imgur_oauth.rb

# Net / encoding
require 'net/http'
require 'net/https'
require 'base64'

# Imgur:
$client_id     = 'xxx'
$client_secret = 'xxx'

# Imgur user tokens:
$refresh_token = 'xxx'
$access_token  = nil

#get_urls = "https://api.imgur.com/oauth2/authorize?client_id=#{client_id}&response_type=token"
# http://example.iana.org/#access_token=xxx&expires_in=3600&token_type=bearer&refresh_token=xxx&account_username=kasperg

def imgur_get_access_token(client_id, client_secret, refresh_token)
  # Get a new access_token:
  #
  # POST: https://api.imgur.com/oauth2/token
  # refresh_token = "#{xxx}"
  # client_id = "#{client_id}"
  # client_secret = "#{client_secret}"
  # grant_type = 'refresh_token'

  uri = URI('https://api.imgur.com/oauth2/token')

  http = Net::HTTP.new(uri.host, uri.port)
  http.use_ssl = true
  http.verify_mode = OpenSSL::SSL::VERIFY_NONE

  request = Net::HTTP::Post.new(uri.request_uri)

  values = {
             'refresh_token' => refresh_token,
             'client_id'     => client_id,
             'client_secret' => client_secret,
             'grant_type'    => 'refresh_token',
           }

  request.set_form_data(values)

  JSON.parse(http.request(request).body)
end

def imgur_upload(access_token, file_name)
  # POST: https://api.imgur.com/3/image
  # header: Authorization: Bearer YOUR_ACCESS_TOKEN
  # image: base64 encoded image

  uri = URI('https://api.imgur.com/3/image')

  http = Net::HTTP.new(uri.host, uri.port)
  http.use_ssl = true
  http.verify_mode = OpenSSL::SSL::VERIFY_NONE

  request = Net::HTTP::Post.new(uri.request_uri)
  request.add_field("Authorization", "Bearer #{access_token}")

  file = File.open(file_name)
  file = Base64.encode64(file.read)
  request.set_form_data({"image" => file})

  JSON.parse(http.request(request).body)
end

def login(client_id, client_secret, refresh_token)
  data = imgur_get_access_token(client_id, client_secret, refresh_token)
  $access_token = data['access_token']
  puts "Logged into imgur..." if $access_token.present?
end

def upload(file_name)
  login($client_id, $client_secret, $refresh_token) if $access_token == nil
  output = imgur_upload($access_token, file_name)

  unless output['success']
    login($client_id, $client_secret, $refresh_token)
    output = imgur_upload($access_token, file_name)
    return nil if output['success'] == false
  end

  return output['data']['link']
end