Add some support for slack/mattermost compatible webhooks

Gemfile

+# frozen_string_literal: true
+
 source 'https://rubygems.org'
 gem 'sinatra'

Gemfile.lock

@@ -19,4 +19,4 @@ DEPENDENCIES
   sinatra
 
 BUNDLED WITH
-   1.14.6
+   2.1.4

config.ru

-require File.expand_path '../nanoapi_app.rb', __FILE__
+# frozen_string_literal: true
+
+require File.expand_path 'nanoapi_app.rb', __dir__
 
 run Sinatra::Application

config.yaml

 ---
 key: foobar
+webhook_keys:
+  - foobar_key
+  - barfoo_key

nanoapi_app.rb

 # frozen_string_literal: true
+
 require 'json'
 require 'sinatra'
 require 'socket'
@@ -9,6 +10,11 @@ def check_key(key)
   halt 401 if key != config['key']
 end
 
+def check_webhook_key(key)
+  config = YAML.load_file 'config.yaml'
+  halt 401 unless config['webhook_keys'].include? key
+end
+
 def forward_message(message)
   sock = TCPSocket.open 'localhost', 2000
   sock.puts message
@@ -30,3 +36,21 @@ post '/v1/message' do
 
   'Message accepted'
 end
+
+post '/v1/webhook/:webhook_key' do
+  check_webhook_key params[:webhook_key]
+
+  halt 400 unless params.key? :payload
+
+  payload = JSON.parse(params[:payload])
+  halt 400 unless payload.key? 'text'
+
+  payload['channel']  = '#shells' unless payload.key? 'channel'
+  payload['username'] = 'webhook' unless payload.key? 'username'
+
+  forward_message({
+    dest: payload['channel'],
+    message: "#{payload['username']}: #{params['text']}"
+  }.to_json)
+  'OK'
+end