Task Table:

- task_id: primary key
- title: str (required, non-empty)
- desc: str (optional, can be empty)
- status: enum{todo, doing, pending, done}
- goal_id: foreign key to goal table (required, each task belongs to exactly one goal)
- start_time: timestamp or None
- finished_time: timestamp or None
- order: float (for ordering unfinished tasks)

Goal Table:

- goal_id: primary key
- title: str (required, non-empty)
- activated: bool (deactivated goals and their tasks are hidden from Task Page GUI)

User Table:

- user_id: primary key
- username: str (unique, required)
- password_hash: str (required)
- role: enum{user, admin} (admin can configure goal limits)
- max_goals: int (maximum goals this user can create, configurable by admin)


GUI:

Page 1. Goal CRUD
- List all goals with activate/deactivate toggle
- Create, edit, delete goals
- Shows goal title and activation status

Page 2. Task CRUD
- Tasks are grouped by their parent goal
- Only activated goals and their tasks are visible
- Focus Rule: Each goal highlights its single "doing" task prominently
- Scroll View: Tasks displayed in a scrollable selector (like time picker widget)
  - Center/focus area shows current task
  - Unfinished tasks ordered by `order` field
  - Finished tasks ordered by `finished_time` (most recent first)
  - Drag-and-drop reordering for unfinished tasks
- Side Panel: Clicking a task opens a side panel for editing task details
- Task status transitions:
  - User manually switches task to "doing" (only one per goal)
  - When "doing" task is completed, status becomes "done" (no auto-promotion)
  - User must manually set next task to "doing"


Constraints:

1. **Focus Rule**: Under each goal, there should be only one "doing" task. The GUI must visually emphasize the "doing" task for each goal.

2. **Ordering Rule**: 
   - Finished tasks are ordered by `finished_time` (descending)
   - Unfinished tasks are ordered by `order` field (ascending)
   - Users can reorder unfinished tasks via drag-and-drop

3. **Scroll View**: Tasks are displayed in a linear scroll view selector (similar to HH:mm time picker). The current task is centered/focused. Users can drag-and-drop to reorder future tasks.

4. **Task-Good Relationship**: Tasks cannot exist without a goal. Each task belongs to exactly one goal.

5. **Goal Limit**: Each user can only create up to their `max_goals` limit. Admin can modify this limit per user.

6. **Visibility**: Deactivated goals and all their tasks are hidden from the Task Page.


Business Rules:

- Task title is required and cannot be empty
- Goal title is required and cannot be empty
- Tasks can be deleted (order values don't need to be continuous)
- Goals can be activated/deactivated (only affects GUI visibility)
- Only one "doing" task per goal at any time
- Users must manually set a task to "doing" status
- Simple user registration with username/password


Tech Stack:

- Backend: Python + Flask (lightweight, good for small apps)
- Frontend: Vanilla JS + HTML/CSS (simple, no build step needed)
- Database: SQLite (lightweight file-based relational database)
- Authentication: Session-based with password hashing (bcrypt)
- Drag-and-drop: HTML5 Drag and Drop API or SortableJS


Multi-User Features:

- User registration and login
- Each user has isolated goals and tasks
- Admin user can:
  - Configure `max_goals_per_user` limit
  - View all users (optional)
- Regular users can only see/manage their own data