From 4c51b9c966656fa9d61bcdb0abe565db97594b29 Mon Sep 17 00:00:00 2001
From: Sebastian Kippe <sebastian@kip.pe>
Date: Tue, 1 Mar 2022 11:13:07 -0600
Subject: [PATCH 1/3] Allow comments for LNURL-PAY invoices

Allows senders to add a short message to payments, which will be stored
as invoice memo by LND/LndHub.
---
 app/controllers/lnurlpay_controller.rb | 16 ++++++++++++++--
 app/services/lndhub.rb                 |  3 ++-
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/app/controllers/lnurlpay_controller.rb b/app/controllers/lnurlpay_controller.rb
index f042919..067ba2b 100644
--- a/app/controllers/lnurlpay_controller.rb
+++ b/app/controllers/lnurlpay_controller.rb
@@ -3,6 +3,7 @@ class LnurlpayController < ApplicationController
 
   MIN_SATS = 100
   MAX_SATS = 1_000_000
+  MAX_COMMENT_CHARS = 100
 
   def index
     render json: {
@@ -12,22 +13,29 @@ class LnurlpayController < ApplicationController
       maxSendable: MAX_SATS * 1000, # msat
       minSendable: MIN_SATS * 1000, # msat
       metadata: metadata(@user.address),
-      commentAllowed: 0
+      commentAllowed: MAX_COMMENT_CHARS
     }
   end
 
   def invoice
     amount = params[:amount].to_i / 1000 # msats
     address = params[:address]
+    comment = params[:comment]
 
     if !valid_amount?(amount)
       render json: { status: "ERROR", reason: "Invalid amount" }
       return
     end
 
+    if !valid_comment?(comment)
+      render json: { status: "ERROR", reason: "Comment too long" }
+      return
+    end
+
     payment_request = @user.ln_create_invoice({
       amount: amount, # we create invoices in sats
-      description_hash: Digest::SHA2.hexdigest(metadata(address))
+      description_hash: Digest::SHA2.hexdigest(metadata(address)),
+      memo: comment
     })
 
     render json: {
@@ -57,4 +65,8 @@ class LnurlpayController < ApplicationController
     amount_in_sats <= MAX_SATS && amount_in_sats >= MIN_SATS
   end
 
+  def valid_comment?(comment)
+    comment.length <= MAX_COMMENT_CHARS
+  end
+
 end
diff --git a/app/services/lndhub.rb b/app/services/lndhub.rb
index 5706148..15fae8e 100644
--- a/app/services/lndhub.rb
+++ b/app/services/lndhub.rb
@@ -49,7 +49,8 @@ class Lndhub
   def addinvoice(payload)
     invoice = post "addinvoice", {
       amt: payload[:amount],
-      description_hash: payload[:description_hash]
+      description_hash: payload[:description_hash],
+      memo: payload[:memo]
     }
 
     invoice["payment_request"]

From 990368353685112871cdca88e390b304102dce02 Mon Sep 17 00:00:00 2001
From: Sebastian Kippe <sebastian@kip.pe>
Date: Tue, 1 Mar 2022 13:26:21 -0600
Subject: [PATCH 2/3] Remove desc hash, always add memo to invoices

---
 app/controllers/lnurlpay_controller.rb | 8 +++++---
 app/services/lndhub.rb                 | 1 -
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/app/controllers/lnurlpay_controller.rb b/app/controllers/lnurlpay_controller.rb
index 067ba2b..3f0d67f 100644
--- a/app/controllers/lnurlpay_controller.rb
+++ b/app/controllers/lnurlpay_controller.rb
@@ -20,7 +20,7 @@ class LnurlpayController < ApplicationController
   def invoice
     amount = params[:amount].to_i / 1000 # msats
     address = params[:address]
-    comment = params[:comment]
+    comment = params[:comment] || ""
 
     if !valid_amount?(amount)
       render json: { status: "ERROR", reason: "Invalid amount" }
@@ -32,10 +32,12 @@ class LnurlpayController < ApplicationController
       return
     end
 
+    memo = "Sats for #{address}"
+    memo = "#{memo}: \"#{comment}\"" if comment.present?
+
     payment_request = @user.ln_create_invoice({
       amount: amount, # we create invoices in sats
-      description_hash: Digest::SHA2.hexdigest(metadata(address)),
-      memo: comment
+      memo: memo
     })
 
     render json: {
diff --git a/app/services/lndhub.rb b/app/services/lndhub.rb
index 15fae8e..ad606cc 100644
--- a/app/services/lndhub.rb
+++ b/app/services/lndhub.rb
@@ -49,7 +49,6 @@ class Lndhub
   def addinvoice(payload)
     invoice = post "addinvoice", {
       amt: payload[:amount],
-      description_hash: payload[:description_hash],
       memo: payload[:memo]
     }
 

From 4c70600d1f1bd08b6a67e28489b8c506b3da12d0 Mon Sep 17 00:00:00 2001
From: Sebastian Kippe <sebastian@kip.pe>
Date: Tue, 1 Mar 2022 13:53:22 -0600
Subject: [PATCH 3/3] Re-add description_hash

Necessary for lnurlpay-enabled wallets
---
 app/controllers/lnurlpay_controller.rb | 3 ++-
 app/services/lndhub.rb                 | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/app/controllers/lnurlpay_controller.rb b/app/controllers/lnurlpay_controller.rb
index 3f0d67f..1ee4044 100644
--- a/app/controllers/lnurlpay_controller.rb
+++ b/app/controllers/lnurlpay_controller.rb
@@ -37,7 +37,8 @@ class LnurlpayController < ApplicationController
 
     payment_request = @user.ln_create_invoice({
       amount: amount, # we create invoices in sats
-      memo: memo
+      memo: memo,
+      description_hash: Digest::SHA2.hexdigest(metadata(address)),
     })
 
     render json: {
diff --git a/app/services/lndhub.rb b/app/services/lndhub.rb
index ad606cc..01f7abf 100644
--- a/app/services/lndhub.rb
+++ b/app/services/lndhub.rb
@@ -49,7 +49,8 @@ class Lndhub
   def addinvoice(payload)
     invoice = post "addinvoice", {
       amt: payload[:amount],
-      memo: payload[:memo]
+      memo: payload[:memo],
+      description_hash: payload[:description_hash]
     }
 
     invoice["payment_request"]