# Admin
## 1. Redefine User Admin
In order to add more admin actions related to User object, we need to redefine the User Admin model.
### Inline
model inline combines 2 model so that info from RegisterUser can be modified and displayed with user info
first, create a class for inline model in `app/admin.py`
```
class UserInline(admin.TabularInline):
    model = RegisterUser
```
More info on [RegisterUser model](https://purduecam2project.github.io/CAM2WebUI/implementationDetail/User.html#creating-a-model).
We need to redefine a `UserAdmin` to do the modification. In list_display, we choose the field we want to see in admin page.
And add the action to `actions` :
```
class UserAdmin(admin.ModelAdmin):
    list_display = (
        'username',
        'email',
        'first_name',
        'last_name',
        'department',
        'organization',
        'is_staff',
        'date_joined',
    )
    inlines = [
        UserInline,
               ]
    actions = []
```
The two field `department` and `organization` are from RegisterUser model, and we cannot display them directly. 
  
We will write them as callable or a string representing an attribute. See [Django Documentation](https://docs.djangoproject.com/en/1.11/ref/contrib/admin/#django.contrib.admin.ModelAdmin.list_display).
```
    # callable that display info from RegisterUser
    def department(self,user):
        return "{}".format(RegisterUser.objects.get(user=user).department)
    department.short_description = 'department'

    def organization(self,user):
        return "{}".format(RegisterUser.objects.get(user=user).organization)
    organization.short_description = 'organization'
```

at last we unregister the previous `User` model provided by Django and register our `UserAdmin` model with the `User` model.
```
admin.site.unregister(User)
admin.site.register(User, UserAdmin)
```
For any action written for User, define the function before UserAdmin class.
  
## 2. Admin action of Send Email from Admin
### Goal
Allow admin to send email to specific users. 
procedure: 
  
1. Log in as admin, and in the main page, go to Users. 
  
2. Using checkbox to choose recipient
             
3. Select "Email Users" in action
             
4. Click "Go" to direct to a web page for admin to input subject and message, and pass a list of user id through session.

### Approach
We will add a new action to User admin called `email user` to redirect the page to our `admin_send_email` page, and pass the id of selected user to `admin_send_email` page.
  
In `app/admin.py`
First we write the action. An admin action takes 3 parameters, self, request and queryset.
The queryset contains every user object we selected under User admin page. 
```
def email_users(self, request, queryset):
    list = queryset.values('email','id')
    
    user_id_selected = []
    for l in list:
        user_id_selected.append(l['id'])
```
we will then use a "request.session](https://docs.djangoproject.com/en/1.11/topics/http/sessions/)"
to pass the `email_selected` and redirect admin to `admin_send_email` page:
```
#open a session and render the email_selected to admin_send_email view
    request.session['user_id_selected'] = user_id_selected
    return redirect('admin_send_email')
email_users.short_description = "Email Users"
```
Give this action a description shown in the action list when admin select actions. Note that it is called outside the function.
  
Add this function to `actions` under UserAdmin model.
```
actions = [email_users]
```

## 3. Export User Data to CSV
### Goal
To create an admin action that download a CSV file containing info of selected user(s).
  
### UserAdmin class and Admin action
[Django Documentation on "Outputting CSV with Django"](https://docs.djangoproject.com/en/1.11/howto/outputting-csv/) 
  
To see how to add actions to Model and how to modify`UserAdmin`,
see [here](https://purduecam2project.github.io/CAM2WebUI/implementationDetail/Email.html#admin-action).
  
### Action Function
Go to `app/admin.py`, find `actions` in class `UserAdmin`, add the new function `export_csv`.
  
And create the function **before** class `UserAdmin`:
```
def export_csv(modeladmin, request, queryset):
    #setup csv writer
    response = HttpResponse(content_type='text/csv')
    response['Content-Disposition'] = 'attachment;filename=CAM2UserList.csv'
    writer = csv.writer(response)
```
The CSV-creation acts on file-like objects such as the HttpResponse in Django.
  
See [Django documentation](https://docs.djangoproject.com/en/1.11/howto/outputting-csv/).
```
    opts = queryset.model._meta  #obtaining User model as meta data because models are not iterable
    required_field_names = [field.name for field in opts.fields] #get names of all fields in User model as a list
    optional_field_names = [field.name for field in RegisterUser._meta.fields] ##get names of all fields in User model as a list
```
We need to seperate them because they will be used for every iteration of selected users. And create another combined list for the final CSV form.
```
    field_names = required_field_names.copy()
    for field in optional_field_names:
        field_names.append(field)
    writer.writerow(field_names)
```
To obtain info of each user, an for loop is used, and the required info and optional info will be gained through each iteration.
  
The field in `required_field_names` and `optional_field_names` decide which info from `User` and `RegisterUser` model we will get.
  
More info on `RegisterUser`, see [here](https://purduecam2project.github.io/CAM2WebUI/implementationDetail/User.html#creating-a-model).
  
```
    for obj in queryset:
        required_info = [getattr(obj, field) for field in required_field_names]
        try:
            optional = RegisterUser.objects.get(user=obj)  # get optional info of user
            optional_info = [getattr(optional, field) for field in optional_field_names]
        except:
            optional_info = ['N/A' for field in optional_field_names]
        for data in optional_info:
            required_info.append(data)
        writer.writerow(required_info)
    return response
```
Give this action a name outside function(no indentation):
```
export_csv.short_description = "Export selected user as csv"
```
Add this function to `actions` under UserAdmin model.
```
actions = [email_users, export_csv]
```