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Add foreign key restraints, expand and fix tests, add deletion and forking.
[misc] / todo.py
diff --git a/todo.py b/todo.py
index c3551a44aefb9040cf406cf133628c08a7c60241..dc3a346efebccc30be5d82e1840b635d79c0b5b2 100644 (file)
--- a/todo.py
+++ b/todo.py
@@ -21,27 +21,28 @@ def today_date(with_time=False):
 
 class AttributeWithHistory:
 
-    def __init__(self, default_if_empty, history=None, then_date='2000-01-01', set_check=None):
+    def __init__(self, parent, name, default_if_empty, history=None, then_date='2000-01-01'):
+        self.parent = parent 
+        self.name = name
         self.default = default_if_empty
         self.then_date = then_date
         self.history = history if history else {}
-        self.set_check = set_check
 
     def set(self, value):
-        print("DEBUG set", value, "HAS SET CHECK?", self.set_check)
-        if self.set_check:
-            print("DEBUG set CALLED SET CHECK")
-            self.set_check(value)
         keys = sorted(self.history.keys())
         if len(self.history) == 0 or value != self.history[keys[-1]]:
             self.history[today_date(with_time=True)] = value
 
     def at(self, queried_date):
-        if 0 == len(self.history):
+        end_of_queried_day = f'{queried_date} 23:59:59'
+        sorted_dates = sorted(self.history.keys())
+        if self.parent.forked_task and (0 == len(sorted_dates) or sorted_dates[0] > end_of_queried_day):
+            return getattr(self.parent.forked_task, self.name).at(queried_date)
+        elif 0 == len(sorted_dates):
             return self.default
-        ret = self.history[sorted(self.history.keys())[0]]
+        ret = self.history[sorted_dates[0]]
         for date_key, item in self.history.items():
-            if date_key > f'{queried_date} 23:59:59':
+            if date_key > end_of_queried_day:
                 break
             ret = item
         return ret
@@ -49,7 +50,11 @@ class AttributeWithHistory:
     @property
     def now(self):
         keys = sorted(self.history.keys())
-        return self.default if 0 == len(self.history) else self.history[keys[-1]]
+        if 0 == len(self.history):
+            if self.parent.forked_task:
+                return getattr(self.parent.forked_task, self.name).now
+            return self.default
+        return self.history[keys[-1]]
 
     @property
     def then(self):
@@ -63,7 +68,6 @@ class TaskLike:
         self.db = db
         self.id_ = id_
         self.comment = comment
-        self.dependers = []
 
     @property
     def visible(self):
@@ -82,8 +86,8 @@ class TaskLike:
     @property
     def deps_chain(self):
         all_deps = set()
-        def add_deps(todo, all_deps):
-            for dep in todo.deps:
+        def add_deps(node, all_deps):
+            for dep in node.deps:
                 all_deps.add(dep)
                 add_deps(dep, all_deps)
         add_deps(self, all_deps)
@@ -91,6 +95,16 @@ class TaskLike:
         chain.sort(key=lambda t: t.deps_depth)
         return chain
 
+    def loop_check(self):
+        loop_msg = "can't set dep, would create loop"
+        def f(node, id_):
+            for dep in node.deps:
+                if id_ == dep.id_:
+                    raise PlomException(loop_msg)
+                f(dep, id_)
+        f(self, self.id_)
+
+
 
 
 class Task(TaskLike):
@@ -102,12 +116,16 @@ class Task(TaskLike):
             tags_history=None,
             default_effort_history=None,
             dep_ids_history=None,
-            comment=''):
+            adoptivity_history=None,
+            comment='',
+            forks_id=None):
         super().__init__(db, id_, comment)
-        self.title = AttributeWithHistory('', title_history, self.db.selected_date)
-        self.tags = AttributeWithHistory(set(), tags_history, self.db.selected_date)
-        self.default_effort = AttributeWithHistory(0.0, default_effort_history, self.db.selected_date)
-        self.dep_ids = AttributeWithHistory(set(), dep_ids_history, self.db.selected_date, set_check=self.dep_loop_checker())
+        self.forks_id = forks_id 
+        self.title = AttributeWithHistory(self, 'title', '', title_history, self.db.selected_date)
+        self.tags = AttributeWithHistory(self, 'tags', set(), tags_history, self.db.selected_date)
+        self.default_effort = AttributeWithHistory(self, 'default_effort', 0.0, default_effort_history, self.db.selected_date)
+        self.dep_ids = AttributeWithHistory(self, 'dep_ids', set(), dep_ids_history, self.db.selected_date)
+        self.fences_adoptions = AttributeWithHistory(self, 'fences_adoptions', False, adoptivity_history, self.db.selected_date)
 
     @classmethod
     def from_dict(cls, db, d, id_):
@@ -118,7 +136,9 @@ class Task(TaskLike):
                {k: set(v) for k, v in d['tags_history'].items()},
                d['default_effort_history'],
                {k: set(v) for k, v in d['deps_history'].items()},
-               d['comment'])
+               d['adoptivity_history'],
+               comment=d['comment'],
+               forks_id=d['forks'])
         return t
 
     def to_dict(self):
@@ -127,9 +147,15 @@ class Task(TaskLike):
             'default_effort_history': self.default_effort.history,
             'tags_history': {k: list(v) for k, v in self.tags.history.items()},
             'deps_history': {k: list(v) for k, v in self.dep_ids.history.items()},
+            'adoptivity_history': self.fences_adoptions.history,
             'comment': self.comment,
+            'forks': self.forks_id,
         }
 
+    @property
+    def forked_task(self):
+        return self.db.tasks[self.forks_id] if self.forks_id else None
+
     @property
     def deps(self):
         deps = []
@@ -150,16 +176,9 @@ class Task(TaskLike):
             return sub_count
         return count_weight(self) 
 
-    def dep_loop_checker(self):
-        def f(dep_ids_now):
-            loop_msg = "can't set dep, would create loop"
-            for id_ in dep_ids_now:
-                if id_ == self.id_:
-                    raise PlomException(loop_msg)
-                elif id_ in self.db.tasks.keys():
-                    dep = self.db.tasks[id_]
-                    f(dep.dep_ids.now)
-        return f 
+    @property
+    def dependers(self):
+        return [t for t in self.db.tasks.values() if self in t.deps]
 
     def matches(self, search):
         if search is None:
@@ -167,6 +186,15 @@ class Task(TaskLike):
         else:
             return search in self.title.now or search in self.comment or search in '$'.join(self.tags.now)
 
+    @property
+    def latest_effort_date(self):
+        todos = [t for t in self.db.todos.values() if t.task.id_ == self.id_]
+        todos.sort(key=lambda t: t.latest_date)
+        if len(todos) > 0:
+            return todos[-1].latest_date 
+        else:
+            return '' 
+
 
 
 class Day:
@@ -234,6 +262,10 @@ class Day:
             todos = trunk 
         return todos
 
+    @property
+    def visible_in_export(self):
+        return len(self.comment) + len([t for t in self.linked_todos_as_list if t.visible]) > 0
+
 
 
 class Todo(TaskLike):
@@ -251,10 +283,15 @@ class Todo(TaskLike):
         super().__init__(db, id_, comment)
         self.task = task 
         self._done = done
+        for k in efforts.keys():
+            try:
+                datetime.strptime(k, DATE_FORMAT)
+            except ValueError:
+                raise PlomException(f'Todo creation: bad date string: {k}')
         self.efforts = efforts if efforts else {}
         self.day_tags = day_tags if day_tags else set()
         self.importance = importance
-        self._dep_ids = dep_ids if dep_ids else [] 
+        self.dep_ids = dep_ids if dep_ids else set() 
         self.already_listed = False
         self.been_observed = False 
 
@@ -269,7 +306,7 @@ class Todo(TaskLike):
                 set(d['day_tags']),
                 d['importance'],
                 d['efforts'],
-                d['deps'])
+                set(d['deps']))
         return todo
 
     def to_dict(self):
@@ -280,7 +317,7 @@ class Todo(TaskLike):
                 'day_tags': list(self.day_tags),
                 'importance': self.importance,
                 'efforts': self.efforts,
-                'deps': self._dep_ids}
+                'deps': list(self.dep_ids)}
 
     @property
     def title(self):
@@ -292,19 +329,11 @@ class Todo(TaskLike):
 
     @property
     def deps(self):
-        return [self.db.todos[id_] for id_ in self._dep_ids]
+        return [self.db.todos[id_] for id_ in self.dep_ids]
 
     @deps.setter
     def deps(self, deps):
-        self._dep_ids = [dep.id_ for dep in deps]
-        def f(deps):
-            loop_msg = "can't set dep, would create loop"
-            for dep in deps: 
-                if dep == self:
-                    raise PlomException(loop_msg)
-                else:
-                    f(dep.deps)
-        f(self.deps)
+        self.dep_ids = {dep.id_ for dep in deps}
 
     @property
     def default_effort(self):
@@ -427,6 +456,10 @@ class Todo(TaskLike):
     def has_dependers(self):
         return len(self.dependers) > 0
 
+    @property
+    def dependers(self):
+        return [t for t in self.db.todos.values() if self.id_ in t.dep_ids]
+
     @property
     def has_deps(self):
         return len(self.deps) > 0
@@ -439,6 +472,39 @@ class Todo(TaskLike):
     def family_effort(self):
         return self.effort_at_selected_date + self.dep_efforts
 
+    def closest_adoptable(self, task_id):
+        print("DEBUG closest_adoptable", self.id_)
+        ranked_adoptables = {self.id_: 0} 
+        def collect_downwards(node, ranked_adoptables, n_steps):
+            print("debug called collect_downwards", node.title, n_steps)
+            if not node.id_ in ranked_adoptables.keys():
+                ranked_adoptables[node.id_] = n_steps
+            for dep in node.deps:
+                collect_downwards(dep, ranked_adoptables, n_steps+1)
+        def collect_upwards(node, adoptables, n_steps):
+            print("debug called collect_upwards", node.title, n_steps)
+            collect_downwards(node, ranked_adoptables, n_steps+1)
+            if not node.task.fences_adoptions.now:
+                print("debug not blocking", node.dependers)
+                for depender in node.dependers:
+                    collect_upwards(depender, ranked_adoptables, n_steps+1)
+                if len(node.dependers) == 0:
+                    print("debug NO DEPENDERS, calling day")
+                    for t in self.db.days[self.latest_date].linked_todos_as_list:
+                        print("debug linked_todos_as_list:", t.title, t.id_)
+                        collect_downwards(t, ranked_adoptables, n_steps)
+            else:
+                print("debug BLOCKING")
+        collect_upwards(self, ranked_adoptables, 0)
+        # for depender in self.dependers:
+        #     collect_upwards(depender, ranked_adoptables, 0)
+        del ranked_adoptables[self.id_]
+        for id_, distance in sorted(ranked_adoptables.items(), key=lambda i:i[1], reverse=True):
+            if self.db.todos[id_].task.id_ == task_id:
+                return self.db.todos[id_]
+        return None
+
+
     def observe(self):
         self.been_observed = True
         return '' 
@@ -470,17 +536,17 @@ class TodoDB(PlomDB):
             t = self.add_task(id_=id_, dict_source=t_dict)
             for tag in t.tags.now:
                 self.t_tags.add(tag)
-        for task in self.tasks.values():
-            for dep in task.deps:
-                dep.dependers += [task]
+        for task in self.tasks.values():
+            for dep in task.deps:
+                dep.dependers += [task]
 
         for id_, todo_dict in d['todos'].items():
-            todo = self.add_todo(todo_dict, id_, link_into_day=False)
+            todo = self.add_todo(todo_dict, id_)
             for tag in todo.day_tags:
                 self.t_tags.add(tag)
-        for todo in self.todos.values():
-            for dep in todo.deps:
-                dep.dependers += [todo]
+        for todo in self.todos.values():
+            for dep in todo.deps:
+                dep.dependers += [todo]
 
         for date, day_dict in d['days'].items():
             self.add_day(dict_source=day_dict, date=date)
@@ -532,41 +598,74 @@ class TodoDB(PlomDB):
         self.tasks[id_] = t
         return t
 
-    def update_task(self, id_, title, default_effort, tags, dep_ids, comment):
+    def fork_task(self, id_):
+        origin = self.tasks[id_]
+        now = today_date(with_time=True)
+        fork_id = str(uuid4())
+        fork = Task(self, fork_id, {}, {}, {}, {}, origin.comment, id_)
+        self.tasks[fork_id] = fork
+        return fork
+
+    def update_task(self, id_, title, default_effort, tags, fences_adoptions, comment, dep_ids, depender_ids):
         task = self.tasks[id_] if id_ in self.tasks.keys() else self.add_task(id_)
         task.title.set(title)
         task.default_effort.set(default_effort)
         task.tags.set(tags)
-        task.dep_ids.set(dep_ids)
+        task.fences_adoptions.set(fences_adoptions)
         task.comment = comment 
+        task.dep_ids.set(dep_ids)
+        for depender in task.dependers:
+            if not depender.id_ in depender_ids:
+                depender_dep_ids = depender.dep_ids.now
+                depender_dep_ids.remove(task.id_)
+                depender.dep_ids.set(depender_dep_ids)
+        for depender_id in depender_ids:
+            depender = self.tasks[depender_id]
+            depender_dep_ids = depender.dep_ids.now
+            depender_dep_ids.add(task.id_)
+            depender.dep_ids.set(depender_dep_ids)
+        task.loop_check()
         return task
 
-    def add_todo(self, todo_dict=None, id_=None, task=None, efforts=None, link_into_day=True, adopt_if_possible=True):
+    def add_todo(self, todo_dict=None, id_=None, task=None, efforts=None, parenthood='', force_new=False, creator=None):
+        make_children = parenthood != 'childless'
+        adopt_if_possible = parenthood == 'adoption'
         id_ = id_ if id_ else str(uuid4())
         if todo_dict:
             todo = Todo.from_dict(self, todo_dict, id_)
+            self.todos[id_] = todo
         elif task and efforts:
             todo = Todo(self, id_, task, efforts=efforts)
-            deps = []
-            for dep_task in task.deps:
-                # if Todo expects dependencies, adopt any compatibles found in DB.selected_date
-                # before creating new depended Todos
-                dep_todo = None
-                if adopt_if_possible and list(efforts.keys())[0] == self.selected_date:
-                    adoptable_todos = [t for t in self.selected_day.linked_todos_as_list
-                                       if t.task.id_ == dep_task.id_]
-                    if len(adoptable_todos) > 0:
-                        dep_todo = adoptable_todos[0]
-                if not dep_todo:
-                    dep_todo = self.add_todo(task=dep_task, efforts=efforts,
-                                               link_into_day=link_into_day,
-                                               adopt_if_possible=adopt_if_possible)
-                deps += [dep_todo]
-            # todo.dep_ids = [dep.id_ for dep in deps]
-            todo.deps = deps 
-        self.todos[id_] = todo 
-        if link_into_day:
-            self.selected_day.linked_todos_as_list += [todo] 
+            print("DEBUG calling add_todo for", task.title.now, id_) 
+            print("debug creator:", creator) 
+            self.todos[id_] = todo
+            if creator:
+                creator.deps += [todo]
+            # deps = []
+            if make_children and todo.latest_date in self.days.keys():
+                for dep_task in task.deps:
+                    # if Todo expects dependencies, adopt any compatibles found in DB.selected_date
+                    # before creating new depended Todos
+                    dep_todo = None
+                    # if not force_new:
+                    if adopt_if_possible:
+                        print("debug trying adoption for", dep_task.title.now)
+                        # adoptable_todos = [t for t in self.days[todo.latest_date].linked_todos_as_list
+                        #                    if t.task.id_ == dep_task.id_]
+                        # if len(adoptable_todos) > 0:
+                        #     dep_todo = adoptable_todos[0]
+                        dep_todo = todo.closest_adoptable(dep_task.id_)
+                        print("debug GOT ADOPTION", dep_todo)
+                    if not dep_todo:
+                        # dep_todo = self.add_todo(task=dep_task, efforts=efforts, force_new)
+                        print("debug no adoption for", dep_task.title.now, id_)
+                        dep_todo = self.add_todo(task=dep_task, efforts=efforts, parenthood=parenthood, creator=todo)
+                    todo.deps += [dep_todo]
+                    # deps += [dep_todo]
+            # todo.deps = deps 
+        for date in todo.efforts.keys():
+            if date in self.days.keys():  # possibly not all Days have been initialized yet
+                self.days[date].linked_todos_as_list += [todo] 
         return todo
 
     def _update_todo_shared(self, id_, done, comment, importance):
@@ -580,11 +679,10 @@ class TodoDB(PlomDB):
         todo = self._update_todo_shared(id_, done, comment, importance)
         todo.efforts[date] = effort 
 
-    def update_todo(self, id_, efforts, done, comment, tags, importance, deps):
+    def update_todo(self, id_, efforts, done, comment, tags, importance, deps, depender_ids):
         todo = self._update_todo_shared(id_, done, comment, importance)
         if len(efforts) == 0 and not todo.deps:
             raise PlomException('todo must have at least one effort!')
-        todo.deps = deps 
         todo.efforts = efforts 
         for date in todo.efforts.keys():
             if not date in self.days.keys():
@@ -592,6 +690,14 @@ class TodoDB(PlomDB):
             if not self in self.days[date].linked_todos_as_list:
                 self.days[date].linked_todos_as_list += [todo]
         todo.day_tags = tags
+        todo.deps = deps 
+        for depender_id in depender_ids:
+            depender = self.todos[depender_id]
+            depender.dep_ids.add(todo.id_)
+        for depender in todo.dependers:
+            if not depender.id_ in depender_ids:
+                depender.dep_ids.remove(todo.id_)
+        todo.loop_check()
 
     def delete_todo(self, id_):
         todo = self.todos[id_]
@@ -601,7 +707,7 @@ class TodoDB(PlomDB):
         for date in dates_to_delete:
             self.delete_effort(todo, date, force=True)
         for depender in todo.dependers:
-            depender._dep_ids.remove(todo.id_)
+            depender.dep_ids.remove(todo.id_)
         del self.todos[id_]
 
     def delete_task(self, id_):
@@ -615,44 +721,22 @@ class TodoDB(PlomDB):
 
     # views
 
-    def show_message(self, message):
+    def get_message(self, message):
         return j2env.get_template('message.html').render(message=message)
 
-    def show_calendar(self, start_date_str, end_date_str):
-        self.tag_filter_and = ['calendar']
-        self.tag_filter_not = ['deleted']
-
-        todays_date_obj = datetime.strptime(today_date(), DATE_FORMAT) 
-        yesterdays_date_obj = todays_date_obj - timedelta(1)
-        def get_day_limit_obj(index, day_limit_string):
-            date_obj = datetime.strptime(sorted(self.days.keys())[index], DATE_FORMAT)
-            if day_limit_string and len(day_limit_string) > 0:
-                if day_limit_string in {'today', 'yesterday'}:
-                    date_obj = todays_date_obj if day_limit_string == 'today' else yesterdays_date_obj
-                else:
-                    date_obj = datetime.strptime(day_limit_string, DATE_FORMAT)
-            return date_obj
-        start_date_obj = get_day_limit_obj(0, start_date_str)
-        end_date_obj = get_day_limit_obj(-1, end_date_str)
-
-        days_to_show = {}
-        for n in range(int((end_date_obj - start_date_obj).days) + 1):
-            date_obj = start_date_obj + timedelta(n)
-            date_str = date_obj.strftime(DATE_FORMAT)
-            if date_str not in self.days.keys():
-                days_to_show[date_str] = self.add_day(date_str)
-            else:
-                days_to_show[date_str] = self.days[date_str]
-            days_to_show[date_str].month_title = date_obj.strftime('%B') if date_obj.day == 1 else None 
-            days_to_show[date_str].weekday = datetime.strptime(date_str, DATE_FORMAT).strftime('%A')[:2]
+    def get_calendar_export(self, start_date_str, end_date_str):
+        days_to_show = self.init_calendar_items(start_date_str, end_date_str)
+        return j2env.get_template('calendar_export.html').render(days=days_to_show)
 
+    def get_calendar(self, start_date_str, end_date_str):
+        days_to_show = self.init_calendar_items(start_date_str, end_date_str)
         return j2env.get_template('calendar.html').render(
                 selected_date=self.selected_date,
                 days=days_to_show,
                 start_date=start_date_str,
                 end_date=end_date_str)
 
-    def show_day_todos(self, undone_sort_order=None, done_sort_order=None, is_tree_shaped=False):
+    def get_day_todos(self, undone_sort_order=None, done_sort_order=None, is_tree_shaped=False, todo_parenthood=None):
         legal_undone_sort_keys = {'title', 'sort_done', 'default_effort', 'importance'} 
         legal_done_sort_keys = {'title', 'effort_at_selected_date', 'family_effort'} 
 
@@ -686,9 +770,10 @@ class TodoDB(PlomDB):
                 done_todos=done_todos,
                 is_tree_shaped=is_tree_shaped,
                 undone_sort=undone_sort_order,
-                done_sort=done_sort_order)
+                done_sort=done_sort_order,
+                parenthood=todo_parenthood)
 
-    def show_todo(self, id_):
+    def get_todo(self, id_, parenthood):
         todo = self.todos[id_]
         filtered_tasks = [t for t in self.tasks.values()
                           if t != todo.task] 
@@ -723,10 +808,16 @@ class TodoDB(PlomDB):
                 dep_slots=dep_slots,
                 suggested_todos=suggested_todos,
                 additional_deps=additional_deps,
+                parentood=parenthood, 
                 dep_todos=todo.deps)
 
-    def show_task(self, id_):
-        task = self.tasks[id_] if id_ else self.add_task()
+    def get_task(self, id_):
+        if id_:
+            if not id_ in self.tasks.keys():
+                raise PlomException('no Task for ID')
+            task = self.tasks[id_]
+        else:
+            task = self.add_task()
         if not id_:
             task.default_effort.set(1.0)
         filtered_tasks = [t for t in self.tasks.values()
@@ -739,7 +830,7 @@ class TodoDB(PlomDB):
                 filtered_tasks=filtered_tasks,
                 task=task)
 
-    def show_tasks(self, search, sort_order=None):
+    def get_tasks(self, search, sort_order=None):
         filtered_tasks = [] 
         for task in [t for t in self.tasks.values() if (not search) or t.matches(search)]:
             filtered_tasks += [task]
@@ -754,6 +845,8 @@ class TodoDB(PlomDB):
             filtered_tasks.sort(key=lambda t: t.default_effort.now)
         elif sort_column == 'weight':
             filtered_tasks.sort(key=lambda t: t.deps_weight)
+        elif sort_column == 'latest_effort_date':
+            filtered_tasks.sort(key=lambda t: t.latest_effort_date)
         if reverse:
             filtered_tasks.reverse()
         return j2env.get_template('tasks.html').render(
@@ -764,6 +857,162 @@ class TodoDB(PlomDB):
                 filter_not=self.tag_filter_not,
                 search=search)
 
+    # posts
+
+    def post_todo(self, id_, postvars, todo_parenthood):
+        if postvars.has('delete') and (not id_ in self.todos.keys()):
+            raise PlomException('can only do this on Todo that already exists')
+        old_todo = self.todos[id_] if id_ in self.todos.keys() else None
+        latest_date = self.selected_date 
+        efforts = {}
+        for i, date in enumerate(postvars.get_all('effort_date', [])):
+            if '' == date:
+                continue
+            latest_date = date
+            efforts[date] = postvars.get_at_index('effort', i, float_if_possible=True)
+        if postvars.has('delete'): 
+            raise PlomException('can only do this on Task that already exists')
+            has_day_effort = len([e for e in efforts.values() if e is not None]) > 0
+            if postvars.has('done')\
+                    or postvars.get('comment')\
+                    or postvars.get_all('tag', [])\
+                    or has_day_effort:
+                raise PlomException('will not remove todo of preserve-worthy values')
+            self.delete_todo(id_) 
+            return False
+        elif postvars.has('update'):
+            if postvars.has('delete_effort'):
+                for date in postvars.get_all('delete_effort'):
+                    self.delete_effort(old_todo, date)
+                    del efforts[date]
+            deps = [self.todos[adopt_id] for adopt_id in postvars.get_all('adopt_dep', [])
+                    if adopt_id in self.todos.keys()] 
+            birth_dep_ids = postvars.get_all('birth_dep', [])
+            for bad_id in [bad_id for bad_id in birth_dep_ids if not bad_id in self.tasks.keys()]:
+                raise PlomException('submitted illegal dep ID')
+            tasks_to_birth = [self.tasks[dep_id] for dep_id in birth_dep_ids]
+            for task in tasks_to_birth:
+                deps += [self.add_todo(task=task,
+                                       efforts={latest_date: None},
+                                       parenthood=todo_parenthood)]
+            depender_ids = postvars.get_all('depender', [])
+            self.update_todo(id_=id_,
+                             efforts=efforts,
+                             done=postvars.has('done'),
+                             comment=postvars.get('comment', ''),
+                             tags=postvars.get_all('tag', []),
+                             importance=postvars.get('importance', float_if_possible=True),
+                             deps=deps,
+                             depender_ids=depender_ids)
+        return True 
+
+    def post_task(self, id_, postvars):
+           if (postvars.has('delete') or postvars.has('fork')) and (not id_ in self.tasks.keys()):
+               raise PlomException('can only do this on Task that already exists')
+           if postvars.has('delete'):
+               if [t for t in self.todos.values() if id_ == t.task.id_]:
+                   raise PlomException('will not remove Task describing existing Todos')
+               if postvars.get('title', '')\
+                       or postvars.get_all('tag', [])\
+                       or postvars.get_all('dep', [])\
+                       or postvars.get('comment', ''):
+                   raise PlomException('will not remove Task of preserve-worthy values')
+               self.delete_task(id_)
+               return None 
+           elif postvars.has('update'):
+               dep_ids = postvars.get_all('dep', [])
+               for bad_id in [bad_id for bad_id in dep_ids if not bad_id in self.tasks.keys()]:
+                   raise PlomException('submitted illegal dep ID')
+               depender_ids = postvars.get_all('depender', [])
+               for bad_id in [bad_id_ for bad_id in depender_ids if not bad_id in self.tasks.keys()]:
+                   raise PlomException('submitted illegal dep ID')
+               task = self.update_task(
+                       id_=id_,
+                       title=postvars.get('title', ''),
+                       default_effort=postvars.get('default_effort', float_if_possible=True), 
+                       tags=postvars.get_all('tag', []),
+                       comment=postvars.get('comment', ''),
+                       fences_adoptions=postvars.get('fences_adoptions', False),
+                       dep_ids=dep_ids,
+                       depender_ids=depender_ids)
+               if postvars.has('add_as_todo'):
+                   self.add_todo(task=task, efforts={postvars.get('new_todo_date'): None})
+           elif postvars.has('fork'):
+               t = self.fork_task(id_)
+               return t.id_
+           return id_
+
+    def post_day_todos(self, postvars, todo_parenthood):
+        if not postvars.has('update'):
+            return
+        self.selected_date = postvars.get('date') 
+        self.selected_day.comment = postvars.get('day_comment', '') 
+        task_id = postvars.get('choose_task', None)
+        if task_id:
+            if task_id not in self.tasks.keys():
+                raise PlomException('illegal task ID entered')
+            self.add_todo(task=self.tasks[task_id], efforts={self.selected_date: None},
+                          parenthood=todo_parenthood)
+        for todo_id in postvars.get_all('choose_todo', []):
+            self.todos[todo_id].efforts[self.selected_date] = None
+        for i, todo_id in enumerate(postvars.get_all('todo_id', [])):
+            old_todo = self.todos[todo_id]
+            done = todo_id in postvars.get_all('done', [])
+            day_effort_input = postvars.get_at_index('effort', i, '') 
+            day_effort = float(day_effort_input) if len(day_effort_input) > 0 else None
+            comment = postvars.get_at_index('effort_comment', i, '') 
+            if (day_effort is not None) and (not done) and day_effort < 0 and 0 == len(comment):
+                if len(old_todo.efforts) > 1:
+                    self.delete_effort(old_todo, self.selected_date) 
+                else:
+                    self.delete_todo(todo_id)
+                continue
+            importance = float(postvars.get_at_index('importance', i))
+            if old_todo\
+                    and old_todo.done == done\
+                    and old_todo.day_effort == day_effort\
+                    and comment == old_todo.comment\
+                    and old_todo.importance == importance:
+                continue
+            self.update_todo_for_day(
+                    todo_id,
+                    self.selected_date,
+                    day_effort,
+                    done,
+                    comment,
+                    importance)
+
+    # helpers
+
+    def init_calendar_items(self, start_date_str, end_date_str):
+        self.tag_filter_and = ['calendar']
+        self.tag_filter_not = ['deleted']
+
+        todays_date_obj = datetime.strptime(today_date(), DATE_FORMAT) 
+        yesterdays_date_obj = todays_date_obj - timedelta(1)
+        def get_day_limit_obj(index, day_limit_string):
+            date_obj = datetime.strptime(sorted(self.days.keys())[index], DATE_FORMAT)
+            if day_limit_string and len(day_limit_string) > 0:
+                if day_limit_string in {'today', 'yesterday'}:
+                    date_obj = todays_date_obj if day_limit_string == 'today' else yesterdays_date_obj
+                else:
+                    date_obj = datetime.strptime(day_limit_string, DATE_FORMAT)
+            return date_obj
+        start_date_obj = get_day_limit_obj(0, start_date_str)
+        end_date_obj = get_day_limit_obj(-1, end_date_str)
+
+        days_to_show = {}
+        for n in range(int((end_date_obj - start_date_obj).days) + 1):
+            date_obj = start_date_obj + timedelta(n)
+            date_str = date_obj.strftime(DATE_FORMAT)
+            if date_str not in self.days.keys():
+                days_to_show[date_str] = self.add_day(date_str)
+            else:
+                days_to_show[date_str] = self.days[date_str]
+            days_to_show[date_str].month_title = date_obj.strftime('%B') if date_obj.day == 1 else None 
+            days_to_show[date_str].weekday = datetime.strptime(date_str, DATE_FORMAT).strftime('%A')[:2]
+        return days_to_show
+
 
 
 class ParamsParser:
@@ -773,7 +1022,6 @@ class ParamsParser:
         self.cookie_db = cookie_db
 
     def get(self, key, default=None, as_bool=False):
-        # boolean = bool == type(default) 
         param = self.params.get(key, [default])[0]
         if as_bool:
             if param == '0':
@@ -785,23 +1033,8 @@ class ParamsParser:
     def cookie_key_from_params_key(self, prefix, key):
         return f'{prefix}:{key}' if prefix else key
 
-    def get_cookied(self, key, default=None, prefix=None, as_bool=False):
-        cookie_key = self.cookie_key_from_params_key(prefix, key) 
-        param = self.get(key, default, as_bool)
-        if param == '-':
-            param = None
-            if cookie_key in self.cookie_db.keys():
-                del self.cookie_db[cookie_key]
-        if param is None and cookie_key in self.cookie_db.keys():
-            param = self.cookie_db[cookie_key]
-        if param is not None:
-            self.cookie_db[cookie_key] = param
-        return param
-
-    def get_cookied_chain(self, key, default=None, prefix=None):
-        cookie_key = self.cookie_key_from_params_key(prefix, key) 
-        params = self.params.get(key, default)
-        if params == ['-']:
+    def _get_cookied(self, cookie_key, params):
+        if params in [['-'], '-']:
             params = None 
             if cookie_key in self.cookie_db.keys():
                 del self.cookie_db[cookie_key]
@@ -811,6 +1044,16 @@ class ParamsParser:
             self.cookie_db[cookie_key] = params
         return params
 
+    def get_cookied(self, key, default=None, prefix=None, as_bool=False):
+        cookie_key = self.cookie_key_from_params_key(prefix, key) 
+        param = self.get(key, default, as_bool)
+        return self._get_cookied(cookie_key, param)
+
+    def get_cookied_chain(self, key, default=None, prefix=None):
+        cookie_key = self.cookie_key_from_params_key(prefix, key) 
+        params = self.params.get(key, default)
+        return self._get_cookied(cookie_key, params)
+
 
 
 class PostvarsParser:
@@ -843,6 +1086,7 @@ class PostvarsParser:
         self.postvars[key] = [value]
 
 
+
 class TodoHandler(PlomHandler):
 
     def config_init(self):
@@ -871,7 +1115,8 @@ class TodoHandler(PlomHandler):
         db = TodoDB()
         redir_params = []
         # if we do encounter a filter post, we repost it (and if empty, the emptying command '-')
-        for param_name, filter_db_name in {('and_tag', 'tag_filter_and'), ('not_tag', 'tag_filter_not')}:
+        for param_name, filter_db_name in {('and_tag', 'tag_filter_and'),
+                                           ('not_tag', 'tag_filter_not')}:
             filter_db = getattr(db, filter_db_name)
             if postvars.has(param_name): 
                 for target in postvars.get_all(param_name, []):
@@ -883,132 +1128,31 @@ class TodoHandler(PlomHandler):
         if site in {'calendar', 'todo'}:
             redir_params += [('end', postvars.get('end', '-'))]
             redir_params += [('start', postvars.get('start', '-'))]
-        # if site in {'tasks', 'pick_tasks'}:
-        #     redir_params += [('search', postvars.get('search', ''))]
-        if postvars.has('filter'): 
-            postvars.set('return_to', '')
-        
+        if site in {'day_todos', 'todo'}:
+            todo_parenthood = postvars.get('parenthood')
+            redir_params += [('parenthood', todo_parenthood)]
+        if site in {'todo', 'task'}:
+            id_ = postvars.get('id')
+
         if 'tasks' == site:
             redir_params += [('search', postvars.get('search', ''))]
-
         elif 'todo' == site:
-            todo_id = postvars.get('todo_id')
-            redir_params += [('id', todo_id)]
-            old_todo = db.todos[todo_id] if todo_id in db.todos.keys() else None
-            efforts = {}
-            latest_date = db.selected_date 
-            for i, date in enumerate(postvars.get_all('effort_date', [])):
-                if '' == date:
-                    continue
-                try:
-                    datetime.strptime(date, DATE_FORMAT)
-                except ValueError:
-                    raise PlomException(f'bad date string')
-                latest_date = date
-                efforts[date] = None
-                if not (old_todo and old_todo.deps):
-                    efforts[date] = postvars.get_at_index('effort', i, on_empty=None,
-                                                          float_if_possible=True)
-            if postvars.has('delete'): 
-                has_day_effort = len([e for e in efforts.values() if e is not None]) > 0
-                if postvars.has('done')\
-                        or postvars.get('comment')\
-                        or postvars.get_all('tag', [])\
-                        or has_day_effort:
-                    raise PlomException('will not remove todo of preserve-worthy values')
-                db.delete_todo(todo_id) 
-                postvars.set('return_to', 'calendar')
-            elif postvars.has('update'):
-                if postvars.has('delete_effort'):
-                    for date in postvars.get_all('delete_effort'):
-                        db.delete_effort(old_todo, date)
-                        del efforts[date]
-                deps = [db.todos[id_] for id_ in postvars.get_all('adopt_dep', [])
-                        if id_ in db.todos.keys()] 
-                for dep in deps:
-                    if not todo_id in [t.id_ for t in dep.dependers]:
-                        dep.dependers += [db.todos[todo_id]]
-                tasks_to_birth = [db.tasks[id_] for id_ in postvars.get_all('birth_dep', [])]
-                for task in tasks_to_birth:
-                    deps += [db.add_todo(task=task, efforts={latest_date: None})]
-                db.update_todo(id_=todo_id,
-                               efforts=efforts,
-                               done=postvars.has('done'),
-                               comment=postvars.get('comment', ''),
-                               tags=postvars.get_all('tag', []),
-                               importance=float(postvars.get('importance')),
-                               deps=deps)
-
+            if db.post_todo(id_, postvars, todo_parenthood):
+                redir_params += [('id', id_)]
+            else:
+                site = 'calendar'
         elif 'task' == site:
-            task_id = postvars.get('task_id')
-            if postvars.has('delete') and task_id in db.tasks.keys():
-                if [t for t in db.todos.values() if task_id == t.task.id_]:
-                    raise PlomException('will not remove Task describing existing Todos')
-                if postvars.get('title', '')\
-                        or postvars.get_all('tag', [])\
-                        or postvars.get_all('dep', [])\
-                        or postvars.get('comment', ''):
-                    raise PlomException('will not remove Task of preserve-worthy values')
-                db.delete_task(task_id)
-            elif postvars.has('update'):
-                dep_ids = postvars.get_all('dep', [])
-                for id_ in [id_ for id_ in dep_ids if not id_ in db.tasks.keys()]:
-                    raise PlomException('submitted illegal dep ID')
-                task = db.update_task(
-                        id_=task_id,
-                        title=postvars.get('title', ''),
-                        default_effort=postvars.get('default_effort', float_if_possible=True), 
-                        tags=postvars.get_all('tag', []),
-                        dep_ids=dep_ids,
-                        comment=postvars.get('comment', ''))
-                if postvars.has('add_as_todo'):
-                    db.add_todo(task=task, efforts={postvars.get('selected_date'): None})
-            redir_params += [('id', task_id)]
-
+            ret = db.post_task(id_, postvars)
+            if ret:
+                redir_params += [('id', ret)]
+            else:
+                site = 'calendar'
         elif 'day_todos' == site:
-            if postvars.has('update'): 
-                db.selected_date = postvars.get('date') 
-                redir_params += [('date', db.selected_date)]
-                db.selected_day.comment = postvars.get('day_comment', '') 
-                task_id = postvars.get('choose_task', None)
-                if task_id:
-                    if task_id not in db.tasks.keys():
-                        raise PlomException('illegal task ID entered')
-                    db.add_todo(task=db.tasks[task_id], efforts={db.selected_date: None},
-                                adopt_if_possible=(not postvars.has('dont_adopt')))
-                for id_ in postvars.get_all('choose_todo', []):
-                    db.todos[id_].efforts[db.selected_date] = None
-                for i, todo_id in enumerate(postvars.get_all('todo_id', [])):
-                    old_todo = db.todos[todo_id]
-                    done = todo_id in postvars.get_all('done', [])
-                    day_effort_input = postvars.get_at_index('effort', i, '') 
-                    day_effort = float(day_effort_input) if len(day_effort_input) > 0 else None
-                    comment = postvars.get_at_index('effort_comment', i, '') 
-                    if (day_effort is not None) and (not done) and day_effort < 0 and 0 == len(comment):
-                        if len(old_todo.efforts) > 1:
-                            db.delete_effort(old_todo, db.selected_date) 
-                        else:
-                            db.delete_todo(todo_id)
-                        continue
-                    importance = float(postvars.get_at_index('importance', i))
-                    if old_todo\
-                            and old_todo.done == done\
-                            and old_todo.day_effort == day_effort\
-                            and comment == old_todo.comment\
-                            and old_todo.importance == importance:
-                        continue
-                    db.update_todo_for_day(
-                            todo_id,
-                            db.selected_date,
-                            day_effort,
-                            done,
-                            comment,
-                            importance)
-
-        homepage = postvars.get('return_to')
-        if not homepage:
-            encoded_params = urlencode(redir_params)
-            homepage = f'{site}?{encoded_params}'
+            db.post_day_todos(postvars, todo_parenthood)
+            redir_params += [('date', db.selected_date)]
+
+        encoded_params = urlencode(redir_params)
+        homepage = f'{site}?{encoded_params}'
         db.write()
         self.redirect(homepage)
 
@@ -1019,18 +1163,24 @@ class TodoHandler(PlomHandler):
         config = self.apps['todo'] if hasattr(self, 'apps') else self.config_init()
         parsed_url = urlparse(self.path)
         site = path_split(parsed_url.path)[1]
+
         cookie_db = self.get_cookie_db(config['cookie_name'])
         params = ParamsParser(parsed_url.query, cookie_db)
-
         selected_date = tag_filter_and = tag_filter_not = None
         if site in {'day_todos', 'calendar', 'task'}:
             selected_date = params.get_cookied('date')
         if site in {'day_todos', 'tasks'}:
             tag_filter_and = params.get_cookied_chain('and_tag', prefix=site)
             tag_filter_not = params.get_cookied_chain('not_tag', prefix=site)
-        db = TodoDB(selected_date, tag_filter_and, tag_filter_not)
+        if site in {'day_todos', 'todo'}:
+            todo_parenthood = params.get_cookied('parenthood', prefix=site)
+        if site in {'calendar', 'calendar_export', ''}:
+            start_date = params.get_cookied('start', prefix=site)
+            end_date = params.get_cookied('end', prefix=site)
         if site in {'todo', 'task'}:
             id_ = params.get('id')
+
+        db = TodoDB(selected_date, tag_filter_and, tag_filter_not)
         if 'reset_cookie' == site:
             cookie_db = {  # sensible defaults
                 params.cookie_key_from_params_key('day_todos', 'tree'): True,
@@ -1038,30 +1188,31 @@ class TodoHandler(PlomHandler):
                 params.cookie_key_from_params_key('todo', 'not_tag'): ['ignore'],
                 params.cookie_key_from_params_key('todo', 'start'): 'yesterday',
                 params.cookie_key_from_params_key('todo', 'end'): 'today'}
-            page = db.show_message('cookie unset!')
+            page = db.get_message('cookie unset!')
         elif 'day_todos' == site:
-            is_tree_shaped = params.get_cookied('tree', prefix=site, as_bool=True)
+            tree_view = params.get_cookied('tree', prefix=site, as_bool=True)
             undone_sort_order = params.get_cookied('undone_sort', prefix=site)
             done_sort_order = params.get_cookied('done_sort', prefix=site)
-            page = db.show_day_todos(undone_sort_order, done_sort_order, is_tree_shaped)
+            page = db.get_day_todos(undone_sort_order, done_sort_order, tree_view, todo_parenthood)
         elif site == 'todo':
-            page = db.show_todo(id_)
+            page = db.get_todo(id_, parenthood=todo_parenthood)
         elif 'task' == site:
-            page = db.show_task(id_)
+            page = db.get_task(id_)
         elif 'tasks' == site:
             sort_order = params.get_cookied('sort', prefix=site)
             search = params.get('search', '')
-            page = db.show_tasks(search, sort_order)
+            page = db.get_tasks(search, sort_order)
         elif 'add_task' == site:
-            page = db.show_task(None)
+            page = db.get_task(None)
+        elif 'calendar_export' == site:
+            page = db.get_calendar_export(start_date, end_date)
         else:  # 'calendar' == site
-            start_date = params.get_cookied('start', prefix=site)
-            end_date = params.get_cookied('end', prefix=site)
-            page = db.show_calendar(start_date, end_date)
+            page = db.get_calendar(start_date, end_date)
 
         self.set_cookie(config['cookie_name'], config['cookie_path'], cookie_db)
         self.send_HTML(page)
 
 
+
 if __name__ == "__main__":
     run_server(server_port, TodoHandler)