From 5947cd393e7b6aee619dfa85edf43d73def323f4 Mon Sep 17 00:00:00 2001
From: Michael Bumann <hello@michaelbumann.com>
Date: Mon, 13 Apr 2020 15:13:01 +0200
Subject: [PATCH 1/6] Actually link the google auth button

---
 app/views/sessions/new.html.erb | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/app/views/sessions/new.html.erb b/app/views/sessions/new.html.erb
index 3f34469..257d009 100644
--- a/app/views/sessions/new.html.erb
+++ b/app/views/sessions/new.html.erb
@@ -6,10 +6,10 @@
       <h1 class="title has-text-centered">
         Login
       </h1>
-      <div class="button google">
+      <%= link_to auth_at_provider_url(provider: 'google'), class: 'button google' do %>
         <svg viewBox="0 0 15 15" class="googleLogo" style="width: 14px; height: 14px; display: block; fill: currentcolor; flex-shrink: 0; backface-visibility: hidden; margin-right: 6px;"><path d="M 7.28571 6.4125L 7.28571 9L 11.3929 9C 11.2143 10.0875 10.1429 12.225 7.28571 12.225C 4.78571 12.225 2.78571 10.0875 2.78571 7.5C 2.78571 4.9125 4.82143 2.775 7.28571 2.775C 8.71429 2.775 9.64286 3.4125 10.1786 3.9375L 12.1429 1.9875C 10.8929 0.75 9.25 0 7.28571 0C 3.25 0 0 3.3375 0 7.5C 0 11.6625 3.25 15 7.28571 15C 11.5 15 14.25 11.9625 14.25 7.6875C 14.25 7.2 14.2143 6.825 14.1429 6.45L 7.28571 6.45L 7.28571 6.4125Z"></path></svg>
         Login with Google
-      </div>
+      <% end %>
       <hr>
       <p>
         As tinyforms builds on Google Sheets.<br>

From 64031261c56fcd5b562eb40d44d2755218049956 Mon Sep 17 00:00:00 2001
From: Michael Bumann <hello@michaelbumann.com>
Date: Mon, 13 Apr 2020 15:18:14 +0200
Subject: [PATCH 2/6] Configurable google auth callback URL

---
 config/initializers/sorcery.rb | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/config/initializers/sorcery.rb b/config/initializers/sorcery.rb
index 4beedb8..3e76ca2 100644
--- a/config/initializers/sorcery.rb
+++ b/config/initializers/sorcery.rb
@@ -152,7 +152,7 @@ Rails.application.config.sorcery.configure do |config|
   #
   config.google.key = ENV['GOOGLE_CLIENT_ID']
   config.google.secret = ENV['GOOGLE_CLIENT_SECRET']
-  config.google.callback_url = "http://localhost:3000/oauth/callback?provider=google"
+  config.google.callback_url = (ENV['GOOGLE_AUTH_CALLBACK_URL'] || "http://localhost:3000/oauth/callback?provider=google")
   config.google.user_info_mapping = {:email => "email", :name => "name", :google_id => "id"}
   config.google.scope = "https://www.googleapis.com/auth/userinfo.email https://www.googleapis.com/auth/userinfo.profile https://www.googleapis.com/auth/spreadsheets"
   config.google.auth_url = '/o/oauth2/auth?access_type=offline&include_granted_scopes=true'

From 80771e74150e68b2c6765fba382f924b89fcae62 Mon Sep 17 00:00:00 2001
From: Michael Bumann <hello@michaelbumann.com>
Date: Mon, 13 Apr 2020 16:14:21 +0200
Subject: [PATCH 3/6] Disable demo submit button and add link to contact

---
 app/javascript/demo.js       | 7 +++++--
 app/views/home/demo.html.erb | 6 ++++--
 config/routes.rb             | 1 +
 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/app/javascript/demo.js b/app/javascript/demo.js
index 09fee25..b23fc05 100644
--- a/app/javascript/demo.js
+++ b/app/javascript/demo.js
@@ -3,10 +3,13 @@ document.addEventListener('DOMContentLoaded', function() {
   if (!demoForm) {
     return;
   }
+  demoForm.addEventListener('submit', function(e) {
+    var submitButton = document.getElementById('demo-submit');
+    submitButton.innerText = 'loading...';
+    submitButton.disabled = 'true'
+  });
 
   demoForm.addEventListener('tinyforms:submitted', function(e) {
-    console.log(e);
-    console.log(e.detail);
     var name = document.getElementById('demo-submission-name');
     var demoFields = document.getElementById('demo-fields');
     var demoSucess = document.getElementById('demo-success');
diff --git a/app/views/home/demo.html.erb b/app/views/home/demo.html.erb
index dfbdac7..8b86836 100644
--- a/app/views/home/demo.html.erb
+++ b/app/views/home/demo.html.erb
@@ -15,7 +15,9 @@
             </p>
             <p>See your entry in the spreadsheet?!</p>
             <p>
-              <%= link_to "Get started now", signup_url, class: 'button' %>
+              <%= link_to "Create your form now!", signup_url, class: 'button' %>
+              <br>
+              or got <%= link_to 'further questions?', contact_url %>
             </p>
           </div>
 
@@ -68,7 +70,7 @@
 
             <div class="field is-grouped">
               <div class="control">
-                <button class="button is-link">Submit</button>
+                <button class="button is-link" id="demo-submit">Submit</button>
               </div>
             </div>
           </div>
diff --git a/config/routes.rb b/config/routes.rb
index dfdec49..6aa0b7e 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -22,5 +22,6 @@ Rails.application.routes.draw do
   get '/auth' => 'sessions#auth', as: :auth
 
   get '/demo' => 'home#demo', as: :demo
+  get '/contact' => 'home#contact', as: :contact
   root 'home#index'
 end

From 7917e921ad3e38a4c16de7aa3a61fb46f28072f9 Mon Sep 17 00:00:00 2001
From: Michael Bumann <hello@michaelbumann.com>
Date: Mon, 13 Apr 2020 16:14:45 +0200
Subject: [PATCH 4/6] Use help route to redirect to notion hosted help center

This makes it easier for us later change the URL
---
 app/views/layouts/_header.html.erb | 2 +-
 config/routes.rb                   | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/app/views/layouts/_header.html.erb b/app/views/layouts/_header.html.erb
index d08b511..a154b74 100644
--- a/app/views/layouts/_header.html.erb
+++ b/app/views/layouts/_header.html.erb
@@ -15,7 +15,7 @@
 
     <div id="navbar-menu" class="navbar-menu">
       <div class="navbar-end">
-        <a href="https://www.notion.so/Tinyforms-Help-Center-04f13b5908bc46cfb4283079a3cb1149" class="navbar-item">Help</a>
+        <%= link_to 'Help', help_url, class: 'navbar-item' %>
         <div class="navbar-item">
           <% if !logged_in? -%>
             <%= link_to "Login", login_url, { :class => "button is-primary"} %>
diff --git a/config/routes.rb b/config/routes.rb
index 6aa0b7e..fcf270a 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -23,5 +23,8 @@ Rails.application.routes.draw do
 
   get '/demo' => 'home#demo', as: :demo
   get '/contact' => 'home#contact', as: :contact
+  get '/help', to: redirect('https://www.notion.so/Tinyforms-Help-Center-04f13b5908bc46cfb4283079a3cb1149')
+
+
   root 'home#index'
 end

From 80fe5f4220f7dac3186d1723a6b23bed929d6fce Mon Sep 17 00:00:00 2001
From: Michael Bumann <hello@michaelbumann.com>
Date: Mon, 13 Apr 2020 16:27:56 +0200
Subject: [PATCH 5/6] Add magic ID value to demo

---
 app/views/home/demo.html.erb | 1 +
 1 file changed, 1 insertion(+)

diff --git a/app/views/home/demo.html.erb b/app/views/home/demo.html.erb
index 8b86836..c810740 100644
--- a/app/views/home/demo.html.erb
+++ b/app/views/home/demo.html.erb
@@ -3,6 +3,7 @@
     <div class="columns">
       <div class="column is-one-third">
         <form class="form demo-form" id="demo-form" action="<%= submission_url(DEMO_FORM) %>" method="POST" enctype="multipart/form-data" data-tinyforms="true">
+          <input type="hidden" name="ID" value="tinyforms_id">
           <h3>Demo</h3>
           <p>
             This short form is connected to the embedded <%= link_to 'document', DEMO_FORM.google_spreadsheet_url %> on the right. <br>

From edf68846479c5f019310fb5735ee3febc2970648 Mon Sep 17 00:00:00 2001
From: Michael Bumann <hello@michaelbumann.com>
Date: Mon, 13 Apr 2020 22:59:46 +0200
Subject: [PATCH 6/6] Add support for Airtable

---
 Gemfile                                       |  2 +-
 Gemfile.lock                                  |  7 ++
 app/models/form.rb                            | 82 ++++++++-----------
 app/models/submission.rb                      |  4 +-
 app/views/forms/index.html.erb                |  2 +-
 app/views/forms/show.html.erb                 |  6 +-
 app/views/home/demo.html.erb                  |  4 +-
 config/application.rb                         | 11 +++
 .../20200413152532_add_airtable_support.rb    |  8 ++
 db/schema.rb                                  |  6 +-
 lib/spreadsheet_backends/airtable.rb          | 36 ++++++++
 lib/spreadsheet_backends/google_sheets.rb     | 71 ++++++++++++++++
 12 files changed, 179 insertions(+), 60 deletions(-)
 create mode 100644 db/migrate/20200413152532_add_airtable_support.rb
 create mode 100644 lib/spreadsheet_backends/airtable.rb
 create mode 100644 lib/spreadsheet_backends/google_sheets.rb

diff --git a/Gemfile b/Gemfile
index 47338e4..e88578c 100644
--- a/Gemfile
+++ b/Gemfile
@@ -24,7 +24,7 @@ gem 'bootsnap', '>= 1.4.2', require: false
 gem 'lockbox'
 
 gem 'aws-sdk-s3', require: false
-# gem 'airrecord'
+gem 'airrecord'
 gem 'google-api-client'
 gem 'rack-cors'
 gem 'sentry-raven'
diff --git a/Gemfile.lock b/Gemfile.lock
index 90a1745..223b8fd 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -58,6 +58,9 @@ GEM
       zeitwerk (~> 2.2)
     addressable (2.7.0)
       public_suffix (>= 2.0.2, < 5.0)
+    airrecord (1.0.5)
+      faraday (>= 0.10, < 2.0)
+      net-http-persistent (>= 2.9)
     aws-eventstream (1.0.3)
     aws-partitions (1.263.0)
     aws-sdk-core (3.89.1)
@@ -80,6 +83,7 @@ GEM
     builder (3.2.4)
     byebug (11.1.1)
     concurrent-ruby (1.1.6)
+    connection_pool (2.2.2)
     crass (1.0.6)
     declarative (0.0.10)
     declarative-option (0.1.0)
@@ -136,6 +140,8 @@ GEM
     multi_json (1.14.1)
     multi_xml (0.6.0)
     multipart-post (2.1.1)
+    net-http-persistent (3.1.0)
+      connection_pool (~> 2.2)
     nio4r (2.5.2)
     nokogiri (1.10.9)
       mini_portile2 (~> 2.4.0)
@@ -252,6 +258,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
+  airrecord
   aws-sdk-s3
   bootsnap (>= 1.4.2)
   byebug
diff --git a/app/models/form.rb b/app/models/form.rb
index b4fa31b..b4bcd37 100644
--- a/app/models/form.rb
+++ b/app/models/form.rb
@@ -1,15 +1,21 @@
-require 'google/apis/sheets_v4'
 class Form < ApplicationRecord
-  # Hash to translate an index to a A1 notation. e.g. 1 => 'B', 27 => 'AA'
-  COLUMN_INDEX_TO_LETTER = Hash.new {|hash,key| hash[key] = hash[key - 1].next }.merge({0 => "A"})
-
   belongs_to :user
   has_many :submissions, dependent: :destroy
+
+  before_validation :insert_defaults, on: :create
   after_create :create_spreadsheet
 
   has_secure_token
 
+  encrypts :airtable_api_key
+  encrypts :airtable_app_key
+
   validates_presence_of :title
+  validates_inclusion_of :backend_name, in: ['google_sheets', 'airtable']
+  # Airtable validations
+  validates_presence_of :airtable_api_key, if: :airtable?
+  validates_presence_of :airtable_app_key, if: :airtable?
+  validates_presence_of :airtable_table, if: :airtable?
 
   # TODO: use counter_cache option on association
   def submissions_count
@@ -28,63 +34,39 @@ class Form < ApplicationRecord
     self.user.active?
   end
 
-  def google_spreadsheet_url
-    "https://docs.google.com/spreadsheets/d/#{google_spreadsheet_id}/edit" if google_spreadsheet_id.present?
+  def airtable?
+    backend_name == 'airtable'
+  end
+
+  def google
+    backend_name == 'google'
+  end
+
+  def backend
+    @backend ||= SpreadsheetBackends.const_get(backend_name.camelize).new(self)
+  end
+
+  def spreadsheet_url
+    backend.url
   end
 
   def create_spreadsheet
-    sheets = Google::Apis::SheetsV4::SheetsService.new
-    sheets.authorization = user.google_authorization
-    create_object = Google::Apis::SheetsV4::Spreadsheet.new(properties: { title: title})
-    spreadsheet = sheets.create_spreadsheet(create_object)
-    update(google_spreadsheet_id: spreadsheet.spreadsheet_id)
+    backend.create
   end
 
-  def spreadsheet_service
-    @spreadsheet_service ||= Google::Apis::SheetsV4::SheetsService.new.tap do |s|
-      s.authorization = user.google_authorization
-    end
+  def append_to_spreadsheet(data)
+    backend.append(data)
   end
 
-  def header_values
-    @header_values ||= begin
-                         values = spreadsheet_service.get_spreadsheet_values(google_spreadsheet_id, 'A1:An').values
-                         # if there are no headers yet, return an empty array
-                         if values
-                          values[0].map(&:strip)
-                         else
-                           []
-                         end
-                       end
-  end
-
-  def append(data)
-    data = data.with_indifferent_access
-    check_spreadsheed_headers!(data)
-
-    values = header_values.map { |key| data[key] }
-    range = "A1:A#{COLUMN_INDEX_TO_LETTER[values.length]}1"
-    value_range = Google::Apis::SheetsV4::ValueRange.new(values: [values], major_dimension: 'ROWS')
-
-    spreadsheet_service.append_spreadsheet_value(google_spreadsheet_id, range, value_range, value_input_option: 'USER_ENTERED')
-  end
-
-  def check_spreadsheed_headers!(data)
-    missing_headers = data.keys.map { |k| k.to_s.strip } - header_values
-    append_missing_headers(missing_headers) unless missing_headers.empty?
-  end
-
-  def append_missing_headers(missing_headers)
-    start_column = COLUMN_INDEX_TO_LETTER[header_values.length]
-    end_column = COLUMN_INDEX_TO_LETTER[header_values.length + missing_headers.length]
-    range = "#{start_column}1:#{end_column}1"
-    value_range = Google::Apis::SheetsV4::ValueRange.new(values: [missing_headers], major_dimension: 'ROWS')
-    spreadsheet_service.update_spreadsheet_value(google_spreadsheet_id, range, value_range, value_input_option: 'USER_ENTERED')
-    @header_values = nil # reset header values to refresh memoization on next access
+  def spreadsheet_headers
+    backend.headers
   end
 
   def to_param
     token
   end
 
+  def insert_defaults
+    self.backend_name ||= airtable_app_key.present? ? 'airtable' : 'google_sheets'
+  end
 end
diff --git a/app/models/submission.rb b/app/models/submission.rb
index 4dfc874..3a60e14 100644
--- a/app/models/submission.rb
+++ b/app/models/submission.rb
@@ -44,7 +44,7 @@ class Submission < ApplicationRecord
   end
 
   def append_to_spreadsheet
-    result = form.append(data)
-    update_column(:appended_at, Time.current) if result.updates.updated_rows > 0
+    form.append_to_spreadsheet(data) &&
+      update_column(:appended_at, Time.current)
   end
 end
diff --git a/app/views/forms/index.html.erb b/app/views/forms/index.html.erb
index 261e4f7..5a9e61a 100644
--- a/app/views/forms/index.html.erb
+++ b/app/views/forms/index.html.erb
@@ -25,7 +25,7 @@
               </div>
               <div class="media-right has-text-right is-size-4">
                 <figure class="image is-48x48 ">
-                  <%= link_to form.google_spreadsheet_url, {class: "has-text-success", target: "__blank"} do %>
+                  <%= link_to form.spreadsheet_url, {class: "has-text-success", target: "__blank"} do %>
                   <i class="far fa-file-excel"></i>
                   <% end %>
                 </figure>
diff --git a/app/views/forms/show.html.erb b/app/views/forms/show.html.erb
index c6679b7..5842b30 100644
--- a/app/views/forms/show.html.erb
+++ b/app/views/forms/show.html.erb
@@ -3,12 +3,12 @@
   <%= submission_url(@form) %>
 </p>
 <p>
-  <%= link_to 'Google spreadsheet', @form.google_spreadsheet_url %>
+  <%= link_to 'Google spreadsheet', @form.spreadsheet_url %>
 </p>
 <table>
   <thead>
     <tr>
-      <% @form.header_values.each do |value| %>
+      <% @form.spreadsheet_headers.each do |value| %>
         <th><%= value %></th>
       <% end %>
     </tr>
@@ -16,7 +16,7 @@
   <tbody>
     <% @submissions.each do |submission| %>
       <tr>
-        <% @form.header_values.each do |column| %>
+        <% @form.spreadsheet_headers.each do |column| %>
           <td><%= submission.data[column] %></td>
         <% end %>
       </tr>
diff --git a/app/views/home/demo.html.erb b/app/views/home/demo.html.erb
index c810740..c75d4bd 100644
--- a/app/views/home/demo.html.erb
+++ b/app/views/home/demo.html.erb
@@ -6,7 +6,7 @@
           <input type="hidden" name="ID" value="tinyforms_id">
           <h3>Demo</h3>
           <p>
-            This short form is connected to the embedded <%= link_to 'document', DEMO_FORM.google_spreadsheet_url %> on the right. <br>
+            This short form is connected to the embedded <%= link_to 'document', DEMO_FORM.spreadsheet_url %> on the right. <br>
             Submit the form and see the update of the document in realtime.
           </p>
 
@@ -80,7 +80,7 @@
 
       <div class="column">
         <iframe id="demo-sheet" style="width:100%;height:100%;" src="https://docs.google.com/spreadsheets/d/<%= DEMO_FORM.google_spreadsheet_id %>/edit?usp=sharing&nocache=<%= Time.now.to_i %>#gid=0&range=<%= DEMO_FORM.submissions.count + 1 %>:<%= DEMO_FORM.submissions.count + 2 %>"></iframe>
-        <p class="has-text-grey has-text-centered">Document not loading? <%= link_to 'Open it here', DEMO_FORM.google_spreadsheet_url %>.</p>
+        <p class="has-text-grey has-text-centered">Document not loading? <%= link_to 'Open it here', DEMO_FORM.spreadsheet_url %>.</p>
       </div>
     </div>
   </div>
diff --git a/config/application.rb b/config/application.rb
index 2dae959..ffe45c8 100644
--- a/config/application.rb
+++ b/config/application.rb
@@ -15,6 +15,17 @@ module Tinyform
     # Application configuration can go into files in config/initializers
     # -- all .rb files in that directory are automatically loaded after loading
     # the framework and any gems in your application.
+    config.generators do |generate|
+      generate.helper false
+      generate.javascript_engine false
+      generate.request_specs false
+      generate.routing_specs false
+      generate.stylesheets false
+      generate.view_specs false
+    end
+
+    config.autoload_paths << Rails.root.join('lib')
+
     config.middleware.insert_before 0, Rack::Cors do
       allow do
         origins '*'
diff --git a/db/migrate/20200413152532_add_airtable_support.rb b/db/migrate/20200413152532_add_airtable_support.rb
new file mode 100644
index 0000000..a5465dc
--- /dev/null
+++ b/db/migrate/20200413152532_add_airtable_support.rb
@@ -0,0 +1,8 @@
+class AddAirtableSupport < ActiveRecord::Migration[6.0]
+  def change
+    add_column :forms, :airtable_app_key_ciphertext, :string
+    add_column :forms, :airtable_api_key_ciphertext, :string
+    add_column :forms, :airtable_table, :string
+    add_column :forms, :backend_name, :string
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 153d317..0c9af99 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2020_04_13_101920) do
+ActiveRecord::Schema.define(version: 2020_04_13_152532) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -57,6 +57,10 @@ ActiveRecord::Schema.define(version: 2020_04_13_101920) do
     t.string "thank_you_url"
     t.datetime "created_at", precision: 6, null: false
     t.datetime "updated_at", precision: 6, null: false
+    t.string "airtable_app_key_ciphertext"
+    t.string "airtable_api_key_ciphertext"
+    t.string "airtable_table"
+    t.string "backend_name"
   end
 
   create_table "submissions", force: :cascade do |t|
diff --git a/lib/spreadsheet_backends/airtable.rb b/lib/spreadsheet_backends/airtable.rb
new file mode 100644
index 0000000..047a8f8
--- /dev/null
+++ b/lib/spreadsheet_backends/airtable.rb
@@ -0,0 +1,36 @@
+require 'airrecord'
+module SpreadsheetBackends
+  class Airtable
+
+    attr_accessor :form, :user
+
+    def initialize(form)
+      @form = form
+      @user = form.user
+    end
+
+    def url
+      "https://airtable.com/#{form.airtable_app_key}"
+    end
+
+    def append(data)
+      result = table.create(data, typecast: true)
+      result.id.present?
+    rescue Airrecord::Error => e
+      return false
+    end
+
+    def create
+      # Airtable must already exist
+      # TODO: maybe add validation here?
+    end
+
+    def headers
+      table.records.first&.fields&.keys # we only know the headers once we have at least one record
+    end
+
+    def table
+      @table ||= Airrecord.table(form.airtable_api_key, form.airtable_app_key, form.airtable_table)
+    end
+  end
+end
diff --git a/lib/spreadsheet_backends/google_sheets.rb b/lib/spreadsheet_backends/google_sheets.rb
new file mode 100644
index 0000000..d2a6ab3
--- /dev/null
+++ b/lib/spreadsheet_backends/google_sheets.rb
@@ -0,0 +1,71 @@
+require 'google/apis/sheets_v4'
+module SpreadsheetBackends
+  class GoogleSheets
+    # Hash to translate an index to a A1 notation. e.g. 1 => 'B', 27 => 'AA'
+    COLUMN_INDEX_TO_LETTER = Hash.new {|hash,key| hash[key] = hash[key - 1].next }.merge({0 => "A"})
+
+    attr_accessor :form, :user
+
+    def initialize(form)
+      @form = form
+      @user = form.user
+    end
+
+    def url
+      "https://docs.google.com/spreadsheets/d/#{form.google_spreadsheet_id}/edit" if form.google_spreadsheet_id.present?
+    end
+
+    def append(data)
+      data = data.with_indifferent_access
+      check_spreadsheed_headers!(data)
+
+      values = headers.map { |key| data[key] }
+      range = "A1:A#{COLUMN_INDEX_TO_LETTER[values.length]}1"
+      value_range = Google::Apis::SheetsV4::ValueRange.new(values: [values], major_dimension: 'ROWS')
+
+      result = spreadsheet_service.append_spreadsheet_value(form.google_spreadsheet_id, range, value_range, value_input_option: 'USER_ENTERED')
+      result.updates.updated_rows > 0
+    end
+
+    def create
+      sheets = Google::Apis::SheetsV4::SheetsService.new
+      sheets.authorization = user.google_authorization
+      create_object = Google::Apis::SheetsV4::Spreadsheet.new(properties: { title: form.title})
+      spreadsheet = sheets.create_spreadsheet(create_object)
+      form.update(google_spreadsheet_id: spreadsheet.spreadsheet_id)
+    end
+
+    def headers
+      @headers ||= begin
+                     values = spreadsheet_service.get_spreadsheet_values(form.google_spreadsheet_id, 'A1:An').values
+                           # if there are no headers yet, return an empty array
+                           if values
+                            values[0].map(&:strip)
+                           else
+                             []
+                           end
+                         end
+    end
+
+    def spreadsheet_service
+      @spreadsheet_service ||= Google::Apis::SheetsV4::SheetsService.new.tap do |s|
+        s.authorization = user.google_authorization
+      end
+    end
+
+    def check_spreadsheed_headers!(data)
+      missing_headers = data.keys.map { |k| k.to_s.strip } - headers
+      append_missing_headers(missing_headers) unless missing_headers.empty?
+    end
+
+    def append_missing_headers(missing_headers)
+      start_column = COLUMN_INDEX_TO_LETTER[headers.length]
+      end_column = COLUMN_INDEX_TO_LETTER[headers.length + missing_headers.length]
+      range = "#{start_column}1:#{end_column}1"
+      value_range = Google::Apis::SheetsV4::ValueRange.new(values: [missing_headers], major_dimension: 'ROWS')
+      spreadsheet_service.update_spreadsheet_value(form.google_spreadsheet_id, range, value_range, value_input_option: 'USER_ENTERED')
+      @headers = nil # reset header values to refresh memoization on next access
+    end
+
+  end
+end