update readme and errors for mint (#107)

README.md

@@ -7,7 +7,7 @@
 
 *Disclaimer: The author is NOT a cryptographer and this work has not been reviewed. This means that there is very likely a fatal flaw somewhere. Cashu is still experimental and not production-ready.*
 
-Cashu is an Ecash implementation based on David Wagner's variant of Chaumian blinding. Token logic based on [minicash](https://github.com/phyro/minicash) ([description](https://gist.github.com/phyro/935badc682057f418842c72961cf096c)) which implements a [Blind Diffie-Hellman Key Exchange](https://cypherpunks.venona.com/date/1996/03/msg01848.html) scheme written down by Ruben Somsen [here](https://gist.github.com/RubenSomsen/be7a4760dd4596d06963d67baf140406). The database mechanics and the Lightning backend uses parts from [LNbits](https://github.com/lnbits/lnbits-legend).
+Cashu is an Ecash implementation based on David Wagner's variant of Chaumian blinding ([protocol specs](https://github.com/cashubtc/nuts)). Token logic based on [minicash](https://github.com/phyro/minicash) ([description](https://gist.github.com/phyro/935badc682057f418842c72961cf096c)) which implements a [Blind Diffie-Hellman Key Exchange](https://cypherpunks.venona.com/date/1996/03/msg01848.html) scheme written down [here](https://gist.github.com/RubenSomsen/be7a4760dd4596d06963d67baf140406). The database mechanics and the Lightning backend uses parts from [LNbits](https://github.com/lnbits/lnbits-legend).
 
 <p align="center">
 <a href="#cashu-client-protocol">Cashu client protocol</a> ·
@@ -29,7 +29,7 @@ Cashu is an Ecash implementation based on David Wagner's variant of Chaumian bli
 - Send tokens to nostr pubkeys
 
 ## Cashu client protocol
-There are ongoing efforts to implement alternative Cashu clients that use the same protocol such as a [Cashu Javascript wallet](https://github.com/motorina0/cashu-js-wallet). If you are interested in helping with Cashu development, please see the [docs](docs/) for the notation and conventions used. 
+There are ongoing efforts to implement alternative Cashu clients that use the same protocol. If you are interested in helping with Cashu development, please refer to the protocol specs [protocol specs](https://github.com/cashubtc/nuts). 
 
 ## Easy Install
 
@@ -149,7 +149,7 @@ cashu send 69
 ```
 You should see the encoded token. Copy the token and send it to another user such as via email or a messenger. The token looks like this:
 ```bash
-W3siYW1vdW50IjogMSwgIkMiOiB7IngiOi...
+eyJwcm9vZnMiOiBbey...
 ```
 
 You can now see that your available balance has dropped by the amount that you reserved for sending if you enter `cashu balance`:
@@ -160,7 +160,7 @@ Balance: 420 sat
 #### Receive tokens
 To receive tokens, another user enters:
 ```bash
-cashu receive W3siYW1vdW50IjogMSwgIkMiOi...
+cashu receive eyJwcm9vZnMiOiBbey...
 ```
 You should see the balance increase:
 ```bash

cashu/mint/ledger.py

@@ -416,14 +416,15 @@ class Ledger:
 
     async def check_fees(self, pr: str):
         """Returns the fees (in msat) required to pay this pr."""
-        decoded_invoice = bolt11.decode(pr)
-        amount = math.ceil(decoded_invoice.amount_msat / 1000)
         # hack: check if it's internal, if it exists, it will return paid = False,
         # if id does not exist (not internal), it returns paid = None
         if LIGHTNING:
+            decoded_invoice = bolt11.decode(pr)
+            amount = math.ceil(decoded_invoice.amount_msat / 1000)
             paid = await self.lightning.get_invoice_status(decoded_invoice.payment_hash)
             internal = paid.paid == False
         else:
+            amount = 0
             internal = True
         fees_msat = fee_reserve(amount * 1000, internal)
         return fees_msat

cashu/mint/router.py

@@ -104,12 +104,15 @@ async def mint(
     name="Melt tokens",
     summary="Melt tokens for a Bitcoin payment that the mint will make for the user in exchange",
 )
-async def melt(payload: PostMeltRequest) -> GetMeltResponse:
+async def melt(payload: PostMeltRequest) -> Union[CashuError, GetMeltResponse]:
     """
     Requests tokens to be destroyed and sent out via Lightning.
     """
-    ok, preimage = await ledger.melt(payload.proofs, payload.invoice)
-    resp = GetMeltResponse(paid=ok, preimage=preimage)
+    try:
+        ok, preimage = await ledger.melt(payload.proofs, payload.invoice)
+        resp = GetMeltResponse(paid=ok, preimage=preimage)
+    except Exception as exc:
+        return CashuError(code=0, error=str(exc))
     return resp