+from django.db import models
+from django.contrib.auth.models import User
+from django.utils.translation import ugettext_lazy as _
+from mercurial import mdiff, simplemerge
+import pickle
+
+class Change(models.Model):
+ """
+ Single document change related to previous change. The "parent"
+ argument points to the version against which this change has been
+ recorded. Initial text will have a null parent.
+
+ Data contains a reverse diff needed to reproduce the initial document.
+ """
+ author = models.ForeignKey(User)
+ patch = models.TextField(blank=True)
+ tree = models.ForeignKey('Document')
+
+ parent = models.ForeignKey('self',
+ null=True, blank=True, default=None,
+ related_name="children")
+
+ merge_parent = models.ForeignKey('self',
+ null=True, blank=True, default=None,
+ related_name="merge_children")
+
+ description = models.TextField(blank=True, default='')
+ created_at = models.DateTimeField(auto_now_add=True)
+
+ class Meta:
+ ordering = ('created_at',)
+
+ def __unicode__(self):
+ return "Id: %r, Tree %r, Parent %r, Patch '''\n%s'''" % (self.id, self.tree_id, self.parent_id, self.patch)
+
+ @staticmethod
+ def make_patch(src, dst):
+ return pickle.dumps(mdiff.textdiff(src, dst))
+
+ def materialize(self):
+ changes = Change.objects.exclude(parent=None).filter(
+ tree=self.tree,
+ created_at__lte=self.created_at).order_by('created_at')
+ text = ''
+ for change in changes:
+ text = change.apply_to(text)
+ return text
+
+ def make_child(self, patch, description):
+ return self.children.create(patch=patch,
+ tree=self.tree,
+ description=description)
+
+ def make_merge_child(self, patch, description):
+ return self.merge_children.create(patch=patch,
+ tree=self.tree,
+ description=description)
+
+ def apply_to(self, text):
+ return mdiff.patch(text, pickle.loads(self.patch.encode('ascii')))
+
+
+ def merge_with(self, other):
+ assert self.tree_id == other.tree_id # same tree
+ if other.parent_id == self.pk:
+ # immediate child
+ return other
+
+ local = self.materialize()
+ base = other.merge_parent.materialize()
+ remote = other.apply_to(base)
+
+ merge = simplemerge.Merge3Text(base, local, remote)
+ result = ''.join(merge.merge_lines())
+ patch = self.make_patch(local, result)
+ return self.children.create(
+ patch=patch,
+ merge_parent=other, tree=self.tree, description=u"Automatic merge")
+
+
+class Document(models.Model):
+ """
+ File in repository.
+
+ """
+ creator = models.ForeignKey(User)
+ head = models.ForeignKey(Change,
+ null=True, blank=True, default=None,
+ help_text=_("This document's current head."))
+
+ # Some meta-data
+ name = models.CharField(max_length=200,
+ help_text=_("Name for this file to display."))
+
+ def __unicode__(self):
+ return "{0}, HEAD: {1}".format(self.name, self.head_id)
+
+ def materialize(self, version=None):
+ if self.head is None:
+ return u''
+ if version is None:
+ version = self.head
+ elif not isinstance(version, Change):
+ version = self.change_set.get(pk=version)
+ return version.materialize()
+
+ def commit(self, **kwargs):
+ if 'parent' not in kwargs:
+ parent = self.head
+ else:
+ parent = kwargs['parent']
+ if not isinstance(parent, Change):
+ parent = Change.objects.get(pk=kwargs['parent'])
+
+ if 'patch' not in kwargs:
+ if 'text' not in kwargs:
+ raise ValueError("You must provide either patch or target document.")
+ patch = Change.make_patch(self.materialize(version=parent), kwargs['text'])
+ else:
+ if 'text' in kwargs:
+ raise ValueError("You can provide only text or patch - not both")
+ patch = kwargs['patch']
+
+ old_head = self.head
+ if parent != old_head:
+ change = parent.make_merge_child(patch, kwargs.get('description', ''))
+ # not Fast-Forward - perform a merge
+ self.head = old_head.merge_with(change)
+ else:
+ self.head = parent.make_child(patch, kwargs.get('description', ''))
+ self.save()
+ return self.head
+
+ def history(self):
+ return self.changes.all()
+
+ @staticmethod
+ def listener_initial_commit(sender, instance, created, **kwargs):
+ if created:
+ instance.head = Change.objects.create(
+ author=instance.creator,
+ patch=pickle.dumps(mdiff.textdiff('', '')),
+ tree=instance)
+ instance.save()
+
+models.signals.post_save.connect(Document.listener_initial_commit, sender=Document)