# Copyright 2012 Google Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

"""CTypes bindings for the Gumbo HTML5 parser.

This exports the raw interface of the library as a set of very thin ctypes
wrappers.  It's intended to be wrapped by other libraries to provide a more
Pythonic API.
"""

__author__ = 'jdtang@google.com (Jonathan Tang)'

import sys
import contextlib
import ctypes
import os.path
import gumboc_tags

DONT_WE_LIKE_PYTHON = sys.version_info[0] == 2

_name_of_lib = 'libgumbo.so'
if sys.platform.startswith('darwin'):
  _name_of_lib = 'libgumbo.dylib'
elif sys.platform.startswith('win'):
  _name_of_lib = "gumbo.dll"

try:
  # First look for a freshly-built .so in the .libs directory, for development.
  _dll = ctypes.cdll.LoadLibrary(os.path.join(
      os.path.dirname(__file__), '..', '..', '.libs', _name_of_lib))
except OSError:
  # PyPI or setuptools install, look in the current directory.
  _dll = ctypes.cdll.LoadLibrary(os.path.join(
      os.path.dirname(__file__), _name_of_lib))
except OSError:
  # System library, on unix or mac osx
  _dll = ctypes.cdll.LoadLibrary(_name_of_lib)

# Some aliases for common types.
_bitvector = ctypes.c_uint
_Ptr = ctypes.POINTER

class EnumMetaclass(type(ctypes.c_uint)):
  def __new__(metaclass, name, bases, cls_dict):
    return super().__new__(metaclass, name, bases, cls_dict)

  def __init__(self, name, bases, cls_dict):
    super().__init__(name, bases, cls_dict)
    if name != 'Enum':
      try:
        for i, value in enumerate(cls_dict['_values_']):
          setattr(self, value, self.from_param(i))
      except KeyError:
        raise ValueError('No _values_ list found inside enum type.')
      except TypeError:
        raise ValueError('_values_ must be a list of names of enum constants.')

def with_metaclass(mcls):
    def decorator(cls):
        body = vars(cls).copy()
        # clean out class body
        body.pop('__dict__', None)
        body.pop('__weakref__', None)
        return mcls(cls.__name__, cls.__bases__, body)
    return decorator

@with_metaclass(EnumMetaclass)
class Enum(ctypes.c_uint):
  @classmethod
  def from_param(cls, param):
    if isinstance(param, Enum):
      if param.__class__ != cls:
        raise ValueError("Can't mix enums of different types")
      return param
    if param < 0 or param > len(cls._values_):
      raise ValueError('%d is out of range for enum type %s; max %d.' %
                       (param, cls.__name__, len(cls._values_)))
    return cls(param)

  def __eq__(self, other):
    return self.value == other.value

  def __ne__(self, other):
    return self.value != other.value

  def __hash__(self):
    return hash(self.value)

  def __repr__(self):
    try:
      return self._values_[self.value]
    except IndexError:
      raise IndexError('Value %d is out of range for %r' %
                       (self.value, self._values_))


class StringPiece(ctypes.Structure):
  _fields_ = [
      ('data', _Ptr(ctypes.c_char)),
      ('length', ctypes.c_size_t),
      ]

  def __len__(self):
    return self.length

  def __str__(self):
    if DONT_WE_LIKE_PYTHON:
      return ctypes.string_at(self.data, self.length)
    return ctypes.string_at(self.data, self.length).decode('utf-8')


class SourcePosition(ctypes.Structure):
  _fields_ = [
      ('line', ctypes.c_uint),
      ('column', ctypes.c_uint),
      ('offset', ctypes.c_uint)
      ]
SourcePosition.EMPTY = SourcePosition.in_dll(_dll, 'kGumboEmptySourcePosition')


class AttributeNamespace(Enum):
  URLS = [
      'http://www.w3.org/1999/xhtml',
      'http://www.w3.org/1999/xlink',
      'http://www.w3.org/XML/1998/namespace',
      'http://www.w3.org/2000/xmlns',
  ]
  _values_ = ['NONE', 'XLINK', 'XML', 'XMLNS']

  def to_url(self):
    return self.URLS[self.value]


class Attribute(ctypes.Structure):
  _fields_ = [
      ('namespace', AttributeNamespace),
      ('name', ctypes.c_char_p),
      ('original_name', StringPiece),
      ('value', ctypes.c_char_p),
      ('original_value', StringPiece),
      ('name_start', SourcePosition),
      ('name_end', SourcePosition),
      ('value_start', SourcePosition),
      ('value_end', SourcePosition)
      ]


class Vector(ctypes.Structure):
  _type_ = ctypes.c_void_p
  _fields_ = [
      ('data', _Ptr(ctypes.c_void_p)),
      ('length', ctypes.c_uint),
      ('capacity', ctypes.c_uint)
      ]

  class Iter(object):
    def __init__(self, vector):
      self.current = 0
      self.vector = vector

    def __iter__(self):
      return self

    def __next__(self):
      # Python 3
      if self.current >= self.vector.length:
        raise StopIteration
      obj = self.vector[self.current]
      self.current += 1
      return obj

    def next(self):
      # Python 2
      return self.__next__()

  def __len__(self):
    return self.length

  def __getitem__(self, i):
    try:
      # Python 2
      numeric_types = (int, long)
    except NameError:
      # Python 3
      numeric_types = int

    if isinstance(i, numeric_types):
      if i < 0:
        i += self.length
      if i > self.length:
        raise IndexError
      array_type = _Ptr(_Ptr(self._type_))
      return ctypes.cast(self.data, array_type)[i].contents
    return list(self)[i]

  def __iter__(self):
    return Vector.Iter(self)


Vector.EMPTY = Vector.in_dll(_dll, 'kGumboEmptyVector')


class AttributeVector(Vector):
  _type_ = Attribute


class NodeVector(Vector):
  # _type_ assigned later, to avoid circular references with Node
  pass


class QuirksMode(Enum):
  _values_ = ['NO_QUIRKS', 'QUIRKS', 'LIMITED_QUIRKS']


class Document(ctypes.Structure):
  _fields_ = [
      ('children', NodeVector),
      ('has_doctype', ctypes.c_bool),
      ('name', ctypes.c_char_p),
      ('public_identifier', ctypes.c_char_p),
      ('system_identifier', ctypes.c_char_p),
      ('doc_type_quirks_mode', QuirksMode),
      ]

  def __repr__(self):
    return 'Document'


class Namespace(Enum):
  URLS = [
      'http://www.w3.org/1999/xhtml',
      'http://www.w3.org/2000/svg',
      'http://www.w3.org/1998/Math/MathML',
  ]
  _values_ = ['HTML', 'SVG', 'MATHML']

  def to_url(self):
    return self.URLS[self.value]


class Tag(Enum):
  @staticmethod
  def from_str(tagname):
    text_ptr = ctypes.c_char_p(tagname.encode('utf-8'))
    return _tag_enum(text_ptr)

  _values_ = gumboc_tags.TagNames + ['UNKNOWN', 'LAST']

class Element(ctypes.Structure):
  _fields_ = [
      ('children', NodeVector),
      ('tag', Tag),
      ('tag_namespace', Namespace),
      ('original_tag', StringPiece),
      ('original_end_tag', StringPiece),
      ('start_pos', SourcePosition),
      ('end_pos', SourcePosition),
      ('attributes', AttributeVector),
      ]

  @property
  def tag_name(self):
    original_tag = StringPiece.from_buffer_copy(self.original_tag)
    _tag_from_original_text(ctypes.byref(original_tag))
    if self.tag_namespace == Namespace.SVG:
      svg_tagname = _normalize_svg_tagname(ctypes.byref(original_tag))
      if svg_tagname is not None:
        if DONT_WE_LIKE_PYTHON:
          return str(svg_tagname)
        return bytes(svg_tagname)
    if self.tag == Tag.UNKNOWN:
      if original_tag.data is None:
        return ''
      if DONT_WE_LIKE_PYTHON:
        return str(original_tag).lower()
      return str(original_tag).lower().encode('utf-8')
    return _tagname(self.tag)

  def __repr__(self):
    return ('<%r>\n' % self.tag +
            '\n'.join(repr(child) for child in self.children) +
            '</%r>' % self.tag)


class Text(ctypes.Structure):
  _fields_ = [
      ('text', ctypes.c_char_p),
      ('original_text', StringPiece),
      ('start_pos', SourcePosition)
      ]

  def __repr__(self):
    return 'Text(%r)' % self.text


class NodeType(Enum):
  _values_ = ['DOCUMENT', 'ELEMENT', 'TEXT', 'CDATA',
              'COMMENT', 'WHITESPACE', 'TEMPLATE']


class NodeUnion(ctypes.Union):
  _fields_ = [
      ('document', Document),
      ('element', Element),
      ('text', Text),
      ]


class Node(ctypes.Structure):
  # _fields_ set later to avoid a circular reference

  def _contents(self):
    # Python3 enters an infinite loop if you use an @property within
    # __getattr__, so we factor it out to a helper.
    if self.type == NodeType.DOCUMENT:
      return self.v.document
    elif self.type in (NodeType.ELEMENT, NodeType.TEMPLATE):
      return self.v.element
    else:
      return self.v.text

  @property
  def contents(self):
    return self._contents()

  def __getattr__(self, name):
    return getattr(self._contents(), name)

  def __setattr__(self, name, value):
    return setattr(self._contents(), name, value)

  def __repr__(self):
    return repr(self.contents)


Node._fields_ = [
    ('type', NodeType),
    # Set the type to Node later to avoid a circular dependency.
    ('parent', _Ptr(Node)),
    ('index_within_parent', ctypes.c_size_t),
    # TODO(jdtang): Make a real list of enum constants for this.
    ('parse_flags', _bitvector),
    ('v', NodeUnion)
    ]
NodeVector._type_ = Node


class Options(ctypes.Structure):
  _fields_ = [
      # TODO(jdtang): Allow the Python API to set the allocator/deallocator
      # function.  Right now these are treated as opaque void pointers.
      ('allocator', ctypes.c_void_p),
      ('deallocator', ctypes.c_void_p),
      ('userdata', ctypes.c_void_p),
      ('tab_stop', ctypes.c_int),
      ('stop_on_first_error', ctypes.c_bool),
      ('max_errors', ctypes.c_int),
      ('fragment_context', Tag),
      ('fragment_namespace', Namespace),
      ]


class Output(ctypes.Structure):
  _fields_ = [
      ('document', _Ptr(Node)),
      ('root', _Ptr(Node)),
      # TODO(jdtang): Error type.
      ('errors', Vector),
      ]

@contextlib.contextmanager
def parse(text, **kwargs):
  options = Options()
  for field_name, _ in Options._fields_:
    try:
      setattr(options, field_name, kwargs[field_name])
    except KeyError:
      setattr(options, field_name, getattr(_DEFAULT_OPTIONS, field_name))
  # We have to manually take a reference to the input text here so that it
  # outlives the parse output.  If we let ctypes do it automatically on function
  # call, it creates a temporary buffer which is destroyed when the call
  # completes, and then the original_text pointers point into invalid memory.
  text_ptr = ctypes.c_char_p(text.encode('utf-8'))
  output = _parse_with_options(ctypes.byref(options), text_ptr, len(text))
  try:
    yield output
  finally:
    _destroy_output(ctypes.byref(options), output)

_DEFAULT_OPTIONS = Options.in_dll(_dll, 'kGumboDefaultOptions')

_parse_with_options = _dll.gumbo_parse_with_options
_parse_with_options.argtypes = [_Ptr(Options), ctypes.c_char_p, ctypes.c_size_t]
_parse_with_options.restype = _Ptr(Output)

_tag_from_original_text = _dll.gumbo_tag_from_original_text
_tag_from_original_text.argtypes = [_Ptr(StringPiece)]
_tag_from_original_text.restype = None

_normalize_svg_tagname = _dll.gumbo_normalize_svg_tagname
_normalize_svg_tagname.argtypes = [_Ptr(StringPiece)]
_normalize_svg_tagname.restype = ctypes.c_char_p

_destroy_output = _dll.gumbo_destroy_output
_destroy_output.argtypes = [_Ptr(Options), _Ptr(Output)]
_destroy_output.restype = None

_tagname = _dll.gumbo_normalized_tagname
_tagname.argtypes = [Tag]
_tagname.restype = ctypes.c_char_p

_tag_enum = _dll.gumbo_tag_enum
_tag_enum.argtypes = [ctypes.c_char_p]
_tag_enum.restype = Tag

__all__ = ['StringPiece', 'SourcePosition', 'AttributeNamespace', 'Attribute',
           'Vector', 'AttributeVector', 'NodeVector', 'QuirksMode', 'Document',
           'Namespace', 'Tag', 'Element', 'Text', 'NodeType', 'Node',
           'Options', 'Output', 'parse']
