nips/89.md

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# NIP-89
## payto: Payment Targets
`draft` `optional` `author:atxmj`
### payto: event broadcasting
Clients *may* allow users to specify a list (one or many) of "payment targets" as specified in the [RFC-8905 (payto:) URI scheme](https://www.rfc-editor.org/rfc/rfc8905.html) standard, each consisting of a pair of values, `payment_target_type` and `authority` (to be labeled as preferred by the client), in order to generate an event of kind `0` (`set_metadata`) specifying "payment targets" that *may* be used for payment or tip invocation from a user's profile, posts, chats, or elsewhere.
The client *may* allow the user to input and perform validation on the `payment_target_type` and `authority` fields (labeled as preferred by the client) as they see fit.
### Example of broadcasting a "payto" event
The client allows the user to add multiple pairs of "payment network" and "address" values to a list of "payment options" in their profile.
The client performs validation on the inputs and warns the user that the "payment network" for the third "payment option" with value `unknowntype` is [not recognized](#recommended-payment-target-types), but allows them to submit it regardless.
The client then broadcasts an event such as
```json
{
"pubkey": "afc93622eb4d79c0fb75e56e0c14553f7214b0a466abeba14cb38968c6755e6a",
"kind": 0,
"content": "{\"payto\": [{\"payment_target_type\": \"bitcoin\", \"authority\": \"bc1qxq66e0t8d7ugdecwnmv58e90tpry23nc84pg9k\"}, {\"payment_target_type\": \"nano\", \"authority\": \"nano_1dctqbmqxfppo9pswbm6kg9d4s4mbraqn8i4m7ob9gnzz91aurmuho48jx3c\"}, {\"payment_target_type\": \"unknowntype\", \"authority\": \"l7tbta5b9xze6ckkfc99uohzxd009b0r\"}]}"
...
}
```
### Recommended Payment Target Types
This is a list of recommended payment target types for clients to recognize and store icons and stylization configurations for.
| Payment Target Type | Long Stylization | Short Stylization | Symbol | References |
| :------------------ | :---------------- | :---------------- | :----- | :--------- |
| bitcoin | Bitcoin | BTC | ₿ | https://bitcoin.design/ |
| lightning | Lightning Network | LBTC | — | https://github.com/shocknet/bitcoin-lightning-logo |
| cashme | Cash App | Cash App | | https://cash.app/press |
| nano | Nano | XNO | Ӿ | https://nano.org/en/currency |
### payto: event observation
On observation of events of kind `0` (`set_metadata`), the event *may* specify the key `"payto"` with a value consisting of a list (one or many) of "payment target" values, each specified as a pair of values `payment_target_type` and `authority` as specified in the [RFC-8905 (payto:) URI scheme](https://www.rfc-editor.org/rfc/rfc8905.html) for payment targets.
For each pair of values in the list, the client *should* assemble a full `payto://` deep link URI and render it as a button or link in the user's profile, posts, chats, or elsewhere, in the format of `payto://<payment_target_type>/<authority>`.
The client *should* store a map of [recognized payment target types](#recommended-payment-target-types) along with a corresponding icon and/or stylization configuration (to be defined by the client).
For ***recognized*** `payment_target_type` values, the client *should* render a button or link using the associated icon and/or stylization.
For ***unrecognized*** `payment_target_type` values, the client *may* chose to either ignore them or use a generic stylization, perhaps using the `payment_target_type` value directly for the button or link.
If a user has specified multiple payment targets, the client *may* choose to render only the first one, render multiple buttons or links, or render a dropdown to select the payment target of choice.
### Example of observing a "payto" event
If a client sees an event like this:
```json
{
"pubkey": "afc93622eb4d79c0fb75e56e0c14553f7214b0a466abeba14cb38968c6755e6a",
"kind": 0,
"content": "{\"payto\": [{\"payment_target_type\": \"bitcoin\", \"authority\": \"bc1qxq66e0t8d7ugdecwnmv58e90tpry23nc84pg9k\"}, {\"payment_target_type\": \"nano\", \"authority\": \"nano_1dctqbmqxfppo9pswbm6kg9d4s4mbraqn8i4m7ob9gnzz91aurmuho48jx3c\"}, {\"payment_target_type\": \"unknowntype\", \"authority\": \"l7tbta5b9xze6ckkfc99uohzxd009b0r\"}]}"
...
}
```
for each payment target it will assemble a deep link payment invocation URI, as
`payto://bitcoin/bc1qxq66e0t8d7ugdecwnmv58e90tpry23nc84pg9k` (*recognized*)
`payto://nano/nano_1dctqbmqxfppo9pswbm6kg9d4s4mbraqn8i4m7ob9gnzz91aurmuho48jx3c` (*recognized*)
`payto://unknowntype/l7tbta5b9xze6ckkfc99uohzxd009b0r` (*unrecognized*)
The client chooses to ignore the third *unrecognized* `payment_target_type`, and only embeds the first two payment target deep links in the user's profile, posts, chats, or elsewhere as buttons, links, or a dropdown selector using the corresponding icons or stylizations for the [*recognized* payment target types](#recommended-payment-target-types).