DONE - Add LNURL Fallback Scheme to Web URL

[pretyflaco]

Description

Implement LNURL Fallback Scheme in a user account's Paycode Print to offer link to user account's Web URL page, e.g. Web URL of user account "ideasarelikeflames": HTTPS://PAY.BBW.SV/IDEASARELIKEFLAMES

Background

There is a need for merchants in Bitcoin Beach to have a static QR code at their point-of-sale, printed out on paper, that customers can scan with their wallet and pay - this eliminates the need for merchant to generate a Bolt11 invoice for each individual customer and improves the payment UX immensely. The challenge here is wallet interoperability:

1. not all wallets support LNURL-pay (yet)
2. users with on-chain wallets need to be able to pay, too
3. there should be only one QR at point-of-sale to avoid customer confusion about which QR to scan

Possible flow:

There is a Fallback Scheme in LNURL. If implemented in the Paycode Print it could eliminate the need for a second QR as fallback for all non LNURL wallets. Then, all users could scan the same QR:

• users with LNURL supported wallets could pay directly,
• all others could scan with phone's camera and be directed to the respective account's Web URL, where they get a Bolt11 invoice, or option to generate on-chain address.

This would present a path to pay for all wallets, while keeping the amount of QRs to start from to one:

• Lightning wallets with LNURL-pay support (direct pay to LNURL)
• Lightning wallet with Bolt11 support (through Web URL)
• On-chain only wallets (through Web URL)

Decoded example (Uppercase):
HTTPS://PAY.BBW.SV/IDEASARELIKEFLAMES?LIGHTNING=LNURL1DP68GURN8GHJ7MRW9E3XJARRDA5KUCN9V93KSTNRDAKJ7TNHV4KXCTTTDEHHWM30D3H82UNVWQHKJER9V9EKZUN9D35KKETXD3SK6ETN7KSR69

In order to keep the QR scan-able (minimize QR code complexity by keeping amount of bits encoded small), the encoded string should be UPPERCASE where possible

Task

Submit a PR that implements the above described feature into galoy-mobile.

Definition of Done

Submit a PR that gets merged to galoy-mobile and leads to closure of this issue

Bounty

2M Sats (0.02 BTC)

Bounty Patrons

Galoy

[kngako]

Anyone working on this?

[abhiShandy]

I have created a PR on Galoy-Pay: GaloyMoney/galoy-pay#359

We might have to test with Galoy-mobile to make sure it is decoded correctly

[agbegin]

PR has been merged! Thank you @abhiShandy and @kngako. Payouts to be sent pending final deployment and testing

GaloyMoney/galoy-pay#359

[UncleSamtoshi]

The bounty has been deployed and can be paid out @agbegin !

[agbegin]

Bounty has been paid out @UncleSamtoshi. Thanks all!