Not accounting for non-RGB inputs in coin selection

RGB-WG / rgb

RGB smart contracts: command-line tool & wallet runtime library for desktop and mobile integration

https://rgb.tech

Apache License 2.0

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Not accounting for non-RGB inputs in coin selection #113

Open nicbus opened 7 months ago

nicbus commented 7 months ago

Trying to execute a few transfers using this branch of rgb-sandbox I run into the following error:

Error: not enough funds to pay fee of 400 sats; all inputs contain 2000 sats and outputs spends 2000 sats out of them.

The wallet should have enough bitcoins as the unspents come up as:

Height     Amount, ṩ    Outpoint                                                                                                                                                                                                                                                                                               
bcrt1q06vjlq89kufjgzenwusm99l6hv5ygxhur8qun8    &9/0                                                                                                                                                                                                                                                                           
107             2000    e6cfb776a1e03165f6e739a6452231ac9d30fb20cbde0ae130ed7b10d20dc7b1:0                                                                                                                                                                                                                                     
106             2000    7a39dd007218bdbf3d6d1a2b919700d9a144a1d2cab20cace5a8ad57df2395b7:0                                                                                                                                                                                                                                     

bcrt1qwke7jgvxuwcwk8q4m4mglgmltyfzasde5c4nsj    &0/0                                                                                                                                                                                                                                                                           
105        100000000    2a0bd1672cfb051c7c0627d1295c07325974b53048a87169c80b44f8698c949e:0

I guess this happens because the input selection is not adding more inputs if needed to cover fees (or outputs), but I haven't dug deeper than this.

dr-orlovsky commented 7 months ago

Yes, you are right in your assumption. I remember writing that logic, but it seems somehow it is skipped. We need to move the issue into BP wallet since it happens there.

shuimuliang commented 7 months ago

Suppose Alice has one UTXO with 2000 sats. 2000 -> 1600 -> 1200 -> 800 -> 400 (it won't be able to broadcast anymore)

dr-orlovsky commented 7 months ago

Suppose Alice has one UTXO with 2000 sats. 2000 -> 1600 -> 1200 -> 800 -> 400 (it won't be able to broadcast anymore)

It would - you just need to add more tx inputs and feed additional sats into the witness transaction

dr-orlovsky commented 5 months ago

Re-opening and changing the name as explained in https://github.com/BP-WG/bp-wallet/issues/13#issuecomment-2021330041

dr-orlovsky commented 5 months ago

Now, there is the question: when and how should we use non-RGB inputs for moving some BTCs to RGB outputs.

In other words, this situation is not a bug but a feature - however possibly bad UX. I just do not know how to make it better: I assume many wallets will differenciate BTC and RGB balances, and if some BTC are "disappearing" after RGB transactions it would be even worse UX...

nicbus commented 5 months ago

I agree that using funds from the "BTC balance" without prior user consent would be bad UX.

I propose doing something similar to what rgb-lib does to handle this. Specifically, I would:

add a command that lets the user spend some "BTC balance" (i.e. keychains 0 or 1) to create new RGB UTXOs
- with default number and size of the UTXOs (e.g. 5 / 5000 sat)
- with options to specify custom values
automatically use RGB UTXOs with 0 allocations to pay for fee or witness transfers (or blind them to allocate assets)
return an informative error in case funds (a.k.a. UTXOs) are needed but none are available, hinting at the command to create RGB UTXOs

dr-orlovsky commented 5 months ago

This is a large feature request, and since rgb cli is not a mainstream wallet I propose to postpone this for v0.12. End-users will be able to do that anyway with proper mobile and web wallets build with rgb-lib