librarian/embeds/__init__.py

   1 import importlib
   2 from lxml import etree
   3
   4 known_types = {
   5     'application/mathml+xml': 'librarian.embeds.mathml.MathML',
   6     'application/x-latex': 'librarian.embeds.latex.LaTeX',
   7 }
   8
   9 class Embed():
  10     @classmethod
  11     def transforms_to(cls, mime_types, downgrade=False):
  12         matches = set()
  13         for name, method in cls.__dict__.iteritems():
  14             if hasattr(method, "embed_converts_to"):
  15                 conv_type, conv_downgrade = method.embed_converts_to
  16                 if downgrade == conv_downgrade and conv_type in mime_types:
  17                     matches.add(conv_type)
  18         return matches
  19
  20     def transform_to(self, mime_type, downgrade=False):
  21         for name, method in type(cls).__dict__.iteritems():
  22             if hasattr(method, "embed_converts_to"):
  23                 conv_type, conv_downgrade = method.embed_converts_to
  24                 if downgrade == conv_downgrade and conv_type == mime_type:
  25                     return method(self)
  26
  27
  28 class DataEmbed(Embed):
  29     def __init__(self, data=None):
  30         self.data = data
  31
  32 class TreeEmbed(Embed):
  33     def __init__(self, tree=None):
  34         if isinstance(tree, etree._Element):
  35             tree = etree.ElementTree(tree)
  36         self.tree = tree
  37
  38 def converts_to(mime_type, downgrade=False):
  39     def decorator(method):
  40         method.embed_converts_to = mime_type, downgrade
  41         return method
  42     return decorator
  43
  44 def downgrades_to(mime_type):
  45     return converts_to(mime_type, True)
  46
  47 def create_embed(mime_type, tree=None, data=None):
  48     embed = known_types.get(mime_type)
  49     if embed is None:
  50         embed = DataEmbed if tree is None else TreeEmbed
  51     else:
  52         mod_name, cls_name = embed.rsplit('.', 1)
  53         mod = importlib.import_module(mod_name)
  54         embed = getattr(mod, cls_name)
  55
  56     return embed(data if tree is None else tree)