More validations, break out validation function

todo/data/import_example.csv

@@ -1,5 +1,6 @@
 Title,Group,Task List,Created Date,Due Date,Completed,Created By,Assigned To,Note,Priority
-Make dinner,Scuba Divers,Example List,2012-03-14,,No,shacker,user1,This is as good as it gets,3
-Bake bread,Scuba Divers,Example List,2012-03-14,2012-03-14,,shacker,,,
-Eat food,Scuba Divers,Example List,,2015-06-24,Yes,,user2,Every generation throws a hero up the pop charts,77
-Be glad,Scuba Divers,Example List,2019-03-07,,,,user2,,1
+Make dinner,Scuba Divers,Example List,2012-03-14,,No,shacker,shacker,This is as good as it gets,3
+Bake bread,Scuba Divers,Example List,2012-03-14,2012-03-14,,nonexistentusername,,,
+Eat food,Coyotes,Example List,,2015-06-24,Yes,user3,user2,Every generation throws a hero up the pop charts,77
+Be glad,Scuba Divers,Example List,2019-03-07,,,user3,user2,,1
+Dog food,Scuba Divers,Example List,2019-03-07,,,,user2,,1

todo/management/commands/import_csv.py

@@ -27,4 +27,5 @@ class Command(BaseCommand):
             # Don't check validity of filepath here; upserter will do that.
             filepath = str(options.get("file"))
 
-        CSVImporter.upsert(filepath)
+        importer = CSVImporter()
+        importer.upsert(filepath)

todo/operations/csv_importer.py

@@ -1,39 +1,118 @@
 import csv
+import logging
 import sys
 from pathlib import Path
 
 from django.contrib.auth import get_user_model
+from django.contrib.auth.models import Group
 from icecream import ic
 
 from todo.models import Task, TaskList
 
+log = logging.getLogger(__name__)
+
 
 class CSVImporter:
-    """Core upsert functionality for CSV import, for re-use by `import_csv` management command, web UI and tests."""
+    """Core upsert functionality for CSV import, for re-use by `import_csv` management command, web UI and tests.
+    For each row processed, first we try and get the correct related objects or set default values, then decide
+    on our upsert logic - create or update? We must enforce internal rules during object creation and take a SAFE
+    approache - for example
+    we shouldn't add a task if it specifies that a user is not a specified group. For that reason, it also doesn't
+    make sense to create new groups from here. In other words, the ingested CSV must accurately represent the current
+    database. Non-conforming rows are skipped and logged. Unlike manual task creation, we won't assume that the person
+    running this ingestion is the task creator - the creator must be specified, and a blank cell is an error. We also
+    do not create new lists - they must already exist.
+
+    Supplies a detailed log of what was and was not imported at the end."""
 
     def __init__(self):
-        pass
+        self.errors = []
+        self.line_count = 0
 
-    def upsert(filepath):
+    def upsert(self, filepath):
 
         if not Path(filepath).exists():
             print(f"Sorry, couldn't find file: {filepath}")
             sys.exit(1)
 
-        # Have arg and good file path, read rows
         with open(filepath, mode="r") as csv_file:
-            csv_reader = csv.DictReader(csv_file)
-            line_count = 0
-            for row in csv_reader:
-                # Title, Group, Task List, Created Date, Due Date, Completed, Created By, Assigned To, Note, Priority
-                newrow = row  # Copy so we can modify  properties
-                newrow["Completed"] = True if row.get("Completed") == "Yes" else False
-                ic(newrow)
+            # Have arg and good file path -- read rows
+            # Inbound columns:
+            # Title, Group, Task List, Created Date, Due Date, Completed, Created By, Assigned To, Note, Priority
 
-                if line_count == 0:
-                    print(f'Column names are {", ".join(row)}')
-                    line_count += 1
-                print(
-                    f"Row {line_count}: Title: {newrow['Title']}, Group: {newrow['Group']}, Completed: {newrow['Completed']}"
-                )
-                line_count += 1
+            csv_reader = csv.DictReader(csv_file)
+            for row in csv_reader:
+                self.line_count += 1
+
+                newrow = self.validate_row(row)  # Copy so we can modify  properties
+                if newrow:
+                    ic(newrow)
+                    print("\n")
+
+            # Report
+            for msg in self.errors:
+                print(msg)
+
+            print(f"\nProcessed {self.line_count} rows")
+            print(f"Inserted xxx rows")
+
+    def validate_row(self, row):
+        """Perform data integrity checks and set default values. Returns a valid object for insertion, or False.
+        Errors are stored for later display."""
+
+        # Task creator must exist
+        if not row.get("Created By"):
+            msg = f"Skipped row {self.line_count}: Missing required task creator."
+            self.errors.append(msg)
+            return False
+
+        created_by = get_user_model().objects.filter(username=row.get("Created By"))
+        if created_by.exists():
+            creator = created_by.first()
+        else:
+            msg = f"Skipped row {self.line_count}: Invalid task creator {row.get('Created By')}"
+            self.errors.append(msg)
+            return False
+
+        # If specified, Assignee must exist
+        if row.get("Assigned To"):
+            assigned = get_user_model().objects.filter(username=row.get("Assigned To"))
+            if assigned.exists():
+                assignee = assigned.first()
+            else:
+                msg = f"Skipped row {self.line_count}: Missing or invalid task assignee {row.get('Assigned To')}"
+                self.errors.append(msg)
+                return False
+        else:
+            assignee = None  # Perfectly valid
+
+        # Group must exist
+        try:
+            target_group = Group.objects.get(name=row.get("Group"))
+        except Group.DoesNotExist:
+            msg = f"Skipped row {self.line_count}: Could not find group {row.get('Group')}."
+            self.errors.append(msg)
+            return False
+
+        # Task creator must be in the target group
+        if target_group not in creator.groups.all():
+            msg = f"Skipped row {self.line_count}: {creator} is not in group {target_group}"
+            self.errors.append(msg)
+            return False
+
+        # Assignee must be in the target group
+        if assignee and target_group not in assignee.groups.all():
+            msg = f"Skipped row {self.line_count}: {assignee} is not in group {target_group}"
+            self.errors.append(msg)
+            return False
+
+        # Group membership checks have passed
+        row["Created By"] = creator
+        row["Group"] = target_group
+        if assignee:
+            row["Assigned To"] = assignee
+
+        # Set Completed default
+        row["Completed"] = True if row.get("Completed") == "Yes" else False
+
+        return row