From 0508c2dcaf1d763890b0852b91821a5d28b57e7b Mon Sep 17 00:00:00 2001
From: Oliver Walters <oliver.henry.walters@gmail.com>
Date: Thu, 5 Sep 2019 13:10:26 +1000
Subject: [PATCH] Use the hash for each line item to calculate the total BOM
 hash

---
 InvenTree/part/models.py      | 53 +++++++++++++++++++++++++++--------
 InvenTree/part/serializers.py |  2 ++
 2 files changed, 44 insertions(+), 11 deletions(-)

diff --git a/InvenTree/part/models.py b/InvenTree/part/models.py
index 2eb8f9f842..5627375a48 100644
--- a/InvenTree/part/models.py
+++ b/InvenTree/part/models.py
@@ -631,24 +631,15 @@ class Part(models.Model):
         """ Return a checksum hash for the BOM for this part.
         Used to determine if the BOM has changed (and needs to be signed off!)
 
-        For hash is calculated from the following fields of each BOM item:
+        The hash is calculated by hashing each line item in the BOM.
 
-        - Part.full_name (if the part name changes, the BOM checksum is invalidated)
-        - Quantity
-        - Reference field
-        - Note field
-        
         returns a string representation of a hash object which can be compared with a stored value
         """
 
         hash = hashlib.md5(str(self.id).encode())
 
         for item in self.bom_items.all().prefetch_related('sub_part'):
-            hash.update(str(item.sub_part.id).encode())
-            hash.update(str(item.sub_part.full_name).encode())
-            hash.update(str(item.quantity).encode())
-            hash.update(str(item.note).encode())
-            hash.update(str(item.reference).encode())
+            hash.update(str(item.get_item_hash()).encode())
 
         return str(hash.digest())
 
@@ -667,6 +658,10 @@ class Part(models.Model):
         - Saves the current date and the checking user
         """
 
+        # Validate each line item too
+        for item in self.bom_items.all():
+            item.validate_hash()
+
         self.bom_checksum = self.get_bom_hash()
         self.bom_checked_by = user
         self.bom_checked_date = datetime.now().date()
@@ -1157,6 +1152,42 @@ class BomItem(models.Model):
 
     checksum = models.CharField(max_length=128, blank=True, help_text='BOM line checksum')
 
+    def get_item_hash(self):
+        """ Calculate the checksum hash of this BOM line item:
+
+        The hash is calculated from the following fields:
+
+        - Part.full_name (if the part name changes, the BOM checksum is invalidated)
+        - Quantity
+        - Reference field
+        - Note field
+
+        """
+
+        # Seed the hash with the ID of this BOM item
+        hash = hashlib.md5(str(self.id).encode())
+
+        # Update the hash based on line information
+        hash.update(str(self.sub_part.id).encode())
+        hash.update(str(self.sub_part.full_name).encode())
+        hash.update(str(self.quantity).encode())
+        hash.update(str(self.note).encode())
+        hash.update(str(self.reference).encode())
+
+        return str(hash.digest())
+
+    def validate_hash(self):
+        """ Mark this item as 'valid' (store the checksum hash) """
+
+        self.checksum = str(self.get_item_hash())
+        self.save()
+
+    @property
+    def is_line_valid(self):
+        """ Check if this line item has been validated by the user """
+
+        return self.get_item_hash() == self.checksum
+
     def clean(self):
         """ Check validity of the BomItem model.
 
diff --git a/InvenTree/part/serializers.py b/InvenTree/part/serializers.py
index 47b34b292f..a8d0df5954 100644
--- a/InvenTree/part/serializers.py
+++ b/InvenTree/part/serializers.py
@@ -131,6 +131,7 @@ class BomItemSerializer(InvenTreeModelSerializer):
     part_detail = PartBriefSerializer(source='part', many=False, read_only=True)
     sub_part_detail = PartBriefSerializer(source='sub_part', many=False, read_only=True)
     price_range = serializers.CharField(read_only=True)
+    validated = serializers.BooleanField(read_only=True, source='is_line_valid')
 
     def __init__(self, *args, **kwargs):
         # part_detail and sub_part_detail serializers are only included if requested.
@@ -171,4 +172,5 @@ class BomItemSerializer(InvenTreeModelSerializer):
             'price_range',
             'overage',
             'note',
+            'validated',
         ]