add deassign todo from user mutation

app/repositories/users.py

@@ -43,3 +43,9 @@ def remove_user(user_id: str) -> User:
 def add_todo_to_user(todo: Todo, user: User) -> bool:
     user.tasks.append(todo)
     return True
+
+
+def remove_todo_from_user(todo, user) -> bool:
+    index = user.tasks.index(todo)
+    user.tasks.pop(index)
+    return True

app/schema/mutations/mutation.py

@@ -6,6 +6,7 @@ from app.schema.mutations.user import (
     UpdateUser,
     DeleteUser,
     AssignTodoToUser,
+    DeassignTodoToUser,
 )
 
 
@@ -20,3 +21,4 @@ class Mutation(graphene.ObjectType):
     update_user = UpdateUser.Field()
     delete_user = DeleteUser.Field()
     assign_todo_to_user = AssignTodoToUser.Field()
+    deassign_todo_to_user = DeassignTodoToUser.Field()

app/schema/mutations/user/__init__.py

@@ -1,4 +1,4 @@
 from .create_user import CreateUser
 from .delete_user import DeleteUser
 from .update_user import UpdateUser
-from .assign_todo_to_user import AssignTodoToUser
+from .assign_todo_to_user import AssignTodoToUser, DeassignTodoToUser

app/schema/mutations/user/assign_todo_to_user.py

@@ -1,7 +1,7 @@
 import graphene
 
 from app.schema.types.response import ResponseField
-from app.usecases.user import assign_todo_to_user
+from app.usecases.user import assign_todo_to_user, deassign_todo_to_user
 
 
 class AssignTodoToUser(graphene.Mutation):
@@ -18,3 +18,19 @@ class AssignTodoToUser(graphene.Mutation):
         return AssignTodoToUser(
             ResponseField(is_success=is_success, error_message=error_message)
         )
+
+
+class DeassignTodoToUser(graphene.Mutation):
+    class Arguments:
+        todo_id = graphene.String()
+        user_id = graphene.String()
+
+    result = graphene.Field(ResponseField)
+
+    def mutate(self, info, todo_id: str, user_id: str):
+        is_success = deassign_todo_to_user(user_id=user_id, todo_id=todo_id)
+        error_message = "Cannot deassign todo to user." if not is_success else None
+
+        return AssignTodoToUser(
+            ResponseField(is_success=is_success, error_message=error_message)
+        )

app/usecases/user/__init__.py

@@ -1,4 +1,4 @@
-from .assign_todo_to_user import assign_todo_to_user
+from .assign_todo_to_user import assign_todo_to_user, deassign_todo_to_user
 from .create_user import create_user
 from .delete_user import delete_user
 from .read_all_users import read_all_users

app/usecases/user/assign_todo_to_user.py

@@ -1,10 +1,10 @@
 from app.models import User, Todo
-from app.repositories.users import add_todo_to_user
+from app.repositories.users import add_todo_to_user, remove_todo_from_user
 from app.usecases.todo import read_todo_by_id
 from app.usecases.user.read_user_by_id import read_user_by_id
 
 
-def is_already_assigned(user: User, todo: Todo) -> bool:
+def is_todo_assigned_to_user(user: User, todo: Todo) -> bool:
     return any([task == todo for task in user.tasks])
 
 
@@ -17,7 +17,22 @@ def assign_todo_to_user(user_id: str, todo_id: str) -> bool:
     if not is_success:
         return False
 
-    if is_already_assigned(user, todo):
+    if is_todo_assigned_to_user(user, todo):
         return False
 
     return add_todo_to_user(todo, user)
+
+
+def deassign_todo_to_user(user_id: str, todo_id: str) -> bool:
+    user, is_success = read_user_by_id(user_id)
+    if not is_success:
+        return False
+
+    todo, is_success = read_todo_by_id(todo_id)
+    if not is_success:
+        return False
+
+    if not is_todo_assigned_to_user(user, todo):
+        return False
+
+    return remove_todo_from_user(todo, user)