class Nokogiri::XML::SAX::ParserContext

def self.file filename
  ctx = LibXML.xmlCreateFileParserCtxt filename
  pc = allocate
  pc.cstruct = LibXML::XmlParserContext.new ctx
  pc
end

def self.io io, encoding
  reader_callback = IoCallbacks.reader(io) # keep a reference to prevent it from being GC'd
  sax_ctx = LibXML.xmlCreateIOParserCtxt(
    nil,
    nil,
    reader_callback,
    nil,
    nil,
    encoding
  )
  pc = allocate
  pc.cstruct = LibXML::XmlParserContext.new sax_ctx
  pc.reader_callback = reader_callback
  pc
end

def self.memory data
  raise(ArgumentError, 'data cannot be nil') if data.nil?
  raise('data cannot be empty') if data.length == 0
  ctx = LibXML::XmlParserContext.new(
    LibXML.xmlCreateMemoryParserCtxt data, data.length
  )
  pc = allocate
  pc.cstruct = ctx
  pc
end

def self.new thing, encoding = 'UTF-8'
  [:read, :close].all? { |x| thing.respond_to?(x) } ?
    io(thing, Parser::ENCODINGS[encoding]) : memory(thing)
end

def parse_with sax_handler, type = :xml
  raise ArgumentError unless XML::SAX::Parser === sax_handler
  sax = sax_handler.cstruct
  cstruct[:sax] = sax
  sax_handler.instance_variable_set(:@ctxt, cstruct)
  LibXML.send(:"#{type}ParseDocument", cstruct)
  cstruct[:sax] = nil
  LibXML.xmlFreeDoc cstruct[:myDoc] unless cstruct[:myDoc].null?
end

def replace_entities
  self.cstruct[:replaceEntities] == 0 ? false : true
end

def replace_entities=(value)
  self.cstruct[:replaceEntities] = value ? 1 : 0
end