#include <xml_node_set.h>
#include <libxml/xpathInternals.h>

static ID decorate ;

static int dealloc_namespace(xmlNsPtr ns)
{
  if (ns->href)
    xmlFree((xmlChar *)ns->href);
  if (ns->prefix)
    xmlFree((xmlChar *)ns->prefix);
  xmlFree(ns);
  return ST_CONTINUE;
}

static void deallocate(nokogiriNodeSetTuple *tuple)
{
  /*
   *  xmlXPathFreeNodeSet() contains an implicit assumption that it is being
   *  called before any of its pointed-to nodes have been free()d. this
   *  assumption lies in the operation where it dereferences nodeTab pointers
   *  while searching for namespace nodes to free.
   *
   *  however, since Ruby's GC mechanism cannot guarantee the strict order in
   *  which ruby objects will be GC'd, nodes may be garbage collected before a
   *  nodeset containing pointers to those nodes. (this is true regardless of
   *  how we declare dependencies between objects with rb_gc_mark().)
   *
   *  as a result, xmlXPathFreeNodeSet() will perform unsafe memory operations,
   *  and calling it would be evil.
   *
   *  so here, we *manually* free the set of namespace nodes that was
   *  constructed at initialization time (see Nokogiri_wrap_xml_node_set()), as
   *  well as the NodeSet, without using the official xmlXPathFreeNodeSet().
   *
   *  there's probably a lesson in here somewhere about intermingling, within a
   *  single array, structs with different memory-ownership semantics. or more
   *  generally, a lesson about building an API in C/C++ that does not contain
   *  assumptions about the strict order in which memory will be released. hey,
   *  that sounds like a great idea for a blog post! get to it!
   *
   *  "In Valgrind We Trust." seriously.
   */
  xmlNodeSetPtr node_set;

  node_set = tuple->node_set;

  if (!node_set)
    return;

  NOKOGIRI_DEBUG_START(node_set) ;
  st_foreach(tuple->namespaces, dealloc_namespace, 0);

  if (node_set->nodeTab != NULL)
    xmlFree(node_set->nodeTab);

  xmlFree(node_set);
  st_free_table(tuple->namespaces);
  free(tuple);
  NOKOGIRI_DEBUG_END(node_set) ;
}

static VALUE allocate(VALUE klass)
{
  return Nokogiri_wrap_xml_node_set(xmlXPathNodeSetCreate(NULL), Qnil);
}


/*
 * call-seq:
 *  dup
 *
 * Duplicate this node set
 */
static VALUE duplicate(VALUE self)
{
  nokogiriNodeSetTuple *tuple;
  xmlNodeSetPtr dupl;

  Data_Get_Struct(self, nokogiriNodeSetTuple, tuple);

  dupl = xmlXPathNodeSetMerge(NULL, tuple->node_set);

  return Nokogiri_wrap_xml_node_set(dupl, rb_iv_get(self, "@document"));
}

/*
 * call-seq:
 *  length
 *
 * Get the length of the node set
 */
static VALUE length(VALUE self)
{
  nokogiriNodeSetTuple *tuple;
  Data_Get_Struct(self, nokogiriNodeSetTuple, tuple);

  return tuple->node_set ? INT2NUM(tuple->node_set->nodeNr) : INT2NUM(0);
}

/*
 * call-seq:
 *  push(node)
 *
 * Append +node+ to the NodeSet.
 */
static VALUE push(VALUE self, VALUE rb_node)
{
  nokogiriNodeSetTuple *tuple;
  xmlNodePtr node;

  if(!(rb_obj_is_kind_of(rb_node, cNokogiriXmlNode) || rb_obj_is_kind_of(rb_node, cNokogiriXmlNamespace)))
    rb_raise(rb_eArgError, "node must be a Nokogiri::XML::Node or Nokogiri::XML::Namespace");

  Data_Get_Struct(self, nokogiriNodeSetTuple, tuple);
  Data_Get_Struct(rb_node, xmlNode, node);
  xmlXPathNodeSetAdd(tuple->node_set, node);
  return self;
}

/*
 *  call-seq:
 *    delete(node)
 *
 *  Delete +node+ from the Nodeset, if it is a member. Returns the deleted node
 *  if found, otherwise returns nil.
 */
static VALUE
delete(VALUE self, VALUE rb_node)
{
    nokogiriNodeSetTuple *tuple;
    xmlNodePtr node;
    xmlNodeSetPtr cur;
    int i;

    if (!(rb_obj_is_kind_of(rb_node, cNokogiriXmlNode) || rb_obj_is_kind_of(rb_node, cNokogiriXmlNamespace)))
	rb_raise(rb_eArgError, "node must be a Nokogiri::XML::Node or Nokogiri::XML::Namespace");

    Data_Get_Struct(self, nokogiriNodeSetTuple, tuple);
    Data_Get_Struct(rb_node, xmlNode, node);
    cur = tuple->node_set;

    if (xmlXPathNodeSetContains(cur, node)) {
	for (i = 0; i < cur->nodeNr; i++)
	    if (cur->nodeTab[i] == node) break;

	cur->nodeNr--;
	for (;i < cur->nodeNr;i++)
	    cur->nodeTab[i] = cur->nodeTab[i + 1];
	cur->nodeTab[cur->nodeNr] = NULL;
	return rb_node;
    }
    return Qnil ;
}


/*
 * call-seq:
 *  &(node_set)
 *
 * Set Intersection — Returns a new NodeSet containing nodes common to the two NodeSets.
 */
static VALUE intersection(VALUE self, VALUE rb_other)
{
  nokogiriNodeSetTuple *tuple, *other;
  xmlNodeSetPtr intersection;

  if(!rb_obj_is_kind_of(rb_other, cNokogiriXmlNodeSet))
    rb_raise(rb_eArgError, "node_set must be a Nokogiri::XML::NodeSet");

  Data_Get_Struct(self, nokogiriNodeSetTuple, tuple);
  Data_Get_Struct(rb_other, nokogiriNodeSetTuple, other);

  intersection = xmlXPathIntersection(tuple->node_set, other->node_set);
  return Nokogiri_wrap_xml_node_set(intersection, rb_iv_get(self, "@document"));
}


/*
 * call-seq:
 *  include?(node)
 *
 *  Returns true if any member of node set equals +node+.
 */
static VALUE include_eh(VALUE self, VALUE rb_node)
{
  nokogiriNodeSetTuple *tuple;
  xmlNodePtr node;

  if(!(rb_obj_is_kind_of(rb_node, cNokogiriXmlNode) || rb_obj_is_kind_of(rb_node, cNokogiriXmlNamespace)))
    rb_raise(rb_eArgError, "node must be a Nokogiri::XML::Node or Nokogiri::XML::Namespace");

  Data_Get_Struct(self, nokogiriNodeSetTuple, tuple);
  Data_Get_Struct(rb_node, xmlNode, node);

  return (xmlXPathNodeSetContains(tuple->node_set, node) ? Qtrue : Qfalse);
}


/*
 * call-seq:
 *  |(node_set)
 *
 * Returns a new set built by merging the set and the elements of the given
 * set.
 */
static VALUE set_union(VALUE self, VALUE rb_other)
{
  nokogiriNodeSetTuple *tuple, *other;
  xmlNodeSetPtr new;

  if(!rb_obj_is_kind_of(rb_other, cNokogiriXmlNodeSet))
    rb_raise(rb_eArgError, "node_set must be a Nokogiri::XML::NodeSet");

  Data_Get_Struct(self, nokogiriNodeSetTuple, tuple);
  Data_Get_Struct(rb_other, nokogiriNodeSetTuple, other);

  new = xmlXPathNodeSetMerge(NULL, tuple->node_set);
  new = xmlXPathNodeSetMerge(new, other->node_set);

  return Nokogiri_wrap_xml_node_set(new, rb_iv_get(self, "@document"));
}

/*
 * call-seq:
 *  -(node_set)
 *
 *  Difference - returns a new NodeSet that is a copy of this NodeSet, removing
 *  each item that also appears in +node_set+
 */
static VALUE minus(VALUE self, VALUE rb_other)
{
  nokogiriNodeSetTuple *tuple, *other;
  xmlNodeSetPtr new;
  int j ;

  if(!rb_obj_is_kind_of(rb_other, cNokogiriXmlNodeSet))
    rb_raise(rb_eArgError, "node_set must be a Nokogiri::XML::NodeSet");

  Data_Get_Struct(self, nokogiriNodeSetTuple, tuple);
  Data_Get_Struct(rb_other, nokogiriNodeSetTuple, other);

  new = xmlXPathNodeSetMerge(NULL, tuple->node_set);
  for (j = 0 ; j < other->node_set->nodeNr ; ++j) {
    xmlXPathNodeSetDel(new, other->node_set->nodeTab[j]);
  }

  return Nokogiri_wrap_xml_node_set(new, rb_iv_get(self, "@document"));
}


static VALUE index_at(VALUE self, long offset)
{
  xmlNodeSetPtr node_set;
  nokogiriNodeSetTuple *tuple;

  Data_Get_Struct(self, nokogiriNodeSetTuple, tuple);
  node_set = tuple->node_set;

  if (offset >= node_set->nodeNr || abs((int)offset) > node_set->nodeNr)
    return Qnil;

  if (offset < 0)
    offset += node_set->nodeNr;

  if (XML_NAMESPACE_DECL == node_set->nodeTab[offset]->type)
    return Nokogiri_wrap_xml_namespace2(rb_iv_get(self, "@document"), (xmlNsPtr)(node_set->nodeTab[offset]));
  return Nokogiri_wrap_xml_node(Qnil, node_set->nodeTab[offset]);
}

static VALUE subseq(VALUE self, long beg, long len)
{
  long j;
  nokogiriNodeSetTuple *tuple;
  xmlNodeSetPtr node_set;
  xmlNodeSetPtr new_set ;

  Data_Get_Struct(self, nokogiriNodeSetTuple, tuple);
  node_set = tuple->node_set;

  if (beg > node_set->nodeNr) return Qnil ;
  if (beg < 0 || len < 0) return Qnil ;

  if ((beg + len) > node_set->nodeNr) {
    len = node_set->nodeNr - beg ;
  }

  new_set = xmlXPathNodeSetCreate(NULL);
  for (j = beg ; j < beg+len ; ++j) {
    xmlXPathNodeSetAddUnique(new_set, node_set->nodeTab[j]);
  }
  return Nokogiri_wrap_xml_node_set(new_set, rb_iv_get(self, "@document"));
}

/*
 * call-seq:
 *  [index] -> Node or nil
 *  [start, length] -> NodeSet or nil
 *  [range] -> NodeSet or nil
 *  slice(index) -> Node or nil
 *  slice(start, length) -> NodeSet or nil
 *  slice(range) -> NodeSet or nil
 *
 * Element reference - returns the node at +index+, or returns a NodeSet
 * containing nodes starting at +start+ and continuing for +length+ elements, or
 * returns a NodeSet containing nodes specified by +range+. Negative +indices+
 * count backward from the end of the +node_set+ (-1 is the last node). Returns
 * nil if the +index+ (or +start+) are out of range.
 */
static VALUE slice(int argc, VALUE *argv, VALUE self)
{
  VALUE arg ;
  long beg, len ;
  xmlNodeSetPtr node_set;
  nokogiriNodeSetTuple *tuple;
  Data_Get_Struct(self, nokogiriNodeSetTuple, tuple);
  node_set = tuple->node_set;

  if (argc == 2) {
    beg = NUM2LONG(argv[0]);
    len = NUM2LONG(argv[1]);
    if (beg < 0) {
      beg += node_set->nodeNr ;
    }
    return subseq(self, beg, len);
  }

  if (argc != 1) {
    rb_scan_args(argc, argv, "11", NULL, NULL);
  }
  arg = argv[0];

  if (FIXNUM_P(arg)) {
    return index_at(self, FIX2LONG(arg));
  }
  
  /* if arg is Range */
  switch (rb_range_beg_len(arg, &beg, &len, (long)node_set->nodeNr, 0)) {
  case Qfalse:
    break;
  case Qnil:
    return Qnil;
  default:
    return subseq(self, beg, len);
  }

  return index_at(self, NUM2LONG(arg));
}


/*
 * call-seq:
 *  to_a
 *
 * Return this list as an Array
 */
static VALUE to_array(VALUE self, VALUE rb_node)
{
  xmlNodeSetPtr set;
  VALUE *elts;
  VALUE list;
  int i;
  nokogiriNodeSetTuple *tuple;

  Data_Get_Struct(self, nokogiriNodeSetTuple, tuple);
  set = tuple->node_set;

  elts = calloc((size_t)set->nodeNr, sizeof(VALUE *));
  for(i = 0; i < set->nodeNr; i++) {
    if (XML_NAMESPACE_DECL == set->nodeTab[i]->type)
      elts[i] = Nokogiri_wrap_xml_namespace2(rb_iv_get(self, "@document"), (xmlNsPtr)(set->nodeTab[i]));
    else
      elts[i] = Nokogiri_wrap_xml_node(Qnil, set->nodeTab[i]);
  }

  list = rb_ary_new4((long)set->nodeNr, elts);

  /*free(elts); */

  return list;
}

/*
 *  call-seq:
 *    unlink
 *
 * Unlink this NodeSet and all Node objects it contains from their current context.
 */
static VALUE unlink_nodeset(VALUE self)
{
  xmlNodeSetPtr node_set;
  int j, nodeNr ;
  nokogiriNodeSetTuple *tuple;

  Data_Get_Struct(self, nokogiriNodeSetTuple, tuple);
  node_set = tuple->node_set;
  nodeNr = node_set->nodeNr ;
  for (j = 0 ; j < nodeNr ; j++) {
    if (XML_NAMESPACE_DECL != node_set->nodeTab[j]->type) {
      VALUE node ;
      xmlNodePtr node_ptr;
      node = Nokogiri_wrap_xml_node(Qnil, node_set->nodeTab[j]);
      rb_funcall(node, rb_intern("unlink"), 0); /* modifies the C struct out from under the object */
      Data_Get_Struct(node, xmlNode, node_ptr);
      node_set->nodeTab[j] = node_ptr ;
    }
  }
  return self ;
}

VALUE Nokogiri_wrap_xml_node_set(xmlNodeSetPtr node_set, VALUE document)
{
  VALUE new_set ;
  int i;
  xmlNodePtr cur;
  xmlNsPtr ns;
  nokogiriNodeSetTuple *tuple;

  new_set = Data_Make_Struct(cNokogiriXmlNodeSet, nokogiriNodeSetTuple, 0,
			     deallocate, tuple);

  tuple->node_set = node_set;
  tuple->namespaces = st_init_numtable();

  if (!NIL_P(document)) {
    rb_iv_set(new_set, "@document", document);
    rb_funcall(document, decorate, 1, new_set);
  }

  if (node_set && node_set->nodeTab) {
    for (i = 0; i < node_set->nodeNr; i++) {
      cur = node_set->nodeTab[i];
      if (cur && cur->type == XML_NAMESPACE_DECL) {
        ns = (xmlNsPtr)cur;
        if (ns->next && ns->next->type != XML_NAMESPACE_DECL)
          st_insert(tuple->namespaces, (st_data_t)cur, (st_data_t)0);
      }
    }
  }

  return new_set ;
}

VALUE cNokogiriXmlNodeSet ;
void init_xml_node_set(void)
{
  VALUE nokogiri = rb_define_module("Nokogiri");
  VALUE xml      = rb_define_module_under(nokogiri, "XML");
  VALUE klass    = rb_define_class_under(xml, "NodeSet", rb_cObject);
  cNokogiriXmlNodeSet = klass;

  rb_define_alloc_func(klass, allocate);
  rb_define_method(klass, "length", length, 0);
  rb_define_method(klass, "[]", slice, -1);
  rb_define_method(klass, "slice", slice, -1);
  rb_define_method(klass, "push", push, 1);
  rb_define_method(klass, "|", set_union, 1);
  rb_define_method(klass, "-", minus, 1);
  rb_define_method(klass, "unlink", unlink_nodeset, 0);
  rb_define_method(klass, "to_a", to_array, 0);
  rb_define_method(klass, "dup", duplicate, 0);
  rb_define_method(klass, "delete", delete, 1);
  rb_define_method(klass, "&", intersection, 1);
  rb_define_method(klass, "include?", include_eh, 1);

  decorate = rb_intern("decorate");
}