Add keysend support for Lightning Address

Allow keysend payments to user addresses. Useful for Podcasting 2.0/v4v.

.env.example

@@ -11,6 +11,7 @@ BTCPAY_API_URL='http://localhost:23001/api/v1'
 
 LNDHUB_API_URL='http://localhost:3023'
 LNDHUB_PUBLIC_URL='https://lndhub.kosmos.org'
+LNDHUB_PUBLIC_KEY='0123d3be18617f39cf645851e3ba63f51fc13f0bb09e3bb25e6fd4de556486d946'
 LNDHUB_ADMIN_UI=true
 LNDHUB_PG_HOST=localhost
 LNDHUB_PG_PORT=5432

app/controllers/lnurlpay_controller.rb

@@ -1,4 +1,5 @@
 class LnurlpayController < ApplicationController
+  before_action :check_feature_enabled
   before_action :find_user_by_address
 
   MIN_SATS = 10
@@ -17,6 +18,20 @@ class LnurlpayController < ApplicationController
     }
   end
 
+  def keysend
+    http_status :not_found unless Setting.lndhub_keysend_enabled?
+
+    render json: {
+      status: "OK",
+      tag: "keysend",
+      pubkey: Setting.lndhub_public_key,
+      customData: [{
+        customKey: "696969",
+        customValue: @user.ln_account
+      }]
+    }
+  end
+
   def invoice
     amount = params[:amount].to_i / 1000 # msats
     address = params[:address]
@@ -72,4 +87,9 @@ class LnurlpayController < ApplicationController
     comment.length <= MAX_COMMENT_CHARS
   end
 
+  private
+
+  def check_feature_enabled
+    http_status :not_found if !Setting.lndhub_enabled?
+  end
 end

app/models/setting.rb

@@ -2,10 +2,27 @@
 class Setting < RailsSettings::Base
   cache_prefix { "v1" }
 
+  #
+  # Registrations
+  #
+
   field :reserved_usernames, type: :array, default: %w[
     account accounts admin donations mail webmaster support
   ]
 
-  field :lndhub_enabled, default: (ENV["LNDHUB_API_URL"].present?.to_s || "false"), type: :boolean
-  field :lndhub_admin_enabled, default: (ENV["LNDHUB_ADMIN_UI"] || "false"), type: :boolean
+  #
+  # Lightning Network
+  #
+
+  field :lndhub_enabled, type: :boolean,
+    default: (ENV["LNDHUB_API_URL"].present?.to_s || false)
+
+  field :lndhub_admin_enabled, type: :boolean,
+    default: (ENV["LNDHUB_ADMIN_UI"] || false)
+
+  field :lndhub_public_key, type: :string,
+    default: (ENV["LNDHUB_PUBLIC_KEY"] || "")
+
+  field :lndhub_keysend_enabled, type: :boolean,
+    default: -> { self.lndhub_public_key.present?.to_s || false }
 end

config/routes.rb

@@ -30,6 +30,7 @@ Rails.application.routes.draw do
 
   get 'lnurlpay/:address', to: 'lnurlpay#index', constraints: { address: /[^\/]+/}
   get 'lnurlpay/:address/invoice', to: 'lnurlpay#invoice', constraints: { address: /[^\/]+/}
+  get 'keysend/:address', to: 'lnurlpay#keysend', constraints: { address: /[^\/]+/}
 
   post 'webhooks/lndhub', to: 'webhooks#lndhub'