Implement slack provider, based on existing plugin.

Currently only implements the “Webhook” method, not the “Web API” method

config/settings.yml

@@ -5,3 +5,21 @@ plugins:
     default: system
   chat_delay_seconds:
     default: 20
+
+#######################################
+########## SLACK SETTINGS #############
+#######################################
+  chat_slack_enabled:
+    default: false
+  chat_slack_outbound_webhook_url:
+    default: ''
+  chat_slack_discourse_excerpt_length:
+    default: 400
+  chat_slack_icon_url:
+    default: ''
+
+#######################################
+######### TELEGRAM SETTINGS ###########
+#######################################
+  chat_telegram_enabled:
+    default: false

lib/discourse_chat/provider/slack/slack_message_formatter.rb

@@ -0,0 +1,49 @@
+module DiscourseChat::Provider::SlackProvider
+  class SlackMessageFormatter < Nokogiri::XML::SAX::Document
+    attr_reader :excerpt
+
+    def initialize
+      @excerpt = ""
+    end
+
+    def self.format(html = '')
+      me = self.new
+      parser = Nokogiri::HTML::SAX::Parser.new(me)
+      parser.parse(html)
+      me.excerpt
+    end
+
+    def start_element(name, attributes = [])
+      case name
+      when "a"
+        attributes = Hash[*attributes.flatten]
+        @in_a = true
+        @excerpt << "<#{absolute_url(attributes['href'])}|"
+      end
+    end
+
+    def end_element(name)
+      case name
+      when "a"
+        @excerpt << ">"
+        @in_a = false
+      end
+    end
+
+    def characters(string)
+      string.strip! if @in_a
+      @excerpt << string
+    end
+
+    private
+
+      def absolute_url(url)
+        uri = URI(url) rescue nil
+
+        return Discourse.current_hostname unless uri
+        uri.host = Discourse.current_hostname if !uri.host
+        uri.scheme = (SiteSetting.force_https ? 'https' : 'http') if !uri.scheme
+        uri.to_s
+      end
+  end
+end

lib/discourse_chat/provider/slack/slack_provider.rb

@@ -1,7 +1,71 @@
-module DiscourseChat
-  module Provider
-    module SlackProvider
+module DiscourseChat::Provider::SlackProvider
   PROVIDER_NAME = "slack".freeze
+
+  def self.excerpt(post, max_length = SiteSetting.chat_slack_discourse_excerpt_length)
+    doc = Nokogiri::HTML.fragment(post.excerpt(max_length,
+      remap_emoji: true,
+      keep_onebox_source: true
+    ))
+
+    SlackMessageFormatter.format(doc.to_html)
   end
+
+  def self.slack_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 = (topic.category.parent_category) ? "[#{topic.category.parent_category.name}/#{topic.category.name}]": "[#{topic.category.name}]"
+
+    icon_url =
+      if !SiteSetting.chat_slack_icon_url.blank?
+        "#{Discourse.base_url}#{SiteSetting.chat_slack_icon_url}"
+      elsif !SiteSetting.logo_small_url.blank?
+        "#{Discourse.base_url}#{SiteSetting.logo_small_url}"
+      end
+
+    message = {
+      channel: channel,
+      username: SiteSetting.title,
+      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.color}",
+      text: ::DiscourseSlack::Slack.excerpt(post),
+      mrkdwn_in: ["text"]
+    }
+
+    record = ::PluginStore.get(DiscourseSlack::PLUGIN_NAME, "topic_#{post.topic.id}_#{channel}")
+
+    if (SiteSetting.slack_access_token.empty? || post.is_first_post? || record.blank? || (record.present? &&  ((Time.now.to_i - record[:ts].split('.')[0].to_i)/ 60) >= 5 ))
+      summary[:title] = "#{topic.title} #{(category == '[uncategorized]')? '' : category} #{topic.tags.present? ? topic.tags.map(&:name).join(', ') : ''}"
+      summary[:title_link] = post.full_url
+      summary[:thumb_url] = post.full_url
+    end
+
+    message[:attachments].push(summary)
+    message
+  end
+
+  def self.trigger_notification(post, channel)
+  	message = slack_message(post, channel)
+
+		http = Net::HTTP.new("hooks.slack.com", 443)
+    http.use_ssl = true
+
+  	req = Net::HTTP::Post.new(URI(SiteSetting.slack_outbound_webhook_url), 'Content-Type' =>'application/json')
+    req.body = message.to_json
+    response = http.request(req)
+
   end
 end