src/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
  12 class Embed():
  13     @classmethod
  14     def transforms_to(cls, mime_types, downgrade=False):
  15         matches = set()
  16         for name, method in cls.__dict__.iteritems():
  17             if hasattr(method, "embed_converts_to"):
  18                 conv_type, conv_downgrade = method.embed_converts_to
  19                 if downgrade == conv_downgrade and conv_type in mime_types:
  20                     matches.add(conv_type)
  21         return matches
  22
  23     def transform_to(self, mime_type, downgrade=False):
  24         for name, method in type(self).__dict__.iteritems():
  25             if hasattr(method, "embed_converts_to"):
  26                 conv_type, conv_downgrade = method.embed_converts_to
  27                 if downgrade == conv_downgrade and conv_type == mime_type:
  28                     return method(self)
  29
  30
  31 class DataEmbed(Embed):
  32     def __init__(self, data=None):
  33         self.data = data
  34
  35
  36 class TreeEmbed(Embed):
  37     def __init__(self, tree=None):
  38         if isinstance(tree, etree._Element):
  39             tree = etree.ElementTree(tree)
  40         self.tree = tree
  41
  42
  43 def converts_to(mime_type, downgrade=False):
  44     def decorator(method):
  45         method.embed_converts_to = mime_type, downgrade
  46         return method
  47     return decorator
  48
  49
  50 def downgrades_to(mime_type):
  51     return converts_to(mime_type, True)
  52
  53
  54 def create_embed(mime_type, tree=None, data=None):
  55     embed = known_types.get(mime_type)
  56     if embed is None:
  57         embed = DataEmbed if tree is None else TreeEmbed
  58     else:
  59         mod_name, cls_name = embed.rsplit('.', 1)
  60         mod = importlib.import_module(mod_name)
  61         embed = getattr(mod, cls_name)
  62
  63     return embed(data if tree is None else tree)