builder: Add initial crate.

core/src/actor.rs

@@ -1,5 +1,5 @@
+use crate::builder::transaction::TxHandler;
 use crate::errors::BridgeError;
-use crate::transaction_builder::TxHandler;
 use crate::utils;
 use bitcoin::sighash::SighashCache;
 use bitcoin::taproot::LeafVersion;
@@ -217,7 +217,7 @@ impl Actor {
 #[cfg(test)]
 mod tests {
     use super::Actor;
-    use crate::transaction_builder::TxHandler;
+    use crate::builder::transaction::TxHandler;
     use bitcoin::{
         absolute::Height, transaction::Version, Amount, Network, OutPoint, Transaction, TxIn, TxOut,
     };

core/src/aggregator.rs

@@ -1,13 +1,13 @@
 use crate::{
     actor::Actor,
+    builder,
     config::BridgeConfig,
     errors::BridgeError,
     musig2::{
         aggregate_nonces, aggregate_partial_signatures, AggregateFromPublicKeys, MuSigAggNonce,
         MuSigPartialSignature, MuSigPubNonce,
     },
     traits::rpc::AggregatorServer,
-    transaction_builder,
     utils::handle_taproot_witness_new,
     ByteArray32, ByteArray66, EVMAddress, UTXO,
 };
@@ -56,7 +56,7 @@ impl Aggregator {
         agg_nonce: &MuSigAggNonce,
         partial_sigs: Vec<MuSigPartialSignature>,
     ) -> Result<[u8; 64], BridgeError> {
-        let mut tx = transaction_builder::create_slash_or_take_tx(
+        let mut tx = builder::transaction::create_slash_or_take_tx(
             deposit_outpoint,
             kickoff_utxo,
             operator_xonly_pk,
@@ -102,7 +102,7 @@ impl Aggregator {
         agg_nonce: &MuSigAggNonce,
         partial_sigs: Vec<MuSigPartialSignature>,
     ) -> Result<[u8; 64], BridgeError> {
-        let move_tx = transaction_builder::create_move_tx(
+        let move_tx = builder::transaction::create_move_tx(
             deposit_outpoint,
             self.nofn_xonly_pk,
             self.config.bridge_amount_sats,
@@ -112,7 +112,7 @@ impl Aggregator {
             txid: move_tx.compute_txid(),
             vout: 0,
         };
-        let slash_or_take_tx_handler = transaction_builder::create_slash_or_take_tx(
+        let slash_or_take_tx_handler = builder::transaction::create_slash_or_take_tx(
             deposit_outpoint,
             kickoff_utxo,
             *operator_xonly_pk,
@@ -135,7 +135,7 @@ impl Aggregator {
         //     serde_json::to_string(&slash_or_take_utxo)?
         // );
 
-        let mut tx_handler = transaction_builder::create_operator_takes_tx(
+        let mut tx_handler = builder::transaction::create_operator_takes_tx(
             bridge_fund_outpoint,
             slash_or_take_utxo,
             *operator_xonly_pk,
@@ -175,7 +175,7 @@ impl Aggregator {
         agg_nonce: &MuSigAggNonce,
         partial_sigs: Vec<MuSigPartialSignature>,
     ) -> Result<[u8; 64], BridgeError> {
-        let mut tx = transaction_builder::create_move_tx_handler(
+        let mut tx = builder::transaction::create_move_tx_handler(
             deposit_outpoint,
             evm_address,
             recovery_taproot_address,
@@ -300,7 +300,7 @@ impl Aggregator {
 
         let move_tx_sig = secp256k1::schnorr::Signature::from_slice(&agg_move_tx_final_sig)?;
 
-        let mut move_tx_handler = transaction_builder::create_move_tx_handler(
+        let mut move_tx_handler = builder::transaction::create_move_tx_handler(
             deposit_outpoint,
             evm_address,
             &recovery_taproot_address,

core/src/builder/address.rs

@@ -0,0 +1,152 @@
+use crate::builder;
+use crate::{utils, EVMAddress};
+use bitcoin::address::NetworkUnchecked;
+use bitcoin::{
+    taproot::{TaprootBuilder, TaprootSpendInfo},
+    Address, ScriptBuf,
+};
+use secp256k1::XOnlyPublicKey;
+
+/// Creates a taproot address with either key path spend or script spend path
+/// addresses. This depends on given arguments.
+///
+/// # Arguments
+///
+/// - `scripts`: If empty, script will be key path spend
+/// - `internal_key`: If not given, will be defaulted to an unspendable x-only public key
+/// - `network`: Bitcoin network
+///
+/// # Returns
+///
+/// - [`Address`]: Generated taproot address
+/// - [`TaprootSpendInfo`]: Taproot spending information
+///
+/// # Panics
+///
+/// Will panic if some of the operations have invalid paramaters.
+pub fn create_taproot_address(
+    scripts: &[ScriptBuf],
+    internal_key: Option<XOnlyPublicKey>,
+    network: bitcoin::Network,
+) -> (Address, TaprootSpendInfo) {
+    let n = scripts.len();
+
+    let taproot_builder = if n == 0 {
+        TaprootBuilder::new()
+    } else if n > 1 {
+        let m: u8 = ((n - 1).ilog2() + 1) as u8; // m = ceil(log(n))
+        let k = 2_usize.pow(m.into()) - n;
+        (0..n).fold(TaprootBuilder::new(), |acc, i| {
+            acc.add_leaf(m - ((i >= n - k) as u8), scripts[i].clone())
+                .unwrap()
+        })
+    } else {
+        TaprootBuilder::new()
+            .add_leaf(0, scripts[0].clone())
+            .unwrap()
+    };
+
+    let tree_info = match internal_key {
+        Some(xonly_pk) => taproot_builder.finalize(&utils::SECP, xonly_pk).unwrap(),
+        None => taproot_builder
+            .finalize(&utils::SECP, *utils::UNSPENDABLE_XONLY_PUBKEY)
+            .unwrap(),
+    };
+
+    let taproot_address = match internal_key {
+        Some(xonly_pk) => Address::p2tr(&utils::SECP, xonly_pk, tree_info.merkle_root(), network),
+        None => Address::p2tr(
+            &utils::SECP,
+            *utils::UNSPENDABLE_XONLY_PUBKEY,
+            tree_info.merkle_root(),
+            network,
+        ),
+    };
+
+    (taproot_address, tree_info)
+}
+
+/// Generates a deposit address for the user. Funds can be spend by N-of-N or
+/// user can take after specified time.
+///
+/// # Parameters
+///
+/// - `nofn_xonly_pk`: N-of-N x-only public key of the depositor
+/// - `recovery_taproot_address`: User's x-only public key that can be used to
+///   take funds after some time
+/// - `user_evm_address`: User's EVM address.
+/// - `amount`: Amount to deposit (in sats)
+/// - `network`: Bitcoin network to work on
+/// - `user_takes_after`: User can take the funds back, after this amounts of
+///   blocks have passed
+///
+/// # Returns
+///
+/// - [`Address`]: Deposit taproot Bitcoin address
+/// - [`TaprootSpendInfo`]: Deposit address's taproot spending information
+///
+/// # Panics
+///
+/// Panics if given parameters are malformed.
+pub fn generate_deposit_address(
+    nofn_xonly_pk: XOnlyPublicKey,
+    recovery_taproot_address: &Address<NetworkUnchecked>,
+    user_evm_address: EVMAddress,
+    amount: u64,
+    network: bitcoin::Network,
+    user_takes_after: u32,
+) -> (Address, TaprootSpendInfo) {
+    let deposit_script =
+        builder::script::create_deposit_script(nofn_xonly_pk, user_evm_address, amount);
+
+    let recovery_script_pubkey = recovery_taproot_address
+        .clone()
+        .assume_checked()
+        .script_pubkey();
+    let recovery_extracted_xonly_pk =
+        XOnlyPublicKey::from_slice(&recovery_script_pubkey.as_bytes()[2..34]).unwrap();
+
+    let script_timelock = builder::script::generate_relative_timelock_script(
+        recovery_extracted_xonly_pk,
+        user_takes_after,
+    );
+
+    create_taproot_address(&[deposit_script, script_timelock], None, network)
+}
+
+/// Shorthand function for creating a MuSig2 taproot address: No scripts and
+/// `nofn_xonly_pk` as the internal key.
+///
+/// # Returns
+///
+/// See [`create_taproot_address`].
+///
+/// - [`Address`]: MuSig2 taproot Bitcoin address
+/// - [`TaprootSpendInfo`]: MuSig2 address's taproot spending information
+pub fn create_musig2_address(
+    nofn_xonly_pk: XOnlyPublicKey,
+    network: bitcoin::Network,
+) -> (Address, TaprootSpendInfo) {
+    create_taproot_address(&[], Some(nofn_xonly_pk), network)
+}
+
+/// Creates a kickoff taproot address with multisig script.
+///
+/// # Returns
+///
+/// See [`create_taproot_address`].
+///
+/// - [`Address`]: Kickoff taproot Bitcoin address
+/// - [`TaprootSpendInfo`]: Kickoff address's taproot spending information
+pub fn create_kickoff_address(
+    nofn_xonly_pk: XOnlyPublicKey,
+    operator_xonly_pk: XOnlyPublicKey,
+    network: bitcoin::Network,
+) -> (Address, TaprootSpendInfo) {
+    let musig2_and_operator_script = builder::script::create_musig2_and_operator_multisig_script(
+        nofn_xonly_pk,
+        operator_xonly_pk,
+    );
+
+    create_taproot_address(&[musig2_and_operator_script], None, network)
+}

core/src/builder/mod.rs

@@ -0,0 +1,3 @@
+pub mod address;
+pub mod script;
+pub mod transaction;