src/librarian/embeds/__init__.py

   1 # This file is part of Librarian, licensed under GNU Affero GPLv3 or later.
   2 # Copyright © Fundacja Wolne Lektury. See NOTICE for more information.
   3 #
   4 import importlib
   5 from lxml import etree
   6
   7 known_types = {
   8     'application/mathml+xml': 'librarian.embeds.mathml.MathML',
   9     'application/x-latex': 'librarian.embeds.latex.LaTeX',
  10 }
  11
  12
  13 class Embed():
  14     @classmethod
  15     def transforms_to(cls, mime_types, downgrade=False):
  16         matches = set()
  17         for name, method in cls.__dict__.iteritems():
  18             if hasattr(method, "embed_converts_to"):
  19                 conv_type, conv_downgrade = method.embed_converts_to
  20                 if downgrade == conv_downgrade and conv_type in mime_types:
  21                     matches.add(conv_type)
  22         return matches
  23
  24     def transform_to(self, mime_type, downgrade=False):
  25         for name, method in type(self).__dict__.iteritems():
  26             if hasattr(method, "embed_converts_to"):
  27                 conv_type, conv_downgrade = method.embed_converts_to
  28                 if downgrade == conv_downgrade and conv_type == mime_type:
  29                     return method(self)
  30
  31
  32 class DataEmbed(Embed):
  33     def __init__(self, data=None):
  34         self.data = data
  35
  36
  37 class TreeEmbed(Embed):
  38     def __init__(self, tree=None):
  39         if isinstance(tree, etree._Element):
  40             tree = etree.ElementTree(tree)
  41         self.tree = tree
  42
  43
  44 def converts_to(mime_type, downgrade=False):
  45     def decorator(method):
  46         method.embed_converts_to = mime_type, downgrade
  47         return method
  48     return decorator
  49
  50
  51 def downgrades_to(mime_type):
  52     return converts_to(mime_type, True)
  53
  54
  55 def create_embed(mime_type, tree=None, data=None):
  56     embed = known_types.get(mime_type)
  57     if embed is None:
  58         embed = DataEmbed if tree is None else TreeEmbed
  59     else:
  60         mod_name, cls_name = embed.rsplit('.', 1)
  61         mod = importlib.import_module(mod_name)
  62         embed = getattr(mod, cls_name)
  63
  64     return embed(data if tree is None else tree)