#include <stdio.h>

#include <libxml/parser.h>
#include <libxml/tree.h>
#include <libxml/xpath.h>
#include <libxml/xpathInternals.h>

static void node_set (xmlXPathParserContextPtr ctxt, int nargs);
static void tokenise (xmlXPathParserContextPtr ctxt, int nargs);

/* usage: ./xpfunctest xml-doc */
int
main (int argc, char **argv)
{
  xmlXPathContextPtr ctxt;
  xmlXPathObjectPtr obj;
  xmlNsPtr ns;
  xmlDocPtr doc;
  xmlNodePtr node;
  xmlChar *string;
  int i;

  argc--;
  argv++;
  if (argc < 2)
    exit (1);

  doc = xmlParseFile (*argv++);
  node = xmlDocGetRootElement (doc);

  ctxt = xmlXPathNewContext (doc);
  ctxt->node = node;
  ns = xmlSearchNsByHref (doc, ctxt->node,
  		          (const xmlChar *) "http://xpath.test/");
  if (ns != NULL)
    xmlXPathRegisterNs (ctxt, ns->prefix, ns->href);

  xmlXPathRegisterFuncNS (ctxt,
  			  (const xmlChar *) "node-set",
  			  (const xmlChar *) "http://xpath.test/",
                          node_set);
  xmlXPathRegisterFuncNS (ctxt,
  			  (const xmlChar *) "tokenize",
  			  (const xmlChar *) "http://xpath.test/",
                          tokenise);


  obj = xmlXPathEval ((const xmlChar *) *argv, ctxt);
  if (obj != NULL)
    {
      if (obj->type == XPATH_NODESET || obj->type == XPATH_XSLT_TREE)
	{
	  if (obj->nodesetval != NULL)
	    for (i = 0; i < obj->nodesetval->nodeNr; i++)
	      {
		xmlElemDump (stdout, doc, obj->nodesetval->nodeTab[i]);
		printf ("\n");
	      }
	}
      else if ((string = xmlXPathCastToString (obj)) != NULL)
	{
	  printf ("string = '%s'\n", string);
	  xmlFree (string);
	}
      xmlXPathFreeObject (obj);
    }

  exit (0);
}

/* taken from libxslt extra.c */
static void
node_set (xmlXPathParserContextPtr ctxt, int nargs)
{
  if (nargs != 1)
    {
      ctxt->error = XPATH_INVALID_ARITY;
      return;
    }
  if ((ctxt->value == NULL)
      || ((ctxt->value->type != XPATH_XSLT_TREE)
          && (ctxt->value->type != XPATH_NODESET)))
    {
      ctxt->error = XPATH_INVALID_TYPE;
      return;
    }
  if (ctxt->value->type == XPATH_XSLT_TREE)
    {
      ctxt->value->type = XPATH_NODESET;
    }
}

/* taken from libexslt string.c and modified to avoid reference to xslt
   context. */
static void
tokenise (xmlXPathParserContextPtr ctxt, int nargs)
{
  xmlChar *str, *delimiters, *cur;
  const xmlChar *token, *delimiter;
  xmlNodePtr node;
  xmlDocPtr doc;
  xmlXPathObjectPtr ret;

  if ((nargs < 1) || (nargs > 2))
    {
      xmlXPathSetArityError (ctxt);
      return;
    }

  if (nargs == 2)
    {
      delimiters = xmlXPathPopString (ctxt);
      if (xmlXPathCheckError (ctxt))
	return;
    }
  else
    {
      delimiters = xmlStrdup ((const xmlChar *) "\t\r\n ");
    }
  if (delimiters == NULL)
    return;

  str = xmlXPathPopString (ctxt);
  if (xmlXPathCheckError (ctxt) || (str == NULL))
    {
      xmlFree (delimiters);
      return;
    }

  doc = ctxt->context->doc;
  ret = xmlXPathNewNodeSet (NULL);
  if (ret != NULL)
    {
      ret->boolval = 1;
      /*
       * This is a hack: token elements are added as children of a
       * fake element node. This is necessary to free them up
       * correctly when freeing the node-set.
       */
      ret->user = (void *) xmlNewDocNode (doc, NULL,
					  (const xmlChar *) "fake", NULL);
      if (ret->user == NULL)
	goto error;
    }

  for (cur = str, token = str; *cur != 0; cur++)
    {
      for (delimiter = delimiters; *delimiter != 0; delimiter++)
	{
	  if (*cur == *delimiter)
	    {
	      if (cur == token)
		{
		  /* discard empty tokens */
		  break;
		}
	      *cur = 0;
	      node = xmlNewDocNode (doc, NULL,
				    (const xmlChar *) "token", token);
	      *cur = *delimiter;
	      token = cur + 1;

	      xmlAddChild ((xmlNodePtr) ret->user, node);
	      xmlXPathNodeSetAdd (ret->nodesetval, node);
	      break;
	    }
	}
    }
  node = xmlNewDocNode (doc, NULL, (const xmlChar *) "token", token);
  xmlAddChild ((xmlNodePtr) ret->user, node);
  xmlXPathNodeSetAdd (ret->nodesetval, node);

  valuePush (ctxt, ret);
  ret = NULL;			/* hack to prevent freeing ret later */

error:
  if (ret != NULL)
    xmlXPathFreeObject (ret);
  if (str != NULL)
    xmlFree (str);
  if (delimiters != NULL)
    xmlFree (delimiters);
}