librarian/embeds/__init__.py

   1 from __future__ import unicode_literals
   2
   3 import importlib
   4 from lxml import etree
   5
   6 known_types = {
   7     'application/mathml+xml': 'librarian.embeds.mathml.MathML',
   8     'application/x-latex': 'librarian.embeds.latex.LaTeX',
   9 }
  10
  11 class Embed():
  12     @classmethod
  13     def transforms_to(cls, mime_types, downgrade=False):
  14         matches = set()
  15         for name, method in cls.__dict__.iteritems():
  16             if hasattr(method, "embed_converts_to"):
  17                 conv_type, conv_downgrade = method.embed_converts_to
  18                 if downgrade == conv_downgrade and conv_type in mime_types:
  19                     matches.add(conv_type)
  20         return matches
  21
  22     def transform_to(self, mime_type, downgrade=False):
  23         for name, method in type(cls).__dict__.iteritems():
  24             if hasattr(method, "embed_converts_to"):
  25                 conv_type, conv_downgrade = method.embed_converts_to
  26                 if downgrade == conv_downgrade and conv_type == mime_type:
  27                     return method(self)
  28
  29
  30 class DataEmbed(Embed):
  31     def __init__(self, data=None):
  32         self.data = data
  33
  34 class TreeEmbed(Embed):
  35     def __init__(self, tree=None):
  36         if isinstance(tree, etree._Element):
  37             tree = etree.ElementTree(tree)
  38         self.tree = tree
  39
  40 def converts_to(mime_type, downgrade=False):
  41     def decorator(method):
  42         method.embed_converts_to = mime_type, downgrade
  43         return method
  44     return decorator
  45
  46 def downgrades_to(mime_type):
  47     return converts_to(mime_type, True)
  48
  49 def create_embed(mime_type, tree=None, data=None):
  50     embed = known_types.get(mime_type)
  51     if embed is None:
  52         embed = DataEmbed if tree is None else TreeEmbed
  53     else:
  54         mod_name, cls_name = embed.rsplit('.', 1)
  55         mod = importlib.import_module(mod_name)
  56         embed = getattr(mod, cls_name)
  57
  58     return embed(data if tree is None else tree)