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

xmlXPathObjectPtr _getXPath(xmlDocPtr doc, xmlChar *xpath);

int main(int argc, char **argv) {
  char *docname;
  xmlDocPtr doc;
  xmlNodeSetPtr nodeset;
  xmlXPathObjectPtr result;
  xmlXPathObjectPtr psXPathTmp;
  char *pszRequest;
  xmlChar *pszService;
  xmlChar *pszVersion;
  int i;
  xmlChar *pszTmp;

  if (argc <= 1) {
    printf("Usage: %s <file>\n", argv[0]);
    return(0);
  }

  /* load document */
  docname = argv[1];
  doc = xmlParseFile(docname);
  if (doc == NULL ) {
    fprintf(stderr,"Document not parsed successfully. \n");
    return 1;
  }

  /* check for request */
  result = _getXPath(doc, (xmlChar *)"/GetCapabilities");

  if (result) {
    pszRequest = "GetCapabilities";
    printf("request = GetCapabilities\n");

    /* check for service */
    psXPathTmp = _getXPath(doc, (xmlChar *)"/GetCapabilities/@service");

    if (psXPathTmp) {
      nodeset = psXPathTmp->nodesetval;
      pszService = xmlNodeListGetString(doc, nodeset->nodeTab[0]->xmlChildrenNode, 1);
      printf("service = %s\n", pszService);
      xmlFree(pszService);
    }

    xmlXPathFreeObject (psXPathTmp);

    /* check for version */
    psXPathTmp = _getXPath(doc, (xmlChar *)"/sos:GetCapabilities/@version");

    if (psXPathTmp) {
      nodeset = psXPathTmp->nodesetval;
      pszVersion = xmlNodeListGetString(doc, nodeset->nodeTab[0]->xmlChildrenNode, 1);
      printf("version = %s\n", pszVersion);
      xmlFree(pszVersion);
    }
    xmlXPathFreeObject (result);
    xmlXPathFreeObject (psXPathTmp);
  }
  xmlFreeDoc(doc);
  xmlCleanupParser();
  return;
}

xmlXPathObjectPtr _getXPath(xmlDocPtr doc, xmlChar *xpath){
  xmlXPathContextPtr context;
  xmlXPathObjectPtr result;

  /* load document */
  context = xmlXPathNewContext(doc);
  if (context == NULL) {
    printf("Error in xmlXPathNewContext\n");
    return NULL;
  }

  /* register namespaces */
  if(xmlXPathRegisterNs(context, "sos", "http://www.opengis.net/sos/1.0") != 0) {
      printf("Couldn't register namespace\n");
      return;
  }

  result = xmlXPathEvalExpression(xpath, context);
  xmlXPathFreeContext(context);
  if (result == NULL) {
    printf("Error in xmlXPathEvalExpression\n");
    return NULL;
  }
  if(xmlXPathNodeSetIsEmpty(result->nodesetval)){
    xmlXPathFreeObject(result);
    /*printf("No result\n");*/
    return NULL;
  }
  return result;
}