From ece41f5f971595c5d005c4beaa984c45471a6647 Mon Sep 17 00:00:00 2001
From: BonfaceKilz
Date: Wed, 2 Jun 2021 07:54:35 +0300
Subject: Get the diff between 2 dicts and return that as a dict

---
 gn3/db/__init__.py               | 16 ++++++++++++++++
 tests/unit/db/test_phenotypes.py |  8 ++++++++
 2 files changed, 24 insertions(+)

diff --git a/gn3/db/__init__.py b/gn3/db/__init__.py
index 1eb7b12..19135fc 100644
--- a/gn3/db/__init__.py
+++ b/gn3/db/__init__.py
@@ -68,3 +68,19 @@ def fetchone(conn: Any,
     with conn.cursor() as cursor:
         cursor.execute(sql)
         return DATACLASSMAP[table](*cursor.fetchone())
+
+
+def diff_from_dict(old: Dict, new: Dict) -> Dict:
+    """Construct a new dict with a specific structure that contains the difference
+between the 2 dicts in the structure:
+
+diff_from_dict({"id": 1, "data": "a"}, {"id": 2, "data": "b"})
+
+Should return:
+
+{"id": {"old": 1, "new": 2}, "data": {"old": "a", "new": "b"}}
+    """
+    dict_ = {}
+    for key, value in old.items():
+        dict_[key] = {"old": old[key], "new": new[key]}
+    return dict_
diff --git a/tests/unit/db/test_phenotypes.py b/tests/unit/db/test_phenotypes.py
index 505714a..b53db23 100644
--- a/tests/unit/db/test_phenotypes.py
+++ b/tests/unit/db/test_phenotypes.py
@@ -4,6 +4,7 @@ from unittest import mock
 
 from gn3.db import fetchone
 from gn3.db import update
+from gn3.db import diff_from_dict
 from gn3.db.phenotypes import Phenotype
 
 
@@ -63,3 +64,10 @@ class TestPhenotypes(TestCase):
                              "Test pre-publication")
             cursor.execute.assert_called_once_with(
                 "SELECT * FROM Phenotype WHERE id = '35'")
+
+    def test_diff_from_dict(self):
+        """Test that a correct diff is generated"""
+        self.assertEqual(diff_from_dict({"id": 1, "data": "a"},
+                                        {"id": 2, "data": "b"}),
+                         {"id": {"old": 1, "new": 2},
+                          "data": {"old": "a", "new": "b"}})
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