1# Imports 

2 

3import difflib 

4from django.conf import settings 

5from django.db import models 

6from django.utils.translation import ugettext_lazy as _ 

7from superdjango.db.history.models import HistoryModel 

8 

9# Exports 

10 

11__all__ = ( 

12 "History", 

13) 

14 

15# Constants 

16 

17AUTH_USER_MODEL = settings.AUTH_USER_MODEL 

18 

19# Models 

20 

21 

22class History(HistoryModel): 

23 """An entry in the record history timeline.""" 

24 

25 field_changes = models.TextField( 

26 _("field changes"), 

27 blank=True, 

28 help_text=_("Fields that changed as part of the history."), 

29 null=True 

30 ) 

31 

32 class Meta: 

33 get_latest_by = "added_dt" 

34 ordering = ["-added_dt"] 

35 verbose_name = _("History Entry") 

36 verbose_name_plural = _("History Entries") 

37 

38 @classmethod 

39 def log_field_changes(cls, instance, verb, fields=None): 

40 """Log changes to fields to the ``field_changes`` field of the history record.""" 

41 if fields is None: 

42 return 

43 

44 a = list() 

45 for change in fields: 

46 # Attempt to make text fields or long character fields look good. 

47 if len(str(change.new_value)) > 128 or len(str(change.old_value)) > 128: 

48 b = list() 

49 diff = difflib.Differ() 

50 for i in diff.compare(str(change.old_value).splitlines(), str(change.new_value).splitlines()): 

51 b.append(i.strip()) 

52 

53 a.append(" ".join(b)) 

54 else: 

55 a.append(str(change)) 

56 

57 instance.field_changes = "\n\n".join(a) 

58 instance.save(update_fields=["field_changes"])