# Default Status Management Implementation

## Overview
Implemented the default status management functionality for custom task statuses, allowing users to designate which status should be automatically assigned to new tasks.

## Requirements Addressed
- **5.1**: Visual indicator for default status
- **5.2**: Set status as default and ensure only one default at a time
- **5.3**: New tasks receive the default status
- **5.4**: Fallback to "not_started" when no custom default exists
- **5.5**: Auto-assign new default when default status is deleted

## Implementation Details

### Frontend Changes

#### CustomTaskStatusManager.vue
Added the following functionality:

1. **"Set as Default" Button**
   - Added button to each non-default custom status
   - Button includes star icon and "Set as Default" text
   - Button is hidden for statuses that are already default
   - Button is disabled during reordering operations

2. **State Management**
   - Added `isSettingDefault` ref to track operation state
   - Disables all "Set as Default" buttons during operation

3. **handleSetAsDefault Method**
   ```typescript
   const handleSetAsDefault = async (customStatus: CustomTaskStatus) => {
     try {
       isSettingDefault.value = true
       
       await customTaskStatusService.updateStatus(
         props.projectId,
         customStatus.id,
         { is_default: true }
       )
       
       toast({
         title: 'Success',
         description: `"${customStatus.name}" is now the default status for new tasks`
       })
       
       await loadStatuses()
       emit('updated')
     } catch (error: any) {
       toast({
         title: 'Error',
         description: error.response?.data?.detail || 'Failed to set default status',
         variant: 'destructive'
       })
     } finally {
       isSettingDefault.value = false
     }
   }
   ```

4. **Visual Indicators**
   - Default status shows "Default" badge with star icon
   - Non-default custom statuses show "Custom" badge
   - System statuses show "System" badge

### Backend Support (Already Implemented)

The backend already had full support for default status management:

1. **Update Endpoint** (`PUT /projects/{id}/task-statuses/{status_id}`)
   - Accepts `is_default` field in update payload
   - When setting a status as default, automatically unsets other defaults
   - Ensures only one status is marked as default at a time

2. **Delete Endpoint** (`DELETE /projects/{id}/task-statuses/{status_id}`)
   - When deleting the default status, automatically assigns the first remaining status as default
   - Handles task reassignment if status is in use

3. **Default Status Resolution**
   - Falls back to "not_started" when no custom default exists
   - Returns `default_status_id` in all API responses

### Service Layer (Already Implemented)

The `customTaskStatus.ts` service already supported the `is_default` field:

```typescript
export interface CustomTaskStatusUpdate {
  name?: string
  color?: string
  is_default?: boolean  // Already present
}
```

## User Experience

### Setting Default Status
1. User views custom statuses list
2. Non-default statuses show "Set as Default" button
3. User clicks button on desired status
4. Success toast appears with confirmation message
5. Status list updates to show new default
6. Previous default status now shows "Set as Default" button

### Visual Feedback
- **Default Badge**: Green badge with star icon and "Default" text
- **Custom Badge**: Gray outline badge with "Custom" text
- **Button State**: Disabled during operations to prevent race conditions
- **Toast Notifications**: Success/error messages for user feedback

### Alternative Method
Users can also set default status through the edit dialog:
1. Click edit button on any status
2. Check "Set as default status for new tasks" checkbox
3. Save changes
4. Status becomes the new default

## Testing

Created comprehensive test files:
- `frontend/test-default-status-management.html` - Full test plan with 10 test cases
- `frontend/test-set-default-status.html` - Quick manual test guide

### Key Test Scenarios
1. ✅ Visual indicator for default status
2. ✅ Set status as default via button
3. ✅ Set status as default via edit dialog
4. ✅ Only one default at a time
5. ✅ Button visibility (hidden for default status)
6. ✅ New tasks receive default status
7. ✅ Fallback to "not_started" when no custom default
8. ✅ Auto-assign new default when default is deleted
9. ✅ Disabled states during operations
10. ✅ API response validation

## Edge Cases Handled

1. **No Custom Statuses**: Falls back to "not_started" as default
2. **Deleting Default Status**: Automatically promotes first remaining status to default
3. **Concurrent Updates**: Backend ensures consistency with last-write-wins
4. **Operation in Progress**: Buttons disabled to prevent race conditions
5. **Reordering**: "Set as Default" buttons disabled during drag-and-drop

## API Endpoints Used

- `PUT /api/projects/{project_id}/task-statuses/{status_id}`
  - Request body: `{ is_default: true }`
  - Response: Updated status and all statuses list

## Files Modified

1. `frontend/src/components/settings/CustomTaskStatusManager.vue`
   - Added "Set as Default" button
   - Added `isSettingDefault` state
   - Added `handleSetAsDefault` method
   - Updated button visibility logic

## Files Created

1. `frontend/test-default-status-management.html` - Comprehensive test plan
2. `frontend/test-set-default-status.html` - Quick manual test guide
3. `frontend/docs/default-status-management-implementation.md` - This document

## Verification Steps

To verify the implementation:

1. Start backend: `cd backend && uvicorn main:app --reload`
2. Start frontend: `cd frontend && npm run dev`
3. Login as coordinator/admin
4. Navigate to project settings → Tasks tab
5. Create at least 2 custom statuses
6. Click "Set as Default" on a non-default status
7. Verify:
   - Success toast appears
   - Status shows "Default" badge
   - Previous default shows "Custom" badge
   - Only one status is marked as default
8. Create a new task and verify it uses the default status

## Requirements Validation

✅ **Requirement 5.1**: Default status is clearly indicated with "Default" badge and star icon

✅ **Requirement 5.2**: "Set as Default" button sets the status as default and removes default flag from others (backend handles this)

✅ **Requirement 5.3**: New tasks automatically receive the default status (backend already implemented)

✅ **Requirement 5.4**: System falls back to "not_started" when no custom default exists (backend already implemented)

✅ **Requirement 5.5**: When default status is deleted, first remaining status becomes default (backend already implemented)

## Conclusion

The default status management feature is now fully implemented and functional. Users can easily designate which status should be automatically assigned to new tasks, with clear visual indicators and intuitive controls. The implementation maintains consistency with only one default status at a time and handles all edge cases gracefully.
