author: andreneves discussion: https://github.com/fiatjaf/lnurl-rfc/pull/50
This allows for a WALLET to pass a custom comment property to a SERVICE that accepts it. This can have multiple use-cases. Better donation flow is an easy one to visualize. The entity donating gets to send a message, whether their name/contact/random text and the issuer gets to be paid to read/voice/receive that message, for example streamers.
This is completely additional/ad-hoc, so current implementations are not affected by this. Any services and wallets that wish to support it do need to add some more business logic.
SERVICE must alter is JSON response to the first callback to include a commentAllowed field, as follows:
{
callback: String,
maxSendable: MilliSatoshi,
minSendable: MilliSatoshi,
metadata: String,
+ commentAllowed: Number,
tag: "payRequest",
}The value of commentAllowed should be the number of characters accepted for the comment query parameter on subsequent callback. (Should be interpreted as 0 if not provided).
Upon seeing a positive commentAllowed attribute on the response from the SERVICE, a WALLET must display a text input where user can enter a comment string (max character count is equal or less than commentAllowed value) along with the other LNURL-pay metadata (text and image).
After gathering input from the user, WALLET must include the comment in its second callback to SERVICE:
- <callback><?|&>amount=<milliSatoshi>
+ <callback><?|&>amount=<milliSatoshi>&comment=<String>GET URL's accept around ~2000 characters for the entire request string. Therefore comment can only be as large as to fit in the URL alongisde any/all of the properties outlined above.