bp-std 0.12.0-rc.3

// Modern, minimalistic & standard-compliant cold wallet library.
//
// SPDX-License-Identifier: Apache-2.0
//
// Written in 2020-2024 by
//     Dr Maxim Orlovsky <orlovsky@lnp-bp.org>
//
// Copyright (C) 2020-2024 LNP/BP Standards Association. All rights reserved.
// Copyright (C) 2020-2024 Dr Maxim Orlovsky. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use std::collections::HashMap;

use amplify::Wrapper;
use bc::secp256k1::{ecdsa, schnorr as bip340, SECP256K1};
use bc::{
    InternalKeypair, InternalPk, LegacyPk, Sighash, TapLeafHash, TapMerklePath, TapNodeHash,
    TapSighash, XOnlyPk,
};
use derive::{KeyOrigin, Sign, XkeyOrigin, Xpriv, XprivAccount};
use psbt::{Psbt, Rejected, Signer};

#[derive(Clone)]
pub struct TestnetRefSigner<'a> {
    pub keys: HashMap<&'a XkeyOrigin, &'a Xpriv>,
    pub key_path: bool,
    pub script_path: Option<TapLeafHash>,
}

impl<'a> TestnetRefSigner<'a> {
    pub fn new(account: &'a XprivAccount) -> Self { Self::with(true, None, [account]) }

    pub fn new_legacy(iter: impl IntoIterator<Item = &'a XprivAccount>) -> Self {
        Self::with(false, None, iter)
    }

    pub fn new_key_spend(iter: impl IntoIterator<Item = &'a XprivAccount>) -> Self {
        Self::with(true, None, iter)
    }

    pub fn new_script_spent(
        leaf: impl Into<TapLeafHash>,
        iter: impl IntoIterator<Item = &'a XprivAccount>,
    ) -> Self {
        Self::with(false, Some(leaf.into()), iter)
    }

    pub fn with(
        key_path: bool,
        script_path: Option<TapLeafHash>,
        iter: impl IntoIterator<Item = &'a XprivAccount>,
    ) -> Self {
        Self {
            keys: iter
                .into_iter()
                .map(|account| (account.origin(), account.xpriv()))
                .inspect(|(origin, xpriv)| {
                    if !xpriv.is_testnet() {
                        panic!(
                            "Extended private key with origin {origin} will not be used for \
                             signing since it belongs to mainnet"
                        );
                    }
                })
                .collect(),
            key_path,
            script_path,
        }
    }
}

impl Signer for TestnetRefSigner<'_> {
    type Sign<'s>
        = Self
    where Self: 's;

    fn approve(&self, _: &Psbt) -> Result<Self::Sign<'_>, Rejected> { Ok(self.clone()) }
}

impl TestnetRefSigner<'_> {
    fn get(&self, origin: Option<&KeyOrigin>) -> Option<Xpriv> {
        let origin = origin?;
        self.keys.iter().find_map(|(xo, xpriv)| {
            if let Some(derivation) = xo.child_derivation(origin) {
                return Some(xpriv.derive_priv(derivation));
            }
            None
        })
    }
}

impl Sign for TestnetRefSigner<'_> {
    fn sign_ecdsa(
        &self,
        message: Sighash,
        pk: LegacyPk,
        origin: Option<&KeyOrigin>,
    ) -> Option<ecdsa::Signature> {
        if !pk.compressed {
            return None;
        }
        let xpriv = self.get(origin)?;
        let sk = xpriv.to_private_ecdsa();
        if sk.public_key(SECP256K1) != pk.pubkey {
            return None;
        }
        Some(sk.sign_ecdsa(message.into()))
    }

    fn sign_bip340_key_only(
        &self,
        message: TapSighash,
        pk: InternalPk,
        origin: Option<&KeyOrigin>,
        merkle_root: Option<TapNodeHash>,
    ) -> Option<bip340::Signature> {
        let xpriv = self.get(origin)?;
        let output_pair =
            InternalKeypair::from(xpriv.to_keypair_bip340()).to_output_keypair(merkle_root).0;
        if output_pair.x_only_public_key().0.serialize()
            != pk.to_output_pk(merkle_root).0.to_byte_array()
        {
            return None;
        }
        Some(output_pair.sign_schnorr(message.as_ref()))
    }

    fn sign_bip340_script_path(
        &self,
        message: TapSighash,
        pk: XOnlyPk,
        origin: Option<&KeyOrigin>,
    ) -> Option<bip340::Signature> {
        let xpriv = self.get(origin)?;
        let sk = xpriv.to_keypair_bip340();
        if sk.x_only_public_key().0 != pk.into_inner() {
            return None;
        }
        Some(sk.sign_schnorr(message.as_ref()))
    }

    fn should_sign_script_path(
        &self,
        _index: usize,
        _merkle_path: &TapMerklePath,
        leaf: TapLeafHash,
    ) -> bool {
        self.script_path == Some(leaf)
    }

    fn should_sign_key_path(&self, _index: usize) -> bool { self.key_path }
}

pub struct TestnetSigner {
    pub keys: Vec<XprivAccount>,
    pub key_path: bool,
    pub script_path: Option<TapLeafHash>,
}

impl TestnetSigner {
    pub fn new(account: XprivAccount) -> Self { Self::with(true, None, [account]) }

    pub fn new_legacy(iter: impl IntoIterator<Item = XprivAccount>) -> Self {
        Self::with(false, None, iter)
    }

    pub fn new_key_spend(iter: impl IntoIterator<Item = XprivAccount>) -> Self {
        Self::with(true, None, iter)
    }

    pub fn new_script_spent(
        leaf: impl Into<TapLeafHash>,
        iter: impl IntoIterator<Item = XprivAccount>,
    ) -> Self {
        Self::with(false, Some(leaf.into()), iter)
    }

    pub fn with(
        key_path: bool,
        script_path: Option<TapLeafHash>,
        iter: impl IntoIterator<Item = XprivAccount>,
    ) -> Self {
        Self {
            keys: iter
                .into_iter()
                .inspect(|account| {
                    if !account.xpriv().is_testnet() {
                        panic!(
                            "Extended private key with origin {} will not be used for signing \
                             since it belongs to mainnet",
                            account.origin()
                        );
                    }
                })
                .collect(),
            key_path,
            script_path,
        }
    }
}

impl Signer for TestnetSigner {
    type Sign<'s> = TestnetRefSigner<'s>;

    fn approve(&self, _: &Psbt) -> Result<Self::Sign<'_>, Rejected> {
        Ok(TestnetRefSigner::with(self.key_path, self.script_path, &self.keys))
    }
}