From b63d8207a959e1963191a59de5e9a2237e72de10 Mon Sep 17 00:00:00 2001
From: evazion <noizave@gmail.com>
Date: Thu, 18 Feb 2021 07:08:45 -0600
Subject: [PATCH] forum: automatically post new forum posts to Discord.

---
 .github/workflows/test.yaml          |  2 +
 app/jobs/discord_notification_job.rb |  7 ++++
 app/logical/d_text.rb                | 23 ++++++++++++
 app/logical/discord_api_client.rb    | 56 ++++++++++++++++++++++++++++
 app/models/forum_post.rb             | 10 +++++
 config/danbooru_default_config.rb    |  8 ++++
 6 files changed, 106 insertions(+)
 create mode 100644 app/jobs/discord_notification_job.rb
 create mode 100644 app/logical/discord_api_client.rb

diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index 0b7557ddc..f2d756acf 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -44,6 +44,8 @@ jobs:
       DANBOORU_PAWOO_CLIENT_SECRET: ${{ secrets.DANBOORU_PAWOO_CLIENT_SECRET }}
       DANBOORU_BARAAG_CLIENT_ID: ${{ secrets.DANBOORU_BARAAG_CLIENT_ID }}
       DANBOORU_BARAAG_CLIENT_SECRET: ${{ secrets.DANBOORU_BARAAG_CLIENT_SECRET }}
+      DANBOORU_DISCORD_WEBHOOK_ID: ${{ secrets.DANBOORU_DISCORD_WEBHOOK_ID }}
+      DANBOORU_DISCORD_WEBHOOK_SECRET: ${{ secrets.DANBOORU_DISCORD_WEBHOOK_SECRET }}
       DANBOORU_RAKISMET_KEY: ${{ secrets.DANBOORU_RAKISMET_KEY }}
       DANBOORU_RAKISMET_URL: ${{ secrets.DANBOORU_RAKISMET_URL }}
       DANBOORU_IP_REGISTRY_API_KEY: ${{ secrets.DANBOORU_IP_REGISTRY_API_KEY }}
diff --git a/app/jobs/discord_notification_job.rb b/app/jobs/discord_notification_job.rb
new file mode 100644
index 000000000..20251c178
--- /dev/null
+++ b/app/jobs/discord_notification_job.rb
@@ -0,0 +1,7 @@
+class DiscordNotificationJob < ApplicationJob
+  retry_on Exception, attempts: 0
+
+  def perform(forum_post:)
+    forum_post.send_discord_notification
+  end
+end
diff --git a/app/logical/d_text.rb b/app/logical/d_text.rb
index f665c4923..61c34db6f 100644
--- a/app/logical/d_text.rb
+++ b/app/logical/d_text.rb
@@ -250,6 +250,29 @@ class DText
     text.gsub(/\A[[:space:]]+|[[:space:]]+\z/, "")
   end
 
+  def self.to_markdown(dtext)
+    html_to_markdown(format_text(dtext))
+  end
+
+  def self.html_to_markdown(html)
+    html = Nokogiri::HTML.fragment(html)
+
+    html.children.map do |node|
+      case node.name
+      when "div", "blockquote", "table"
+        "" # strip [expand], [quote], and [table] tags
+      when "br"
+        "\n"
+      when "text"
+        node.text.gsub(/_/, '\_').gsub(/\*/, '\*')
+      when "p", "h1", "h2", "h3", "h4", "h5", "h6"
+        html_to_markdown(node.inner_html) + "\n\n"
+      else
+        html_to_markdown(node.inner_html)
+      end
+    end.join
+  end
+
   def self.from_html(text, inline: false, &block)
     html = Nokogiri::HTML.fragment(text)
 
diff --git a/app/logical/discord_api_client.rb b/app/logical/discord_api_client.rb
new file mode 100644
index 000000000..8a1131058
--- /dev/null
+++ b/app/logical/discord_api_client.rb
@@ -0,0 +1,56 @@
+class DiscordApiClient
+  attr_reader :webhook_id, :webhook_secret, :http
+
+  def initialize(webhook_id: Danbooru.config.discord_webhook_id, webhook_secret: Danbooru.config.discord_webhook_secret, http: Danbooru::Http.new)
+    @webhook_id = webhook_id
+    @webhook_secret = webhook_secret
+    @http = http
+  end
+
+  def enabled?
+    webhook_id.present? && webhook_secret.present?
+  end
+
+  # https://discord.com/developers/docs/resources/webhook#execute-webhook
+  def post_message(forum_post)
+    return unless enabled?
+
+    http.post(webhook_url, params: { wait: true }, json: build_message(forum_post))
+  end
+
+  # https://discord.com/developers/docs/resources/channel#embed-object
+  def build_message(forum_post)
+    {
+      embeds: [{
+        title: forum_post.topic.title,
+        description: convert_dtext(forum_post.body),
+        timestamp: forum_post.created_at.iso8601,
+        url: Routes.url_for(forum_post),
+        author: {
+          name: forum_post.creator.name,
+          url: Routes.url_for(forum_post.creator)
+        },
+        fields: [
+          {
+            name: "Replies",
+            value: forum_post.topic.response_count,
+            inline: true
+          },
+          {
+            name: "Users",
+            value: forum_post.topic.forum_posts.distinct.count(:creator_id),
+            inline: true
+          }
+        ]
+      }]
+    }
+  end
+
+  def convert_dtext(dtext)
+    DText.to_markdown(dtext).truncate(2000)
+  end
+
+  def webhook_url
+    "https://discord.com/api/webhooks/#{webhook_id}/#{webhook_secret}"
+  end
+end
diff --git a/app/models/forum_post.rb b/app/models/forum_post.rb
index 16941f3c9..79ffd795a 100644
--- a/app/models/forum_post.rb
+++ b/app/models/forum_post.rb
@@ -23,6 +23,7 @@ class ForumPost < ApplicationRecord
   after_destroy(:if => ->(rec) {rec.updater_id != rec.creator_id}) do |rec|
     ModAction.log("#{CurrentUser.user.name} deleted forum ##{rec.id}", :forum_post_delete)
   end
+  after_create_commit :async_send_discord_notification
 
   deletable
   mentionable(
@@ -153,6 +154,15 @@ class ForumPost < ApplicationRecord
     end
   end
 
+  def async_send_discord_notification
+    DiscordNotificationJob.perform_later(forum_post: self)
+  end
+
+  def send_discord_notification
+    return unless policy(User.anonymous).show?
+    DiscordApiClient.new.post_message(self)
+  end
+
   def build_response
     dup.tap do |x|
       x.body = x.quoted_response
diff --git a/config/danbooru_default_config.rb b/config/danbooru_default_config.rb
index 291d79974..7bd5bc404 100644
--- a/config/danbooru_default_config.rb
+++ b/config/danbooru_default_config.rb
@@ -394,6 +394,14 @@ module Danbooru
     def twitter_api_secret
     end
 
+    # If defined, Danbooru will automatically post new forum posts to the
+    # Discord channel belonging to this webhook.
+    def discord_webhook_id
+    end
+
+    def discord_webhook_secret
+    end
+
     # you should override this
     def email_key
       "zDMSATq0W3hmA5p3rKTgD"