/* Interface to libxml2.
   Copyright (C) 2010-2023 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

#include "lisp.h"
#include "buffer.h"

#ifdef HAVE_LIBXML2

#include <libxml/tree.h>
#include <libxml/parser.h>
#include <libxml/HTMLparser.h>


#ifdef WINDOWSNT

# include <windows.h>
# include "w32common.h"
# include "w32.h"

DEF_DLL_FN (htmlDocPtr, htmlReadMemory,
	     (const char *, int, const char *, const char *, int));
DEF_DLL_FN (xmlDocPtr, xmlReadMemory,
	     (const char *, int, const char *, const char *, int));
DEF_DLL_FN (xmlNodePtr, xmlDocGetRootElement, (xmlDocPtr));
DEF_DLL_FN (void, xmlFreeDoc, (xmlDocPtr));
DEF_DLL_FN (void, xmlCleanupParser, (void));
DEF_DLL_FN (void, xmlCheckVersion, (int));

static bool
libxml2_loaded_p (void)
{
  Lisp_Object found = Fassq (Qlibxml2, Vlibrary_cache);

  return CONSP (found) && EQ (XCDR (found), Qt);
}

# undef htmlReadMemory
# undef xmlCheckVersion
# undef xmlCleanupParser
# undef xmlDocGetRootElement
# undef xmlFreeDoc
# undef xmlReadMemory

# define htmlReadMemory fn_htmlReadMemory
# define xmlCheckVersion fn_xmlCheckVersion
# define xmlCleanupParser fn_xmlCleanupParser
# define xmlDocGetRootElement fn_xmlDocGetRootElement
# define xmlFreeDoc fn_xmlFreeDoc
# define xmlReadMemory fn_xmlReadMemory

static bool
load_dll_functions (HMODULE library)
{
  LOAD_DLL_FN (library, htmlReadMemory);
  LOAD_DLL_FN (library, xmlReadMemory);
  LOAD_DLL_FN (library, xmlDocGetRootElement);
  LOAD_DLL_FN (library, xmlFreeDoc);
  LOAD_DLL_FN (library, xmlCleanupParser);
  LOAD_DLL_FN (library, xmlCheckVersion);
  return true;
}

#else  /* !WINDOWSNT */

static bool
libxml2_loaded_p (void)
{
  return true;
}

#endif	/* !WINDOWSNT */

static bool
init_libxml2_functions (void)
{
#ifdef WINDOWSNT
  if (libxml2_loaded_p ())
    return true;
  else
    {
      HMODULE library;

      if (!(library = w32_delayed_load (Qlibxml2)))
	{
	  message1 ("libxml2 library not found");
	  return false;
	}

      if (! load_dll_functions (library))
	goto bad_library;

      Vlibrary_cache = Fcons (Fcons (Qlibxml2, Qt), Vlibrary_cache);
      return true;
    }

 bad_library:
  Vlibrary_cache = Fcons (Fcons (Qlibxml2, Qnil), Vlibrary_cache);

  return false;
#else  /* !WINDOWSNT */
  return true;
#endif	/* !WINDOWSNT */
}

static Lisp_Object
make_dom (xmlNode *node)
{
  if (node->type == XML_ELEMENT_NODE)
    {
      Lisp_Object result = list1 (intern ((char *) node->name));
      xmlNode *child;
      xmlAttr *property;
      Lisp_Object plist = Qnil;

      /* First add the attributes. */
      property = node->properties;
      while (property != NULL)
	{
	  if (property->children &&
	      property->children->content)
	    {
	      char *content = (char *) property->children->content;
	      plist = Fcons (Fcons (intern ((char *) property->name),
				    build_string (content)),
			     plist);
	    }
	  property = property->next;
	}
      result = Fcons (Fnreverse (plist), result);

      /* Then add the children of the node. */
      child = node->children;
      while (child != NULL)
	{
	  result = Fcons (make_dom (child), result);
	  child = child->next;
	}

      return Fnreverse (result);
    }
  else if (node->type == XML_TEXT_NODE || node->type == XML_CDATA_SECTION_NODE)
    {
      if (node->content)
	return build_string ((char *) node->content);
      else
	return Qnil;
    }
  else if (node->type == XML_COMMENT_NODE)
    {
      if (node->content)
	return list3 (intern ("comment"), Qnil,
		      build_string ((char *) node->content));
      else
	return Qnil;
    }
  else
    return Qnil;
}

static Lisp_Object
parse_region (Lisp_Object start, Lisp_Object end, Lisp_Object base_url,
	      Lisp_Object discard_comments, bool htmlp)
{
  xmlDoc *doc;
  Lisp_Object result = Qnil;
  const char *burl = "";
  ptrdiff_t istart, iend, istart_byte, iend_byte;
  unsigned char *buftext;

  xmlCheckVersion (LIBXML_VERSION);

  if (NILP (start))
    start = Fpoint_min ();

  if (NILP (end))
    end = Fpoint_max ();

  validate_region (&start, &end);

  istart = XFIXNUM (start);
  iend = XFIXNUM (end);
  istart_byte = CHAR_TO_BYTE (istart);
  iend_byte = CHAR_TO_BYTE (iend);

  if (istart < GPT && GPT < iend)
    move_gap_both (iend, iend_byte);

  if (! NILP (base_url))
    {
      CHECK_STRING (base_url);
      burl = SSDATA (base_url);
    }

  buftext = BYTE_POS_ADDR (istart_byte);
#ifdef REL_ALLOC
  /* Prevent ralloc.c from relocating the current buffer while libxml2
     functions below read its text.  */
  r_alloc_inhibit_buffer_relocation (1);
#endif
  if (htmlp)
    doc = htmlReadMemory ((char *)buftext,
			  iend_byte - istart_byte, burl, "utf-8",
			  HTML_PARSE_RECOVER|HTML_PARSE_NONET|
			  HTML_PARSE_NOWARNING|HTML_PARSE_NOERROR|
			  HTML_PARSE_NOBLANKS);
  else
    doc = xmlReadMemory ((char *)buftext,
			 iend_byte - istart_byte, burl, "utf-8",
			 XML_PARSE_NONET|XML_PARSE_NOWARNING|
			 XML_PARSE_NOBLANKS |XML_PARSE_NOERROR);

#ifdef REL_ALLOC
  r_alloc_inhibit_buffer_relocation (0);
#endif
  /* If the assertion below fails, malloc was called inside the above
     libxml2 functions, and ralloc.c caused relocation of buffer text,
     so we could have read from unrelated memory.  */
  eassert (buftext == BYTE_POS_ADDR (istart_byte));

  if (doc != NULL)
    {
      Lisp_Object r = Qnil;
      if (NILP(discard_comments))
        {
          /* If the document has toplevel comments, then this should
             get us the nodes and the comments. */
          xmlNode *n = doc->children;

          while (n) {
            if (!NILP (r))
              result = Fcons (r, result);
            r = make_dom (n);
            n = n->next;
          }
        }

      if (NILP (result)) {
	/* The document doesn't have toplevel comments or we discarded
	   them.  Get the tree the proper way. */
	xmlNode *node = xmlDocGetRootElement (doc);
	if (node != NULL)
	  result = make_dom (node);
      } else
	result = Fcons (Qtop, Fcons (Qnil, Fnreverse (Fcons (r, result))));

      xmlFreeDoc (doc);
    }

  return result;
}

void
xml_cleanup_parser (void)
{
  if (libxml2_loaded_p ())
    xmlCleanupParser ();
}

DEFUN ("libxml-parse-html-region", Flibxml_parse_html_region,
       Slibxml_parse_html_region,
       0, 4, 0,
       doc: /* Parse the region as an HTML document and return the parse tree.
If START is nil, it defaults to `point-min'.  If END is nil, it
defaults to `point-max'.

If BASE-URL is non-nil, it is used to expand relative URLs.

If you want comments to be stripped, use the `xml-remove-comments'
function to strip comments before calling this function.  */)
  (Lisp_Object start, Lisp_Object end, Lisp_Object base_url, Lisp_Object discard_comments)
{
  if (init_libxml2_functions ())
    return parse_region (start, end, base_url, discard_comments, true);
  return Qnil;
}

DEFUN ("libxml-parse-xml-region", Flibxml_parse_xml_region,
       Slibxml_parse_xml_region,
       0, 4, 0,
       doc: /* Parse the region as an XML document and return the parse tree.
If START is nil, it defaults to `point-min'.  If END is nil, it
defaults to `point-max'.

If BASE-URL is non-nil, it is used to expand relative URLs.

If you want comments to be stripped, use the `xml-remove-comments'
function to strip comments before calling this function.  */)
  (Lisp_Object start, Lisp_Object end, Lisp_Object base_url, Lisp_Object discard_comments)
{
  if (init_libxml2_functions ())
    return parse_region (start, end, base_url, discard_comments, false);
  return Qnil;
}
#endif /* HAVE_LIBXML2 */



DEFUN ("libxml-available-p", Flibxml_available_p, Slibxml_available_p, 0, 0, 0,
       doc: /* Return t if libxml2 support is available in this instance of Emacs.*/)
  (void)
{
#ifdef HAVE_LIBXML2
# ifdef WINDOWSNT
  Lisp_Object found = Fassq (Qlibxml2, Vlibrary_cache);
  if (CONSP (found))
    return XCDR (found);
  else
    {
      Lisp_Object status;
      status = init_libxml2_functions () ? Qt : Qnil;
      Vlibrary_cache = Fcons (Fcons (Qlibxml2, status), Vlibrary_cache);
      return status;
    }
# else
  return Qt;
# endif /* WINDOWSNT */
#else
  return Qnil;
#endif	/* HAVE_LIBXML2 */
}

/***********************************************************************
			    Initialization
 ***********************************************************************/
void
syms_of_xml (void)
{
#ifdef HAVE_LIBXML2
  defsubr (&Slibxml_parse_html_region);
  defsubr (&Slibxml_parse_xml_region);
#endif
  defsubr (&Slibxml_available_p);
}