#include "nse_xml.h"

extern "C" {
#include <libxml/HTMLparser.h>
#include <libxml/xpath.h>
}

typedef struct XmlDocumentData {
  xmlDocPtr document;
} XmlDocumentData;

// create a lua XmlDocument
int create_document( lua_State * L, xmlDocPtr doc ) {
  if ( doc ) {
    // parsing successful
    XmlDocumentData * doc_data;
    doc_data = (XmlDocumentData *) lua_newuserdata( L, sizeof(XmlDocumentData));
    // set metatable for userdata
    luaL_getmetatable( L, "XmlDocument" );
    lua_setmetatable( L, -2 );
    doc_data->document = doc;
  } else  {
    // parsing failed
    luaL_error( L , "parsing document failed." );
  }
  return 1;
}

// takes an html document as string and returns a XmlDocument
int xml_parse_html( lua_State * L ) {
  const char * doc_string = luaL_checkstring( L, 1 );
  lua_pop(L, 1);
  char * url = NULL;
  char * encoding = NULL;

  int options = HTML_PARSE_RECOVER | HTML_PARSE_NOERROR | HTML_PARSE_NOWARNING | HTML_PARSE_NONET;
  htmlDocPtr doc = htmlReadDoc( (xmlChar *) doc_string, url, encoding, options );

  return create_document( L, doc );
}

// takes an xml document as string and returns a XmlDocument
int xml_parse_xml( lua_State * L ) {
  const char * doc_string = luaL_checkstring( L, 1 );
  lua_pop(L, 1);
  char * url = NULL;
  char * encoding = NULL;

  int options = XML_PARSE_RECOVER | XML_PARSE_NOERROR | XML_PARSE_NOWARNING | XML_PARSE_NONET;
  xmlDocPtr doc = xmlReadDoc( (xmlChar *) doc_string, url, encoding, options );

  return create_document( L, doc );
}


static const struct luaL_reg xml_methods[] = {
  { "parse_html", xml_parse_html },
  { "parse_xml", xml_parse_xml },
  { NULL, NULL }
};

// takes an xpath expression and return the match(es) as string(s)
int xmldoc_find( lua_State * L ) {
  XmlDocumentData * doc = (XmlDocumentData *) luaL_checkudata(L, 1, "XmlDocument");
  const char * xpath = luaL_checkstring( L, 2 );
  xmlXPathContextPtr context = xmlXPathNewContext( doc->document );

  if ( !context ) luaL_error( L, "Error creating context." );

  xmlXPathObjectPtr result = xmlXPathEvalExpression((xmlChar *) xpath, context);
  xmlXPathFreeContext(context);
  if ( !result ) luaL_error( L, "Error while evaluating XPath expression." );

  if( xmlXPathNodeSetIsEmpty( result->nodesetval ) ) {
    // empty resultset
    lua_pushnil( L );
    xmlXPathFreeNodeSetList( result );
    return 1;
  } else {
    // we found something .. return first match as string
    xmlNodeSetPtr nodeset = result->nodesetval;
    char * tmp = (char *) xmlXPathCastNodeToString( nodeset->nodeTab[0] );
    lua_pushstring( L, tmp );
    free( tmp );
    xmlXPathFreeNodeSetList( result );
    return 1;
  }
}

// takes an xpath expression and return the match(es) as table containing the string(s)
int xmldoc_find_all( lua_State * L ) {
  XmlDocumentData * doc = (XmlDocumentData *) luaL_checkudata(L, 1, "XmlDocument");
  const char * xpath = luaL_checkstring( L, 2 );
  xmlXPathContextPtr context = xmlXPathNewContext( doc->document );

  if ( !context ) luaL_error( L, "Error creating context." );

  xmlXPathObjectPtr result = xmlXPathEvalExpression((xmlChar *) xpath, context);
  xmlXPathFreeContext(context);
  if ( !result ) luaL_error( L, "Error while evaluating XPath expression." );

  lua_newtable( L );

  if( xmlXPathNodeSetIsEmpty( result->nodesetval ) ) {
    // empty resultset
  } else {
    int i;
    // we found something
    xmlNodeSetPtr nodeset = result->nodesetval;
    for ( i = 0; i < nodeset->nodeNr; i++) {
      lua_pushnumber( L, i + 1 );
      char * tmp = (char *) xmlXPathCastNodeToString( nodeset->nodeTab[i] );
      lua_pushstring( L, tmp );
      free( tmp );
      lua_rawset( L, -3 );
    }
  }
  xmlXPathFreeNodeSetList( result );
  return 1;
}

int xmldoc_free( lua_State * L ) {
  XmlDocumentData * doc = (XmlDocumentData *) luaL_checkudata(L, 1, "XmlDocument");
  free( doc->document );
  return 0;
}

// XmlDocument methods
static const struct luaL_reg xmldoc_methods[] = {
  { "find", xmldoc_find },
  { "find_all", xmldoc_find_all},
  { "__gc", xmldoc_free },
  { NULL, NULL }
};


// initializer function, called when library is required
int luaopen_xml( lua_State * L ) {

  // create metatable
  luaL_newmetatable( L, "XmlDocument" );
  // metatable.__index = metatable
  lua_pushvalue( L, -1 );
  lua_setfield( L, -2, "__index" );
  // register methods
  luaL_register( L, NULL, xmldoc_methods );

  luaL_register( L, "xml", xml_methods );
  return 1;
}