feat: nwc

[asmogo]

Description

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Notes to the reviewers

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Suggested CHANGELOG Updates

CHANGED

ADDED

REMOVED

FIXED

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Checklist

• I followed the code style guidelines
• I ran just quick-check before committing
• If the Wallet API was modified (added/removed/changed), I have reflected those changes in the FFI bindings (crates/cdk-ffi)

[codecov]

Codecov Report

❌ Patch coverage is 40.00000% with 357 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.65%. Comparing base (d481edc) to head (74d01e5).
⚠️ Report is 13 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/cdk-nwc/src/service.rs	41.49%	172 Missing ⚠️
crates/cdk-ffi/src/nwc.rs	0.00%	119 Missing ⚠️
crates/cdk/src/wallet/nwc.rs	63.73%	66 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2150      +/-   ##
==========================================
+ Coverage   71.55%   71.65%   +0.10%     
==========================================
  Files         356      359       +3     
  Lines       73999    75095    +1096     
==========================================
+ Hits        52950    53813     +863     
- Misses      21049    21282     +233     

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[asmogo]

closes #2106

[asmogo]

I have tested this with https://nwc-playground.vercel.app/

[thesimplekid]

I see there is a nwc crate https://github.com/rust-nostr/nostr/tree/master/crates/nwc for the client side of this. I think it would be good to use that to add some end to end tests in for this or maybe just an example would suffice.

[thesimplekid]

Right now handle_request(...).await runs inside the relay notification callback, so requests are processed serially. For a pay_invoice request this can take a while: we need to get a melt quote, pay it, and wait for the LN invoice/payment flow to complete. While that is happening, other requests from the client will not be processed.

I wonder if we eventually want to spawn request handling here, probably with a bounded concurrency limit. That said, I think it is fine to leave the implementation serial for now since this only becomes noticeable if a client sends many zaps/requests at once and payments are slow.

[thesimplekid]

Suggested change

	wallet: Wallet,
	wallet: Arc<Wallet>,

We should make this an Arc<> as we eventually want to remove clone from the Wallet. And I think the FFI aligns with this already

[thesimplekid]

MakeInvoiceRequest accepts a description_hash but we can't support this in cashu so I think we should error if this is set.

[thesimplekid]

Not all mints support setting the description as its optional https://github.com/cashubtc/nuts/blob/main/23.md#mint-quote. So to avoid silently attempting to create an invoice without the correct description I think we should check the mint info before getting the quote if the description is set in the request.

This is important for ZAPs as the invoice description has to be set to the zap receipt I believe.

[thesimplekid]

I would rename this to max_payment_msat. budget made me think it was some sort of cumulatively daily budget, which would maybe something useful we could add later, I think many nostr apps allow you to set things like hourly, daily zap budgets?

[thesimplekid]

Could we use the cdk Amount type we have to_sat and to_msat fns instead of having the logic here as well?

cdk/crates/cashu/src/amount.rs

Lines 569 to 583 in 04d39a6

	/// Convert to millisatoshis and return the raw u64 value
	///
	/// Returns an error if the unit cannot be converted to Msat
	/// (i.e., the unit is not Sat or Msat).
	pub fn to_msat(&self) -> Result<u64, Error> {
	self.convert_to(&CurrencyUnit::Msat).map(|a| a.value())
	}
	/// Convert to satoshis and return the raw u64 value
	///
	/// Returns an error if the unit cannot be converted to Sat
	/// (i.e., the unit is not Sat or Msat).
	pub fn to_sat(&self) -> Result<u64, Error> {
	self.convert_to(&CurrencyUnit::Sat).map(|a| a.value())
	}

.

So I think we could use that internally and convert at the boundary?

[thesimplekid]

Should these both be the expiry?