paJYgc12

1# You were presented with a following request from mobile team:
2#
3#  - We want to show in-app banners to our user
4#  - We want to be able to create/delete/deactivate banners from site admin
5#  - We want to specify application screen and user cohort for a banner
6#    Possible screens: [ deliveries, meal_selection ]
7#    Possible user cohorts: [ trial, loyal, returning, all ]
8#  - We want to be able to specify A/B test key for a banner, and only show it to users participating as variant in this experiment
9#  - At a given screen user should only be eligible for one banner
10#  - We want an API endpoint to fetch a banner for the user
11#  - We want information about banners for user to be included in "/api/v1/initial_data" API endpoint(an endpoint that gathers all data for an initial app load and is thoroughly cached)
12#  - Further down the road we will want other things(like footer, etc.) implemented with the same rules(screen, cohort matching)
13#
14# Let's implement given request on a high-level(class structure, db tables)
15
16
17
18User.   group
19Banner
20
21
22Service that returns need benner by screen (token user id and group) -> banner -> A\B test API -> banner or nil
23
24class Banner < Model
25  title
26  decr 
27  id
28  experiment_key
29
30  screen :enum, [:delivery, :prices]
31end
32
33
34class User < Model
35  id
36  token 
37
38  def group
39  end
40end
41
42-------------
43
44class API::BannersController < ApplicationController
45  def show_banner
46    result = ::Services::Banners::FindBanner.new().call(current_user, banner_params[:screen])
47
48    if result.success? 
49      banner = result.value
50
51      return json: { status: :ok, BannerSerializer.new(banner) }
52    end
53  end
54
55  private 
56
57  def banner_params
58    params.require(:banner).permit(:screen)
59  end
60end
61
62------------
63
64class Services::Banners::FindBanner < ::Base::Service
65  attr_reader :user
66  attr_reader :screen
67
68  def call
69    cohorta = user.cohorta
70
71    banner = Banner.find_by(user: user, screen: screen)
72
73    return success unless banner
74    return success(banner) unless banner.experiment_key
75    
76    experiment_user_group = Expirement.find_by(key: banner.experiment_key)&.assign(user) #=> #{user_group}
77
78    experiment_user_group ? success(banner) : success
79  end
80end
81
82-------------------------
83
84
85context 'valid user & screen' do
86  it 'successfully returns a banner when there is an experiment'
87  end
88
89  it 'successfully returns a banner when there is no an experiment'
90  end
91
92  it 'returns success without banner when there is no banner'
93  end
94end
95
96context 'invalid user & screen' do
97  it 'returns success without banner when there is no banner with such screen'
98  end
99end
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114----
115
116def succees(value)
117  [true, value]
118end
119
120def error
121  [false, nil]
122end