Add Mattermost support

config/locales/client.en.yml

@@ -98,4 +98,16 @@ en:
               help: The webhook URL created in your HipChat integration
             color:
               title: Color
-              help: The colour of the message in HipChat. Must be one of yellow,green,red,purple,gray,random
+              help: The colour of the message in HipChat. Must be one of yellow,green,red,purple,gray,random
+
+        #######################################
+        ######### MATTERMOST STRINGS ##########
+        #######################################
+        mattermost:
+          title: "Mattermost"
+          param:
+            identifier:
+              title: Channel
+              help: "e.g. #channel, @username."
+          errors:
+            channel_not_found: "The specified channel does not exist on Mattermost"

config/locales/server.en.yml

@@ -36,8 +36,16 @@ en:
     ########## HIPCHAT SETTINGS ###########
     #######################################
     chat_integration_hipchat_enabled: "Enable the Hipchat chat-integration provider"
-    chat_integration_icon_url: "Icon for posts to hipchat (defaults to forum logo)"
+    chat_integration_hipchat_icon_url: "Icon for posts to hipchat (defaults to forum logo)"
     chat_integration_hipchat_excerpt_length: "Hipchat post excerpt length"
+
+    #######################################
+    ######## MATTERMOST SETTINGS ##########
+    #######################################
+    chat_integration_mattermost_enabled: "Enable the Mattermost chat-integration provider"
+    chat_integration_mattermost_webhook_url: 'URL for the Mattermost webhook'
+    chat_integration_mattermost_icon_url: "Icon for posts to mattermost (defaults to forum logo)"
+    chat_integration_mattermost_excerpt_length: "Mattermost post excerpt length"
   
   chat_integration:
     

config/settings.yml

@@ -58,3 +58,15 @@ plugins:
     default: ''
   chat_integration_hipchat_excerpt_length:
     default: 400
+
+#######################################
+######## MATTERMOST SETTINGS ##########
+#######################################
+  chat_integration_mattermost_enabled:
+    default: false
+  chat_integration_mattermost_webhook_url:
+    default: ''
+  chat_integration_mattermost_icon_url:
+    default: ''
+  chat_integration_mattermost_excerpt_length:
+    default: 400

lib/discourse_chat/provider.rb

@@ -93,3 +93,4 @@ require_relative "provider/slack/slack_provider.rb"
 require_relative "provider/telegram/telegram_provider.rb"
 require_relative "provider/discord/discord_provider.rb"
 require_relative "provider/hipchat/hipchat_provider.rb"
+require_relative "provider/mattermost/mattermost_provider.rb"

lib/discourse_chat/provider/discord/discord_provider.rb

@@ -47,6 +47,7 @@ module DiscourseChat
       end
 
       def self.trigger_notification(post, channel)
+        # Adding ?wait=true means that we actually get a success/failure response, rather than returning asynchronously
         webhook_url = channel.data['webhook_url']+'?wait=true'
 
         message = generate_discord_message(post)

lib/discourse_chat/provider/mattermost/mattermost_provider.rb

@@ -0,0 +1,84 @@
+module DiscourseChat
+  module Provider
+    module MattermostProvider
+      PROVIDER_NAME = "mattermost".freeze
+      PROVIDER_ENABLED_SETTING = :chat_integration_mattermost_enabled
+      CHANNEL_PARAMETERS = [
+                          {key: "identifier", regex: '^[@#]\S*$'}
+                       ]
+
+      def self.send_via_webhook(message)
+
+        uri = URI(SiteSetting.chat_integration_mattermost_webhook_url)
+
+        http = Net::HTTP.new(uri.host, uri.port)
+        http.use_ssl = (uri.scheme == 'https')
+        req = Net::HTTP::Post.new(uri, 'Content-Type' =>'application/json')
+        req.body = message.to_json
+        response = http.request(req)
+
+        unless response.kind_of? Net::HTTPSuccess
+          if response.body.include? "Couldn't find the channel"
+            error_key = 'chat_integration.provider.mattermost.errors.channel_not_found'
+          else
+            error_key = nil
+          end
+          raise ::DiscourseChat::ProviderError.new info: {error_key: error_key, request: req.body, response_code:response.code, response_body:response.body}
+        end
+        
+      end
+
+      def self.mattermost_message(post, channel)
+        display_name = "@#{post.user.username}"
+        full_name = post.user.name || ""
+
+        if !(full_name.strip.empty?) && (full_name.strip.gsub(' ', '_').casecmp(post.user.username) != 0) && (full_name.strip.gsub(' ', '').casecmp(post.user.username) != 0)
+          display_name = "#{full_name} @#{post.user.username}"
+        end
+
+        topic = post.topic
+
+        category = ''
+        if topic.category
+          category = (topic.category.parent_category) ? "[#{topic.category.parent_category.name}/#{topic.category.name}]": "[#{topic.category.name}]"
+        end
+
+        icon_url =
+          if !SiteSetting.chat_integration_slack_icon_url.blank?
+            UrlHelper.absolute(SiteSetting.chat_integration_mattermost_icon_url)
+          elsif !SiteSetting.logo_small_url.blank?
+            UrlHelper.absolute(SiteSetting.logo_small_url)
+          end
+
+        message = {
+          channel: channel,
+          username: SiteSetting.title || "Discourse",
+          icon_url: icon_url,
+          attachments: []
+        }
+
+        summary = {
+          fallback: "#{topic.title} - #{display_name}",
+          author_name: display_name,
+          author_icon: post.user.small_avatar_url,
+          color: topic.category ? "##{topic.category.color}" : nil,
+          text: post.excerpt(SiteSetting.chat_integration_mattermost_excerpt_length, text_entities: true, strip_links: true, remap_emoji: true),
+          title: "#{topic.title} #{(category == '[uncategorized]')? '' : category} #{topic.tags.present? ? topic.tags.map(&:name).join(', ') : ''}",
+          title_link: post.full_url,
+          thumb_url: post.full_url,
+        }
+
+        message[:attachments].push(summary)
+        message
+      end
+
+      def self.trigger_notification(post, channel)
+        channel_id = channel.data['identifier']
+        message = mattermost_message(post, channel_id)
+  
+        self.send_via_webhook(message)
+      end
+
+    end
+  end
+end

spec/lib/discourse_chat/provider/mattermost/mattermost_provider_spec.rb

@@ -0,0 +1,29 @@
+require 'rails_helper'
+
+RSpec.describe DiscourseChat::Provider::MattermostProvider do
+  let(:post) { Fabricate(:post) }
+
+  describe '.trigger_notifications' do
+    before do
+      SiteSetting.chat_integration_mattermost_enabled = true
+      SiteSetting.chat_integration_mattermost_webhook_url = "https://mattermost.blah/hook/abcd"
+    end
+
+    let(:chan1){DiscourseChat::Channel.create!(provider:'mattermost', data:{identifier: "#awesomechannel"})}
+
+    it 'sends a webhook request' do
+      stub1 = stub_request(:post, 'https://mattermost.blah/hook/abcd').to_return(status: 200)
+      described_class.trigger_notification(post, chan1)
+      expect(stub1).to have_been_requested.once
+    end
+
+    it 'handles errors correctly' do 
+      stub1 = stub_request(:post, "https://mattermost.blah/hook/abcd").to_return(status: 500, body: "error")
+      expect(stub1).to have_been_requested.times(0)
+      expect{described_class.trigger_notification(post, chan1)}.to raise_exception(::DiscourseChat::ProviderError)
+      expect(stub1).to have_been_requested.once
+    end
+
+  end
+
+end