super(writer);
  
          this.writer = writer;
          this.headWriter = new StringWriter();
          this.docRenderingContext = docRenderingContext;
          this.mermaidConfig = mermaid;
  
          /* the template is expected to have used the main tag, which can be used only once */
          super.contentStack.push(HtmlMarkup.MAIN);
      }
  
      /** {@inheritDoc} */
      @Override
      public void title_() {
          if (getTextBuffer().length() > 0) {
              title = getTextBuffer().toString();
          }
  
          resetTextBuffer();
      }
 
     /**
      * {@inheritDoc}
      *
      * Reset text buffer, since text content before title must not be in title.
      * @see org.apache.maven.doxia.module.xhtml5.Xhtml5Sink#title()
      */
     @Override
     public void title(SinkEventAttributes attributes) {
         resetTextBuffer();
     }
 
     /** {@inheritDoc} */
     @Override
     public void author(SinkEventAttributes attributes) {
         resetTextBuffer();
     }
 
     /** {@inheritDoc} */
     @Override
     public void author_() {
         if (getTextBuffer().length() > 0) {
             String text = getTextBuffer().toString().trim();
             authors.add(text);
         }
 
         resetTextBuffer();
     }
 
     /** {@inheritDoc} */
     @Override
     public void date(SinkEventAttributes attributes) {
         resetTextBuffer();
     }
 
     /** {@inheritDoc} */
     @Override
     public void date_() {
         if (getTextBuffer().length() > 0) {
             date = getTextBuffer().toString().trim();
         }
 
         resetTextBuffer();
     }
 
     @Override
     public void verbatim(SinkEventAttributes attributes) {
         if (mermaidConfig != null && normalizeClassAttributesForMermaid(attributes)) {
             containsMermaidDiagram = true;
             // remove the decoration code for Mermaid diagrams (otherwise Skins may add line numbers to the code
             // element, which breaks Mermaid rendering)
             SinkEventAttributes filteredAttributes = (SinkEventAttributes)
                     SinkUtils.filterAttributes(attributes, new String[] {SinkEventAttributes.DECORATION});
             super.verbatim(filteredAttributes);
         } else {
             // write subsequent verbatim content to a buffer, to be able to detect Mermaid diagrams in it and remove
             // code element if needed
             verbatimBuffer = new StringBuilder();
             super.verbatim(attributes);
         }
     }
 
     @Override
     public void verbatim_() {
         flushVerbatimBuffer(false);
         super.verbatim_();
     }
 
     @Override
     public void inline(SinkEventAttributes attributes) {
         if (attributes.containsAttributes(SinkEventAttributeSet.Semantics.CODE)
                 && mermaidConfig != null
                 && normalizeClassAttributesForMermaid(attributes)) {
             containsMermaidDiagram = true;
             // writes to buffer
             super.inline(attributes);
             // remove code element from inline stack to prevent closing it
             inlineStack.pop();
             insideMermaidCodeElement = true;
             // remove the code element from the verbatim buffer, to prevent Skins from adding line numbers to it, which
             // breaks Mermaid rendering
             flushVerbatimBuffer(true);
         } else {
             flushVerbatimBuffer(false);
             super.inline(attributes);
         }
     }
 
     @Override
     public void inline_() {
         if (insideMermaidCodeElement) {
             // this is the end of the code tag (which has been removed), so no need to close it
             insideMermaidCodeElement = false;
         } else {
             super.inline_();
         }
     }
 
     private void flushVerbatimBuffer(boolean stripCodeElement) {
         if (verbatimBuffer != null) {
             String buffer = verbatimBuffer.toString();
             if (stripCodeElement) {
                 // remove code element and instead add attributes to the parent element <pre> to prevent the skin from
                 // adding code highlighting/line numbers, which breaks Mermaid rendering
                 buffer = buffer.replaceFirst("<pre><code([^>]*)>", "<pre$1>");
             }
             verbatimBuffer = null;
             write(buffer);
         }
     }
 
     /**
      * Normalize class attributes for Mermaid diagrams, to allow using either "mermaid" or "language-mermaid" as class.
      *
      * @param attributes the attributes to check and normalize.
      * @return {@code true} if the attributes indicate a Mermaid diagram, {@code false} otherwise.
      */
     boolean normalizeClassAttributesForMermaid(SinkEventAttributes attributes) {
         String lang = attributes != null ? (String) attributes.getAttribute(SinkEventAttributes.CLASS) : null;
         if ("language-mermaid"
                 .equals(lang)) { // "language-" prefix is used by some markdown parsers, e.g. flexmark-java
             attributes.addAttribute(SinkEventAttributes.CLASS, "mermaid");
             return true;
         } else if ("mermaid".equals(lang)) {
             return true;
         }
         return false;
     }
 
     /**
      * Include the Mermaid rendering script (either internal or external) and call it on diagrams afterwards.
      * @see <a href="https://mermaid.ai/open-source/intro/getting-started.html#_4-calling-the-mermaid-javascript-api">Calling the Mermaid JavaScript API</a>
      */
     private void writeMermaidScript() {
         if (mermaidConfig.getExternalJs() != null) {
             write(mermaidConfig.getExternalJs().asScriptTag());
         } else {
             write("\n<script src=\"");
             write(docRenderingContext.getRelativePath());
 
             if (mermaidConfig.isUseTiny()) {
                 // use integrated tiny version of mermaid, which is smaller and faster to load, but has some limitations
                 // (e.g. no sequence diagrams)
                 write("/js/mermaid-" + DefaultSiteRenderer.MERMAID_VERSION + ".tiny.min.js");
             } else {
                 // use integrated full version of mermaid, which is larger and slower to load, but has all features
                 write("/js/mermaid-" + DefaultSiteRenderer.MERMAID_VERSION + ".min.js");
             }
             write("\"></script>\n");
         }
         write("\n<script>\n");
         if (mermaidConfig.getConfig() != null) {
             write("mermaid.initialize(" + mermaidConfig.getConfig() + ");\n");
         } else {
             // By default, mermaid.run will be called when the document is ready, rendering all elements with
             // class="mermaid".
             write("mermaid.initialize({startOnLoad:true, securityLevel: 'loose'});\n");
         }
         write("</script>\n");
     }
 
     /**
      * {@inheritDoc}
      *
      * Do nothing.
      * @see org.apache.maven.doxia.module.xhtml5.Xhtml5Sink#body_()
      */
     @Override
     public void body_() {
         if (containsMermaidDiagram && mermaidConfig != null) {
             writeMermaidScript();
         }
     }
 
     /**
      * {@inheritDoc}
      *
      * Do nothing.
      * @see org.apache.maven.doxia.module.xhtml5.Xhtml5Sink#body()
      */
     @Override
     public void body(SinkEventAttributes attributes) {
         // nop
     }
 
     /** {@inheritDoc} */
     @Override
     public void head_() {
         setHeadFlag(false);
     }
 
     /** {@inheritDoc} */
     @Override
     public void head(SinkEventAttributes attributes) {
         setHeadFlag(true);
     }
 
     /** {@inheritDoc} */
     @Override
     protected void write(String text) {
         String txt = text;
 
         if (isHeadFlag()) {
             headWriter.write(unifyEOLs(txt));
 
             return;
         }
 
         if (docRenderingContext != null) {
             String relativePathToBasedir = docRenderingContext.getRelativePath();
 
             if (relativePathToBasedir == null) {
                 txt = txt == null || txt.isEmpty() ? txt : txt.replace("$relativePath", ".");
             } else {
                 txt = txt == null || txt.isEmpty() || relativePathToBasedir == null
                         ? txt
                         : txt.replace("$relativePath", relativePathToBasedir);
             }
         }
 
         if (verbatimBuffer != null) {
             verbatimBuffer.append(unifyEOLs(txt));
             return;
         }
         super.write(txt);
     }
 
     // DocumentContent interface
 
     /** {@inheritDoc} */
     public String getTitle() {
         return title;
     }
 
     /** {@inheritDoc} */
     public List<String> getAuthors() {
         return authors;
     }
 
     /** {@inheritDoc} */
     public String getDate() {
         return date;
     }
 
     /** {@inheritDoc} */
     public String getBody() {
         String body = writer.toString();
 
         return body.length() > 0 ? body : null;
     }
 
     /** {@inheritDoc} */
     public String getHead() {
         String head = headWriter.toString();
 
         return head.length() > 0 ? head : null;
     }
 
     /** {@inheritDoc} */
     public DocumentRenderingContext getRenderingContext() {
         return docRenderingContext;
     }
 }