Add version control system functionality with branch management, history tracking, and merge operations

history_tracking/signals.py

@@ -0,0 +1,138 @@
+from django.db.models.signals import post_save
+from django.dispatch import receiver
+from simple_history.signals import post_create_historical_record
+from django.contrib.auth import get_user_model
+from django.db import transaction
+from .models import VersionBranch, ChangeSet, HistoricalModel
+from .managers import ChangeTracker
+import threading
+
+User = get_user_model()
+
+# Thread-local storage for tracking active changesets
+_changeset_context = threading.local()
+
+def get_current_branch():
+    """Get the currently active branch for the thread"""
+    return getattr(_changeset_context, 'current_branch', None)
+
+def set_current_branch(branch):
+    """Set the active branch for the current thread"""
+    _changeset_context.current_branch = branch
+
+def clear_current_branch():
+    """Clear the active branch for the current thread"""
+    if hasattr(_changeset_context, 'current_branch'):
+        del _changeset_context.current_branch
+
+class ChangesetContextManager:
+    """Context manager for tracking changes in a specific branch"""
+    
+    def __init__(self, branch, user=None):
+        self.branch = branch
+        self.user = user
+        self.previous_branch = None
+    
+    def __enter__(self):
+        self.previous_branch = get_current_branch()
+        set_current_branch(self.branch)
+        return self
+    
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        set_current_branch(self.previous_branch)
+
+@receiver(post_create_historical_record)
+def handle_history_record(sender, instance, history_instance, **kwargs):
+    """Handle creation of historical records by adding them to changesets"""
+    # Only handle records from HistoricalModel subclasses
+    if not isinstance(instance, HistoricalModel):
+        return
+    
+    branch = get_current_branch()
+    if not branch:
+        # If no branch is set, use the default branch
+        branch, _ = VersionBranch.objects.get_or_create(
+            name='main',
+            defaults={
+                'metadata': {
+                    'type': 'default_branch',
+                    'created_automatically': True
+                }
+            }
+        )
+    
+    # Create or get active changeset for the current branch
+    changeset = getattr(_changeset_context, 'active_changeset', None)
+    if not changeset:
+        changeset = ChangeSet.objects.create(
+            branch=branch,
+            created_by=history_instance.history_user,
+            description=f"Automatic change tracking: {history_instance.history_type}",
+            metadata={
+                'auto_tracked': True,
+                'model': instance._meta.model_name,
+                'history_type': history_instance.history_type
+            },
+            status='applied'
+        )
+        _changeset_context.active_changeset = changeset
+    
+    # Add the historical record to the changeset
+    changeset.historical_records.add(history_instance)
+
+@receiver(post_save, sender=ChangeSet)
+def handle_changeset_save(sender, instance, created, **kwargs):
+    """Handle changeset creation by updating related objects"""
+    if created and instance.status == 'applied':
+        # Clear the active changeset if this is the one we were using
+        active_changeset = getattr(_changeset_context, 'active_changeset', None)
+        if active_changeset and active_changeset.id == instance.id:
+            delattr(_changeset_context, 'active_changeset')
+        
+        # Update branch metadata
+        branch = instance.branch
+        if not branch.metadata.get('first_change'):
+            branch.metadata['first_change'] = instance.created_at.isoformat()
+        branch.metadata['last_change'] = instance.created_at.isoformat()
+        branch.metadata['change_count'] = branch.changesets.count()
+        branch.save()
+
+def start_changeset(branch, user=None, description=None):
+    """Start a new changeset in the given branch"""
+    changeset = ChangeSet.objects.create(
+        branch=branch,
+        created_by=user,
+        description=description or "Manual changeset",
+        status='pending'
+    )
+    _changeset_context.active_changeset = changeset
+    return changeset
+
+def commit_changeset(success=True):
+    """Commit the current changeset"""
+    changeset = getattr(_changeset_context, 'active_changeset', None)
+    if changeset:
+        changeset.status = 'applied' if success else 'failed'
+        changeset.save()
+        delattr(_changeset_context, 'active_changeset')
+    return changeset
+
+class ChangesetManager:
+    """Context manager for handling changesets"""
+    
+    def __init__(self, branch, user=None, description=None):
+        self.branch = branch
+        self.user = user
+        self.description = description
+        self.changeset = None
+    
+    def __enter__(self):
+        self.changeset = start_changeset(
+            self.branch,
+            self.user,
+            self.description
+        )
+        return self.changeset
+    
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        commit_changeset(success=exc_type is None)