text: /*
   * MD4C: Markdown parser for C
   * (http://github.com/mity/md4c)
   *
   * Copyright (c) 2016-2019 Martin Mitas
   *
   * Permission is hereby granted, free of charge, to any person obtaining a
   * copy of this software and associated documentation files (the "Software"),
   * to deal in the Software without restriction, including without limitation
   * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   * and/or sell copies of the Software, and to permit persons to whom the
   * Software is furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
   * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
   * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
   * IN THE SOFTWARE.
   */
  
  #include <stdio.h>
  #include <string.h>
  
  #include "md4c-html.h"
  #include "entity.h"
  
  
  #if !defined(__STDC_VERSION__) || __STDC_VERSION__ < 199409L
      /* C89/90 or old compilers in general may not understand "inline". */
      #if defined __GNUC__
          #define inline __inline__
      #elif defined _MSC_VER
          #define inline __inline
      #else
          #define inline
      #endif
  #endif
  
  #ifdef _WIN32
      #define snprintf _snprintf
  #endif
  
  
  
  typedef struct MD_HTML_tag MD_HTML;
  struct MD_HTML_tag {
      void (*process_output)(const MD_CHAR*, MD_SIZE, void*);
      void* userdata;
      unsigned flags;
      int image_nesting_level;
      char escape_map[256];
  };
  
  #define NEED_HTML_ESC_FLAG   0x1
  #define NEED_URL_ESC_FLAG    0x2
  
  
  /*****************************************
   ***  HTML rendering helper functions  ***
   *****************************************/
  
  #define ISDIGIT(ch)     ('0' <= (ch) && (ch) <= '9')
  #define ISLOWER(ch)     ('a' <= (ch) && (ch) <= 'z')
  #define ISUPPER(ch)     ('A' <= (ch) && (ch) <= 'Z')
  #define ISALNUM(ch)     (ISLOWER(ch) || ISUPPER(ch) || ISDIGIT(ch))
  
  
  static inline void
  render_verbatim(MD_HTML* r, const MD_CHAR* text, MD_SIZE size)
  {
      r->process_output(text, size, r->userdata);
  }
  
  /* Keep this as a macro. Most compiler should then be smart enough to replace
   * the strlen() call with a compile-time constant if the string is a C literal. */
  #define RENDER_VERBATIM(r, verbatim)                                    \
          render_verbatim((r), (verbatim), (MD_SIZE) (strlen(verbatim)))
  
  
  static void
  render_html_escaped(MD_HTML* r, const MD_CHAR* data, MD_SIZE size)
  {
      MD_OFFSET beg = 0;
      MD_OFFSET off = 0;
  
      /* Some characters need to be escaped in normal HTML text. */
      #define NEED_HTML_ESC(ch)   (r->escape_map[(unsigned char)(ch)] & NEED_HTML_ESC_FLAG)
  
      while(1) {
          /* Optimization: Use some loop unrolling. */
          while(off + 3 < size  &&  !NEED_HTML_ESC(data[off+0])  &&  !NEED_HTML_ESC(data[off+1])
                                &&  !NEED_HTML_ESC(data[off+2])  &&  !NEED_HTML_ESC(data[off+3]))
              off += 4;
          while(off < size  &&  !NEED_HTML_ESC(data[off]))
              off++;
  
          if(off > beg)
              render_verbatim(r, data + beg, off - beg);
  
          if(off < size) {
              switch(data[off]) {
                  case '&':   RENDER_VERBATIM(r, "&amp;"); break;
                  case '<':   RENDER_VERBATIM(r, "&lt;"); break;
                  case '>':   RENDER_VERBATIM(r, "&gt;"); break;
                  case '"':   RENDER_VERBATIM(r, "&quot;"); break;
              }
              off++;
          } else {
              break;
          }
          beg = off;
      }
  }
  
  static void
  render_url_escaped(MD_HTML* r, const MD_CHAR* data, MD_SIZE size)
  {
      static const MD_CHAR hex_chars[] = "0123456789ABCDEF";
      MD_OFFSET beg = 0;
      MD_OFFSET off = 0;
  
      /* Some characters need to be escaped in URL attributes. */
      #define NEED_URL_ESC(ch)    (r->escape_map[(unsigned char)(ch)] & NEED_URL_ESC_FLAG)
  
      while(1) {
          while(off < size  &&  !NEED_URL_ESC(data[off]))
              off++;
          if(off > beg)
              render_verbatim(r, data + beg, off - beg);
  
          if(off < size) {
              char hex[3];
  
              switch(data[off]) {
                  case '&':   RENDER_VERBATIM(r, "&amp;"); break;
                  default:
                      hex[0] = '%';
                      hex[1] = hex_chars[((unsigned)data[off] >> 4) & 0xf];
                      hex[2] = hex_chars[((unsigned)data[off] >> 0) & 0xf];
                      render_verbatim(r, hex, 3);
                      break;
              }
              off++;
          } else {
              break;
          }
  
          beg = off;
      }
  }
  
  static unsigned
  hex_val(char ch)
  {
      if('0' <= ch && ch <= '9')
          return ch - '0';
      if('A' <= ch && ch <= 'Z')
          return ch - 'A' + 10;
      else
          return ch - 'a' + 10;
  }
  
  static void
  render_utf8_codepoint(MD_HTML* r, unsigned codepoint,
                        void (*fn_append)(MD_HTML*, const MD_CHAR*, MD_SIZE))
  {
      static const MD_CHAR utf8_replacement_char[] = { 0xef, 0xbf, 0xbd };
  
      unsigned char utf8[4];
      size_t n;
  
      if(codepoint <= 0x7f) {
          n = 1;
          utf8[0] = codepoint;
      } else if(codepoint <= 0x7ff) {
          n = 2;
          utf8[0] = 0xc0 | ((codepoint >>  6) & 0x1f);
          utf8[1] = 0x80 + ((codepoint >>  0) & 0x3f);
      } else if(codepoint <= 0xffff) {
          n = 3;
          utf8[0] = 0xe0 | ((codepoint >> 12) & 0xf);
          utf8[1] = 0x80 + ((codepoint >>  6) & 0x3f);
          utf8[2] = 0x80 + ((codepoint >>  0) & 0x3f);
      } else {
          n = 4;
          utf8[0] = 0xf0 | ((codepoint >> 18) & 0x7);
          utf8[1] = 0x80 + ((codepoint >> 12) & 0x3f);
          utf8[2] = 0x80 + ((codepoint >>  6) & 0x3f);
          utf8[3] = 0x80 + ((codepoint >>  0) & 0x3f);
      }
  
      if(0 < codepoint  &&  codepoint <= 0x10ffff)
          fn_append(r, (char*)utf8, n);
      else
          fn_append(r, utf8_replacement_char, 3);
  }
  
  /* Translate entity to its UTF-8 equivalent, or output the verbatim one
   * if such entity is unknown (or if the translation is disabled). */
  static void
  render_entity(MD_HTML* r, const MD_CHAR* text, MD_SIZE size,
                void (*fn_append)(MD_HTML*, const MD_CHAR*, MD_SIZE))
  {
      if(r->flags & MD_HTML_FLAG_VERBATIM_ENTITIES) {
          render_verbatim(r, text, size);
          return;
      }
  
      /* We assume UTF-8 output is what is desired. */
      if(size > 3 && text[1] == '#') {
          unsigned codepoint = 0;
  
          if(text[2] == 'x' || text[2] == 'X') {
              /* Hexadecimal entity (e.g. "&#x1234abcd;")). */
              MD_SIZE i;
              for(i = 3; i < size-1; i++)
                  codepoint = 16 * codepoint + hex_val(text[i]);
          } else {
              /* Decimal entity (e.g. "&1234;") */
              MD_SIZE i;
              for(i = 2; i < size-1; i++)
                  codepoint = 10 * codepoint + (text[i] - '0');
          }
  
          render_utf8_codepoint(r, codepoint, fn_append);
          return;
      } else {
          /* Named entity (e.g. "&nbsp;"). */
          const struct entity* ent;
  
          ent = entity_lookup(text, size);
          if(ent != NULL) {
              render_utf8_codepoint(r, ent->codepoints[0], fn_append);
              if(ent->codepoints[1])
                  render_utf8_codepoint(r, ent->codepoints[1], fn_append);
              return;
          }
      }
  
      fn_append(r, text, size);
  }
  
  static void
  render_attribute(MD_HTML* r, const MD_ATTRIBUTE* attr,
                   void (*fn_append)(MD_HTML*, const MD_CHAR*, MD_SIZE))
  {
      int i;
  
      for(i = 0; attr->substr_offsets[i] < attr->size; i++) {
          MD_TEXTTYPE type = attr->substr_types[i];
          MD_OFFSET off = attr->substr_offsets[i];
          MD_SIZE size = attr->substr_offsets[i+1] - off;
          const MD_CHAR* text = attr->text + off;
  
          switch(type) {
              case MD_TEXT_NULLCHAR:  render_utf8_codepoint(r, 0x0000, render_verbatim); break;
              case MD_TEXT_ENTITY:    render_entity(r, text, size, fn_append); break;
              default:                fn_append(r, text, size); break;
          }
      }
  }
  
  
  static void
  render_open_ol_block(MD_HTML* r, const MD_BLOCK_OL_DETAIL* det)
  {
      char buf[64];
  
      if(det->start == 1) {
          RENDER_VERBATIM(r, "<ol>\n");
          return;
      }
  
      snprintf(buf, sizeof(buf), "<ol start=\"%u\">\n", det->start);
      RENDER_VERBATIM(r, buf);
  }
  
  static void
  render_open_li_block(MD_HTML* r, const MD_BLOCK_LI_DETAIL* det)
  {
      if(det->is_task) {
          RENDER_VERBATIM(r, "<li class=\"task-list-item\">"
                            "<input type=\"checkbox\" class=\"task-list-item-checkbox\" disabled");
          if(det->task_mark == 'x' || det->task_mark == 'X')
              RENDER_VERBATIM(r, " checked");
          RENDER_VERBATIM(r, ">");
      } else {
          RENDER_VERBATIM(r, "<li>");
      }
  }
  
  static void
  render_open_code_block(MD_HTML* r, const MD_BLOCK_CODE_DETAIL* det)
  {
      RENDER_VERBATIM(r, "<pre><code");
  
      /* If known, output the HTML 5 attribute class="language-LANGNAME". */
      if(det->lang.text != NULL) {
          RENDER_VERBATIM(r, " class=\"language-");
          render_attribute(r, &det->lang, render_html_escaped);
          RENDER_VERBATIM(r, "\"");
      }
  
      RENDER_VERBATIM(r, ">");
  }
  
  static void
  render_open_td_block(MD_HTML* r, const MD_CHAR* cell_type, const MD_BLOCK_TD_DETAIL* det)
  {
      RENDER_VERBATIM(r, "<");
      RENDER_VERBATIM(r, cell_type);
  
      switch(det->align) {
          case MD_ALIGN_LEFT:     RENDER_VERBATIM(r, " align=\"left\">"); break;
          case MD_ALIGN_CENTER:   RENDER_VERBATIM(r, " align=\"center\">"); break;
          case MD_ALIGN_RIGHT:    RENDER_VERBATIM(r, " align=\"right\">"); break;
          default:                RENDER_VERBATIM(r, ">"); break;
      }
  }
  
  static void
  render_open_a_span(MD_HTML* r, const MD_SPAN_A_DETAIL* det)
  {
      RENDER_VERBATIM(r, "<a href=\"");
      render_attribute(r, &det->href, render_url_escaped);
  
      if(det->title.text != NULL) {
          RENDER_VERBATIM(r, "\" title=\"");
          render_attribute(r, &det->title, render_html_escaped);
      }
  
      // add curly braces style {} for external links
      if (!strncmp("http", det->href.text, 4)) {
          RENDER_VERBATIM(r, "\" class=\"external");
      }
  
      RENDER_VERBATIM(r, "\">");
  }
  
  static void
  render_open_img_span(MD_HTML* r, const MD_SPAN_IMG_DETAIL* det)
  {
      RENDER_VERBATIM(r, "<img src=\"");
      render_attribute(r, &det->src, render_url_escaped);
  
      RENDER_VERBATIM(r, "\" alt=\"");
  
      r->image_nesting_level++;
  }
  
  static void
  render_close_img_span(MD_HTML* r, const MD_SPAN_IMG_DETAIL* det)
  {
      if(det->title.text != NULL) {
          RENDER_VERBATIM(r, "\" title=\"");
          render_attribute(r, &det->title, render_html_escaped);
      }
  
      RENDER_VERBATIM(r, (r->flags & MD_HTML_FLAG_XHTML) ? "\" />" : "\">");
  
      r->image_nesting_level--;
  }
  
  static void
  render_open_wikilink_span(MD_HTML* r, const MD_SPAN_WIKILINK_DETAIL* det)
  {
      RENDER_VERBATIM(r, "<x-wikilink data-target=\"");
      render_attribute(r, &det->target, render_html_escaped);
  
      RENDER_VERBATIM(r, "\">");
  }
  
  
  /**************************************
   ***  HTML renderer implementation  ***
   **************************************/
  
  static int
  enter_block_callback(MD_BLOCKTYPE type, void* detail, void* userdata)
  {
      static const MD_CHAR* head[6] = { "<h1>", "<h2>", "<h3>", "<h4>", "<h5>", "<h6>" };
      MD_HTML* r = (MD_HTML*) userdata;
  
      switch(type) {
          case MD_BLOCK_DOC:      /* noop */ break;
          case MD_BLOCK_QUOTE:    RENDER_VERBATIM(r, "<blockquote>\n"); break;
          case MD_BLOCK_UL:       RENDER_VERBATIM(r, "<ul>\n"); break;
          case MD_BLOCK_OL:       render_open_ol_block(r, (const MD_BLOCK_OL_DETAIL*)detail); break;
          case MD_BLOCK_LI:       render_open_li_block(r, (const MD_BLOCK_LI_DETAIL*)detail); break;
          case MD_BLOCK_HR:       RENDER_VERBATIM(r, (r->flags & MD_HTML_FLAG_XHTML) ? "<hr />\n" : "<hr>\n"); break;
          case MD_BLOCK_H:        RENDER_VERBATIM(r, head[((MD_BLOCK_H_DETAIL*)detail)->level - 1]); break;
          case MD_BLOCK_CODE:     render_open_code_block(r, (const MD_BLOCK_CODE_DETAIL*) detail); break;
          case MD_BLOCK_HTML:     /* noop */ break;
          case MD_BLOCK_P:        RENDER_VERBATIM(r, "<p>"); break;
          case MD_BLOCK_TABLE:    RENDER_VERBATIM(r, "<table>\n"); break;
          case MD_BLOCK_THEAD:    RENDER_VERBATIM(r, "<thead>\n"); break;
          case MD_BLOCK_TBODY:    RENDER_VERBATIM(r, "<tbody>\n"); break;
          case MD_BLOCK_TR:       RENDER_VERBATIM(r, "<tr>\n"); break;
          case MD_BLOCK_TH:       render_open_td_block(r, "th", (MD_BLOCK_TD_DETAIL*)detail); break;
          case MD_BLOCK_TD:       render_open_td_block(r, "td", (MD_BLOCK_TD_DETAIL*)detail); break;
      }
  
      return 0;
  }
  
  static int
  leave_block_callback(MD_BLOCKTYPE type, void* detail, void* userdata)
  {
      static const MD_CHAR* head[6] = { "</h1>\n", "</h2>\n", "</h3>\n", "</h4>\n", "</h5>\n", "</h6>\n" };
      MD_HTML* r = (MD_HTML*) userdata;
  
      switch(type) {
          case MD_BLOCK_DOC:      /*noop*/ break;
          case MD_BLOCK_QUOTE:    RENDER_VERBATIM(r, "</blockquote>\n"); break;
          case MD_BLOCK_UL:       RENDER_VERBATIM(r, "</ul>\n"); break;
          case MD_BLOCK_OL:       RENDER_VERBATIM(r, "</ol>\n"); break;
          case MD_BLOCK_LI:       RENDER_VERBATIM(r, "</li>\n"); break;
          case MD_BLOCK_HR:       /*noop*/ break;
          case MD_BLOCK_H:        RENDER_VERBATIM(r, head[((MD_BLOCK_H_DETAIL*)detail)->level - 1]); break;
          case MD_BLOCK_CODE:     RENDER_VERBATIM(r, "</code></pre>\n"); break;
          case MD_BLOCK_HTML:     /* noop */ break;
          case MD_BLOCK_P:        RENDER_VERBATIM(r, "</p>\n"); break;
          case MD_BLOCK_TABLE:    RENDER_VERBATIM(r, "</table>\n"); break;
          case MD_BLOCK_THEAD:    RENDER_VERBATIM(r, "</thead>\n"); break;
          case MD_BLOCK_TBODY:    RENDER_VERBATIM(r, "</tbody>\n"); break;
          case MD_BLOCK_TR:       RENDER_VERBATIM(r, "</tr>\n"); break;
          case MD_BLOCK_TH:       RENDER_VERBATIM(r, "</th>\n"); break;
          case MD_BLOCK_TD:       RENDER_VERBATIM(r, "</td>\n"); break;
      }
  
      return 0;
  }
  
  static int
  enter_span_callback(MD_SPANTYPE type, void* detail, void* userdata)
  {
      MD_HTML* r = (MD_HTML*) userdata;
  
      if(r->image_nesting_level > 0) {
          /* We are inside a Markdown image label. Markdown allows to use any
           * emphasis and other rich contents in that context similarly as in
           * any link label.
           *
           * However, unlike in the case of links (where that contents becomes
           * contents of the <a>...</a> tag), in the case of images the contents
           * is supposed to fall into the attribute alt: <img alt="...">.
           *
           * In that context we naturally cannot output nested HTML tags. So lets
           * suppress them and only output the plain text (i.e. what falls into
           * text() callback).
           *
           * This make-it-a-plain-text approach is the recommended practice by
           * CommonMark specification (for HTML output).
           */
          return 0;
      }
  
      switch(type) {
          case MD_SPAN_EM:                RENDER_VERBATIM(r, "<em>"); break;
          case MD_SPAN_STRONG:            RENDER_VERBATIM(r, "<strong>"); break;
          case MD_SPAN_U:                 RENDER_VERBATIM(r, "<u>"); break;
          case MD_SPAN_A:                 render_open_a_span(r, (MD_SPAN_A_DETAIL*) detail); break;
          case MD_SPAN_IMG:               render_open_img_span(r, (MD_SPAN_IMG_DETAIL*) detail); break;
          case MD_SPAN_CODE:              RENDER_VERBATIM(r, "<code>"); break;
          case MD_SPAN_DEL:               RENDER_VERBATIM(r, "<del>"); break;
          case MD_SPAN_LATEXMATH:         RENDER_VERBATIM(r, "<x-equation>"); break;
          case MD_SPAN_LATEXMATH_DISPLAY: RENDER_VERBATIM(r, "<x-equation type=\"display\">"); break;
          case MD_SPAN_WIKILINK:          render_open_wikilink_span(r, (MD_SPAN_WIKILINK_DETAIL*) detail); break;
      }
  
      return 0;
  }
  
  static int
  leave_span_callback(MD_SPANTYPE type, void* detail, void* userdata)
  {
      MD_HTML* r = (MD_HTML*) userdata;
  
      if(r->image_nesting_level > 0) {
          /* Ditto as in enter_span_callback(), except we have to allow the
           * end of the <img> tag. */
          if(r->image_nesting_level == 1  &&  type == MD_SPAN_IMG)
              render_close_img_span(r, (MD_SPAN_IMG_DETAIL*) detail);
          return 0;
      }
  
      switch(type) {
          case MD_SPAN_EM:                RENDER_VERBATIM(r, "</em>"); break;
          case MD_SPAN_STRONG:            RENDER_VERBATIM(r, "</strong>"); break;
          case MD_SPAN_U:                 RENDER_VERBATIM(r, "</u>"); break;
          case MD_SPAN_A:                 RENDER_VERBATIM(r, "</a>"); break;
          case MD_SPAN_IMG:               /*noop, handled above*/ break;
          case MD_SPAN_CODE:              RENDER_VERBATIM(r, "</code>"); break;
          case MD_SPAN_DEL:               RENDER_VERBATIM(r, "</del>"); break;
          case MD_SPAN_LATEXMATH:         /*fall through*/
          case MD_SPAN_LATEXMATH_DISPLAY: RENDER_VERBATIM(r, "</x-equation>"); break;
          case MD_SPAN_WIKILINK:          RENDER_VERBATIM(r, "</x-wikilink>"); break;
      }
  
      return 0;
  }
  
  static int
  text_callback(MD_TEXTTYPE type, const MD_CHAR* text, MD_SIZE size, void* userdata)
  {
      MD_HTML* r = (MD_HTML*) userdata;
  
      switch(type) {
          case MD_TEXT_NULLCHAR:  render_utf8_codepoint(r, 0x0000, render_verbatim); break;
          case MD_TEXT_BR:        RENDER_VERBATIM(r, (r->image_nesting_level == 0
                                          ? ((r->flags & MD_HTML_FLAG_XHTML) ? "<br />\n" : "<br>\n")
                                          : " "));
                                  break;
          case MD_TEXT_SOFTBR:    RENDER_VERBATIM(r, (r->image_nesting_level == 0 ? "\n" : " ")); break;
          case MD_TEXT_HTML:      render_verbatim(r, text, size); break;
          case MD_TEXT_ENTITY:    render_entity(r, text, size, render_html_escaped); break;
          default:                render_html_escaped(r, text, size); break;
      }
  
      return 0;
  }
  
  static void
  debug_log_callback(const char* msg, void* userdata)
  {
      MD_HTML* r = (MD_HTML*) userdata;
      if(r->flags & MD_HTML_FLAG_DEBUG)
          fprintf(stderr, "MD4C: %s\n", msg);
  }
  
  int
  md_html(const MD_CHAR* input, MD_SIZE input_size,
          void (*process_output)(const MD_CHAR*, MD_SIZE, void*),
          void* userdata, unsigned parser_flags, unsigned renderer_flags)
  {
      MD_HTML render = { process_output, userdata, renderer_flags, 0, { 0 } };
      int i;
  
      MD_PARSER parser = {
          0,
          parser_flags,
          enter_block_callback,
          leave_block_callback,
          enter_span_callback,
          leave_span_callback,
          text_callback,
          debug_log_callback,
          NULL
      };
  
      /* Build map of characters which need escaping. */
      for(i = 0; i < 256; i++) {
          unsigned char ch = (unsigned char) i;
  
          if(strchr("\"&<>", ch) != NULL)
              render.escape_map[i] |= NEED_HTML_ESC_FLAG;
  
          if(!ISALNUM(ch)  &&  strchr("-_.+!*(),%#@?=;:/,+$", ch) == NULL)
              render.escape_map[i] |= NEED_URL_ESC_FLAG;
      }
  
      /* Consider skipping UTF-8 byte order mark (BOM). */
      if(renderer_flags & MD_HTML_FLAG_SKIP_UTF8_BOM  &&  sizeof(MD_CHAR) == 1) {
          static const MD_CHAR bom[3] = { 0xef, 0xbb, 0xbf };
          if(input_size >= sizeof(bom)  &&  memcmp(input, bom, sizeof(bom)) == 0) {
              input += sizeof(bom);
              input_size -= sizeof(bom);
          }
      }
  
      return md_parse(input, input_size, &parser, (void*) &render);
  }
  
  