Framework for replacement of MetaInformation

src/calibre/ebooks/metadata/book/__init__.py

@@ -6,7 +6,8 @@ __copyright__ = '2010, Kovid Goyal <kovid@kovidgoyal.net>'
 __docformat__ = 'restructuredtext en'
 
 '''
-All fields must have a NULL value represented as None
+All fields must have a NULL value represented as None for simple types,
+an empty list/dictionary for complex types and (None, None) for cover_data
 '''
 
 SOCIAL_METADATA_FIELDS = frozenset([
@@ -61,7 +62,7 @@ PUBLICATION_METADATA_FIELDS = frozenset([
     ])
 
 BOOK_STRUCTURE_FIELDS = frozenset([
-    # These are used by code
+    # These are used by code, Null values are None.
     'toc', 'spine', 'guide', 'manifest',
     ])
 

src/calibre/ebooks/metadata/book/base.py

@@ -0,0 +1,129 @@
+#!/usr/bin/env python
+# vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:ai
+
+__license__   = 'GPL v3'
+__copyright__ = '2010, Kovid Goyal <kovid@kovidgoyal.net>'
+__docformat__ = 'restructuredtext en'
+
+import copy
+
+from calibre.ebooks.metadata.book import RESERVED_METADATA_FIELDS
+
+NULL_VALUES = {
+                'user_metadata': {},
+                'cover_data'   : (None, None),
+                'tags'         : [],
+                'classifiers'  : {},
+                'languages'    : [],
+                'device_collections': [],
+                'authors'      : [_('Unknown')],
+                'title'        : _('Unknown'),
+}
+
+class Metadata(object):
+
+    '''
+    This class must expose a superset of the API of MetaInformation in terms
+    of attribute access and methods. Only the __init__ method is different.
+    MetaInformation will simply become a function that creates and fills in
+    the attributes of this class.
+
+    Please keep the method based API of this class to a minimum. Every method
+    becomes a reserved field name.
+    '''
+
+    def __init__(self):
+        object.__setattr__(self, '_data', copy.deepcopy(NULL_VALUES))
+
+    def __getattribute__(self, field):
+        _data = object.__getattribute__(self, '_data')
+        if field in RESERVED_METADATA_FIELDS:
+            return _data.get(field, None)
+        try:
+            return object.__getattribute__(self, field)
+        except AttributeError:
+            pass
+        if field in _data['user_metadata'].iterkeys():
+            # TODO: getting user metadata values
+            pass
+        raise AttributeError(
+                'Metadata object has no attribute named: '+ repr(field))
+
+
+    def __setattr__(self, field, val):
+        _data = object.__getattribute__(self, '_data')
+        if field in RESERVED_METADATA_FIELDS:
+            if field != 'user_metadata':
+                if not val:
+                    val = NULL_VALUES[field]
+                _data[field] = val
+            else:
+                raise AttributeError('You cannot set user_metadata directly.')
+        elif field in _data['user_metadata'].iterkeys():
+            # TODO: Setting custom column values
+            pass
+        else:
+            # You are allowed to stick arbitrary attributes onto this object as
+            # long as they dont conflict with global or user metadata names
+            # Don't abuse this privilege
+            self.__dict__[field] = val
+
+    @property
+    def reserved_names(self):
+        'The set of names you cannot use for your own purposes on this object'
+        _data = object.__getattribute__(self, '_data')
+        return frozenset(RESERVED_FIELD_NAMES).union(frozenset(
+            _data['user_metadata'].iterkeys()))
+
+    @property
+    def user_metadata_names(self):
+        'The set of user metadata names this object knows about'
+        _data = object.__getattribute__(self, '_data')
+        return frozenset(_data['user_metadata'].iterkeys())
+
+    # Old MetaInformation API {{{
+    def copy(self):
+        pass
+
+    def print_all_attributes(self):
+        pass
+
+    def smart_update(self, other):
+        pass
+
+    def format_series_index(self):
+        pass
+
+    def authors_from_string(self, raw):
+        pass
+
+    def format_authors(self):
+        pass
+
+    def format_tags(self):
+        pass
+
+    def format_rating(self):
+        return unicode(self.rating)
+
+    def __unicode__(self):
+        pass
+
+    def to_html(self):
+        pass
+
+    def __str__(self):
+        return self.__unicode__().encode('utf-8')
+
+    def __nonzero__(self):
+        return True
+
+    # }}}
+
+_m = Metadata()
+RESERVED_FIELD_NAMES = \
+        frozenset(_m.__dict__.iterkeys()).union( # _data
+        RESERVED_METADATA_FIELDS).union(
+        frozenset(Metadata.__dict__.iterkeys())) # methods defined in Metadata
+del _m
+

src/calibre/gui2/dialogs/config/create_custom_column.py

@@ -10,7 +10,7 @@ from PyQt4.Qt import QDialog, Qt, QListWidgetItem, QVariant
 
 from calibre.gui2.dialogs.config.create_custom_column_ui import Ui_QCreateCustomColumn
 from calibre.gui2 import error_dialog
-from calibre.ebooks.metadata.book import RESERVED_METADATA_FIELDS
+from calibre.ebooks.metadata.book.base import RESERVED_FIELD_NAMES
 
 class CreateCustomColumn(QDialog, Ui_QCreateCustomColumn):
 
@@ -103,7 +103,7 @@ class CreateCustomColumn(QDialog, Ui_QCreateCustomColumn):
             return self.simple_error('', _('No lookup name was provided'))
         if not col_heading:
             return self.simple_error('', _('No column heading was provided'))
-        if col in RESERVED_METADATA_FIELDS:
+        if col in RESERVED_FIELD_NAMES:
             return self.simple_error('', _('The lookup name %s is reserved and cannot be used')%col)
         bad_col = False
         if col in self.parent.custcols: