Add a convenience formatter function to slice up hierarchical tag fields.

src/calibre/utils/formatter_functions.py

@@ -11,7 +11,7 @@ __docformat__ = 'restructuredtext en'
 import inspect, re, traceback, sys
 
 from calibre.utils.titlecase import titlecase
-from calibre.utils.icu import capitalize, strcmp
+from calibre.utils.icu import capitalize, strcmp, sort_key
 from calibre.utils.date import parse_date, format_date
 
 
@@ -427,8 +427,8 @@ class BuiltinSublist(BuiltinFormatterFunction):
     name = 'sublist'
     arg_count = 4
     doc = _('sublist(val, start_index, end_index, separator) -- interpret the '
-            ' value as a list of items separated by `separator`, returning a '
+            'value as a list of items separated by `separator`, returning a '
-            ' new list made from the `start_index`th to the `end_index`th item. '
+            'new list made from the `start_index`th to the `end_index`th item. '
             'The first item is number zero. If an index is negative, then it '
             'counts from the end of the list. As a special case, an end_index '
             'of zero is assumed to be the length of the list. Examples using '
@@ -451,6 +451,43 @@ class BuiltinSublist(BuiltinFormatterFunction):
         except:
             return ''
 
+class BuiltinSubitems(BuiltinFormatterFunction):
+    name = 'subitems'
+    arg_count = 3
+    doc = _('subitems(val, start_index, end_index) -- This function is used to '
+            'break apart lists of items such as genres. It interprets the value '
+            'as a comma-separated list of items, where each item is a period-'
+            'separated list. Returns a new list made by first finding all the'
+            'period-separated items, then for each such item extracting the '
+            'start_index`th to the `end_index`th components, then combining '
+            'the results back together. The first component in a period-'
+            'separated list has an index of zero. If an index is negative, '
+            'then it counts from the end of the list. As a special case, an '
+            'end_index of zero is assumed to be the length of the list. '
+            'Example using basic template mode and assuming a #genre value of '
+            '"A.B.C": {#genre:subgroup(0,1)} returns A. '
+            '{#genre:sublist(0,2)} returns A.B. {#genre:subgroup(1,0)} returns '
+            'C. Assuming a #genre value of "A.B.C,D.E.F", {#genre:subgroup(0,1)} '
+            'returns A,D. {#genre:sublist(0,2)} returns A.B,D.E')
+
+    def evaluate(self, formatter, kwargs, mi, locals, val, start_index, end_index):
+        if not val:
+            return ''
+        si = int(start_index)
+        ei = int(end_index)
+        items = [v.strip() for v in val.split(',')]
+        rv = set()
+        for item in items:
+            component = item.split('.')
+            try:
+                if ei == 0:
+                    rv.add('.'.join(component[si:]))
+                else:
+                    rv.add('.'.join(component[si:ei]))
+            except:
+                pass
+        return ', '.join(sorted(rv, key=sort_key))
+
 class BuiltinFormat_date(BuiltinFormatterFunction):
     name = 'format_date'
     arg_count = 2
@@ -532,6 +569,7 @@ builtin_select      = BuiltinSelect()
 builtin_shorten     = BuiltinShorten()
 builtin_strcat      = BuiltinStrcat()
 builtin_strcmp      = BuiltinStrcmp()
+builtin_subitems    = BuiltinSubitems()
 builtin_sublist     = BuiltinSublist()
 builtin_substr      = BuiltinSubstr()
 builtin_subtract    = BuiltinSubtract()