From a661d7e1a62520a7fb4adb59e4b761c1ad2a2b04 Mon Sep 17 00:00:00 2001
From: Oliver Walters <oliver.henry.walters@gmail.com>
Date: Sun, 22 Mar 2020 17:59:23 +1100
Subject: [PATCH] Abstract the PartAttachment class

Now "Attachments" are much easier to implement for different models
---
 InvenTree/InvenTree/models.py                 | 48 +++++++++++++++++++
 .../migrations/0032_auto_20200322_0453.py     | 19 ++++++++
 InvenTree/part/models.py                      | 24 ++--------
 3 files changed, 72 insertions(+), 19 deletions(-)
 create mode 100644 InvenTree/part/migrations/0032_auto_20200322_0453.py

diff --git a/InvenTree/InvenTree/models.py b/InvenTree/InvenTree/models.py
index a60935b4b6..d2a5c5daa6 100644
--- a/InvenTree/InvenTree/models.py
+++ b/InvenTree/InvenTree/models.py
@@ -4,8 +4,11 @@ Generic models which provide extra functionality over base Django model types.
 
 from __future__ import unicode_literals
 
+import os
+
 from django.db import models
 from django.contrib.contenttypes.models import ContentType
+from django.utils.translation import gettext_lazy as _
 
 from django.db.models.signals import pre_delete
 from django.dispatch import receiver
@@ -15,6 +18,51 @@ from mptt.models import MPTTModel, TreeForeignKey
 from .validators import validate_tree_name
 
 
+def rename_attachment(instance, filename):
+    """
+    Function for renaming an attachment file.
+    The subdirectory for the uploaded file is determined by the implementing class.
+
+        Args:
+        instance: Instance of a PartAttachment object
+        filename: name of uploaded file
+
+    Returns:
+        path to store file, format: '<subdir>/<id>/filename'
+    """
+
+    # Construct a path to store a file attachment for a given model type
+    return os.path.join(instance.getSubdir(), filename)
+
+
+class InvenTreeAttachment(models.Model):
+    """ Provides an abstracted class for managing file attachments.
+
+    Attributes:
+        attachment: File
+        comment: String descriptor for the attachment
+    """
+    def getSubdir(self):
+        """
+        Return the subdirectory under which attachments should be stored.
+        Note: Re-implement this for each subclass of InvenTreeAttachment
+        """
+
+        return "attachments"
+
+    attachment = models.FileField(upload_to=rename_attachment,
+                                  help_text=_('Select file to attach'))
+
+    comment = models.CharField(max_length=100, help_text=_('File comment'))
+
+    @property
+    def basename(self):
+        return os.path.basename(self.attachment.name)
+
+    class Meta:
+        abstract = True
+
+
 class InvenTreeTree(MPTTModel):
     """ Provides an abstracted self-referencing tree model for data categories.
 
diff --git a/InvenTree/part/migrations/0032_auto_20200322_0453.py b/InvenTree/part/migrations/0032_auto_20200322_0453.py
new file mode 100644
index 0000000000..29fb25f1e7
--- /dev/null
+++ b/InvenTree/part/migrations/0032_auto_20200322_0453.py
@@ -0,0 +1,19 @@
+# Generated by Django 2.2.9 on 2020-03-22 04:53
+
+import InvenTree.models
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('part', '0031_auto_20200318_1044'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='partattachment',
+            name='attachment',
+            field=models.FileField(help_text='Select file to attach', upload_to=InvenTree.models.rename_attachment),
+        ),
+    ]
diff --git a/InvenTree/part/models.py b/InvenTree/part/models.py
index d8cb8b07e0..427cf4dcea 100644
--- a/InvenTree/part/models.py
+++ b/InvenTree/part/models.py
@@ -34,7 +34,7 @@ import hashlib
 
 from InvenTree import helpers
 from InvenTree import validators
-from InvenTree.models import InvenTreeTree
+from InvenTree.models import InvenTreeTree, InvenTreeAttachment
 from InvenTree.fields import InvenTreeURLField
 from InvenTree.helpers import decimal2string
 
@@ -941,28 +941,14 @@ def attach_file(instance, filename):
     return os.path.join('part_files', str(instance.part.id), filename)
 
 
-class PartAttachment(models.Model):
-    """ A PartAttachment links a file to a part
-    Parts can have multiple files such as datasheets, etc
-
-    Attributes:
-        part: Link to a Part object
-        attachment: File
-        comment: String descriptor for the attachment
-    """
+class PartAttachment(InvenTreeAttachment):
+    
+    def getSubdir(self):
+        return os.path.join("part_files", str(self.part.id))
 
     part = models.ForeignKey(Part, on_delete=models.CASCADE,
                              related_name='attachments')
 
-    attachment = models.FileField(upload_to=attach_file,
-                                  help_text=_('Select file to attach'))
-
-    comment = models.CharField(max_length=100, help_text=_('File comment'))
-
-    @property
-    def basename(self):
-        return os.path.basename(self.attachment.name)
-
 
 class PartStar(models.Model):
     """ A PartStar object creates a relationship between a User and a Part.