Raise an error for :user token type with a login link inside

See mauricew/ruby-twitch-api#22 (comment)

README.md

@@ -71,8 +71,16 @@ You can pass nothing to `#check_tokens`, then client will generate new ones.
 If you've specified `:token_type` as `:application` or have not specify it at all (default),
 there will be an Application Access Token (without refresh token).
 
-Otherwise, for User Access Token you will be asked to open a Twitch link in a browser
-and login as user for whom tokens are intended.
+Otherwise, for User Access Token here will be raised a `TwitchOAuth2::Error` with Twitch link
+inside `#metadata[:link]`.
+
+If you have a web-application with N users, you can redirect them to this link
+and use `redirect_uri` to your application for callbacks.
+
+Otherwise, if you have something like CLI tool, you can print instructions with a link for user.
+
+Then you can use `#token(token_type: :user, code: 'a code from params in redirect uri')`
+and get your `:access_token` and `:refresh_token`.
 
 #### Reusing tokens
 

lib/twitch_oauth2/client.rb

@@ -46,26 +46,29 @@ def refreshed_tokens(refresh_token:)
 			refresh(refresh_token: refresh_token).slice(:access_token, :refresh_token)
 		end
 
-		private
+		def token(token_type:, code: nil)
+			response = CONNECTION.post(
+				'token',
+				client_id: @client_id,
+				client_secret: @client_secret,
+				code: code,
+				grant_type: grant_type_by_token_type(token_type),
+				redirect_uri: @redirect_uri
+			)
 
-		def flow(token_type:)
-			code = request_code if token_type == :user
+			return response.body if response.success?
 
-			token(code: code, token_type: token_type).slice(:access_token, :refresh_token)
+			raise Error, response.body[:message]
 		end
 
-		def request_code
-			link = authorize
+		private
 
-			puts <<~TEXT
-				1. Open URL in your browser:
-					#{link}
-				2. Login to Twitch.
-				3. Copy the `code` parameter from redirected URL.
-				4. Insert below:
-			TEXT
+		def flow(token_type:)
+			if token_type == :user
+				raise Error.new('Use `error.metadata[:link]` for getting new tokens', link: authorize)
+			end
 
-			$stdin.gets.chomp
+			token(token_type: token_type).slice(:access_token, :refresh_token)
 		end
 
 		def authorize
@@ -83,21 +86,6 @@ def authorize
 			raise Error, response.body[:message]
 		end
 
-		def token(code:, token_type:)
-			response = CONNECTION.post(
-				'token',
-				client_id: @client_id,
-				client_secret: @client_secret,
-				code: code,
-				grant_type: grant_type_by_token_type(token_type),
-				redirect_uri: @redirect_uri
-			)
-
-			return response.body if response.success?
-
-			raise Error, response.body[:message]
-		end
-
 		def grant_type_by_token_type(token_type)
 			case token_type
 			when :user then :authorization_code

lib/twitch_oauth2/error.rb

@@ -1,6 +1,14 @@
 # frozen_string_literal: true
 
 module TwitchOAuth2
+	## Error during Twitch OAuth2 operations
 	class Error < StandardError
+		attr_reader :metadata
+
+		def initialize(message, metadata = {})
+			super message
+
+			@metadata = metadata
+		end
 	end
 end

spec/spec_helper.rb

@@ -50,6 +50,12 @@
 		URI.decode_www_form(interaction.request.body).to_h['code']
 	end
 
+	config.filter_sensitive_data('<CODE>') do |interaction|
+		JSON.parse(interaction.request.body).to_h['code']
+	rescue JSON::ParserError
+		## this is not JSON
+	end
+
 	config.filter_sensitive_data('<ACCESS_TOKEN>') do |interaction|
 		if interaction.response.headers['content-type'].include? 'application/json'
 			JSON.parse(interaction.response.body)['access_token']