descriptor-wallet 0.4.0

Library for building descriptor-based bitcoin wallets
Documentation 
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// Descriptor wallet library extending bitcoin & miniscript functionality
// by LNP/BP Association (https://lnp-bp.org)
// Written in 2020-2021 by
//     Dr. Maxim Orlovsky <orlovsky@pandoracore.com>
//
// To the extent possible under law, the author(s) have dedicated all
// copyright and related and neighboring rights to this software to
// the public domain worldwide. This software is distributed without
// any warranty.
//
// You should have received a copy of the Apache-2.0 License
// along with this software.
// If not, see <https://opensource.org/licenses/Apache-2.0>.

use std::cell::RefCell;

use bitcoin::{Transaction, Txid};
use electrum_client::{Client, ElectrumApi, Error};

use super::{TxResolver, TxResolverError};

pub struct ElectrumTxResolver {
    client: RefCell<Client>,
}

impl ElectrumTxResolver {
    pub fn new(server: &str) -> Result<Self, Error> {
        Ok(ElectrumTxResolver {
            client: RefCell::new(Client::new(server)?),
        })
    }
}

impl TxResolver for &ElectrumTxResolver {
    fn resolve(
        &self,
        txid: &Txid,
    ) -> Result<Option<(Transaction, u64)>, TxResolverError> {
        let tx = self.client.borrow_mut().transaction_get(txid)?;

        let input_amount = tx
            .input
            .iter()
            .map(|i| -> Result<_, Error> {
                Ok((
                    self.client
                        .borrow_mut()
                        .transaction_get(&i.previous_output.txid)?,
                    i.previous_output.vout,
                ))
            })
            .collect::<Result<Vec<_>, Error>>()?
            .into_iter()
            .map(|(tx, vout)| tx.output[vout as usize].value)
            .fold(0, |sum, i| i + sum);
        let output_amount = tx.output.iter().fold(0, |sum, o| sum + o.value);
        let fee = input_amount
            .checked_sub(output_amount)
            .ok_or(TxResolverError)?;

        Ok(Some((tx, fee)))
    }
}