FEATURE: Add nodeinfo endpoint

app/controllers/discourse_activity_pub/nodeinfo_controller.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+module DiscourseActivityPub
+  class NodeinfoController < ApplicationController
+    requires_plugin DiscourseActivityPub::PLUGIN_NAME
+
+    include DiscourseActivityPub::EnabledVerification
+
+    skip_before_action :preload_json, :redirect_to_login_if_required, :check_xhr
+
+    before_action :ensure_site_enabled
+
+    def index
+      render json: Nodeinfo.index, content_type: "application/jrd+json"
+    end
+
+    def show
+      nodeinfo = Nodeinfo.new(params[:version])
+      raise Discourse::NotFound unless nodeinfo.supported_version?
+      render_serialized(nodeinfo, NodeinfoSerializer, root: false)
+    end
+  end
+end

app/serializers/discourse_activity_pub/nodeinfo_serializer.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+module DiscourseActivityPub
+  class NodeinfoSerializer < ActiveModel::Serializer
+    attributes :version, :software, :protocols, :services, :usage, :openRegistrations, :metadata
+
+    def software
+      format(object.software).as_json
+    end
+
+    def services
+      format(object.services).as_json
+    end
+
+    def usage
+      format(object.usage).as_json
+    end
+
+    def openRegistrations
+      object.open_registrations
+    end
+
+    def metadata
+      format(object.metadata).as_json
+    end
+
+    protected
+
+    def format(hash)
+      hash.deep_transform_keys do |key|
+        case key
+        when :active_half_year
+          "activeHalfyear"
+        else
+          key.to_s.camelize(:lower)
+        end
+      end
+    end
+  end
+end

lib/discourse_activity_pub/nodeinfo.rb

@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+module DiscourseActivityPub
+  class Nodeinfo
+    include ActiveModel::Serialization
+
+    VERSION = "2.1"
+    SOFTWARE_NAME = "discourse"
+
+    # See https://github.com/jhass/nodeinfo/blob/main/schemas/2.1/schema.json for supported enums.
+    SUPPORTED_PROTOCOLS = %w[activitypub]
+    SUPPORTED_INBOUND_SERVICES = %w[rss2.0 pop3]
+    SUPPORTED_OUTBOUND_SERVICES = %w[rss2.0 smtp]
+
+    attr_reader :version
+
+    def initialize(version)
+      @version = version.to_s
+    end
+
+    def supported_version?
+      version == VERSION
+    end
+
+    def software
+      { name: SOFTWARE_NAME, version: Discourse::VERSION::STRING }
+    end
+
+    def protocols
+      SUPPORTED_PROTOCOLS
+    end
+
+    def services
+      { inbound: SUPPORTED_INBOUND_SERVICES, outbound: SUPPORTED_OUTBOUND_SERVICES }
+    end
+
+    def usage
+      {
+        users: {
+          total: ::Statistics.nodeinfo[:users_total],
+          active_month: ::Statistics.nodeinfo[:users_seen_month],
+          active_half_year: ::Statistics.nodeinfo[:users_seen_half_year],
+        },
+        local_posts: ::Statistics.nodeinfo[:posts_local],
+        local_comments: ::Statistics.nodeinfo[:replies_local],
+      }
+    end
+
+    def open_registrations
+      !SiteSetting.login_required
+    end
+
+    # Compare https://mastodon.social/nodeinfo/2.0
+    def metadata
+      { node_name: SiteSetting.title, node_description: SiteSetting.site_description }
+    end
+
+    def self.index
+      {
+        links: [
+          {
+            rel: "http://nodeinfo.diaspora.software/ns/schema/#{VERSION}",
+            href: "#{Discourse.base_url_no_prefix}/nodeinfo/#{VERSION}",
+          },
+        ],
+      }.as_json
+    end
+  end
+end

lib/discourse_activity_pub/statistics.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+module DiscourseActivityPub
+  module Statistics
+    # https://github.com/jhass/nodeinfo/blob/main/schemas/2.2/schema.json#usage
+    def nodeinfo
+      {
+        users_total: active_users.count,
+        users_seen_half_year: active_users.where("last_seen_at > ?", 180.days.ago).count,
+        users_seen_month: active_users.where("last_seen_at > ?", 30.days.ago).count,
+        posts_local: local_posts.where("reply_to_post_number IS NULL").count,
+        replies_local: local_posts.where("reply_to_post_number IS NOT NULL").count,
+      }
+    end
+
+    def active_users
+      valid_users.where("staged IS FALSE")
+    end
+
+    def local_posts
+      ::Post.where("user_id NOT IN (SELECT id FROM users WHERE staged IS TRUE)")
+    end
+  end
+end

plugin.rb

@@ -36,6 +36,11 @@ module ::DiscourseActivityPub
     mount ::DiscourseActivityPub::Engine, at: "ap"
 
     get ".well-known/webfinger" => "discourse_activity_pub/webfinger#index"
+    get ".well-known/nodeinfo" => "discourse_activity_pub/nodeinfo#index"
+    get "/nodeinfo/:version" => "discourse_activity_pub/nodeinfo#show",
+        :constraints => {
+          version: /[0-9\.]+/,
+        }
     post "/webfinger/handle/validate" => "discourse_activity_pub/webfinger/handle#validate",
          :defaults => {
            format: :json,
@@ -195,6 +200,7 @@ module ::DiscourseActivityPub
     add_to_class(:post, field_name.to_sym) { custom_fields[field_name] }
   end
   PostAction.prepend DiscourseActivityPub::PostAction
+  Statistics.singleton_class.prepend DiscourseActivityPub::Statistics
 
   ##
   ## Discourse serialization

spec/fixtures/nodeinfo/2.1/schema.json

@@ -0,0 +1,188 @@
+{
+  "$schema": "http://json-schema.org/draft-04/schema#",
+  "id": "http://nodeinfo.diaspora.software/ns/schema/2.1#",
+  "description": "NodeInfo schema version 2.1.",
+  "type": "object",
+  "additionalProperties": false,
+  "required": [
+    "version",
+    "software",
+    "protocols",
+    "services",
+    "openRegistrations",
+    "usage",
+    "metadata"
+  ],
+  "properties": {
+    "version": {
+      "description": "The schema version, must be 2.1.",
+      "enum": [
+        "2.1"
+      ]
+    },
+    "software": {
+      "description": "Metadata about server software in use.",
+      "type": "object",
+      "additionalProperties": false,
+      "required": [
+        "name",
+        "version"
+      ],
+      "properties": {
+        "name": {
+          "description": "The canonical name of this server software.",
+          "type": "string",
+          "pattern": "^[a-z0-9-]+$"
+        },
+        "version": {
+          "description": "The version of this server software.",
+          "type": "string"
+        },
+        "repository": {
+          "description": "The url of the source code repository of this server software.",
+          "type": "string"
+        },
+        "homepage": {
+          "description": "The url of the homepage of this server software.",
+          "type": "string"
+        }
+      }
+    },
+    "protocols": {
+      "description": "The protocols supported on this server.",
+      "type": "array",
+      "minItems": 1,
+      "items": {
+        "enum": [
+          "activitypub",
+          "buddycloud",
+          "dfrn",
+          "diaspora",
+          "libertree",
+          "ostatus",
+          "pumpio",
+          "tent",
+          "xmpp",
+          "zot"
+        ]
+      }
+    },
+    "services": {
+      "description": "The third party sites this server can connect to via their application API.",
+      "type": "object",
+      "additionalProperties": false,
+      "required": [
+        "inbound",
+        "outbound"
+      ],
+      "properties": {
+        "inbound": {
+          "description": "The third party sites this server can retrieve messages from for combined display with regular traffic.",
+          "type": "array",
+          "minItems": 0,
+          "items": {
+            "enum": [
+              "atom1.0",
+              "gnusocial",
+              "imap",
+              "pnut",
+              "pop3",
+              "pumpio",
+              "rss2.0",
+              "twitter"
+            ]
+          }
+        },
+        "outbound": {
+          "description": "The third party sites this server can publish messages to on the behalf of a user.",
+          "type": "array",
+          "minItems": 0,
+          "items": {
+            "enum": [
+              "atom1.0",
+              "blogger",
+              "buddycloud",
+              "diaspora",
+              "dreamwidth",
+              "drupal",
+              "facebook",
+              "friendica",
+              "gnusocial",
+              "google",
+              "insanejournal",
+              "libertree",
+              "linkedin",
+              "livejournal",
+              "mediagoblin",
+              "myspace",
+              "pinterest",
+              "pnut",
+              "posterous",
+              "pumpio",
+              "redmatrix",
+              "rss2.0",
+              "smtp",
+              "tent",
+              "tumblr",
+              "twitter",
+              "wordpress",
+              "xmpp"
+            ]
+          }
+        }
+      }
+    },
+    "openRegistrations": {
+      "description": "Whether this server allows open self-registration.",
+      "type": "boolean"
+    },
+    "usage": {
+      "description": "Usage statistics for this server.",
+      "type": "object",
+      "additionalProperties": false,
+      "required": [
+        "users"
+      ],
+      "properties": {
+        "users": {
+          "description": "statistics about the users of this server.",
+          "type": "object",
+          "additionalProperties": false,
+          "properties": {
+            "total": {
+              "description": "The total amount of on this server registered users.",
+              "type": "integer",
+              "minimum": 0
+            },
+            "activeHalfyear": {
+              "description": "The amount of users that signed in at least once in the last 180 days.",
+              "type": "integer",
+              "minimum": 0
+            },
+            "activeMonth": {
+              "description": "The amount of users that signed in at least once in the last 30 days.",
+              "type": "integer",
+              "minimum": 0
+            }
+          }
+        },
+        "localPosts": {
+          "description": "The amount of posts that were made by users that are registered on this server.",
+          "type": "integer",
+          "minimum": 0
+        },
+        "localComments": {
+          "description": "The amount of comments that were made by users that are registered on this server.",
+          "type": "integer",
+          "minimum": 0
+        }
+      }
+    },
+    "metadata": {
+      "description": "Free form key value pairs for software specific values. Clients should not rely on any specific key present.",
+      "type": "object",
+      "minProperties": 0,
+      "additionalProperties": true
+    }
+  }
+}